THE ARUP JOURNAL

SEPTEMBER 1970

5f Vol. 5 No. 3 September 1 970 Contents Conclusion Published by Ove Arup & Partners Consulting Engineers By close collaboration with the architect and Arup Associates Architects and Engineers the precast manufacturer, we set out to THEARUP 1 3 Fitzroy Street. London. W1 P 6BQ isolate as many problems as possible and solve them before erection on site began. In Editor: Peter Hoggett this way erection was controlled by produc• Art Editor: Desmond Wyeth MSIA tion. To ensure that components were avail• JOURNAL Editorial Assistant: David Brown able when required entailed a detailed study An engineer looks at architecture. 2 of the components, the erection technique by Ove Arup and not least, the time allowed. Had it been possible to produce only basic shapes for Prestressed concrete congress, 4 deck and ceiling panels the overall time for Prague. June 1 970, production and erection might have been by D. Dowrick significantly reduced but it would have meant additional, noisy work on site cutting holes. The Carlton Centre, 5 The short time for erection of the shell has by R. Heydenrych given finishing trades and service engineers a The use of prestressing 6 dry and spacious surrounding in which to foundation strengthening at work. York Minster, A rigorous cost analysis has shown that by D. Dowrick certain items proved uneconomic since they serve no primary function. One must realize St. Katharine Docks. 10 that the cost per item for erection, within by M. Tucker limits, is constant regardless of size of com• The changing face of concrete, 20 ponent. Brockham Park now has, in addition by T. O'Brien to its other amenities, a building that blends perfectly with its surroundings and that is a Beecham Research Laboratories : 24 Fig. 7 radical departure from the stables ! an exercise in simplicity, North Block during erection of the frame (Photo : Beecham Research Laboratories) by A. Hart Average cost of the precast frame superstructure per ft2. - Fig. 8 excluding fascia In situ concrete link block between North & South Blocks Item North Block South Block Fascia panels are precast as for the main blocks (Photo: Beecham Research Laboratories) Supply

Front cover: I warehouse, St.Katharine dock, seen from the new Dock House (Photo: Henk Snoek) 1) Trusses 14/1 12/6

Back cover: Cameo of Thomas Telford (Reproduced with the permission of Mrs. N. S. Telford) 2) Columns 2/6 3/2

3) Deck Panels 1/11 1/11 architecture from the many tangible proofs of engineering. Here there is steady progress in An engineer looks its existence encompass such acknowledged the achievement of engineering aims, and a 4) Ceiling 7/4 7/4 landmarks as Vitruvius's De Architectura. and very much greater agreement about what is 5) Siporex 3/1 * 3/1 * at architecture Norberg-Sciiulz's latter day Intentions in good and bad engineering. architecture, many less systematic but more What is the reason for this difference, and Erect Ove Arup impassioned pleadings by actual and would- how can it be maintained in view of the fact be architectural practitioners, and the weekly that there is no clear border line between 1) Trusses 3/6 4/2 outpourings of esoteric critics in architectural engineering and architectural structures. 2/4 journals whose claim to fame rests on their Whether you call a bridge architecture or 2) Columns 1/10 This paper was given at being incomprehensible, or so it appears to a engineering is optional—if we attach the Leicester University Arts Festival on 3) Deck Panels 2/6 2/6 mere engineer. normal vague meaning to these words it is 11 February, 1969 4) Ceiling 5/- 5/- What all these have in common is: both. And that in fact applies to all man-made structures—they are both structures—i.e. Introduction 1 that they are all different, if that isn't too 5) Siporex • • engineering structures and pieces of architec• The title for my talk is An engineer looks at Irish ture, in different proportions, if you like. ~;.' JZZv^ ' ZL ~7 •til ': * Total 29/5 29/8 architecture. The engineer is me, of course, and 2 that they deal almost exclusively with The question arises, can one separate the (excluding the only reason for bringing him into the title aesthetic considerations of order, balance, structural from the architectural part? Can a ceiling panels) is to indicate that I am only an engineer, and space, form, light and shade, textures—in structure be a bad engineering structure and cannot claim to be an expert on architectural short, the visual organization of the material, •Supply & Erect good architecture or vice versa? That is a theory, so what I say about architecture may and are less concerned with function or very important question, which I will return not meet with the approval of the pundits. But economy to later, when I have dealt with my first I have had a great deal of experience in helping 3 that although they may be a very valuable query. architects to design buildings and other aid to the understanding of different architec• structures, and I have tried my hand at the tural viewpoints, they are too vague to be a The reason for the difference between the latter myself, and it was always the intention guide to architectural creation. What I mean architectural and engineering 'climate', so to that the result should rank as architecture, is, you cannot look up in a book on architec• speak, is very complex. It is partly a matter of preferably good architecture. Unfortunately ture where to draw the next line on a drawing terminology, partly a matter of historical that doesn't mean that I can give you any board, as the engineer can if he has forgotten accident, and the consequent training of satisfactory or generally accepted definition the formula for analysing the strength of a architects and engineers, and mostly a matter of the term, and I doubt whether anybody else beam. Books and drawings may enable an of what is commonly supposed to be the can. I can only give you my own point of architect to produce a building in the Gothic difference in content or context—architecture view. or even Miesian style, but that is not nowadays being concerned with producing works of t'^Mlll II III' mi '^l A building can be a piece of architecture. But considered an acceptable substitute for true art; engineering with utility structures. of another building, some might say that it and original architecture—whatever that may isn't architecture. In other words, buildings are mean Structural requirements architecture only if they fulfil certain condi• No, the architect nowadays is definitely on If we continue to use the word structure in its tions. Which conditions?—general confu• his own. in an ocean of complete permissive• widest sense, in which it can mean a building, sion. ness and an almost infinite choice of means. a silo, a bridge, dam or road, in fact anything Architecture can also mean a discipline, like It can be a relief, therefore, if his choice is built by man which stays put—for a time at philosophy, medicine, law. building science, limited by impossible site conditions and a least—so as to avoid 'static hardware' or some sociology or Art—with a capital A. In fact shortage of materials or technical resources. such concoction—we have seen that to call architecture was once considered the mother A corollary, or in any case in keeping with some of them architecture and othersengineer- of arts, a valid art form like painting, poetry or this chaotic state of affairs, is the fact that ing structures is rather arbitrary. drama, and many attempts have been made, architecture cannot be said to have progressed We demand of all of them that they should and are still being made, to produce a theory from old times till now. Few would argue that function well, last well, look well and cost of architecture which will enable us to modern architecture is a marked improve• little, but if we survey the whole field of distinguish architecture from mere building, ment on the architecture of earlier epochs, possible structures, the emphasis placed on good from bad architecture, and which will be that our great architects are greater than their these four demands differs widely. Fig. 9 a guide to the creation of architecture. ancient confreres. Perhaps such a comparison They must all fulfil their particular function, North Block on completion of the structural frame (Photo: Beecham Research Laboratories) 2 These attempts to distil the volatile essence of is meaningless. But look at the contrast in for that is the reason for building them. But the the requirements and asbestos shims were functions vary, from those which are easily and the people actually using the buildings. familiar with the means of execution and used to carry all temporary loads. Asbestos defined but difficult to fulfil, for instance to They felt it as a duty to help in formulating the their cost. It is a fallacy to believe that more packs were prelevelled centrally in each slot build a bridge over a gorge, to others which are brief, a task which grew more and more com• accountancy and cost planning will in them• before the column was lifted into position. easy enough to fulfil if only we could manage plicated, and which demanded the expertise selves make building more efficient. These This eliminated the lengthy process of to define them. A teaching hospital, involving of architects and engineers. The field of obviously have their use but chopping some• adjusting the level of the column by crane several authorities and a large number of architecture was widened to include housing, thing off a design by lowering standards does and required only that the length of the doctors all with their different and often schools, hospitals—and gradually all struc• not create anything. For that you must go column remained constant. Each column was conflicting demands, and which moreover tures which clutter up our environment, for back to the drawing board and make a better r held in position with four push-pull props may very likely become obsolete before it is their architectural quality concerns us all. design. To get the right materials in the right enabling adjustment for verticality. place is what gets building costs down. 1 finished, owing to changing demands, At the same time engineering technology also belongs to the latter category. invaded the whole field of building and Design is creative accountancy. 1 By virtue of their size and weight, trusses I proved slow to erect. Asbestos shims 25 mm They must also all last well—that is, they must construction. In fact the realization of The future (1 in.) thick were placed on the front edge of be stable and able to withstand wear and tear architects' dreams depended on engineering To use our resources efficiently there are two the corbel receiving the truss. The four main by natural forces or imposed loads. But this knowledge. The whole way of building has kinds of question we have to make up our ! trusses on the grid were placed in position may be a simple or a very complicated matter changed—it will soon all be engineering. minds about: what to build, and how to build, and clamped to the column with ply side- —the latter a characteristic of daring needs and means, more or less! Of course The need for co-operation shutters and clamps. The next stage was to engineering structure. they are intertwined in various ways, for what This demands collaboration of architects and ensure that the trusses were square to one They should also all look well—they create we decide to build depends largely on what engineers, a topic which has been discussed I another and vertical. The narrow gap between our man-made environment which is of we can afford to build, and this depends 0 ad nauseam these last 30 or 40 years. the end of the truss and the face of the concern to us all. But again the emphasis again on the means available or employed. To begin with, the civil engineering consul• column was mortared up and the in situ varies widely—between, for instance, a So that those who decide what to build must tants, the heirs of Telford and Brunei, were concrete stitch made. Once the stitch had retaining wall and a cathedral. be advised by those who know how to build reluctant to enter the field of ordinary gone off, the two secondary trusses within And finally they should all cost as little as But I think this distinction can help us to throw the main frame were erected using the same possible, but again, the need for economy building—there wasn't much engineering in some light on the role of engineers and procedure. When the stitching had been varies. Economy is a matter of devising a it, it was fiddly, unremunerative work and they architects in building. were certainly not prepared to act as mere completed the frame was stable and a dry sensible way of building the structure, and How to build will more and more become a assistants to architects—they didn't think pack mortar (1 :1) was packed firmly around even the richest client doesn't want to spend matter of engineering, it will at least have to much of them anyhow. V2 the spigot at the foot of the column and under more than necessary. employ engineering methods and will need an * ,»•.•*. . ' the full area of the cruciform. Attempts to Roughly speaking engineering structures are The architects, on their side, naturally wanted attitude of mind mostly found among consolidate the dry pack with a Kango those which have an easily defined and to retain complete control over the design— engineers. That the designers must be hammer proved unsuccessful and packing undisputed function and which present you have to, when you are producing a thoroughly familiar with the means of con• was done by hand with a hammer and a piece structural problems of some intricacy, whereas masterpiece, you cannot tolerate interference struction and their cost has already been Fig. 4 of steel. A similar process was used for the those where aesthetic and functional prob• from people who know nothing about the mentioned—as I have said so often, designing North Block : layout of trusses below first floor level 25 mm (1 in.) gap between corbel and truss, lems dominate are classed as architecture. finer points of architectural composition—or means indicating a sensible way of building. (Photo: Beecham Research Laboratories) but in this case the operation was made easier Or we could say that the first are those where for that matter, from those who do. But a new The engineer, however, is used to working to by the position and nature of the gap. The dry a civil engineer is in charge and responsible proletariat in the form of structural engineers a definite brief. What he has to achieve is pack takes all vertical loads and the wet stitch grew up, somewhat more narrowly based than i for the design, whereas the second are fairly easily defined—to span a river, to store provides continuity and frame action. We designed by architects. civil engineers, but with a deeper knowledge of grain, etc. He is dealing with the art of / assumed that the asbestos packs carried none engineering structure, and willing to offer directing the Great Sources of Power in of the final vertical loads. The two professions their help under the architect's direction—the I i Nature for the use and convenience of man— 1 These two ways of classifying structure lead normal process of specialization. And many 1 Erection of ceiling panels was almost as swift but he does not give so much thought to to more or less the same result, and correspond other kinds of engineers and experts are as deck panels but more care was needed to whether it will in fact benefit man. He will to the difference in training and background coming into the picture. Buildings nowadays ensure that the finish on the underside was see to it that the thing functions well, last of the two professions. At least this was the are full of services and gadgets which account not damaged. The nominal 10 mm (% in.) gap well and costs little, provided somebody tells case before the drastic changes brought about for a greater and greater part of the total cost. between the panels and the bottom boom of him what the function is going to be. And the by the modern movement in architecture and All these changes have brought about a pretty the truss was mortared up and pointed, 'looks well' part is not always his strong suit. the technological advance since then. En• chaotic state of affairs. People, old habits, producing an air-tight seal. He has both feet on the ground, not given to gineers built bridges, railways, harbours, old ways of thinking, do not change so rapidly. dabbling in airy-fairy aesthetic notions, or so Before placing the first floor deck panels, dams, tunnels, factories—in fact all the utility There are powerful personal interests at stake. it is generally assumed. 1 lengths of reinforcement were slotted through structures called into being by the industrial New ways of building demand larger jobs to The modern architect, on the other hand, is the links projecting from the top boom of the revolution, whereas architects were con• be tackled by larger organizations, different endeavouring to design an environment for trusses and through the cruciform slot in the cerned exclusively with 'fine' buildings, with financial arrangements, collaboration of differ• people to live in and work in and enjoy—a very head of the column. Full continuity was Building as an art. an art which could trace ent departments not in the habit of speaking to different and very much more complex obtained when the gap between deck panels its origins back to antiquity. Ordinary houses each other, in fact a complete reorganization business—for we humans enjoy so many r. was concreted up. In the vicinity of the were at that time, and are still to some extent, of the whole building industry. At the moment different things. column heads the level of the in situ stitch the province of builders. Architecture was every possible combination of new and old was left 76 mm (3 in.) low to enable the next confined to mansions or important public methods and attitudes is in evidence. A house is a machine to live in—Corbusier's lift of columns to be placed. buildings and these were designed by archi• It would take far too long to sort out this dictum, which has loomed large in the public tects on quite different principles. The image of modern architects, has perhaps not As erection of the fascia was not structurally complicated situation now—and I am just as architect then had a client who knew, or always been rightly interpreted, as Joe I f important, this was erected last in the lost as anybody else anyhow. But one thing thought he knew, what he wanted, and a Chamberlin pointed out in his lecture to the sequence. The waling beams were positioned is obvious—what we build is always a whole, well-established tradition of buildings based RIBA in 1 969. The machine part is largely the Fig. 5 Fig. 6 on asbestos packs on the cantilever fins of the an entity—a building, a precinct, a town with on a few materials and supported by crafts• engineer's business—but to live in is not a Connection detail between corner column Typical connection detail prior to columns and a wet stitch and dry pack roads, etc.—and all these entities interact men who knew their job and were proud of it. simple matter. Man lives not by bread alone. and precast truss. Side shutters for concreting of truss completed their fixing. Projecting bolts on the and influence each other. If you split the He could therefore concentrate on creating Man needs life and company as well as calm in situ concrete stitch being fixed to cruciform section column waling beams enabled each fascia panel to be design of these entities amongst a number of architectural masterpieces according to the and privacy, he needs the sun and air and (Photo: Beecham Research Laboratories) (Photo: Beecham Research Laboratories) located in position. To prevent the panel specialist designers each acting more or less prevailing rules of the game. In fact the green plants and birds singing as well as the rotating outwards two adjustable props tied it independently, you won't get an entity, but a highlights of architectural achievement were excitement of the metropolis, he needs work back to the deck until an in situ stitch could be hotch-potch. There must be co-ordination, felt to lie in the past rather than in the future. and play and relaxation—he wants to be able made. Although an in situ balcony was integration, a proper assessment of priorities Engineers looked the other way. to drive his car anywhere—but he doesn't poured later the connection at each end of the based on the true interest of the community. It was in part the great engineering achieve• At the moment we are far from achieving this want his peace disturbed by other cars. And Erection procedure with a 38 mm (1% in.) thick floor screed, waling beam was designed to resist the full ments in the last century which triggered off a integration. We are just about drowning in his needs tend to grow faster than our means tolerances were reasonably liberal. Each overturning force imposed by the panels. Having established firmly the principle that change in architectural philosophy. The specialization. It is perhaps the biggest to satisfy them. Man is quite a problem. panel was bedded on 1.6 mm ( Via in.) thick the simpler the components, the quicker a The second phase, from first floor level to Bauhaus. the whole Modern Movement, problem we have to face. Architects have long been grappling with this shims of Hyload placed under all the rib project is completed, the erection of the two roof, was erected by the same method with accepted the new structural materials and the It means much more than the much discussed problem. It cannot be solved by computers seatings. To reduce any live feeling in the blocks has been incredibly swift. Had it not the exception that 610 mm (2 ft.) wide, technological advance with enthusiasm and collaboration of the design team. Design or technology—it is a question of sensitivity, panels, an in situ concrete stitch was made been for a recurrent fault in the tower crane, 1 50 mm (6 in.) Siporex planks span between dreamt about building a new and better decisions are taken by all sorts of authorities, of understanding the deeper needs of along the top of the supporting beam. Erec• erection would have been completed without trusses in place of deck panels. world. It partly misfired, for enthusiasm for the financiers, etc., outside the design team human nature. tion of these panels was dependent on their hitch. visual manifestations of technology was not proper. It means, for instance, that the Ministry availability on site, but as many as 40 were The main contractor, James Longley & Co. Amongst these experts the architects should enough to effect a radical change in architec• Basically the completed structure can be 2 2 of Transport must collaborate with local erected per day 41 8 m (4500 ft. ). Ltd., started work on site in May 1 969 and the play a decisive role, for it is their task to compared to a table standing on top of first precast components were placed in mid- tural thinking—the Modern Movement in planning authorities, that city architects must ensure the artistic quality, the character, the another table, i.e. the continuity at the foot The original complex detail for fixing precast September. The South Block was completed many cases amounted to no more than a new work hand in hand with city engineers and visual harmony of our environment. of the columns is negligible while the joint columns involved ducts cast in, projecting in 1 6 weeks including a 5-week delay due to style. But one radical change in outlook took extend the other hand to those who frame our For me, then, everything we build is architec• at the top produces complete continuity. So dowel bars and grouting up. The final detail crane breakdown. The North Block was com• place which changed the way we look at bye-laws and building regulations and to ture—different kinds of architecture, even much of the design load is dead weight that required simply a cruciform shaped spigot cast pleted by the beginning of May 1970 in 15 architecture today. Architects acquired a government on a local and national level. And when the structural problems dominate. An we were not too concerned with this concept. on the base of the column and a 76 mm weeks. These figures represent the time spent social conscience, they were no longer con• it means further that the gap between design engineering structure is not a good structure On completion of the substructure a thorough (3 in.) deep cruciform slot in the head of the on erection of the precast units only and do tent to cater for the whims of rich clients, they and execution which is such an ingrained if it is not also a pleasant thing to look at. dreamt of a better world where technology check was made of the compatibility of the column below. Prior to erection, tests were not include construction of basements, semi• feature of the building industry must be And a piece of architecture is not perfect if the could make everybody share in the good life. in situ work to accept the first precast made on the suitability of several materials for basements or stairs. The total length of bridged somehow. For the designer must be structure is second-rate, if the roof leaks and The client was therefore society as a whole. 26 elements. Since all deck panels are finished use as shims. It was found that asbestos met contract is for 21 months. the heating fails. for holes by indicating on individual unit Member group reports International recommendations for the drawings the size and location of hole Pre-stressed design and construction of concrete Various countries presented group reports on required. From six basic shapes over 400 * 5 structures recent major works under the three headings variations were obtained! The 1.7 m (5 ft. concrete congress, Something of a landmark in engineering of Bridges, Buildings and Other Structures. 6 in.) deep void between ceiling and deck is affairs was witnessed with the presentation of The British report on bridges was delivered by easily accessible and the service engineer was Prague, June 1970 these recommendations jointly agreed by the D. Lee of Maunsell & Partners, and included presented with a large area with few con• Ey3L' CEB and FIP. This new document is a step the Western Avenue extension and the Calder straints. River bridge, but, I thought, was not very well forward on the 1966 draft recommendations, There is a second, less heavily serviced void illustrated. In fact, it was striking how much incorporating many amendments and addi• between the ceiling to the first floor and the more interesting the German and Italian bridge tions to the original text. roof. Access between floors is provided by an David Dowrick reports were than those of other countries. One important facet of the document is the oil-draulic lift in the South Block and stairs in J. Sutherland presented the British report on adoption of SI units and it struck me as still both blocks formed of in situ concrete spine buildings and. despite apologising for a lack rather strange to see Newtons rather than Kgf beams with precast terrazzo treads. In the link of material, gave an outstanding talk which in an international document. It is significant, block there is a spiral staircase, approximately incidentally mentioned several Arup jobs. Ron however, that concrete stresses are quoted in 2.4 m (7 ft. 9 in.) diameter, formed entirely of 2 2 Heydenrych presented the South African The 6th congress of the Federation Inter• N/cm rather than N/mm . allowing an easier precast terrazzo units. 2 group report on buildings which included ®— nationale de la Precontrainte was held in comparison with the European Kgf/cm . mention of our Standard Bank and Carlton • Prague and attracted 2300 delegates from at International co-operation is certainly not at Manufacture of components • Centre projects in Johannesburg. His des• ! least 49 countries including Kuwait and its best regarding what one might have hoped 1 cription of the latter follows this article. All the precast components were manufac• Monaco but excluding China. About 80 would be the simple, quantitative issue of tured at the Southampton works of Reema British delegates attended including Arupians units. It is apparent that confusion will reign Construction Ltd., who were also the L Individual technical contributions Povl Ahm, Duncan Michael. Ken Shaw. over this subject for many years to come. nominated sub-contractor for the erection. Keith Ranawake and myself. The Arup con• Another point of comparison with intended This FIP Congress saw the innovation of Units were transported to the site by road and, tingent was swelled by the presence of our British practice is the terminology for design technical contributions by individuals as with the exception of deck and ceiling panels, South African colleagues, Ron Heydenrych limit states. The CEB/FIP document prefers distinct from group and commission reports. no special arrangements had to be made. The M and Ian Scott who brought their wives, as did 'ultimate limit state' to 'limit state of local These were divided into English, German and dimensions of the latter were such that they K Povl Ahm and Keith Ranawake. Most of the damage'. I personally prefer the CEB/FIP French language sessions (without translation were classified as a wide load and required a British delegation stayed at the International terms, the word 'ultimate' being widely used services) which were held concurrently in the police escort for sections of the route The Hotel, a vast pile of a place, massive bureau• internationally, and 'serviceability' being more Technical University. Thusthese sessions were consequent delays on site were reduced cratic architecture with primitive plumbing on a pleasantly human scale in terms of both t meaningful than 'local damage'. The proposed towards the end of construction by stock• KEY PLAN and non-automatic lifts—all very Russian. Try British unified concrete code will take enough lecture hall and audience size, compared with piling units. the Park Hotel if you go to Prague. the impersonality of the vast Congress Hall. getting used to without such new terms as In order to accommodate the vast numbers- Despite the shortness of time allowed for the Few problems were encountered in casting well as all the other changes. the congress was held mainly in the Julius presentation of these papers, they generally the various units although the geometry of An interesting inclusion is the recommenda• Fig. 2 Fucik Hall with some smaller meetings in the proved interesting, covering a wide range of some was complex. To standardize the tions for dimensioning of punching shear First floor layout Technical University. The congress timetable subjects such as ground anchors and the pre• manufacture as much as possible, similar reinforcement in flat slabs. was very crowded, taking five and a half days stressing of cylindrical wine reservoirs with members in different trusses were made from 9 a.m. until 6 p.m. and included lectures, heated cables. One of the more valuable dimensionally the same. The trusses were Commission reports cast on their side on a steel palate which could reports, technical papers and some visits to papers dealt with a prestressed folded plate i local building sites. It is hoped that the Several FIP Commissions presented reports on hangar by S. Firnkas (USA). This roof has a be rotated to a vertical plane. The weight of following account will give a reasonable idea subjects ranging from fire resistance to pre- free span of 77 m (252 ft.) which is believed trusses was such that they had to be cast of the wide ranging nature of the material fabrication. Each commission has an inter• by its designers to be the longest free span outdoors and lifted from the mould by a presented. national membership and does much to draw folded plate ever constructed. It is certainly track-mounted tower crane. With two moulds tjEH experience from widely differing sources and the longest I have heard of. The vertical in operation the production was a continuous increase the chances of general acceptance of structural depth of the folded plates is 4.27 m process involving a 24-hour cycle. As the Lectures • the recommendations. (14 ft.) Of interest is the means of dealing with units were cast outdoors it was not possible to B. Gerwick (USA) opened the proceedings the considerable horizontal and vertical have a refined curing procedure, but it was with a fascinating if sometimes rather possible to withdraw the steel formers after 3 On durability movements in such a large roof, due to futuristic lecture on floating or submerged prestressing and gravity loads, shrinkage, only a few hours and to lift the finished truss This to me was one of the most significant structures in prestressed concrete, his subjects creep and temperature effects. The whole roof from the palate the day after casting. Only one reports as it brought an encouraging rebuttal ranging from ships to undersea oil tanks and sites on four spherical bearings situated on truss presented any problem—a primary truss to those doubting Thomases who keep pre• undersea nuclear power stations. With the flexible corner columns. Full data on pre• with a corbel, capable of carrying a secondary : I dicting that all our prestressed structures will latter two types of project the problems of dicted and final cambers was given. truss, on each face. In this case it was neces• have short lives due to insidious dangers such • controlling cracking must become onerous Three of the papers in the technical contribu• sary to leave out the concrete round the area Of as corrosion of tendons, creep, relaxation, etc. indeed on we poor designers, not to mention tions sessions were about Arup jobs. Duncan of the corbels and to form them when the truss A world-wide survey has been carried out the contractors. Michael presented one on the suspended had been lifted from the mould. With some which examined the state of 200,000 complex reinforcement details in the trusses, 33-9 11-3 33—9 11-3 33-9 Y. Guyon (France) discussed composite frame of the Standard Bank, Johannesburg, prestressed structures and has shown an steel fixing provided some problems during structures of steel and prestressed concrete, a and I presented two papers, one on the extremely low proportion of cases causing the first castings but as production proceeded combination of materials with which I was Sydney Opera House roof and the other on the 3 concern. Most of the damage was repairable it became possible to form the complete unfamiliar. He drew a number of examples new foundations of York Minster. It was and the maiority of reported accidents date reinforcement cage and position it in the from France and Belgium, and claimed that gratifying to hear Mr. Burr Bennett (USA) from the early days of prestressing techniques mould as a single unit. Due to a combination of some advantages could be found for the make very complimentary remarks about all and many of the causes are unlikely to be hot weather, a hot steel palate and warm system on certain projects. The idea apparently three of these projects during his summary of repeated owing to the advantages of concrete, it was found that the top boom of Fig. 3 is to combine the constructional advantages the technical contributions to the full congress experience. Certain types of high alumina the trusses was susceptible to cracking. To Typical cross sections E-E and F-F of North Block of steelwork and the stress advantages of on the final day. As no Arup paper on the York cement are banned, and the grouting of cable some extent this was controlled by adding prestressed concrete. When questioned on Minster works has been in print before, we ducts is fully discussed and recommendations extra reinforcement, but the problem was not economics, M. Guyon hedged his bets even are reproducing the Prague paper on page 6 made. considered critical. Lifting sockets were cast more than we usually do in engineering. of this issue. into the top boom above the penultimate Unfortunately M. Guyon spoke far too quickly mould. To obtain the desired appearance on were made before the architect chose a vertical members. and most of his message was lost. Report on seismic structures the underside, ceiling panels were cast in a sea-dredged gravel aggregate. The exhibition R. Baus lectured on fatigue and breakdown This report consists mainly of design recom• With the exception of those columns with fibre glass mould, whereas deck panels were The question of tolerances being so critical it of prestressed concrete and presented so much mendations prepared since the last congress A most impressive display of technical cantilevered fins, the casting of the cruciform cast in timber. To standardize panels in the was necessary for us to examine thoroughly detail that he completely failed to communi• and should be read in conjunction with the expertise was given in the Congress Exhibition section was quite straightforward. We had event of services being added or subtracted, all the moulds before the first units were cast. cate to such a huge audience, especially via existing FIP/CEB document Practical recom• on behalf of 29 organizations from France. assumed that the cantilever truss would be each ceiling panel had conduit cast in In this way a standard was set and the translators. The only reason I mention his mendations for the design and construction of Germany, Italy. Switzerland, the UK and quite separate but at the suggestion of the vertically at the rib intersections and each necessity to check individual components lecture is to make the point that speaking to a prestressed concrete structures. There are Czechoslavakia. Designers, contractors and manufacturer it was made integral with the deck panel had Uni-struts cast into the was eliminated. Occasional spot checks were large international audience requires a special some useful comments on ductility and the suppliers of prestressing steels and stressing columns to reduce erection times. Columns underside of the ribs. made by us to ensure uniformity. Although the approach and anyone intending to do so design of columns and connections. systems were represented. were cast on their sides in a steel mould. Lifting eyes were cast into the top side of the specification called for certain dimensional should consult a few past audience members It was most interesting to observe how the Those columns with a fin were cast with the units at the four corners and burnt off on site. tolerances, a proviso was added that in the first ! The report on prefabrication German stressing systems are generally fin flat and where two fins were required the Production of these units was fast since their event of units being outside these tolerances promoted by the bigger contractors, in con• second was added when the concrete had size meant that they could be cast indoors and they would be accepted if the tolerances were The rules are: This was discussed at some length and trast to the British systems which are supply gone off and it was possible to rotate the not cumulative or the efficiency of the mentioned the stressing together of precast the reinforcement in them was simple. 1 speak slowly (and fix) only. There would almost certainly column through 90°. The arrangement of structure was unimpaired. units, in particular Coventry Cathedral, Architecturally the fascia panels are one of the 2 use simple language as far as possible for be more prestressing done in this country if holes for lifting purposes was such as to Glasgow Airport, and the Sydney Opera more important components and it was these All the structural components were in your theme allow the column to be lifted vertically. 2 2 House in relation to the use of epoxy glued there was a similar technical commitment to units that required extensive post-casting 41.4 N/mm (6000 lb./in. ) concrete. Where Although the deck and ceiling panels were 3 any slides must be extremely clear and joints. Of interest were the splicing of long prestressing amongst our contractors. It is no treatment. They were cast face down in it was necessary to cast units outdoors it was basically similar with 150 mm (6 in.) wide varied with very few words which must be piles (over 30 m (100 ft.) long), and a new accident that PSC and CCL are being forced timber moulds with a ribbed fibreglass base. found more practical to use an independent ribs in two directions at 1.1 m (3 ft. 9 in ) printed as large as possible system of tolerance control developed in East into more and more site operations. After striking they were grit blasted and the ready-mixed concrete supplier than the centres, they were not cast from the same 4 avoid using complex equations Germany. Of interest to Arupians was the stand of the ribs knapped. Several preliminary castings factory's own mixing plant. British Consultants Bureau. Roger Kemp is to could have been made of the opportunities Prague was a beautiful venue for an inter• be congratulated for his organization of the offered by the site to create a striking modern national congress, but also a sad one. The Beecham display of ourwork which included Gateshead bridge in a city which once knew how to build people speak surprisingly openly about their Viaduct, Sydney Opera House, Standard beautifully. One point of technical interest, political troubles, and no-one likes the Research Bank, Glasgow Airport and Lusaka Aircraft however, was the use of its cross-section intervention of a foreign power in the manage• Dry pack under Concrete stitch Column above truss Hangers among other jobs. which was of the single box girder type. The ment of their affairs. Ken, Duncan, and I had Laboratories: deck is to be used for road traffic while under• the pleasure of visiting the most hospitable 2N*r H Continuity rods at eoch Insltu slab to rails Technical visits ground trains will run inside the box. families of two of our London colleagues and an exercise support threaded under links cast after erection Levelling bolts nuts S. of cladding bearing washers Arrangements had been made with the Czechs of helping, we hope, in some way to span the in simplicity for visits to various building sites around Social events gap that divides them. Prague, most involving prestressed concrete. Thanks are due to the FIP committee who 2'Woodwool Some of us chose a trip which took us to a managed to arrange an evening of free Alan Hart Sealing strip warehouse and a bridge. The former was a entertainment for delegates who could choose Conclusion very large storehouse for motor vehicle spare between the State Opera at the National Although the very poor translation service was parts just out of Prague. The superstructure Concrete f Theatre, the Czech Philharmonic at the disappointing and diminished what we could slilctl At llilch. was entirely precast, including columns, Smetana Concert Hall and the Symphony get out of the Congress, there nevertheless prestressed trusses and roof slabs, while the Orchestra of Czech Radio at the Dvorak Hall. was much that was stimulating, technically walls were clad with Siporex slabs made Those of us who went to hear the Philhar• and otherwise. We all have many more friends Introduction locally under licence. monic playing Dvorak voted it a superb in the industry, and the proceedings, when Set in the Surrey countryside, facing the Dry pock Grouting to be D completed before asbestos shim Although the roof trusses incorporated some performance. published, will be a useful document. southern slopes of Box Hill, near Dorking, is concrete stitch Asbestos shim nice design ideas, their construction left much Another evening we went to see the Magic Finally I would suggest that, as well as the Brockham Park, a large country mansion Sxf to be desired, the members varying wildly in Lantern which has to be seen to be believed— papers we presented, other Arup work was acquired shortly after the last war by the thickness and the reinforcement cage often an extremely imaginative combination of worth recording at the Congress in some way. Beecham Group. Installed in this idyllic setting bereft of any cover. One can only presume films, puppets and live actors. Then on Friday James Sutherland actually had difficulty get• are research scientists regarded somewhat that the present political troubles have night all delegates and wives attended a ting enough material for his summary of warily by local residents in the fear that a new Celng panels affected the morale and incentive of the men slap-up reception at the beautiful Cernin British prestressed concrete developments. An Frankenstein is being created. on mortar producing these goods. Palace (of Maseryk suicide fame). Oldrich example of valuable experience which has not been properly published is John Nutt's It was here, in an area where one would We then visited the Nusle bridge, a major Cernik was our official host but didn't appear account of grouting difficulties on Sydney expect to see thatching straw rather than construction of several large spans across a for reasons which have since become clear. Opera House roof. Who else is sitting on Siporex planks, that a new research laboratory deep valley in Prague. The bridge was of As an ally of Dubcek he has been obliged to Dowel bars between knowledge worth sharing ? was required. The actual position in the merlocking loops orthodox style and one felt that a lot more relinquish his post. grounds was originally the stables and an old walled garden. More recently the stables have housed the scientists and their complex equipment. The contract for the new labora• tories is worth approximately £1 m, of which In order to control the deterioration of the give rise to appreciable movements and one third represents the cost of the structure. The earth face and to allow for a simple propping provision must be made to absorb these Originally planned as a phased operation procedure, 1.1 m (3 ft. 6 in.) diameter cast-in movements. allowing rehousing of the scientists as the Carlton Centre situ piles were installed at approximately 2.3 m In addition, the problems associated with project proceeded, the building work went (7 ft. 6 in.) centres along the perimeter of the constructing a building around a maze of ahead in one phase and temporary accommo• site. These piles were, in general, carried down supporting props are very real. The design, dation was provided by the erection of below the lowest basement level. Later in the therefore, aimed at an open and relatively Portakabins. Ron Heydenrych contract, gunite arches were formed between simple bracing structure, but nevertheless The requirement was for a building of the piles to complete a continuous permanent having facilities for incorporating sophisti• approximately 5630 m2 (66.000 ft.2) provid• retaining wall. cated control devices. The Carlton Centre, which is situated in the ing office accommodation and heavily serviced The bending strength of the piles allowed bulk Becauseof the fall of theground. 6.1 m (20ft.). business district of Johannesburg, is one of laboratories. To minimize interference to the excavation to proceed without further prop• the piles of two sides required propping at the largest central city complexes in Africa. occupants, services had to be easily acces• ping to a depth of excavation against the piles two intermediate levels, but on the other two The development comprises a 50-storey office sible. of 10.7 m (35 ft ). This depth was the maxi• sides a single prop at approximately % height tower, a 600-bed hotel and 4.05 hectares mum clear height to which the piles could act was satisfactory. (10 acres) of shopping. Parking facilities are The structural concept as cantilever bulkheads. provided for 2,500 cars. In order to maintain The bracing structure took the form of a Working closely with the architect, William open areas at street level, the majority of the The 29.5 m (97 ft.) depth and extent of the temporary rectangular prestressed concrete Holford & Partners (Canterbury office), the shopping, parking and servicing facilities are excavation made conventional inclined or grid. While the principal structural behaviour project gradually evolved as a structure situated in a seven-level basement. The flying shores impractical, but an essential of the grid was as a compression ring it was similar in principle to that adopted by Arup basement extends over an area of 165 m requirement in all central city developments necessary to ensure full stability with un• Associates at Loughborough: a highly (540 ft.) by 1 38 m (450 ft.) with the general is the careful control of ground movements. balanced loading conditions and. for this modular structure of precast components. The level of the lowest basement varying between Normal elastic shortening and temperature reason, the additional struts across the site 1 tartan grid chosen was based on a module of E2 Jtitch 23.5 m (77 ft.) and 29.5 m (97 ft.) below the variations on any bracing structure of this size were added. 0.9 m (3 ft.) and 230 mm (9 in.) while the surrounding streets. The variation in depth main structural grid is 10.3 m x 10.3 m occurs because of a 6.1 m (20 ft.) cross-slope (33 ft. 9 in. x 33 ft. 9 in.). The building con• on the surrounding streets. Fig. 1 sists of two separate, two-storey blocks with The site geology comprises residual soils from The excavation for the Carlton Centre an intermediate link block. Although basically basement Fig. 1 deeply weathered strata of various igneous a two-storey building there are basements in (Photo: A. A. Gordon. Johannesburg) Typical first floor jointing details and metamorphic rocks. A feature of the each block housing plant and materials. To geology is the great variation in the con• reduce excavation to a minimum, a system of sistency of the materials. The greatest design shallow basements or undercrofts was hazard, however, was the extreme fissuring of developed with deep basements where the parent rock. Generally, the natural water required. The relative areas of deep basement where the geometry of the block dictated holes cast through to allow pipes to pass down table was about 12 m (40 ft.) below the are 10% in the larger block and 70% in the otherwise, each truss spans 10.3 m (33 ft. the re-entrant angles of the column. To carry surface. smaller block. All undercrofts are deep enough 9 in.) and carries the loads from precast the fascia, side and corner columns were cast to permit movement within them to check concrete deck panels on the top boom and with cantilever fins which support an L-sec- Studies of the economic viability of the pipe runs. The substructure is entirely of in precast concrete ceiling panels on the bottom tion precast concrete waling beam, spanning project indicated that the earliest possible situ reinforced concrete. The structure sup• boom. At first floor level the depth of the 10.3 m (33 ft. 9 in.). The fascia of each block start on construction was vital. Consequently, porting the ground floor deck is generally truss is 1.7 m (5 ft. 8 in.) and its weight is consists of ribbed precast concrete panels it was decided to proceed with a preliminary brick sleeper walls with reinforced concrete 6 tons. The depth reduces at roof level to 3.4 m (11 ft. 3 in.) long, weighing 3.5 tons, contract aimed at excavating and stabilizing beams over basement areas. In the South 1.4 m (4 ft. 6 in.) and the weight decreases with the aggregate exposed, and storey the basement. During the 12 months' Block, 2323 m2 (25,000 ft.2) columns are proportionally. Primary trusses generally span height, smoked glazing. At first floor level a contract period allowed for this work, the carried individually on pad footings, but in between columns and carry the loads from narrow balcony is provided and precast detailed design and documentation on the the North Block. 13.252 m2 (35,000 ft.2) two secondary trusses. concrete handrails are positioned in upstands main contract was completed. where columns are grouped, one footing The precast concrete columns are cruciform cast onto the fascia panels. Two problems existed in ensuring the safety serves each group. The sub-soil on the site section, 530 mm x 530 mm (1 ft. 9 in. x A coffered profile was chosen for deck and of the excavation; firstly, some form of is mainly fissured Weald Clay. 1 ft. 9 in.) overall, with a fair-faced finish. The ceiling panels which are approximately strutting was needed to control the deteriora• Since complete flexibility of structure was length of each column was determined by the 3.3 m x 3.3 m (11 ft. x 11 ft.) and weigh tion of the earth face and, secondly, a system required, an arrangement of precast concrete clear height required and the depth of truss 3.25 tons. Although the basic shape of each of props was required to control the overall primary trusses on the main structural grid supported, and each column weighs approxi• unit remained unchanged, corner details movement of the sides of the excavation. was adopted. The basic grid is sub-divided mately 2.5 tons. In order to carry the vertical varied and six basic shapes for each type of Before any work was carried out on the site, into areas 10.3 m x 3.4 m (33 ft. 9 in. x loading from the trusses, columns were cast panel emerged. By precasting we were able to the water table was lowered by means of a 11 ft. 3 in.) by secondary trusses. Except with cruciform shaped corbels. All corbels had anticipate the service engineer's requirements ring of well points surrounding the site. The grid was cast on to grid piles and installed architect considers relevant to the quality of Cracks present an even more intractable factory nature of this situation will be when the excavated level was about 9 m the particular surfaces. It is surprising that problem and, until the day arrives when non- apparent to all designers and clients. (30 ft.) below ground. this procedure is not used more often for in shrinking cements are available and widely The question of defects in exposed concrete After completion of the grid, precast props situ concrete work, where quality finishes used, this problem will loom large in all work is very depressing. Once a defect is were erected against the perimeter piles on the are sometimes more difficult to achieve. With concrete jobs. In situ concrete usually gives there, it is nearly impossible to restore the two deeper sides, while the bracing on the any work there is an initial learning phase more trouble than precast work, due to the concrete to what was originally intended. A other two sides was achieved by casting the ft while difficulties are ironed out and opera• sizes of continuous concrete members substandard product is obtained. This really grid directly against the piles. Before pro• tives become familiar with the procedures. involved and the way they are restrained. is a subject in which the cliche 'preservation ceeding with further excavation, the grid was How often has this learning taken place at Cracks from thermal movements or structural is better than cure' applies entirely. prestressed and external forces were applied low levels in the building (for example the deflections will always be a problem. main entrance area) where appearance was through jacks placed between the props and The question 'How can I fill this crack?' Conclusions most important? By the time the roof is normally receives the answer 'Why do you the grid. The discussion in this paper has ranged quite reached the quality is approaching what the want to fill it?' as the answer to this condi• The bracing grid represents an unusual usage widely over design, construction and main• architect wanted. tions the repair method to be used. The few of prestressed concrete in that the majority of tenance problems with concrete surfaces. reasons why cracks may have to be sealed the axial load was applied by external jacking With in situ concrete work there is usually a Mention has been made of the vast store of are as follows: forces. The grid was analysed under the clerk of works around to keep an eye on information standing around us, in the form anticipated loading conditions from earth things, if not a resident engineer. If the 1 to obscure them of examples of different degrees of weather• pressure together with unbalanced loading former understands the problems of making ing on a wide range of concrete surfaces, good fair-faced concrete, so much the better. 2 to prevent them becoming visually exag• applied over short lengths of the perimeter, in i i gerated by weathering detailed in a variety of ways. It is tempting to order to check the sensitivity of the design to With precast work, this continuous super• think that this source can be easily tapped and 3 to prevent water penetration into a building abnormal conditions. & vision is lacking. The product is presented to the information used in future designs. In the designer for acceptance. Visual checks are 4 to prevent water leaching lime out, giving The stress conditions in the grid were complex reality this will be very difficult to achieve. made and the unit incorporated in the build• white deposits and longitudinal cables were added in order to The most effective feed-back procedure is for ing. Concealed defects like badly positioned 5 to prevent corrosion of reinforcement each architect to use his eyes and learn for control peak stresses in the members and to —- reinforcement only become apparent later to increase the ultimate load strength of the grid. 6 to restore structural continuity himself He must then develop a recall system the consternation of all concerned. Cover in his mind so that his observations may be Prestressing was also applied transversely in Four main types of repair may be con• meter checks on precast concrete units should used in his design thinking. Too often, the order to resist the bending from vertical loads be a matter of routine, even if they are only templated : as well as to increase the factor of safety 11 observations are made, but not recalled when done on a sample of say 25% of the total. i cut a chase along line and fill with flexible it comes to a design problem. against beam shear failure. The grid was F or rigid sealant On a more formal basis, there is a need for a designed to be used as part of the con• Rectification of defects struction access roadway to the site and was ii rub cement + polymer emulsion into sur• new text book, probably backed by C & CA also used for the majority of storage areas and One of the most depressing things about fair- face and the Concrete Society, covering the faced concrete work is the difficulty of making principles of design to achieve various site offices. An important advantage of the in trickle in polymer or latex emulsion sealers repairs that will both look the same initially effects and including many examples of design was the easy access for maintenance Fig. 2 iv pump in epoxy or polyester resin sealer and will weather the same It is certainly actual buildings. Of course, one problem and adjustment of the jacks. Artist's impression of the completed Carlton Centre Before doing any of these things, it is neces• easier to do the former than the latter, but that bedevils this kind of work is that the The grid was prestressed using 26 mm (1 in.) sary to be reasonably sure why the cracks even so. the result is often disappointing to newsworthy items are those where some• Dyckerhoff rods and, in general, unbonded have formed, and to decide whether they are all concerned. The main types of defects are thing has gone wrong, but the architects cables were used to permit easy removal prior Hydraulic oil was used as the pressure likely to continue moving. If they will move, steel for a number of reasons. Although cracks (from whatever cause), damaged or responsible are understandably reluctant to to demolition of the grid. the only procedure is (i) using a flexible filler, medium in the jacks. The forces in the jacks demolition would have been easier with steel, honeycombed arrises and corners, and mis• have their design mistakes highlighted. prestressed concrete was markedly more and accept the damage to the appearance. The design horizontal earth loads on the together with the change in thermal condi• placed reinforcement. Perhaps seminars of this type will help to 2 tions of the grid were monitored regularly and economic, and in addition, the forming of the If structural continuity is required, method (iv) grids were of the order of 4300 kN/m With corners and arrises, the main problem change their attitudes. 2 the jacks adjusted to suit changing conditions. connections in steel with the very large loads should be used, provided that checks are (40 tons/ft. ). The axial loads in the members with making good is to ensure that the patch The jacks were loaded to % of the full design involved would have created difficult engineer• made to ensure that the properties of the were very large and gave rise to elastic sticks and remains sticking indefinitely. The load and increased to nearly full design load in ing problems. material really will give what is required, and References deformations of approximately 100 mm trouble is that the materials that stick well those areas where the ground movements that the degree of filling likely to be achieved (4 in.) across the site. Similar movements of Although the grid represented a major (e.g. resins) weather in a quite different 1 STONE, P. A. The economics of main• approached certain danger marks. (often quite low) will be enough. Obscuring the order of approximately 50 mm (2 in.) were engineering structure, its total cost, including manner from the surrounding concrete due tenance. Conference report on main• Stability of the basement in its final condition the cracks can be done by method (ii), but the anticipated from temperature effects. In order demolition, was no more than 1 V?% of the to their different absorption characteristics tenance of buildings. MPBW, 1965. durability of the filling is questionable as very to control movements of the supported earth was provided by the permanent floor slabs of total cost of the complex, and the saving in and occasionally problems of colour stability. 2 STONE. P. A. Building design evaluation: little penetration is obtained. It would easily face. 400 kN (400 ton) Freyssinet flat jacks the building. As these slabs were constructed, contract time afforded by the use of this With some concrete finishes it is difficult to costs-in-use. Spon. 1967. were built into the seatings of the inclined the load in the grid was adjusted to transfer the temporary prestressed structure fully justified fall out if movement occurred. If it is going match the appearance in a patch. This is 3 WHITE, R. B. The changing appearance precast props against the grid. Similarly, jacks loads to the permanent structure. After com• this cost. to stay in it must have similar weathering particularly true with exposed aggregate or of buildings HMSO. 1967. were placed against each pile on the other pletion of the slabs, the grid was demolished Skidmore, Owings 6- Merrill and Rhodes- tooled finishes. characteristics to the surrounding concrete. 4 PARTRIDGE. J. The weathering of St. two sides of the site, and, by placing a number with the help of explosives. Harrison, Hoffe 6- Partners are the architects Misplaced reinforcement presents a different Polymer or latex emulsion sealers have been Anne's College. Oxford. (In: Concrete of jacks in series, it was possible to allow for a Prestressed concrete was chosen for this and the contractors are Murray & Roberts type of problem. It may be misplaced from quite widely used for trickling into cracks. Quarterly No. 82. pp. 20-25. July-Sept. maximum movement of 150 mm (6 in.). temporary grid in preference to structural Holdings Ltd. the position shown on the drawing; but still They are sold as flexible crack sealers. Figures 1969) are not available for their success rate, but it be 20-25 mm (% in.-1 in.) below the surface. 5 LEVITT, M. An assessment of the durability is probably very low. Much of the trouble The question arises in precast concrete work of concrete by the initial surface absorb- comes from their use in cracks subject to as to whether the unit should be rejected, tion test RILEM. Symposium on durability movement, but with an extension/compres• have one section broken out and recast or be of concrete. Vol. 1, Academia. Prague, deformation of the superstructure. The basic After a good deal of investigation, including accepted without modification. The latter sion capability of less than 10%. very small 1 969. The use of trouble was that the area of the foundations extensive exploratory excavation, it was alternative may depend upon the contractural absolute movements at cracks are required was too small for the stratum of clay imme• discovered that the effective area of the relationships, on the quality of the concrete to fail them. prestressing in diately underlying the building which had footings was such that the factor of safety in the region of the defective cover to rein• Defects that only appear after a time can be lead to excessive differential settlements and against shear failure in the clay was possibly forcement and on the exposure conditions foundation rotations. as low as 1.3. Also the masonry below floor very troublesome for a different reason. On once the unit is on the building. It is rare to one job in London some 3000 similar There were three principal zones of damage : level was found to be badly deformed in accept recasting of parts of precast concrete strengthening at bending and cracked in shear. The main cladding units were installed. . After three 1 the central tower area units, as this presents great difficulties with years, four of them failed due to corrosion of problem was to strengthen the foundations of the types of sections normally involved. With York Minster 2 the western towers the four main piers supporting the central reinforcement. This was traced to excessive in situ work, the larger members often enable calcium chloride coupled with very per• 3 the east end tower. A number of different strengthening breaking out. re-positioning the steel by schemes was studied, the one finally chosen meable concrete. The problem was how At the east end. the whole of the east wall was bending, and recasting to be done. Obviously having prestressing as its essential element. many other units would show defects in time. David Dowrick slowly but surely rotating outwards due to it depends on the amount involved. The problem of the western towers was A number of samples were taken from two yielding of the clay under the toe of the In cases where the position of steel only similar to that for the central tower founda• areas of the building and analysed for chloride. footing. The structural solution was to replace varies slightly from where it should be. the tions, and required a similar if simpler solution The two areas showed differentcharacteristics. Summary the existing foundation with a new concrete question is frequently asked. 'Is there any• suggesting variability in batches of units. to that used for the central tower. Only the thing with which I can coat the surface to York Minster is one of England's great mediae• one twice the size, but, as no prestressing was They also showed that the chances of having latter will be considered in the following make good the deficiency?'. As will be val cathedrals. It is about 1 58 m (51 5 ft.) long used, this will not be further discussed in the further defective units were fairly high, but discussion. apparent from the section on surface finishes, and 75 m (245 ft.) wide across the transepts. present paper. that the total number of these would not be this magic substance is not yet available. In Its present superstructure was built between In the central tower area, however, the The central tower foundation scheme all that large. Of course, the actual units that certain cases, where the cover has been only 1225 AD and 1472 AD. and it stands on the greatest danger was not from continuing The great weight of the central tower is will give trouble can only be found by 10-1 5 mm (% in.-% in.) the concrete over the site of former Roman buildings which were foundation movement. The cracking of the carried mostly by the four main piers, each of sampling every unit. The client is therefore bars has been removed and replaced by an followed by a series of Saxon and Norman superstructure had been caused by differential which carries a vertical load of about faced with the fact that he has a building on impermeable resin mortar. This procedure is churches. At the time of writing the Minster settlement of the tower with respect to the 38.500 kN (3.850 tons) at floor level, while which he knows he probably has a small alright for concealed concrete or concrete was undergoing extensive restoration to a adjacent structure, but little further settlement the smaller columns adjacent carry about proportion of defective units, but that to find that is to be painted, but it has serious short• total expected cost of about £2 m. A large part was likely. Thus although some superstructural 3,000 kN (300 tons) each. Exploratory these before they actually fail will be very comings for exposed fair-faced concrete for of this expenditure is due to underpinning and control of the cracks was necessary, the excavations revealed that the columns were costly. All he can do is to institute a regular the same reasons as given for patching strengthening of the existing foundations, the cracking was important largely in that it pro• built on the remnants of the walls of the (annual) inspection procedure and wait for corners with this type of material. inadequacy of which had caused substantial voked a study of the foundations. previous Romanesque-style Minster. These them to show up. The exceedingly unsatis• Norman walls (c. 1070 AD) were in turn (1 25 lbf./in.2). The resulting stress regime can (1% in.) rods used on site. The rods were This series of photographs has been supported by strip footings, the tops of which be considered as one of 'partial prestressing'. continuously threaded which maximized their selected to illustrate some of the points made were about 2 m (6 ft. 6 in.) below the present In order to provide prestressing ducts through bond characteristics. in the article. It is deliberately biased floor. The Norman footings were either 4 m the foundations, it was necessary to drill An initial prestress of 540 N/mm2 (35 tonsf./ towards defects and failures in order to (1 2.5 ft.) or 6.5 m (21 ft.) wide, and were about 75 mm (3 in.) diameter holes through the in.2) was used. Prestress losses proved emphasise the point that it is possible to 2 m (6 ft. 6 in.) thick, apparently having been ancient masonry. The following is a simplified negligible on bars which were restressed learn from experience. It is extremely rare to well founded on the virgin clay or on the very summary of the construction procedure : several weeks after installation which is find the seamier side of weathering deeply founded Roman footings. Each of the probably not surprising considering the discussed openly and illustrated in this way. 1 the first pour of concrete was cast including four corners of the tower was treated separately comparatively low levels of stress in the rods Most buildings only get into print when steel duct-tubes on the drilling side but similarly, so it will be convenient in the in the foundation. Nevertheless it would they are new and unweathered. following discussion to refer mainly to the NW 2 the upper concrete collar was cast and the appear that the relaxation properties of this pier. It was desired to make the effective whole masonry footing was pressure-grouted Unfortunately black and white photographs stainless steel were favourable for prestressing foundation area about twice what it had been in an attempt to fill any voids and cracks do not show all the subtleties of concrete purposes, but unfortunately no laboratory as well as to stabilize the cracked areas. As the As the new areas of concrete footing initially weathering as changes of colour are figures were available for relaxation at any main pier load was extremely high, and as the supported only their own weight, it was important. stress levels. masonry was in a rather delicate condition, it necessary to induce artificially their full load Couplers was necessary to find a method of strengthen• capacity. For this purpose 'compression pads' Fig. 1 ing which would incur the least disturbance were cast below the main foundations. After The maximum length of rod that could be Uniformity of weathering is achieved to the existing footings. horizontal prestressing of the whole founda• readily manufactured was 5.5 m (18 ft.), and through uniform exposure and uniform tion, the flat-jacks between the compression in certain places on site it was necessary to use absorbency of surface. The in situ board- After studying various strengthening schemes, pads and the main foundation will be inflated, shorter rods because of limited clearance for marked concrete is contrasted with the it was finally decided to encase the Norman thereby vertically stressing the new founda• insertion into the ducts. Purpose-made precast exposed aggregate panels. The light footings in concrete, incorporating the NW tion-bearing area; this second post-stressing couplers were used to join the rod. tapers streak is due to the cleansing effect of a pier and the adjacent nave and transept action transfers the desired amount of load being provided to facilitate threading the water discharge. The colour of the wider columns on one huge footing about 14.5 m from the existing masonry to the new footings. coupled rods through the masonry which was cylinder has changed from grey to (48 ft.) square. This would utilize all the (At the time of writing this process had not subject to partial blockage with chips yellow-brown as the cement has been cracked masonry footings as well as providing been carried out) loosened by the drilling. The couplers were leached away exposing the sand. (About some completely new areas of footing in 44 mm (1% in.) diameter and were made of seven years) concrete. The total effect would be to spread the same steel as the rods. Materials and techniques the load from the columns over a much larger Anchorages Fig. 2 Prestressing tendons area of clay. The new average bearing pressure The rods were anchored with a nut and an White in situ board-marked concrete fares 2 on the clay would be about 290 kN/m Because the whole strengthening work anchorage plate which were made of FV520B no better in city atmospheres. (About 2 (2.7 tonsf./ft. ) improving the safety factor clearly had to be a once-for-all conservation eight years) and AISI 304 stainless steel respectively. The against shear failure in the clay from about operation with a life expectancy of hundreds rods and nuts had UNS threads, and the nut 1.3 to 2.5. of years, it was decided to make the prestress• Fig. 3 was the heavy duty size All the above ing hardware of stainless steel. The rods were This is another example of the superior stainless steel items were fabricated by The new concrete and the ancient masonry made from a high-strength alloy manufactured Frederick Mountford (Birmingham) Ltd. weathering of precast exposed aggregate were unified by prestressing them together. by Firth-Vickers Stainless Steels Ltd. and Jacking panels. (About three years) There are four layers of main prestressing rods, designated FV520B. It was a precipitation- two layers in each orthogonal direction hardened stainless steel which had been over- The rods were stressed using a Macalloy Fig. 4 passing right under the main pier, thus pro• aged in a temperature of 550°C (1022°F) for Mark 10 jack with a modified attachment to One technique for overcoming this viding the tensile reinforcement necessary in two hours, a guaranteed minimum 0.1% suit the UNS cut thread. The jack was very problem is to paint the in situ concrete with the bottom of this large spread footing. This proof stress of 800 N/mm2 (52 tonsf./in 2) was reliable and simple to use. concrete coloured paint. Of course, this main part of the new foundation is 2.1 m agreed for this project. The ultimate strength Laboratory tests looks unsightly when it begins to break 2 2 (7 ft.) deep with an average compression due averaged over 920 N/mm (60 tonsf./in. ). An independent authority was commissioned down. Note the mould growth on the 2 to the prestress of only 0.86 N/mm These properties were achieved for the 32 mm to carry out strength tests and tolerance plinth where the detailing provides a water trap. (About four years)

Fig. 5 With older concrete the quality may be such that the erosion of the surface through acidic rainwater attack may outpace dirt deposition. The surface is self cleansing, but the appearance is still not satisfactory. (About eight years)

Fig. 6 The black and white photograph does not \ZA Norman foundations adequately show that the retaining wall and Norman walling bridge have turned green with mould, whilst the wall of the building has turned brown due to exposure of the sand. The difference o o is attributable to the moisture content difference between walls of heated and Th% Present M/nst+r I unheated spaces. (About forty years) ri n n n n n _n n n n Fig. 7 Prestnt NW. Pier Smooth white permeable concrete weathers so badly in cities, that the appearance may be disfigured before the building is o o 17 finished. (New) IE

Fig. 8 I Own It is nearly impossible to patch concrete in I such a way that the patch weathers uniformly with the rest of the concrete. The roof edge concrete is turning green with mould. Note also the tell-tale signs of Fig.3 f rs reinforcement corrosion on one transom. (About seven years) u u U—u—u—u—u—u 5

! 5 o Ur u ^ to K> 20 JO m

Fig. 1 Norman foundations in central tower area inspections of samples of all components popular. This is deep ribbing, either with or 4 green stains from copper, flashings, permanently wet. but this, of course, can be Fig. 2 throughout the production period. Some without broken tips. Although it has been in bronze fixing devices, bronze sculptures an advantage. Once again the life expectancy North west pier. initial tests were done on the strength of the use for a relatively short time only, the results 5 black bituminous stains from badly made of the materials is variable, and depends to Foundation layout assembled rods, couplers and anchorages to are looking quite good. roof trim details, from accidental spillage some extent on how complete a seal is ensure that the strength of the individual Of course, the traditional technique of of waterproofing compounds on site, obtained in the first instance. The existence of items was fully realized in the assembly. dispersing water down a facade by using from bleeding of material from joint pinholes through the coating can allow water cornices, is still valid today. Current ideas for to penetrate and blistering may occur later. Drilling fillers of the impregnated fibre or cork the design of buildings usually do not accept types One trouble is that with rough concrete Right from the outset it was obvious that the this particular trick, but it has to be recognized surfaces it is difficult to obtain a complete film. 6 stains from spillage of structural jointing success of the whole foundation proposal as a valid weapon in the architects' efforts to It is interesting to reflect on the fact that when materials such as epoxy or polyester depended on the drilling operation. The drill control weathering. By throwing the water off concrete is painted, the necessity for main• resins, or from more mundane materials Existing Norman walls and footing Prestressed shots varied in length from 6.4 m (21 ft.) to the facade, one does not remove it from the tenance is generally accepted. When clear such as grout concrete 16 m (50 ft.) through 11th century masonry building. However, the wind tends to spread it treatments are applied they are expected to be foundations of doubtful quality. Although the contractor out on the surface below, so that uniformity 7 oily staining from the bleeding of con• maintenance-free. Yet it is more difficult to had had wide experience in rock drilling, no of weathering is obtained. This principle stituents of poor mastics and sealants develop a durable clear varnish than one one had any knowledge of the problems of should be used much more than it is at present. into the pores of the concrete containing pigments. accurate drilling through this type of material. Another detail currently in use for controlling 8 oil and grease stains from site plant, The whole problem centred on obtaining the weathering, is to collect the water in channels particularly cranes The use of applied surface finishes does required drilling accuracy, which was deter• enable the weathering of concrete to be at every level and pipe it away. Cost considera• 9 dirty smears around windows caused by mined by the alternate layers of rods being controlled in another way (i.e. other than by tions usually dictate against complete plumb• careless window cleaning under difficult only 230 mm (9 in.) apart vertically. the careful detailing approach outlined above). ing of facades, but some buildings have been conditions It must be recognized that when they are / An accuracy of 25 mm (1 in.) off line in the erected in which the water is piped through 10 miscellaneous stains caused by inter• concrete cladding panels and discharged into used, a maintenance cost will be incurred (or above length of shot is easily achieved when action between the surface and vandals, their effectiveness will diminish) and this must drilling in a homogeneous medium such as open-drained joints. The water is most sprayed paint being the current favourite frequently collected below the windows so be examined in the light of other claims on HMl Pier solid rock or good concrete, but this is not so 11 mould growth resulting from interaction that dirt settling on the glass is not transferred resources. in ancient masonry. Some preliminary drill with the environment in general shots carried out before concreting had begun to the concrete below Obviously the deliber• Quality control 12 finally, deposition of salts on the surface were encouraging, indicating accuracies of the ate channelling of water into joints puts a Some of the construction problems involved due to numerous possible interactions, order of 25 mm (1 in.) in a length of 6 or 7 m greater strain on the waterproofing system, in the use of exposed concrete have been with adjacent brickwork, cracks within \ (19 ft. 6 in. or 23 ft.). Also, during work and if it is less than perfect the leakage can be mentioned above under staining. There are the concrete itself, cracks within adjacent already completed on the superstructure, 46 spectacular. Other problems arise from many others. The main one to be discussed concrete, proximity to areas treated with drill shots about 20 m (67 ft.) long had been blockage of the plastic drainage tubes in the here is quality control. concrete panels. This detail is probably quite de-icing salts, and contact with the put through the walls of the 15th century The requirements for quality of a concrete unsuitable for use on a building near trees, ground central tower. These had indicated that surface are difficult to specify. Yet. unless the unless regular rodding out is done when the The list is depressingly long and contains a sufficient accuracy could be obtained provided attributes considered to be important by the windows are cleaned. If blockages are not mixture of problems arising during construc• all voids in the masonry were well grouted. architect are clearly described, the contractor removed, severe damage due to the freezing tion, and problems arising subsequently. will have some difficulty knowing just what The drilling in the superstructure was carried of trapped water could result. With many of the very expensive concrete is wanted. These attributes may include NAVE out with a rotary-percussive tungsten-tipped The overall staining of a concrete panel may surfaces being used today, elaborate protec• freedom from blowholes, sharp arrises, low pneumatic drill rigidly mounted on a special also be influenced by the type of jointing tion procedures have to be employed. Most permeability of surfaces, a particular texture cradle. Unfortunately, when work really started between panels, regardless of whether the of the long-term stains can be avoided at the and uniformity of texture, certain dimensional on the foundation drilling, this drill proved to water is drained into the joints or not. With design and specification stage. However, tolerances, the absence of crazing or cracks, be too inaccurate, at least under the NW pier. filled joints the water is kept on the surface, their avoidance requires a degree of attention and uniformity of colour both within one unit The two chief factors contributing to this were but with open drained types it is allowed in to detail that it is often not possible to give. and between one and another. In some cases firstly, the poor mortar in the 11th century and then expelled Current detailing of these There will be many more examples of staining sub-contracts for the supply of precast masonry due to a very low lime content, and joints encourages the water to flow forward like those green concrete roof edge beams at concrete cladding are let on extremely T secondly, the presence of a grid of large oak to the face by means of 'wash-boarding' Churchill College, Cambridge. minimal documents. At worst these consist of S baulks used by the Norman masons to rein• grooves and by turning the bottom of each drawings showing the units required and a force their footings. Both these factors baffle strip forward. The effect of discharging Applied finishes general statement of the type of concrete detracted from the homogeneity of the the water in this way is to encourage differen• The search for an invisible surface sealant (i.e. exposed 19 mm (% in.) Cornish granite masonry. The attempt to solidify the masonry tial weathering between the edge of the that may be applied to concrete has sometimes aggregate with white cement matrix). After by preliminary grouting had not been as panel and the remainder. taken on the character of a search for the approval of a sample panel for appearance, beneficial as desired. The problem of differential water absorption philosopher's stone. Who will find the key casting commences. between panels and joint fillers (where these for transmuting the base absorbent concrete After many rather dismal weeks of attempts are of mortar) is well known and need only surface into a noble impermeable one, The difficulties of contractors in guessing with rotary-percussion drilling, the first be noted here for completeness. Jointing resistant to the ravages of time? Must we what standard of finish is expected obviously really consistent success was achieved using mortars are usually more permeable, thus forever use the controversial rejuvenation affects their pricing of tenders. They may a diamond-studded coring drill, with only i collecting more dirt than the surrounding drug procaine (i.e. silicone) to alleviate the often price for 'normal' fair-faced concrete rotary and no percussive action. While this concrete. symptoms of ageing, subjecting the subject only to find later that the architect's idea of system was being used to keep the job going (concrete surface) to regular courses of the this corresponds more to the contractors' 'high further experimentation was carried out with a material in order to maintain the efficiency of quality' category of finish. It is essential for different rotary-percussive technique, and Interactions with other materials the treatment ? designers to recognize that there are no / eventually a vole hammer drill proved to have Concrete surfaces are relatively sensitive to ^20-0 Silicones act by lining the pores of the con• absolute standards in this matter. Various about the same accuracy as the coring staining from contact with other materials. crete, altering their surface tensions and categories may be identified and compared machine in this material. This was a most The comparison is particularly marked when making them water-repellent rather than with one another, and in general the same important development as the overall speed they are compared to brick. The normal water-absorbent. The surface remains clean units will cost different amounts depending of the vole hammer was three or four times variation between individual bricks obscures because the dirt does not penetrate. The on the quality category. that of the corer and its overall operational many stains that may occur on a wall. How• 7 period of effectiveness of this treatment is The shortcomings of the cube test as a quality cost was corresponding much less. ever, this sensitivity is not so great that real N. W.Pier variable, but there do seem to have been control test for fair-faced concrete are widely difficulties are experienced in using the All the drilling equipment was supplied by some advances recently. Some materials recognized. Unfortunately visual observation material adjacent to others. It is merely Holman Brothers Ltd. and the very latest appear to work for only 3-5 years, while of the surface is also not enough. For good sufficient to require fairly careful attention to innovations in techniques were applied. At others are claiming lives of about 12 years. weathering on a well detailed building, a be paid to detailing. the time of going to press there was still much The period varies with the concrete being concrete surface of uniform (and usually low) drilling to be done and further improvements The list of materials causing staining on used, and with the environment. permeability is required. A technique has been 2 nd Pour may still be effected. concrete is quite long, even when the dis- Some other proprietary formulations are developed by the Research Committee of the colorations arising from interactions with available which claim to act in a similar way Cast Stone and Concrete Products Industry5 Acknowledgements i formwork and release agents are not con• to silicones, but have a longer life. Claims of which enables quality to be assessed by the The above works were executed for the Dean sidered. The following notes illustrate the this type are very difficult to evaluate owing initial surface water absorption. The rate at ;o-6 and Chapter of York Minster by the following : sources of the main problems, and serve to to a lack of accelerated tests. Their effective• which water penetrates the surface is emphasize further the necessity of seeing any ;-6" Architect: B. M. Feilden, Norwich. ness in the short-term may be checked, and measured, and compared both with other concrete surface within the context of the one should not be too surprised if some of readings on the same concrete and with Consulting Engineers: Ove Arup & Partners. overall building. these materials fail to perform at all. readings that have been obtained on a wide Contractor: Shepherd Construction Ltd. 1 brown rust stains from pyrites in aggre• The other main way of trying to modify the range of concrete surfaces. York. gates surface performance without completely The visual requirements are most usually obliterating the appearance is to use a clear 2 rust from scaffolding, starter bars, struc• controlled by the use of an agreed sample varnish. A few products are available based tural steel, badly treated bolts, tying wire panel. For large projects this usually consists The Carlton Centre and York Minster articles on methyl methacrylate. The idea with these of full size panels or assemblies of panels. left in shutters, misplaced reinforcement Fig. 3 I 1 are reproduced with the permission of the is to form a complete skin of varnish over the For smaller ones, a more limited specimen 3 rust stains from the soluble compounds North west pier Cement and Concrete Association and the surface, blocking all the pores in the process. will be used. Whatever the job, the sample in the early patina on cladding made from Foundation prestressing layout Concrete Society. They tend to make the surface appear should include all the features that the 21 weathering steels of infinite life and stain resistance. Speaking it is essential to look at them both in terms of The changing in broad terms the choice is as follows: the surface itself and in terms of the building (B)Upper reinforced as a whole. The prevailing weather conditions 1 accept regular (five year) cleaning of N.W. concrete collar face of concrete concrete surfaces, and continue detailing in an area can be significantly modified by the PIER in the way it is usually done today, or form of the building itself. However, certain 2 aim for controlled weathering of concrete general statements may be made. Turlogh O'Brien surfaces by changing the approach to The tendency for dirt to be deposited depends detailing, or on the rate at which rainwater moves over the Floor level surface. This rate is affected by: 3 develop a new form of concrete, or a new This paper was delivered at the C & CA invisible long-life surface coating which 1 height seminar for architects on appearance & resists stain formation 2 orientation weathering of concrete, held on 7 May 1970 Observation of the extent to which clients are 3 shelter from adjacent buildings (c) Prestressed concrete prepared to pay for regular cleaning of 4 shelter from parts of the same building concrete surfaces suggests that only the foundation The objective of this paper is to discuss the 5 the shape of the units owners of prestige office blocks are normally (B)Flat jacks appearance and weathering of concrete sur• willing to do this. Public and university 6 the texture of the surface faces in the context of the overall require• buildings may receive attention at longer ments for the building fabric and for its Most people are familiar with the variation in intervals. Housing and schools projects are performance in time. The use of exposed dirt deposition that is observed over the height unlikely to be cleaned merely to restore a concrete has a sufficiently long history for the of taller buildings. Although the best examples particular appearance. If this is the true (?) Stainless (?) Existing Norman (A)Concrete base likely behaviour on any new structure to be are older buildings which have had time to Fig. 4 situation with regard to cleaning costs, then steel rods masonry footings anticipated with reasonable reliability. Obser• collect considerable dirt (e.g. University of Section through completed foundation in the short term, choice 2 (above) is the only vation of many recent buildings suggests London Senate House), the effect can be alternative. that, although this information is available, it seen on some quite recent buildings in the is often ignored. Before making value judge• With the trend towards variety in concrete main cities. The upper parts are washed ments about this it is necessary to examine finishes, the architect is increasingly having cleaner by the faster moving water. the particular requirements for each building. to rely upon the expert advice of other people, A similar effect is observed with orientation. These may be circumstances in which it is particularly his consulting engineer and the Once again it is the older buildings that show perfectly justifiable to neglect weathering specialist concrete companies. This trend the most marked effect. One can find stone problems. should be welcomed, provided that the basis columns washed clean on one face, but for the collaboration is fully understood. The When considering the types of effects pro• remaining quite black on the others. The specialist company must be able to deal with duced by weathering on concrete surfaces, prevailing wind tends to drive the rain harder all queries raised by the designers. There is a it is clear that the distinction between changes from one side on more occasions in the year, trend towards competition between com• that merely alter the appearance and those thus producing a greater washing effect. panies on the quality of advice they give in that affect 'performance' is difficult to define Adjacent buildings may provide shelter from addition to quality and price of the product. precisely. At one extreme, streaks of dirt may driving rain, so reducing the cleaning effect. This trend is also welcome if the companies change the appearance considerably without Sheltered areas are darker. are able to find the people with the necessary doing any physical damage. At the other The degree of exposure of external concrete knowledge and experience to give the right extreme, the surface may break up under surfaces on a building may vary from severe type of advice. On the designers' side, the weathering. In between there are a whole (e.g. a roof parapet) to completely sheltered architect and engineer must know sufficient range of effects which may be classed as (e.g. the soffit of a concrete slab over a about the nature and behaviour of concrete to changes in appearance or as damage, concourse or parking area at the entrance to a be able to evaluate the advice given. It must depending on your point of view. Thus the always remain the architect's job to integrate building). In between these extremes are a stage at which 'crazing' becomes 'cracking' all the specialist technical advice he receives, whole range of possible exposures, each of may vary with the type of building and with thus producing unified design for the whole which will have different degrees of shelter. Fig. 5 the observer. Surface flaking or loss of building. Contributing specialists must realize Considerations of this type can lead one to Distortions in Norman walls aggregate (from some types of finish) may be more often than they seem to that there are question whether it is advisable to use the below present floor level very difficult to classify. more problems to building design than just same concrete surface details all the way up a due to column on the right Some people may suggest that any change concrete surfaces. tall building, on different elevations, and in (Photo : by courtesy of the Royal in the basic surface, through the formation of different relationships to other elements of the Commission on Historic Monuments) any cracks, or through loss of material, should Sources of information and advice building. Although the concrete surfaces may be classed as damage, whilst only those Despite the fact that concrete has been start looking the same, they will not stay like which result in streaking or staining should be subjected to weathering for many years, the that for long. classed as appearance changes. This view is literature on the subject is not very extensive. The use of highly shaped concrete panels as not very helpful as it would imply that almost The journals Concrete and Concrete Quarterly cladding is a particularly noticeable trend at all external concrete surfaces are in need of regularly feature examples of building with present. In some cases these have been maintenance. The alternative view would be interesting concrete surfaces. Unfortunately carefully detailed so that the weathering will to look at the question more from an economic few of these had been weathered for very enhance the effects of light and shade4. In n point of view. Any form of maintenance of a long before the photographs were taken. other cases these effects do not appear to have concrete surface costs money, and the Occasional research papers and guidance been very carefully considered, with the expenditure has to be justified by the results notes have appeared but they do not usually result that a few buildings of this type have obtained. The size of the annual maintenance cover the topic in any comprehensive way. been cleaned after exposure for only a few bill in this country has been published at Building Research Station have published a years Of course, in these cases, regular various conferences, and the consensus of book3 which shows the changing appearance cleaning may have been intended from the opinion seems to be that it is too high. Any of buildings with a variety of surface finishes. start tendency to design surfaces which are known The principles illustrated for some surfaces, to require high maintenance must be sub• The emphasis on shapes for facade concrete e.g. stone, can be relevant to concrete as well. jected to close scrutiny. units highlights another well-known but The architect in search of advice has a range The techniques of comparing alternative widely overlooked detailing problem. The of people to whom he can turn. The role of the capital costs of designs against the 'whole main feature of concrete weathering which is specialist companies in this has been dis• life' costs have been expounded in various normally regarded as unsightly is the differen• 1, 2 cussed above. In addition, the cement manu• places , although they do not appear to be tial staining that occurs through differential facturers are often able to be of considerable extensively used. Obviously, these techniques surface absorption and concentrated zones assistance. The role of research associations can be used to deal with the question of of fast and slow water flow. Carefully handled, is fairly widely known. In this field the maintenance and cleaning of concrete sur• this can be used to enhance the elevation. Too Cement and Concrete Association and the faces. However, their application to this often it is not evaluated and the intended Research Committee for the Cast Stone and problem is complicated by the question of effect is lost. Cill details seem particularly Cast Concrete Products Industry have estab• aesthetics. It is difficult to put a figure to the prone to trouble on this score. In other lished sound reputations. However, it is amount one is prepared to spend to maintain cases the preferred water flow patterns necessary to repeat that the advice given a particular appearance. result from the surface texture rather than its carries only a moral responsibility, not a legal The relevance of all this to the subject of this shape. A nominally flat surface will not be so one. A reputation for sound advice is impor• flat that water will wash uniformly over it. seminar lies in the fact that observation shows Fig. 6 tant to most organizations, but in the end the The maxim is that flat concrete is streaky that both the material and the way it is detailed North west pier. architect has the responsibility for the design concrete. The use of textured surfaces, at present do not result in maintenance-free Drilling ducts for reinforcement and specification. particularly exposed aggregate types, is partly surfaces. Yet despite this, and despite the fact through foundations designed to disperse the water flow and so that the detailing principles required to limit (Photo: copyright Water flow on surfaces give uniform colour change The trouble is staining are widely known, designers often Shepherd Building Group) 20 talk as if they believe concrete to be a material In considering the effects of water flow on the that this degree of texture is often not enough. changing appearance of concrete surfaces. A more extreme texturing is currently very investigation of the warehouses and more docks were enclosed by boundary walls of St. Katharine Docks recently in the detailed site investigation for impressive size, effectively preventing the Phase 1. The following account concentrates pilfering which afflicted the older wharves. on the history of the existing structures at St. The success of the dock companies was Malcolm Tucker Katharine's, with a brief description of the new guaranteed by 21 year privilege clauses in scheme. A fuller account of the engineering their Acts of Parliament, giving them mono• problems is given in the supplement of polies in the handling of certain classes of Introduction goods. Increasing trade, the high cost of road Newsletter 38. For certain historical informa• ..... The upper parts of the Port of London are in a tion I am indebted to an article by my friend, transport from the docks, and the exorbitant state of rapid decline, not only because of the Paul Carter13. charges of the existing companies encouraged increasing size of ships, but also because 19th a group of City merchants, towards the end of century warehouses cannot be adapted to Origins of the Docks the 21 year period, to consider the building of modern methods of mechanical handling. The The early 1 9th century saw a revolution in the a new dock hard by the City of London. The older docks have been closing one by one and Port of London. Prior to 1800, trade was Warehousing Act of 1823, initiating bonded, new investment has been concentrated on handled almost exclusively at riverside duty free warehouses, was a further stimulus to 'i Tilbury. One of the victims has been the St. wharves, which became grossly inadequate new building. In 1824 the celebrated civil Katharine Docks, which closed in 1968. For for the increasing trade with the distant engineer, Thomas Telford, was asked to pre• over 30 years the warehouses at St. Katharine's colonies. The great era of commercial dock pare a scheme for the St. Katharine Docks, have been internationally recognized as building in London commenced with the and Philip Hardwick was appointed as important examples of functional architecture West India Docks (1799—1 802), the London architect. Against strong opposition from and the docks' closure has posed serious Docks (1802—1805) and the East India vested interests, an Act was eventually questions of their future. The Greater London Docks (1 803—1 806). These were constructed obtained in June 1825. The scheme then Council bought the docks from the Port of principally on undeveloped marshland beyond pressed ahead with great haste, the western London Authority for £1.800,000 and in 1 969 the eastern extremities of the City and com• dock and associated warehouses being they launched an open competition for their prised large rectangular basins ringed with opened with celebration in October 1 828, and redevelopment, with a pretty demanding austere warehouses of five or six storeys, set the whole scheme being completed 12 brief that included the retention of as many as back behind broad quays. Besides greatly months later. possible of the listed buildings. increasing the available wharfing and ware• The winning scheme was presented by housing space, the new docks offered two Taylor Woodrow Property Company Ltd. with distinct advantages. Firstly, with the use of The roles of Telford and Hardwick Renton Howard Wood Associates as archi• locks to impound the water at a constant Thomas Telford (1757—1 834) was already tects and Ove Arup & Partners as consulting level, loading and unloading were unaffected 67 years old when he was asked in 1824 to engineers. I was involved in structural by the rise and fall of the tides. Secondly, the prepare a scheme for the St. Katharine Docks t 1 and the bulk of his achievements was behind • • him. He was able to draw on his very con• mm siderable experience, which, in the field of Fig. 1 marine engineering alone, included the

Architect's model of the proposed redevelopment. I warehouse harbours of Aberdeen, Dundee and several I is retained intact in the centre of the dock. B warehouse is lesser Scottish ports, and three ship canals. shown in modified form, facing the Tower of London. The His commitments were, however, consider• water area is adapted as a marina (Photo: Henk Snoek) able, not least being his appointment as consulting engineer to the Exchequer Loan CI Commissioners under the Poor Employment mm Act of 1 81 7, which involved the approval and inspection of public works throughout the country. For supervising the construction of the docks he therefore relied heavily on his

resident engineer, Thomas Rhodes, a car• •- penter by training, who had worked for him on the Menai Bridge. In his autobiography Telford confines his remarks on the con• struction to praise of Rhodes and criticism of the pace with which the work had to be executed. Philip Hardwick (1792—1870) was in his t early thirties and, with his architectural practice largely confined to London, he would have given personal attention to the works. Presentation drawings for the ware• houses are attributable to him and working i drawings executed under his direction are at the RIBA.

Planning considerations The chosen site, a net 9'/4 hectares (23 acres) just east of the Tower, was already built up. More than 1,200 dwellings had to be pulled down and The Times quoted the incredible figure of 11,300 inhabitants (i.e. a mean density of 500 persons per acre) as being displaced. In the 19th century such clearance schemes were regarded as of public benefit r and yet no provision was made for the : m rehousing of the displaced population. The i W/i ancient hospital of St. Katharine, a com• munity of lay brethren which managed to survive the Dissolution, was found a new site in Regent's Park, and its 15th century church was demolished. By chance, some drawings by A.W.N. Pugin and his assistants of some i fine mediaeval work in the church are now housed in the RIBA library within 6 ft. of Hardwick's drawings of the dock warehouses. Fig. 19 All physical remains were obliterated by the Architect's model of the proposed excavations for the docks. redevelopment, showing The site is irregular in shape and constricted. the Theatrevision Centre V Wharves along the river front were not (Photo : Henk Snoek) acquired and public access to these along the southern edge of the site had to be maintained. 19 10 Some current uses hotel of international class, a multi-denomi• SOURCES OF REFERENCE A government owned distillery (possibly for The area acquired by the GLC for redevelop• national chapel, a complex of theatre and rum), at one time the King's Brewhouse, was ment excludes the new Dock House and C conference facilities called the 'Theatre- A Contemporary sources allowed to remain, and a wooden framed warehouse, still used by the Port of London vision Centre' and an under-cover sports building of this establishment, marked on old 1 PORT OF LONDON AUTHORITY. Authority, but includes the whole of the river centre. There will be a floating restaurant in drawings as a 'sugar crushing house' Original drawings of the warehouses, etc. frontage. Large 1 9th century warehouses on the river and parking for 20 tourist coaches. survives to this day as G warehouse. To In RIBA drawings collection. Irongate Wharf and St. Katharine's Wharf 1,850 car parking places will be provided, accommodate the maximum amount of ware• were recently demolished, exposing a new principally underground at vault level. The 2 ibid. Bound volume of drawings. housing and length of quay, Telford had to view of Tower Bridge. The paddle steamer. traffic generated by such a high density 3 ibid. Contemporary paintings and prints. abandon preconceptions of rectangularity and symmetry which characterized previous Princess Elizabeth, has recently been moored scheme has posed its problems. No traffic 4 TELFORD. T. Life of Thomas Telford, r docks. He also divided the water area, there for conversion to a licensed restaurant is to be allowed across the middle of the edited by John Rickman. Hansard. 1838. i 1 dock, grade separation between road and i amounting in all to 4.2 hectares (10/4 acres), and will ultimately be incorporated in the new 5 'The opening of St. Katharine's Docks'. water traffic at the entrance lock cannot be into three parts, namely an eastern dock, a scheme. A bit of old dockland activity The Times, p. 2. 27 October 1 828. survives in a quaint two-storeyed group of achieved, and access to the surrounding road western dock and an entrance basin, thereby 6 HORWOOD. R. Plan of London. West• buildings called Harrison's Wharf, where network is in various ways restricted. increasing the length of quay. The entrance minster and Southwark, 1799. In Guild• wines are stored. Next door, on a blitzed site, basin was a not uncommon feature of docks The present scheme was probably selected hall library. I WHk • -Am .. a reinforced concrete yacht is under con• I of this period. Its purpose was to facilitate the because it makes a bold attempt to retain some struction. passage of vessels in and out of the dock in of the existing buildings. The Italianate I B Modern surveys *~4 the limited period of high tide, as is described Inside the docks, most buildings lie empty, warehouse on the central spit is to be kept 1 ORDNANCE SURVEY. Map of London : later. A lock, crossed by a swing bridge, but a thriving colony of artists and industrial more or less as it is and converted to flats with 60 in./1 mile, circa 1892. connected the basin to the river. Stop locks designers has a short term lease of I warehouse a yacht club on the ground floor. By modifica• (single pairs of gates) separated the docks 8 THAMES BASIN ARCHAEOLOGICAL and films are shot from time to time in the tion of the Theatrevision Centre the preserva• from the entrance basin, to maintain a OBSERVERS GROUP. Photographic warehouses. The London Ambulance Service tion of the Dockmaster's House has now also constant water level in the docks if that in the have a weekly training session on the site. been secured. B warehouse, the only survey. 1 966-7. I 1 entrance basin dropped. Telford in his auto• The London Seamanship School has a small Hardwick warehouse to be retained in the 9 OVE ARUP AND PARTNERS. Job no. biography suggests that one dock might be lecture room and boys venture daily out into scheme since C warehouse is not in GLC 1485 Report on investigations on the emptied of water for cleaning and repair the dock for lifeboat practice. ownership, will undergo more extensive site of the new Dock House. 1961. while the other dock remained in full use, alterations. It is intended to convert it into an 10 ibid. Job. no. 7259/01 Physical survey of although this advantage could not apply to the Redevelopment proposals industrial exhibition centre for the benefit of B and I warehouses for the St. Katharine entrance basin and, in any case, the stop locks City-based exporters. Its present lightweight Fig. 2 Fig. 3 The Taylor Woodrow Group's redevelopment Dock Redevelopment Competition. pointed the wrong way. In practice, the docks and fire-prone wooden floors must be Street facade of H warehouse (1852) The Dockmaster's House proposals, estimated to cost £22 m., are to be 1969. were never drained, silt which was washed in replaced by concrete floors and columns on demonstrating the impregnability of on the river front completed by 1 978. The most notable 11 PORT OF LONDON AUTHORITY. Infor• from the river being removed instead by new foundations. Major sections of the outer the Customs Wall (Photo : Malcolm Tucker) feature of the scheme is the retention of the mation derived from PLA staff. dredging. A modern engineer might have walls may also be removed to make way for (Photo: Malcolm Tucker) doubts about the stability of the dock walls if water area as a marina. When this has been 12 TERRESEARCH LTD. Site investigation service and circulation stacks, some of which the water were removed. deducted from the total site area, 5.75 hectares for St. Katharine by the Tower Hotel. may project over the dock. Around the docks on three sides, six multi• (14.2 acres) remain. A fair proportion of this 1970. storey warehouse blocks (stacks) were will be taken up by 300 local authority houses, Job staff are currently struggling with the planned. These were built hard up against the a primary school and community facilities, design of the first phase of the scheme, the C Derivative sources and background Fig. 4 water's edge, being supported above the augmented by a further 320 private houses, 85 3-bedroom hotel on the site of A warehouse, information B warehouse dock facade quay on giant columns. This was a novel idea, ringing the eastern dock. Two of the existing which has got to be substantially complete by 1 3 CARTER. P. St. Katharine Docks. London (Photo : Malcolm Tucker) partly to save space and partly to enable goods warehouses are to be retained for a trade 31 March 1973 to qualify for a government Archaeologist, 1 (3), pp. 51-56. 1 (4). to be hoisted directly from the holds of ships centre and a yacht club and this leaves the subsidy under the 1 969 Development of pp. 80-83, 1969. into the warehouses. In the earlier docks, the southern edge of the site for an 853 bedroom Tourism Act. 14 SHEPHERD-BARRON, W. Presidential warehouses had been set back, behind a wide address. Institution of Civil Engineers. quay where cargoes were unloaded and Proceedings, 3 (1). pp. 12-42. January sorted before dispatch to the warehouses. The 1954. new system eliminated double handling, with 15 BROADBANK. Sir J. G. History of the a corresponding reduction in spillages and Port of London. Vol. 1. O'Connor. 1 921. pilfering. Cargoes could also be unloaded on to the quays, which extended beneath the 1 6 WILSON, A. London's industrial heritage. warehouses, but these were somewhat David & Charles. 1 967. congested by the supports for the structure 17 RICHARDS, J. M. and DE MARE, E. The above. Unfortunately, a ship's cargo would functional tradition in early industrial frequently be destined for more than one building. Architectural Press. 1958. warehouse, in which case it was necessary 18 SKEMPTON, A. W. and JOHNSON. for the ship to move its berth several times, H. R. The first iron frames. Architectural which reduced the efficiency of the system. Review, 131 (781). pp. 175-186, 1962. The principle was adopted by Jesse Hartley 19 ROLT. L. T. C. Thomas Telford. Long• for his impressive docks in Liverpool (e.g. mans. 1958. Albert Dock 1 843. Stanley Dock 1 857). but it was not used for the later docks in London. 20 WARE. D. A short dictionary of British On the central spit between the docks was a architects. Allen & Unwin. 1 967. large two-storeyed wooden transit shed known as the King's Warehouse, probably used for goods bound for export. Most of the area beneath the quays was given over to vaults ideally suited for the storage of wines. In the north west corner of the site, facing the City, were sited the dock's administrative offices, known as the Dock House. The • warehouses and the Dock House were

• notable works of the architect. Philip m it Hardwick, and are described in more detail ill ~5s later.

111! M • The construction of the quay walls 7> Acquisition and clearance of the site com• menced immediately the Act of Parliament was obtained. Detailed working plans were prepared, contracts were let and excavations begun. Within a year, on 3 May 1826, the first foundations of the quay walls were laid. Fig. 18 I Excavated material, mostly clayey sand, was r A jigger winch, probably of 1 828. T a •*T ' i I shipped by barge to Chelsea, where the found in A warehouse and contractor, Thomas Cubitt, was currently removed to the Science Museum laying out Belgravia on reclaimed land. (Photo: Malcolm Tucker) The description of the quay walls in Telford's autobiography corresponds with an original drawing now at the RIBA. and has been 11 largely verified by recent site investigations. Below the footings of the quay walls, says laid diagonally in alternate directions, and Original levels of construction, related to Telford, wooden sheet piling 230 mm (9 in.) grouted up with liquid mortar made from Newlyn Datum were as follows: Bottom of thick, was driven into the ground a distance of Dorking lime and sand, leaving practically no docks: —4.3 m ( — 14 ft.): quay level: 4.3 m (14 ft.), which would have penetrated voids. The outer leaves of the wall were tied + 5.8 m (+19 ft.); impounded level of the London Clay beneath. The joints in the together at two levels by bond courses of water: +3.4 m ( + 11 ft.); standing water- piling were caulked for the top 0.9 m (3 ft.) Millstone Grit blocks. 380 mm (1 ft. 3 in.) table + 0.9 m (+ 3 ft.). A 300 mm (1 ft.) layer of lime concrete was thick. Similar blocks, measuring typically Telford mentions the thick stratum of alluvial then laid as a footing and the dock walls 1.3 m x 1 m deep x 460 mm thick flint gravel, known as the Thames Ballast, built thereon. The floor of the docks was lined (4 ft. 2 in. x 3 ft. 4 in. x 1 ft. 6 in.) were used for which extends over a considerable part of the with puddled clay and a curtain of this clay the coping. The stone was brought from docks. This rests on the London Clay, the was placed also behind the walls. The quay Bramley Fall near Leeds. surface of which represents an old valley walls were constructed of London stock bricks It is not known how inflowing water was floor, and falls fairly steeply towards the river. and are 10 m (33 ft.) high at the face. They coped with while these works were being Although in the north west corner of the are 3 m (10 ft.) thick at the base, reducing by performed. A painting in the possession of the docks buildings at high level are founded a concave batter on the outer face to 1.6 m Port of London Authority shows the whole directly on the London Clay, in the south east (5 ft. 3 in.) at the top. the back face being site excavated to a fair depth with battered corner the gravel exceeds 6.5 m (21 ft.) in vertical. Counterfort buttresses 1.1 m (3 ft. sides and construction of the walls proceeding thickness and extends some 1.2 m—1.5 m 9 in.) square project behind the wall at 5.5 m in the dry. Horse driven pumps must have (4 ft.—5 ft.) beneath the base of the quay wall. (18 ft.) centres. For 350 mm (1 ft. 2 in.) from been kept constantly at work. Telford pays It was necessary to prevent the water the face of the wall. Telford specified the best tribute to his resident engineer, Thomas impounded in the docks from draining away Blue-Lias lime mortar. The interior of the wall Rhodes, for his mastery of these problems. through the porous gravel. was built of flushed brickwork, bricks being The end result is a completely watertight dock the most serious loss of water being by evaporation. The floor level of the vaults beneath the warehouses is 1.7 m (5 ft. 6 in.) below the present water level, but the walls adjacent to the dock exhibit only a moderate peeling of the whitewash. The present water table in the gravel is about 1.2 m (4 ft.) below the vault floor and represents the mean level Fig. 13 above of the water in the Thames. Under a 6 m Fishbelly flanged beams for a mezzanine (20 ft.) tidal range, the ground water level floor of 1 855, inserted between the shows a sinusoidal fluctuation of only 1 25 mm original cruciform columns (5 in ), lagging a quarter of a cycle behind the of C warehouse tides. However, the half tide Thames Barrier (Photo: Malcolm Tucker) might raise the water table to the level of the floor of the vaults.

The entrance lock The reference level used for 1 9th century dock schemes was Trinity High Water, representing the high water level of ordinary spring tides. This is now taken as being 3.5 m (11 ft. 5 in.) above the Newlyn Datum of the Ordnance Survey but in Telford's day it seems to have been a few inches lower. Water was to be Fig. 15 right impounded in the docks at around Trinity Cast iron retracting footbridge of 1828 High Water Level. 2.4 m (8 ft.) below quay at entrance to the Eastern Dock level and the sill of the upper lock gates was (Photo: Malcolm Tucker) 7.3 m (24 ft.) below this. The lock was 1 3 7 m (45 ft.) wide and 55 m (180 ft.) long between gates. In cross- section, the sides of the lock curved round to meet the invert, forming a three centred inverted arch like the bottom of a boat. The lower gate sills of the lock were at 8.5 m Fig. 14 below Fig. 16 below Fig. 17 below (28 ft.) below THW, 1.2 m (4 ft.) below the Cast iron clamp (c.1 855) to support the Recess in quay for the bowsprit of a A jigger rib on H warehouse upper sills, and the approach channel was later mezzanine floor sailing ship. Note mooring rig (Photo : Malcolm Tucker) dredged out to the centre of the river so that (Photo : Malcolm Tucker) (Photo: Malcolm Tucker) the vessels of the largest draught could use the lock during the period when river level was within 1.2 m (4 ft.) of THW, i.e. from three hours before to one hour after an ordinary spring tide. Vessels of up to 1,000 tons burthen could enter the docks. Large vessels were liable to become stranded upon the bed of the Thames at low tide, the river being moderately shallow above Blackwall, and so the period of the tide during which such vessels could enter the dock was critical. Two entrance locks in parallel were proposed in the initial scheme, but only one was built. It was essential that the single entrance lock could be operated quickly and efficiently. Traffic had to be regulated and water levels controlled. This was achieved by means of the entrance basin and two steam pumps. Before high tide, vessels wishing to leave the docks assembled in the entrance basin and 1 the stop locks were closed behind them. Vessels passed in and outthrough the entrance lock for as long as the tide permitted. At high tide, vessels could sail in and out without 1 working the lock. There might be some drop in the level of the water in the basin when the lock was being worked, but the ships at the Fig. 5 quays were unaffected, being isolated by the Doric columns on the quay beneath B warehouse. stop locks. When the critical period for traffic Note rainwater drain pipe (Photo: Malcolm Tucker) movements had passed, the stop locks were 12 17 quay, for instance to power a ship's derrick. Wooden patterns for casting spare parts for the hydraulic equipment have survived in B warehouse. An account of the dock equipment would be incomplete without mention of the various hand barrows used around the quays. With flat platforms of various sizes, sometimes with quaint arrangements of wheels and often with attractive wooden handles, these barrows resemble illustrations of a hundred years or so ago, and are still used.

Later history of the docks The warehouses at St. Katharine's were devoted to such commodities as wool, tea, I sugar, silks, hides, indigo and ivory. Trade with Australia was strong and convicts for transportation are supposed to have been quartered in the vaults beneath I warehouse. It is, however, a reflection on the small size of vessels for which the docks were planned, that one day soon after the opening the 4.2 hectares (10)4 acres) of water could boast 92 ^ vessels. From the mid-19th century, trade began to drift away to larger docks down river, and goods were brought in lighters from there instead for warehousing. However, wine for instance was still being imported by coaster from continental ports before the last war. Latterly the warehouses were used almost exclusively for tea. ' » One end of A warehouse was burnt in 1937 and never repaired. The warehouses around the eastern dock were burnt out by incendiary bombs on 7 September 1940 and have been demolished except for a fragment of D warehouse and one solitary column. Fortun• ately the western dock fared somewhat better, for although the Dock House and part of C warehouse were blitzed, this has been successfully made good with a modern yet sympathetic office building for the Port of London Authority Police by Andrew Renton and Partners (OAP job no. 1485), which has won Civic Trust and other awards. Demolition of A warehouse for Phase 1 of the redevelop• ment was scheduled to start in July this year, but up to the time of writing the western dock still conveyed much of the character of the original scheme, with its disciplined archi• tecture, essential enclosure and vital unity of scale.

Fig. 10 left I warehouse (1858) from the west. It is largely open at quay level (Photo: Malcolm Tucker)

Fig. 11 left Fireproof interior of I warehouse (1858), with brick jack arches on riveted iron beams on tubular columns (Photo : Malcolm Tucker)

Fig. 12 below Massive sandstone stair treads in I warehouse (Photo : Malcolm Tucker)

Fig. 6 View along the quay beneath B warehouse, interrupted at intervals by fire walls (Photo: Malcolm Tucker) now filled and emptied by gravity, but the first example having been in Derby in 1792. ground floor is open, the walls resting on iron sluice valves are worked automatically by a The cast iron interior columns at St. Katharine's columns 320 mm (1214 in.) in diameter and sophisticated system of hydraulic controls. are of a cruciform section, with web stiffeners 2.1 m (6 ft. 1014 in.) high. A cartway. 5.5 m It is ironic that the reconstructed lock was at intervals. Web dimensions run from (18 ft.) wide and two storeys high, runs hailed as the most advanced in Europe, yet for 190 x 32 mm to 245 x 45 mm (714 in. x 1 % in. within the building. Floors are of fire-proof two years now it has lain idle. to 9% in. x 1% in.) overall according to load, jack arch construction on riveted iron while larger sections. 315 x 48 mm I-beams on circular columns. It is not known whether the nicely detailed light iron roof The Hardwick warehouses (12% in. x 17B in.) were needed where columns rise unrestrained through the mez• trusses are original. The original warehouses were designed by zanine level on the quay. Cruciform columns Philip Hardwick, who was later the architect In 1853-55 mezzanine floors were inserted were originated by Telford for the construction behind the Doric colonnade of C and A of the lamented Doric Propylaea at Euston of an aqueduct at Longdon-on-Tern on the Station. Those around the West Dock (later warehouses and may still be seen. Cast iron Shrewsbury Canal in 1795-6. The cruciform beams with fish-belly flanges rest on brackets known as A, B and C) were built in 1827- section has less resistance to buckling than 1828 and those around the East Dock (later ingeniously clamped to the cruciform columns. the hollow cylindrical sections used in later The soffits of the wooden floors exposed known as D, E and F) were built in 1828— warehouses but it was easier to cast. The live 1829. The six warehouses, or 'stacks', were above the quays were fire-proofed at some load capacity of the structure is about time with hollow clay tiles. The quays them• substantially similar in design, although their 2 2 6 kN/m (1 25 Ibf/ft. ) and self-weight a mere selves were paved with large iron plates. ground areas varied somewhat to suit the 1.4 kN/m2 (30 Ibf/ft.2) geometry of the site. They were characterized George Aitcheson died in 1861 and was The vast interiors ot the warehouses, with by the two-storeyed open colonnade on the succeeded as company architect by his son of their slender supports, are an impressive sight, edge of the quay, above which, in all but E the same name However, no more buildings seen however by very few members of the warehouse, rose five storeys of brick. Height of significance were erected at the dock. public. Although once quite common, struc• from quay to parapet was about 24 m (78 ft. George Aitcheson Junior had a successful tures of this type are diminishing in number 8 in.), and individual stacks extended up to 26 architectural practice in the City and the West extremely fast. The redevelopment proposes bays 143 m (470 ft.) in length (B warehouse) End, designing inter alia some of the first to retain much of the outer walls of B ware• 20 and 11 bays 43 m (140 ft.) in depth (D and F iron-framed office buildings. house, but the functional requirements of its warehouses). They were undercut at quay new use demand that it be largely gutted. It is level to a depth of up to 1 5 m (50 ft.) on the Ancillary equipment anticipated that a large number of visitors will dock side. The portions that survive can be Telford's cast iron swing bridge across the be attracted to the site and one hopes that at taken as typical of the remainder. entrance lock has been replaced by a plate- least a portion of one floor can be preserved to girder structure of 1895. However, an original They exhibit a noble simplicity characteristic illustrate this phase in the history of building. footbridge, probably to Telford's design, of the functional tradition, obscured, un• The scheme already envisages the conversion crosses the entrance to the eastern dock. It is fortunately, by 140 years' accumulation of of some of the vaults into a restaurant. in the form of two cast iron cantilever trusses grime, and the bricking up of many of the The extensive vaults beneath the warehouses which retract longitudinally into the quays by windows. Their outer loadbearing walls are of were intended for the storage of wine and means of rack mechanisms. The Boulton & yellow London Stocks, under a plain Portland spirits in casks Brick tunnel vaults of Watt engines have also gone. Winches once Stone coping. The unfluted Doric columns segmental section are used to buttress the used for the manual operation of the lock along the quay are of cast iron, 5.1 m external walls, while the internal bays com• gates have fairly recently been removed. Cast (1 6 ft. 9 in.) high. 1.1 m (3 ft. 9 in.) diameter prise intersecting groin vaults on stocky cast iron bollards associated with the entrance and Fig. 7 above at the base and 38 to 50 mm (114 to 2 in.) iron columns. The vault floors, 3 65 m (1 2 ft.) re-opened and vessels directed to their stop locks are embossed with the words St. thick. The columns are spaced at 5.5 m (1 8 ft.) below quay level, are of earth or concrete, berths. Conventionally the lock would have General view of B warehouse (1828) Katharine Docks 1 828. Bollards were not used centres and cast iron beams span between sometimes with runways for trolleys em• been filled by water flowing under gravity from Tower Bridge for mooring, rings being recessed in the quay them, clad with Portland Stone. These bedded. The warehouse walls are founded on through sluice gates, known as paddles, in the (Photo: Malcolm Tucker) walls for this purpose. An interesting feature colonnades make a major architectural conventional splayed strip footings of brick, upper gates and sides of the chamber, and is the chamfering on the top of the quay wall contribution. Window openings on a regular 1 65 m (5 ft. 5 in.) below the vault floors, and similarly emptied through the lower gates. At in certain places to accommodate the bow• grid in the walls above have large cast iron the iron columns bear by inverted segmental St. Katharine's this method was considered sprits of sailing vessels. too slow and two Boulton and Watt 80 window frames of standard type under arches on to similar strip footings. horsepower beam engines were installed to segmental arches, while at intervals there are Wrought iron jibs of 430 Kg (8V4 cwt.) SWL The Dock House pump water from the river via a culvert 52 m vertical lines of loopholes, i.e. doorways projected from the walls of the topmost floors Fig. 8 left This was a handsome neo-classical building (170 ft.) long The water could be pumped through which goods were hoisted into the to hoist goods up the sides of the warehouses Intersecting king post trusses containing the administrative offices of the into the entrance basin to maintain the warehouses. Each bay is recessed by half a These and various other devices in the in the roof of B warehouse company, set diagonally in the north west water level or directly into the lock chamber brick between pilasters with a semi-circular original scheme were supplied by Joseph (Photo : Malcolm Tucker) angle of the west dock, to face the City. to speed the filling of the lock. With the relieving arch beneath the parapet. Along St. Bramah. The hand winches or 'jiggers' used The central bays of the stucco facade were assistance of the steam pumps, the water level Katharine's Way the walls of B warehouse rise for hoisting were partly counterbalanced by a embellished by four Greek Doric columns in the lock could be raised 37 m (12 ft.) in direct from the pavement, with no windows at weight descending through the building. beneath a bold entablature, set upon a 514 minutes and, as a bonus, the reservoir street level giving an impregnable appearance Goods being lowered were controlled by a smooth-rusticated ground floor. The building function of the entrance basin was rendered appropriate to a warehouse holding bonded band brake on the winch, operated via a foot was gutted during an air raid in 1940 and largely superfluous To conserve water an goods. This long external frontage, which treadle by a 'jiggerman' who leant out later demolished. Original working drawings, additional pair of lock gates was fitted at the Fig. 9 below might otherwise have had a bleak and precariously through the loophole on a dated 1827-28. including some signed by middle of the lock so that small vessels could Groined vaults on cast iron unfriendly character, is broken into units of curved bracket at waist level. Philip Hardwick, are now at the RIBA. lock through using only half the volume of columns under C warehouse (1828) manageable proportion by re-entrant service At various later dates large cranes with water, an important consideration at low tide. (Photo: J. Flowerday) areas. Likewise, the long facades facing the Later warehouses by George Aitcheson slewing and luffing jibs were mounted on the docks are subtly modulated by the setting walls, especially of B warehouse They are These, and the stop gates, have long since In the mid 19th century two further ware• back of certain bays a distance of 1.8 m (6 ft.) notable for their use of hydraulic power. Water been removed houses were built. The architect to the dock (which enabled goods to be hoisted from the under a pressure of about 5.5 N/mm2 company at this time was George Aitcheson, Adjacent to the lock is the Dockmaster's quays). (800 psi) from central pumping stations a contemporary of Hardwick, the latter House, in the elegant yet functional style of became available in the mid 1 850's. The mode The slate clad roofs, of a complicated hipped having retired from practice owing to ill the period, with broad eaves and a bowed end of operation is that of a hydraulic lift. Sheaves construction with intersecting king-post health. Aitcheson does not seem to have been towards the river. It shows distinct signs of of pulleys were fixed at either end of a trusses, are hidden from view behind the an architect of particular note, but it may be differential settlement of a long term nature. hydraulic ram, one on the fixed cylinder and parapet. Internally, cast iron columns on a bay significant that both he and Hardwick worked The explanation would lie with the depth the other on the piston, and the hoisting rope module of 3.7 x 5.5 m (12 ft. 1 in. x 18 ft.) for the London and Birmingham Railway of backfill behind the lock wall. Moreover, the or chain was wound round these three or four support conventional wooden floors, with Company. lock lies on or near the site of a former inlet, times, so that a stroke of ten feet, for instance, wooden beams 305 mm wide x 355 mm deep H warehouse was built in 1852 on the also known as St. Katharine's Dock. There would move the rope through 60 ft or 80 ft. (1 ft. x 1 ft. 2 in.) spanning the longer southern side of the entrance basin. Four may be some connection here with the use of Not only the hoisting, but also the slewing direction in pairs. The floor to floor height is storeys of yellow brick rise sheer from St. loadbearing wooden piles beneath the sills of and luffing, were accomplished using such generally 3.65 mm (12 ft.) diminishing to Katharine's Way with very small window the lock gates, illustrated in Telford's auto• rams The cast iron cylinders of the rams, 3.35 m (11 ft.), and depth of construction openings. On the quay side are spindly two- biography. Loadbearing piles are not recorded measuring up to 300 mm (1 ft.) diameter and is 690 mm (2 ft. 3 in ). Fireproof construction storeyed columns of tubular section. Wooden as having been used in other parts of the site. up to 3 65 m (12 ft.) long, are mounted using brick jack-arch floors and iron beams floor beams are strengthened by miniature vertically inside the warehouses It would be In the reconstruction of 1 957 the walls of the could have been used and this was indeed iron trusses suspended beneath. Internal nice to see some of these preserved in situ. lock chamber were retained, but the gate sills done for the ceiling of the strong room in the columns are of circular section and the roof is Internal lifts and some of the jiggers were also had to be rebuilt. The new sills, at —2 9 m Dock House. Expense considerations probably of wood. converted to hydraulic power. The hydraulic ( 9 ft. 7 in.) Newlyn Datum, are several feet ruled it out for the warehouses. However, the I warehouse replaced the King's Ware• machinery of the swing bridge across the lock higher than the original sills. The level of warehouses were divided up into sections by house on the T-shaped central spit between was renewed with stainless steel rams in impounded water has been raised by 450 mm fire walls, with heavy sheet-iron doors. These the docks. It was built in 1858-60 and its 1957. Another manifestation of the principle (1 ft. 6in.). The conventional wooden mitre cross walls also provide lateral stability architecture is more ornate, including an was the 'hydraulic devil', a small portable gates were replaced by single steel gates, against wind loading. The use of cast iron Italianate campanile, while it is structurally ram-winch which could be connected up to pivoted horizontally, which are lowered by columns for large industrial buildings had much less substantial than the earlier build• the hydraulic mains at various points on the cables into the bottom of the lock. The lock is become well established by the 1820's, the ings. It is notable that almost the entire now filled and emptied by gravity, but the first example having been in Derby in 1792. ground floor is open, the walls resting on iron sluice valves are worked automatically by a The cast iron interior columns at St. Katharine's columns 320 mm (1214 in.) in diameter and sophisticated system of hydraulic controls. are of a cruciform section, with web stiffeners 2.1 m (6 ft. 1014 in.) high. A cartway. 5.5 m It is ironic that the reconstructed lock was at intervals. Web dimensions run from (18 ft.) wide and two storeys high, runs hailed as the most advanced in Europe, yet for 190 x 32 mm to 245 x 45 mm (714 in. x 1 % in. within the building. Floors are of fire-proof two years now it has lain idle. to 9% in. x 1% in.) overall according to load, jack arch construction on riveted iron while larger sections. 315 x 48 mm I-beams on circular columns. It is not known whether the nicely detailed light iron roof The Hardwick warehouses (12% in. x 17B in.) were needed where columns rise unrestrained through the mez• trusses are original. The original warehouses were designed by zanine level on the quay. Cruciform columns Philip Hardwick, who was later the architect In 1853-55 mezzanine floors were inserted were originated by Telford for the construction behind the Doric colonnade of C and A of the lamented Doric Propylaea at Euston of an aqueduct at Longdon-on-Tern on the Station. Those around the West Dock (later warehouses and may still be seen. Cast iron Shrewsbury Canal in 1795-6. The cruciform beams with fish-belly flanges rest on brackets known as A, B and C) were built in 1827- section has less resistance to buckling than 1828 and those around the East Dock (later ingeniously clamped to the cruciform columns. the hollow cylindrical sections used in later The soffits of the wooden floors exposed known as D, E and F) were built in 1828— warehouses but it was easier to cast. The live 1829. The six warehouses, or 'stacks', were above the quays were fire-proofed at some load capacity of the structure is about time with hollow clay tiles. The quays them• substantially similar in design, although their 2 2 6 kN/m (1 25 Ibf/ft. ) and self-weight a mere selves were paved with large iron plates. ground areas varied somewhat to suit the 1.4 kN/m2 (30 Ibf/ft.2) geometry of the site. They were characterized George Aitcheson died in 1861 and was The vast interiors ot the warehouses, with by the two-storeyed open colonnade on the succeeded as company architect by his son of their slender supports, are an impressive sight, edge of the quay, above which, in all but E the same name However, no more buildings seen however by very few members of the warehouse, rose five storeys of brick. Height of significance were erected at the dock. public. Although once quite common, struc• from quay to parapet was about 24 m (78 ft. George Aitcheson Junior had a successful tures of this type are diminishing in number 8 in.), and individual stacks extended up to 26 architectural practice in the City and the West extremely fast. The redevelopment proposes bays 143 m (470 ft.) in length (B warehouse) End, designing inter alia some of the first to retain much of the outer walls of B ware• 20 and 11 bays 43 m (140 ft.) in depth (D and F iron-framed office buildings. house, but the functional requirements of its warehouses). They were undercut at quay new use demand that it be largely gutted. It is level to a depth of up to 1 5 m (50 ft.) on the Ancillary equipment anticipated that a large number of visitors will dock side. The portions that survive can be Telford's cast iron swing bridge across the be attracted to the site and one hopes that at taken as typical of the remainder. entrance lock has been replaced by a plate- least a portion of one floor can be preserved to girder structure of 1895. However, an original They exhibit a noble simplicity characteristic illustrate this phase in the history of building. footbridge, probably to Telford's design, of the functional tradition, obscured, un• The scheme already envisages the conversion crosses the entrance to the eastern dock. It is fortunately, by 140 years' accumulation of of some of the vaults into a restaurant. in the form of two cast iron cantilever trusses grime, and the bricking up of many of the The extensive vaults beneath the warehouses which retract longitudinally into the quays by windows. Their outer loadbearing walls are of were intended for the storage of wine and means of rack mechanisms. The Boulton & yellow London Stocks, under a plain Portland spirits in casks Brick tunnel vaults of Watt engines have also gone. Winches once Stone coping. The unfluted Doric columns segmental section are used to buttress the used for the manual operation of the lock along the quay are of cast iron, 5.1 m external walls, while the internal bays com• gates have fairly recently been removed. Cast (1 6 ft. 9 in.) high. 1.1 m (3 ft. 9 in.) diameter prise intersecting groin vaults on stocky cast iron bollards associated with the entrance and Fig. 7 above at the base and 38 to 50 mm (114 to 2 in.) iron columns. The vault floors, 3 65 m (1 2 ft.) re-opened and vessels directed to their stop locks are embossed with the words St. thick. The columns are spaced at 5.5 m (1 8 ft.) below quay level, are of earth or concrete, berths. Conventionally the lock would have General view of B warehouse (1828) Katharine Docks 1 828. Bollards were not used centres and cast iron beams span between sometimes with runways for trolleys em• been filled by water flowing under gravity from Tower Bridge for mooring, rings being recessed in the quay them, clad with Portland Stone. These bedded. The warehouse walls are founded on through sluice gates, known as paddles, in the (Photo: Malcolm Tucker) walls for this purpose. An interesting feature colonnades make a major architectural conventional splayed strip footings of brick, upper gates and sides of the chamber, and is the chamfering on the top of the quay wall contribution. Window openings on a regular 1 65 m (5 ft. 5 in.) below the vault floors, and similarly emptied through the lower gates. At in certain places to accommodate the bow• grid in the walls above have large cast iron the iron columns bear by inverted segmental St. Katharine's this method was considered sprits of sailing vessels. too slow and two Boulton and Watt 80 window frames of standard type under arches on to similar strip footings. horsepower beam engines were installed to segmental arches, while at intervals there are Wrought iron jibs of 430 Kg (8V4 cwt.) SWL The Dock House pump water from the river via a culvert 52 m vertical lines of loopholes, i.e. doorways projected from the walls of the topmost floors Fig. 8 left This was a handsome neo-classical building (170 ft.) long The water could be pumped through which goods were hoisted into the to hoist goods up the sides of the warehouses Intersecting king post trusses containing the administrative offices of the into the entrance basin to maintain the warehouses. Each bay is recessed by half a These and various other devices in the in the roof of B warehouse company, set diagonally in the north west water level or directly into the lock chamber brick between pilasters with a semi-circular original scheme were supplied by Joseph (Photo : Malcolm Tucker) angle of the west dock, to face the City. to speed the filling of the lock. With the relieving arch beneath the parapet. Along St. Bramah. The hand winches or 'jiggers' used The central bays of the stucco facade were assistance of the steam pumps, the water level Katharine's Way the walls of B warehouse rise for hoisting were partly counterbalanced by a embellished by four Greek Doric columns in the lock could be raised 37 m (12 ft.) in direct from the pavement, with no windows at weight descending through the building. beneath a bold entablature, set upon a 514 minutes and, as a bonus, the reservoir street level giving an impregnable appearance Goods being lowered were controlled by a smooth-rusticated ground floor. The building function of the entrance basin was rendered appropriate to a warehouse holding bonded band brake on the winch, operated via a foot was gutted during an air raid in 1940 and largely superfluous To conserve water an goods. This long external frontage, which treadle by a 'jiggerman' who leant out later demolished. Original working drawings, additional pair of lock gates was fitted at the Fig. 9 below might otherwise have had a bleak and precariously through the loophole on a dated 1827-28. including some signed by middle of the lock so that small vessels could Groined vaults on cast iron unfriendly character, is broken into units of curved bracket at waist level. Philip Hardwick, are now at the RIBA. lock through using only half the volume of columns under C warehouse (1828) manageable proportion by re-entrant service At various later dates large cranes with water, an important consideration at low tide. (Photo: J. Flowerday) areas. Likewise, the long facades facing the Later warehouses by George Aitcheson slewing and luffing jibs were mounted on the docks are subtly modulated by the setting walls, especially of B warehouse They are These, and the stop gates, have long since In the mid 19th century two further ware• back of certain bays a distance of 1.8 m (6 ft.) notable for their use of hydraulic power. Water been removed houses were built. The architect to the dock (which enabled goods to be hoisted from the under a pressure of about 5.5 N/mm2 company at this time was George Aitcheson, Adjacent to the lock is the Dockmaster's quays). (800 psi) from central pumping stations a contemporary of Hardwick, the latter House, in the elegant yet functional style of became available in the mid 1 850's. The mode The slate clad roofs, of a complicated hipped having retired from practice owing to ill the period, with broad eaves and a bowed end of operation is that of a hydraulic lift. Sheaves construction with intersecting king-post health. Aitcheson does not seem to have been towards the river. It shows distinct signs of of pulleys were fixed at either end of a trusses, are hidden from view behind the an architect of particular note, but it may be differential settlement of a long term nature. hydraulic ram, one on the fixed cylinder and parapet. Internally, cast iron columns on a bay significant that both he and Hardwick worked The explanation would lie with the depth the other on the piston, and the hoisting rope module of 3.7 x 5.5 m (12 ft. 1 in. x 18 ft.) for the London and Birmingham Railway of backfill behind the lock wall. Moreover, the or chain was wound round these three or four support conventional wooden floors, with Company. lock lies on or near the site of a former inlet, times, so that a stroke of ten feet, for instance, wooden beams 305 mm wide x 355 mm deep H warehouse was built in 1852 on the also known as St. Katharine's Dock. There would move the rope through 60 ft or 80 ft. (1 ft. x 1 ft. 2 in.) spanning the longer southern side of the entrance basin. Four may be some connection here with the use of Not only the hoisting, but also the slewing direction in pairs. The floor to floor height is storeys of yellow brick rise sheer from St. loadbearing wooden piles beneath the sills of and luffing, were accomplished using such generally 3.65 mm (12 ft.) diminishing to Katharine's Way with very small window the lock gates, illustrated in Telford's auto• rams The cast iron cylinders of the rams, 3.35 m (11 ft.), and depth of construction openings. On the quay side are spindly two- biography. Loadbearing piles are not recorded measuring up to 300 mm (1 ft.) diameter and is 690 mm (2 ft. 3 in ). Fireproof construction storeyed columns of tubular section. Wooden as having been used in other parts of the site. up to 3 65 m (12 ft.) long, are mounted using brick jack-arch floors and iron beams floor beams are strengthened by miniature vertically inside the warehouses It would be In the reconstruction of 1 957 the walls of the could have been used and this was indeed iron trusses suspended beneath. Internal nice to see some of these preserved in situ. lock chamber were retained, but the gate sills done for the ceiling of the strong room in the columns are of circular section and the roof is Internal lifts and some of the jiggers were also had to be rebuilt. The new sills, at —2 9 m Dock House. Expense considerations probably of wood. converted to hydraulic power. The hydraulic ( 9 ft. 7 in.) Newlyn Datum, are several feet ruled it out for the warehouses. However, the I warehouse replaced the King's Ware• machinery of the swing bridge across the lock higher than the original sills. The level of warehouses were divided up into sections by house on the T-shaped central spit between was renewed with stainless steel rams in impounded water has been raised by 450 mm fire walls, with heavy sheet-iron doors. These the docks. It was built in 1858-60 and its 1957. Another manifestation of the principle (1 ft. 6in.). The conventional wooden mitre cross walls also provide lateral stability architecture is more ornate, including an was the 'hydraulic devil', a small portable gates were replaced by single steel gates, against wind loading. The use of cast iron Italianate campanile, while it is structurally ram-winch which could be connected up to pivoted horizontally, which are lowered by columns for large industrial buildings had much less substantial than the earlier build• the hydraulic mains at various points on the cables into the bottom of the lock. The lock is become well established by the 1820's, the ings. It is notable that almost the entire quay, for instance to power a ship's derrick. Wooden patterns for casting spare parts for the hydraulic equipment have survived in B warehouse. An account of the dock equipment would be incomplete without mention of the various hand barrows used around the quays. With flat platforms of various sizes, sometimes with quaint arrangements of wheels and often with attractive wooden handles, these barrows resemble illustrations of a hundred years or so ago, and are still used.

Later history of the docks The warehouses at St. Katharine's were devoted to such commodities as wool, tea, I sugar, silks, hides, indigo and ivory. Trade with Australia was strong and convicts for transportation are supposed to have been quartered in the vaults beneath I warehouse. It is, however, a reflection on the small size of vessels for which the docks were planned, that one day soon after the opening the 4.2 hectares (10)4 acres) of water could boast 92 ^ vessels. From the mid-19th century, trade began to drift away to larger docks down river, and goods were brought in lighters from there instead for warehousing. However, wine for instance was still being imported by coaster from continental ports before the last war. Latterly the warehouses were used almost exclusively for tea. ' » One end of A warehouse was burnt in 1937 and never repaired. The warehouses around the eastern dock were burnt out by incendiary bombs on 7 September 1940 and have been demolished except for a fragment of D warehouse and one solitary column. Fortun• ately the western dock fared somewhat better, for although the Dock House and part of C warehouse were blitzed, this has been successfully made good with a modern yet sympathetic office building for the Port of London Authority Police by Andrew Renton and Partners (OAP job no. 1485), which has won Civic Trust and other awards. Demolition of A warehouse for Phase 1 of the redevelop• ment was scheduled to start in July this year, but up to the time of writing the western dock still conveyed much of the character of the original scheme, with its disciplined archi• tecture, essential enclosure and vital unity of scale.

Fig. 10 left I warehouse (1858) from the west. It is largely open at quay level (Photo: Malcolm Tucker)

Fig. 11 left Fireproof interior of I warehouse (1858), with brick jack arches on riveted iron beams on tubular columns (Photo : Malcolm Tucker)

Fig. 12 below Massive sandstone stair treads in I warehouse (Photo : Malcolm Tucker)

Fig. 6 View along the quay beneath B warehouse, interrupted at intervals by fire walls (Photo: Malcolm Tucker) largely verified by recent site investigations. Below the footings of the quay walls, says laid diagonally in alternate directions, and Original levels of construction, related to Telford, wooden sheet piling 230 mm (9 in.) grouted up with liquid mortar made from Newlyn Datum were as follows: Bottom of thick, was driven into the ground a distance of Dorking lime and sand, leaving practically no docks: —4.3 m ( — 14 ft.): quay level: 4.3 m (14 ft.), which would have penetrated voids. The outer leaves of the wall were tied + 5.8 m (+19 ft.); impounded level of the London Clay beneath. The joints in the together at two levels by bond courses of water: +3.4 m ( + 11 ft.); standing water- piling were caulked for the top 0.9 m (3 ft.) Millstone Grit blocks. 380 mm (1 ft. 3 in.) table + 0.9 m (+ 3 ft.). A 300 mm (1 ft.) layer of lime concrete was thick. Similar blocks, measuring typically Telford mentions the thick stratum of alluvial then laid as a footing and the dock walls 1.3 m x 1 m deep x 460 mm thick flint gravel, known as the Thames Ballast, built thereon. The floor of the docks was lined (4 ft. 2 in. x 3 ft. 4 in. x 1 ft. 6 in.) were used for which extends over a considerable part of the with puddled clay and a curtain of this clay the coping. The stone was brought from docks. This rests on the London Clay, the was placed also behind the walls. The quay Bramley Fall near Leeds. surface of which represents an old valley walls were constructed of London stock bricks It is not known how inflowing water was floor, and falls fairly steeply towards the river. and are 10 m (33 ft.) high at the face. They coped with while these works were being Although in the north west corner of the are 3 m (10 ft.) thick at the base, reducing by performed. A painting in the possession of the docks buildings at high level are founded a concave batter on the outer face to 1.6 m Port of London Authority shows the whole directly on the London Clay, in the south east (5 ft. 3 in.) at the top. the back face being site excavated to a fair depth with battered corner the gravel exceeds 6.5 m (21 ft.) in vertical. Counterfort buttresses 1.1 m (3 ft. sides and construction of the walls proceeding thickness and extends some 1.2 m—1.5 m 9 in.) square project behind the wall at 5.5 m in the dry. Horse driven pumps must have (4 ft.—5 ft.) beneath the base of the quay wall. (18 ft.) centres. For 350 mm (1 ft. 2 in.) from been kept constantly at work. Telford pays It was necessary to prevent the water the face of the wall. Telford specified the best tribute to his resident engineer, Thomas impounded in the docks from draining away Blue-Lias lime mortar. The interior of the wall Rhodes, for his mastery of these problems. through the porous gravel. was built of flushed brickwork, bricks being The end result is a completely watertight dock the most serious loss of water being by evaporation. The floor level of the vaults beneath the warehouses is 1.7 m (5 ft. 6 in.) below the present water level, but the walls adjacent to the dock exhibit only a moderate peeling of the whitewash. The present water table in the gravel is about 1.2 m (4 ft.) below the vault floor and represents the mean level Fig. 13 above of the water in the Thames. Under a 6 m Fishbelly flanged beams for a mezzanine (20 ft.) tidal range, the ground water level floor of 1 855, inserted between the shows a sinusoidal fluctuation of only 1 25 mm original cruciform columns (5 in ), lagging a quarter of a cycle behind the of C warehouse tides. However, the half tide Thames Barrier (Photo: Malcolm Tucker) might raise the water table to the level of the floor of the vaults.

The entrance lock The reference level used for 1 9th century dock schemes was Trinity High Water, representing the high water level of ordinary spring tides. This is now taken as being 3.5 m (11 ft. 5 in.) above the Newlyn Datum of the Ordnance Survey but in Telford's day it seems to have been a few inches lower. Water was to be Fig. 15 right impounded in the docks at around Trinity Cast iron retracting footbridge of 1828 High Water Level. 2.4 m (8 ft.) below quay at entrance to the Eastern Dock level and the sill of the upper lock gates was (Photo: Malcolm Tucker) 7.3 m (24 ft.) below this. The lock was 1 3 7 m (45 ft.) wide and 55 m (180 ft.) long between gates. In cross- section, the sides of the lock curved round to meet the invert, forming a three centred inverted arch like the bottom of a boat. The lower gate sills of the lock were at 8.5 m Fig. 14 below Fig. 16 below Fig. 17 below (28 ft.) below THW, 1.2 m (4 ft.) below the Cast iron clamp (c.1 855) to support the Recess in quay for the bowsprit of a A jigger rib on H warehouse upper sills, and the approach channel was later mezzanine floor sailing ship. Note mooring rig (Photo : Malcolm Tucker) dredged out to the centre of the river so that (Photo : Malcolm Tucker) (Photo: Malcolm Tucker) the vessels of the largest draught could use the lock during the period when river level was within 1.2 m (4 ft.) of THW, i.e. from three hours before to one hour after an ordinary spring tide. Vessels of up to 1,000 tons burthen could enter the docks. Large vessels were liable to become stranded upon the bed of the Thames at low tide, the river being moderately shallow above Blackwall, and so the period of the tide during which such vessels could enter the dock was critical. Two entrance locks in parallel were proposed in the initial scheme, but only one was built. It was essential that the single entrance lock could be operated quickly and efficiently. Traffic had to be regulated and water levels controlled. This was achieved by means of the entrance basin and two steam pumps. Before high tide, vessels wishing to leave the docks assembled in the entrance basin and 1 the stop locks were closed behind them. Vessels passed in and outthrough the entrance lock for as long as the tide permitted. At high tide, vessels could sail in and out without 1 working the lock. There might be some drop in the level of the water in the basin when the lock was being worked, but the ships at the Fig. 5 quays were unaffected, being isolated by the Doric columns on the quay beneath B warehouse. stop locks. When the critical period for traffic Note rainwater drain pipe (Photo: Malcolm Tucker) movements had passed, the stop locks were 12 17 Some current uses hotel of international class, a multi-denomi• SOURCES OF REFERENCE A government owned distillery (possibly for The area acquired by the GLC for redevelop• national chapel, a complex of theatre and rum), at one time the King's Brewhouse, was ment excludes the new Dock House and C conference facilities called the 'Theatre- A Contemporary sources allowed to remain, and a wooden framed warehouse, still used by the Port of London vision Centre' and an under-cover sports building of this establishment, marked on old 1 PORT OF LONDON AUTHORITY. Authority, but includes the whole of the river centre. There will be a floating restaurant in drawings as a 'sugar crushing house' Original drawings of the warehouses, etc. frontage. Large 1 9th century warehouses on the river and parking for 20 tourist coaches. survives to this day as G warehouse. To In RIBA drawings collection. Irongate Wharf and St. Katharine's Wharf 1,850 car parking places will be provided, accommodate the maximum amount of ware• were recently demolished, exposing a new principally underground at vault level. The 2 ibid. Bound volume of drawings. housing and length of quay, Telford had to view of Tower Bridge. The paddle steamer. traffic generated by such a high density 3 ibid. Contemporary paintings and prints. abandon preconceptions of rectangularity and symmetry which characterized previous Princess Elizabeth, has recently been moored scheme has posed its problems. No traffic 4 TELFORD. T. Life of Thomas Telford, r docks. He also divided the water area, there for conversion to a licensed restaurant is to be allowed across the middle of the edited by John Rickman. Hansard. 1838. i 1 dock, grade separation between road and i amounting in all to 4.2 hectares (10/4 acres), and will ultimately be incorporated in the new 5 'The opening of St. Katharine's Docks'. water traffic at the entrance lock cannot be into three parts, namely an eastern dock, a scheme. A bit of old dockland activity The Times, p. 2. 27 October 1 828. survives in a quaint two-storeyed group of achieved, and access to the surrounding road western dock and an entrance basin, thereby 6 HORWOOD. R. Plan of London. West• buildings called Harrison's Wharf, where network is in various ways restricted. increasing the length of quay. The entrance minster and Southwark, 1799. In Guild• wines are stored. Next door, on a blitzed site, basin was a not uncommon feature of docks The present scheme was probably selected hall library. I WHk • -Am .. a reinforced concrete yacht is under con• I of this period. Its purpose was to facilitate the because it makes a bold attempt to retain some struction. passage of vessels in and out of the dock in of the existing buildings. The Italianate I B Modern surveys *~4 the limited period of high tide, as is described Inside the docks, most buildings lie empty, warehouse on the central spit is to be kept 1 ORDNANCE SURVEY. Map of London : later. A lock, crossed by a swing bridge, but a thriving colony of artists and industrial more or less as it is and converted to flats with 60 in./1 mile, circa 1892. connected the basin to the river. Stop locks designers has a short term lease of I warehouse a yacht club on the ground floor. By modifica• (single pairs of gates) separated the docks 8 THAMES BASIN ARCHAEOLOGICAL and films are shot from time to time in the tion of the Theatrevision Centre the preserva• from the entrance basin, to maintain a OBSERVERS GROUP. Photographic warehouses. The London Ambulance Service tion of the Dockmaster's House has now also constant water level in the docks if that in the have a weekly training session on the site. been secured. B warehouse, the only survey. 1 966-7. I 1 entrance basin dropped. Telford in his auto• The London Seamanship School has a small Hardwick warehouse to be retained in the 9 OVE ARUP AND PARTNERS. Job no. biography suggests that one dock might be lecture room and boys venture daily out into scheme since C warehouse is not in GLC 1485 Report on investigations on the emptied of water for cleaning and repair the dock for lifeboat practice. ownership, will undergo more extensive site of the new Dock House. 1961. while the other dock remained in full use, alterations. It is intended to convert it into an 10 ibid. Job. no. 7259/01 Physical survey of although this advantage could not apply to the Redevelopment proposals industrial exhibition centre for the benefit of B and I warehouses for the St. Katharine entrance basin and, in any case, the stop locks City-based exporters. Its present lightweight Fig. 2 Fig. 3 The Taylor Woodrow Group's redevelopment Dock Redevelopment Competition. pointed the wrong way. In practice, the docks and fire-prone wooden floors must be Street facade of H warehouse (1852) The Dockmaster's House proposals, estimated to cost £22 m., are to be 1969. were never drained, silt which was washed in replaced by concrete floors and columns on demonstrating the impregnability of on the river front completed by 1 978. The most notable 11 PORT OF LONDON AUTHORITY. Infor• from the river being removed instead by new foundations. Major sections of the outer the Customs Wall (Photo : Malcolm Tucker) feature of the scheme is the retention of the mation derived from PLA staff. dredging. A modern engineer might have walls may also be removed to make way for (Photo: Malcolm Tucker) doubts about the stability of the dock walls if water area as a marina. When this has been 12 TERRESEARCH LTD. Site investigation service and circulation stacks, some of which the water were removed. deducted from the total site area, 5.75 hectares for St. Katharine by the Tower Hotel. may project over the dock. Around the docks on three sides, six multi• (14.2 acres) remain. A fair proportion of this 1970. storey warehouse blocks (stacks) were will be taken up by 300 local authority houses, Job staff are currently struggling with the planned. These were built hard up against the a primary school and community facilities, design of the first phase of the scheme, the C Derivative sources and background Fig. 4 water's edge, being supported above the augmented by a further 320 private houses, 85 3-bedroom hotel on the site of A warehouse, information B warehouse dock facade quay on giant columns. This was a novel idea, ringing the eastern dock. Two of the existing which has got to be substantially complete by 1 3 CARTER. P. St. Katharine Docks. London (Photo : Malcolm Tucker) partly to save space and partly to enable goods warehouses are to be retained for a trade 31 March 1973 to qualify for a government Archaeologist, 1 (3), pp. 51-56. 1 (4). to be hoisted directly from the holds of ships centre and a yacht club and this leaves the subsidy under the 1 969 Development of pp. 80-83, 1969. into the warehouses. In the earlier docks, the southern edge of the site for an 853 bedroom Tourism Act. 14 SHEPHERD-BARRON, W. Presidential warehouses had been set back, behind a wide address. Institution of Civil Engineers. quay where cargoes were unloaded and Proceedings, 3 (1). pp. 12-42. January sorted before dispatch to the warehouses. The 1954. new system eliminated double handling, with 15 BROADBANK. Sir J. G. History of the a corresponding reduction in spillages and Port of London. Vol. 1. O'Connor. 1 921. pilfering. Cargoes could also be unloaded on to the quays, which extended beneath the 1 6 WILSON, A. London's industrial heritage. warehouses, but these were somewhat David & Charles. 1 967. congested by the supports for the structure 17 RICHARDS, J. M. and DE MARE, E. The above. Unfortunately, a ship's cargo would functional tradition in early industrial frequently be destined for more than one building. Architectural Press. 1958. warehouse, in which case it was necessary 18 SKEMPTON, A. W. and JOHNSON. for the ship to move its berth several times, H. R. The first iron frames. Architectural which reduced the efficiency of the system. Review, 131 (781). pp. 175-186, 1962. The principle was adopted by Jesse Hartley 19 ROLT. L. T. C. Thomas Telford. Long• for his impressive docks in Liverpool (e.g. mans. 1958. Albert Dock 1 843. Stanley Dock 1 857). but it was not used for the later docks in London. 20 WARE. D. A short dictionary of British On the central spit between the docks was a architects. Allen & Unwin. 1 967. large two-storeyed wooden transit shed known as the King's Warehouse, probably used for goods bound for export. Most of the area beneath the quays was given over to vaults ideally suited for the storage of wines. In the north west corner of the site, facing the City, were sited the dock's administrative offices, known as the Dock House. The • warehouses and the Dock House were

• notable works of the architect. Philip m it Hardwick, and are described in more detail ill ~5s later.

111! M • The construction of the quay walls 7> Acquisition and clearance of the site com• menced immediately the Act of Parliament was obtained. Detailed working plans were prepared, contracts were let and excavations begun. Within a year, on 3 May 1826, the first foundations of the quay walls were laid. Fig. 18 I Excavated material, mostly clayey sand, was r A jigger winch, probably of 1 828. T a •*T ' i I shipped by barge to Chelsea, where the found in A warehouse and contractor, Thomas Cubitt, was currently removed to the Science Museum laying out Belgravia on reclaimed land. (Photo: Malcolm Tucker) The description of the quay walls in Telford's autobiography corresponds with an original drawing now at the RIBA. and has been 11 investigation of the warehouses and more docks were enclosed by boundary walls of St. Katharine Docks recently in the detailed site investigation for impressive size, effectively preventing the Phase 1. The following account concentrates pilfering which afflicted the older wharves. on the history of the existing structures at St. The success of the dock companies was Malcolm Tucker Katharine's, with a brief description of the new guaranteed by 21 year privilege clauses in scheme. A fuller account of the engineering their Acts of Parliament, giving them mono• problems is given in the supplement of polies in the handling of certain classes of Introduction goods. Increasing trade, the high cost of road Newsletter 38. For certain historical informa• ..... The upper parts of the Port of London are in a tion I am indebted to an article by my friend, transport from the docks, and the exorbitant state of rapid decline, not only because of the Paul Carter13. charges of the existing companies encouraged increasing size of ships, but also because 19th a group of City merchants, towards the end of century warehouses cannot be adapted to Origins of the Docks the 21 year period, to consider the building of modern methods of mechanical handling. The The early 1 9th century saw a revolution in the a new dock hard by the City of London. The older docks have been closing one by one and Port of London. Prior to 1800, trade was Warehousing Act of 1823, initiating bonded, new investment has been concentrated on handled almost exclusively at riverside duty free warehouses, was a further stimulus to 'i Tilbury. One of the victims has been the St. wharves, which became grossly inadequate new building. In 1824 the celebrated civil Katharine Docks, which closed in 1968. For for the increasing trade with the distant engineer, Thomas Telford, was asked to pre• over 30 years the warehouses at St. Katharine's colonies. The great era of commercial dock pare a scheme for the St. Katharine Docks, have been internationally recognized as building in London commenced with the and Philip Hardwick was appointed as important examples of functional architecture West India Docks (1799—1 802), the London architect. Against strong opposition from and the docks' closure has posed serious Docks (1802—1805) and the East India vested interests, an Act was eventually questions of their future. The Greater London Docks (1 803—1 806). These were constructed obtained in June 1825. The scheme then Council bought the docks from the Port of principally on undeveloped marshland beyond pressed ahead with great haste, the western London Authority for £1.800,000 and in 1 969 the eastern extremities of the City and com• dock and associated warehouses being they launched an open competition for their prised large rectangular basins ringed with opened with celebration in October 1 828, and redevelopment, with a pretty demanding austere warehouses of five or six storeys, set the whole scheme being completed 12 brief that included the retention of as many as back behind broad quays. Besides greatly months later. possible of the listed buildings. increasing the available wharfing and ware• The winning scheme was presented by housing space, the new docks offered two Taylor Woodrow Property Company Ltd. with distinct advantages. Firstly, with the use of The roles of Telford and Hardwick Renton Howard Wood Associates as archi• locks to impound the water at a constant Thomas Telford (1757—1 834) was already tects and Ove Arup & Partners as consulting level, loading and unloading were unaffected 67 years old when he was asked in 1824 to engineers. I was involved in structural by the rise and fall of the tides. Secondly, the prepare a scheme for the St. Katharine Docks t 1 and the bulk of his achievements was behind • • him. He was able to draw on his very con• mm siderable experience, which, in the field of Fig. 1 marine engineering alone, included the

Architect's model of the proposed redevelopment. I warehouse harbours of Aberdeen, Dundee and several I is retained intact in the centre of the dock. B warehouse is lesser Scottish ports, and three ship canals. shown in modified form, facing the Tower of London. The His commitments were, however, consider• water area is adapted as a marina (Photo: Henk Snoek) able, not least being his appointment as consulting engineer to the Exchequer Loan CI Commissioners under the Poor Employment mm Act of 1 81 7, which involved the approval and inspection of public works throughout the country. For supervising the construction of the docks he therefore relied heavily on his

resident engineer, Thomas Rhodes, a car• •- penter by training, who had worked for him on the Menai Bridge. In his autobiography Telford confines his remarks on the con• struction to praise of Rhodes and criticism of the pace with which the work had to be executed. Philip Hardwick (1792—1870) was in his t early thirties and, with his architectural practice largely confined to London, he would have given personal attention to the works. Presentation drawings for the ware• houses are attributable to him and working i drawings executed under his direction are at the RIBA.

Planning considerations The chosen site, a net 9'/4 hectares (23 acres) just east of the Tower, was already built up. More than 1,200 dwellings had to be pulled down and The Times quoted the incredible figure of 11,300 inhabitants (i.e. a mean density of 500 persons per acre) as being displaced. In the 19th century such clearance schemes were regarded as of public benefit r and yet no provision was made for the : m rehousing of the displaced population. The i W/i ancient hospital of St. Katharine, a com• munity of lay brethren which managed to survive the Dissolution, was found a new site in Regent's Park, and its 15th century church was demolished. By chance, some drawings by A.W.N. Pugin and his assistants of some i fine mediaeval work in the church are now housed in the RIBA library within 6 ft. of Hardwick's drawings of the dock warehouses. Fig. 19 All physical remains were obliterated by the Architect's model of the proposed excavations for the docks. redevelopment, showing The site is irregular in shape and constricted. the Theatrevision Centre V Wharves along the river front were not (Photo : Henk Snoek) acquired and public access to these along the southern edge of the site had to be maintained. 19 10 of infinite life and stain resistance. Speaking it is essential to look at them both in terms of The changing in broad terms the choice is as follows: the surface itself and in terms of the building (B)Upper reinforced as a whole. The prevailing weather conditions 1 accept regular (five year) cleaning of N.W. concrete collar face of concrete concrete surfaces, and continue detailing in an area can be significantly modified by the PIER in the way it is usually done today, or form of the building itself. However, certain 2 aim for controlled weathering of concrete general statements may be made. Turlogh O'Brien surfaces by changing the approach to The tendency for dirt to be deposited depends detailing, or on the rate at which rainwater moves over the Floor level surface. This rate is affected by: 3 develop a new form of concrete, or a new This paper was delivered at the C & CA invisible long-life surface coating which 1 height seminar for architects on appearance & resists stain formation 2 orientation weathering of concrete, held on 7 May 1970 Observation of the extent to which clients are 3 shelter from adjacent buildings (c) Prestressed concrete prepared to pay for regular cleaning of 4 shelter from parts of the same building concrete surfaces suggests that only the foundation The objective of this paper is to discuss the 5 the shape of the units owners of prestige office blocks are normally (B)Flat jacks appearance and weathering of concrete sur• willing to do this. Public and university 6 the texture of the surface faces in the context of the overall require• buildings may receive attention at longer ments for the building fabric and for its Most people are familiar with the variation in intervals. Housing and schools projects are performance in time. The use of exposed dirt deposition that is observed over the height unlikely to be cleaned merely to restore a concrete has a sufficiently long history for the of taller buildings. Although the best examples particular appearance. If this is the true (?) Stainless (?) Existing Norman (A)Concrete base likely behaviour on any new structure to be are older buildings which have had time to Fig. 4 situation with regard to cleaning costs, then steel rods masonry footings anticipated with reasonable reliability. Obser• collect considerable dirt (e.g. University of Section through completed foundation in the short term, choice 2 (above) is the only vation of many recent buildings suggests London Senate House), the effect can be alternative. that, although this information is available, it seen on some quite recent buildings in the is often ignored. Before making value judge• With the trend towards variety in concrete main cities. The upper parts are washed ments about this it is necessary to examine finishes, the architect is increasingly having cleaner by the faster moving water. the particular requirements for each building. to rely upon the expert advice of other people, A similar effect is observed with orientation. These may be circumstances in which it is particularly his consulting engineer and the Once again it is the older buildings that show perfectly justifiable to neglect weathering specialist concrete companies. This trend the most marked effect. One can find stone problems. should be welcomed, provided that the basis columns washed clean on one face, but for the collaboration is fully understood. The When considering the types of effects pro• remaining quite black on the others. The specialist company must be able to deal with duced by weathering on concrete surfaces, prevailing wind tends to drive the rain harder all queries raised by the designers. There is a it is clear that the distinction between changes from one side on more occasions in the year, trend towards competition between com• that merely alter the appearance and those thus producing a greater washing effect. panies on the quality of advice they give in that affect 'performance' is difficult to define Adjacent buildings may provide shelter from addition to quality and price of the product. precisely. At one extreme, streaks of dirt may driving rain, so reducing the cleaning effect. This trend is also welcome if the companies change the appearance considerably without Sheltered areas are darker. are able to find the people with the necessary doing any physical damage. At the other The degree of exposure of external concrete knowledge and experience to give the right extreme, the surface may break up under surfaces on a building may vary from severe type of advice. On the designers' side, the weathering. In between there are a whole (e.g. a roof parapet) to completely sheltered architect and engineer must know sufficient range of effects which may be classed as (e.g. the soffit of a concrete slab over a about the nature and behaviour of concrete to changes in appearance or as damage, concourse or parking area at the entrance to a be able to evaluate the advice given. It must depending on your point of view. Thus the always remain the architect's job to integrate building). In between these extremes are a stage at which 'crazing' becomes 'cracking' all the specialist technical advice he receives, whole range of possible exposures, each of may vary with the type of building and with thus producing unified design for the whole which will have different degrees of shelter. Fig. 5 the observer. Surface flaking or loss of building. Contributing specialists must realize Considerations of this type can lead one to Distortions in Norman walls aggregate (from some types of finish) may be more often than they seem to that there are question whether it is advisable to use the below present floor level very difficult to classify. more problems to building design than just same concrete surface details all the way up a due to column on the right Some people may suggest that any change concrete surfaces. tall building, on different elevations, and in (Photo : by courtesy of the Royal in the basic surface, through the formation of different relationships to other elements of the Commission on Historic Monuments) any cracks, or through loss of material, should Sources of information and advice building. Although the concrete surfaces may be classed as damage, whilst only those Despite the fact that concrete has been start looking the same, they will not stay like which result in streaking or staining should be subjected to weathering for many years, the that for long. classed as appearance changes. This view is literature on the subject is not very extensive. The use of highly shaped concrete panels as not very helpful as it would imply that almost The journals Concrete and Concrete Quarterly cladding is a particularly noticeable trend at all external concrete surfaces are in need of regularly feature examples of building with present. In some cases these have been maintenance. The alternative view would be interesting concrete surfaces. Unfortunately carefully detailed so that the weathering will to look at the question more from an economic few of these had been weathered for very enhance the effects of light and shade4. In n point of view. Any form of maintenance of a long before the photographs were taken. other cases these effects do not appear to have concrete surface costs money, and the Occasional research papers and guidance been very carefully considered, with the expenditure has to be justified by the results notes have appeared but they do not usually result that a few buildings of this type have obtained. The size of the annual maintenance cover the topic in any comprehensive way. been cleaned after exposure for only a few bill in this country has been published at Building Research Station have published a years Of course, in these cases, regular various conferences, and the consensus of book3 which shows the changing appearance cleaning may have been intended from the opinion seems to be that it is too high. Any of buildings with a variety of surface finishes. start tendency to design surfaces which are known The principles illustrated for some surfaces, to require high maintenance must be sub• The emphasis on shapes for facade concrete e.g. stone, can be relevant to concrete as well. jected to close scrutiny. units highlights another well-known but The architect in search of advice has a range The techniques of comparing alternative widely overlooked detailing problem. The of people to whom he can turn. The role of the capital costs of designs against the 'whole main feature of concrete weathering which is specialist companies in this has been dis• life' costs have been expounded in various normally regarded as unsightly is the differen• 1, 2 cussed above. In addition, the cement manu• places , although they do not appear to be tial staining that occurs through differential facturers are often able to be of considerable extensively used. Obviously, these techniques surface absorption and concentrated zones assistance. The role of research associations can be used to deal with the question of of fast and slow water flow. Carefully handled, is fairly widely known. In this field the maintenance and cleaning of concrete sur• this can be used to enhance the elevation. Too Cement and Concrete Association and the faces. However, their application to this often it is not evaluated and the intended Research Committee for the Cast Stone and problem is complicated by the question of effect is lost. Cill details seem particularly Cast Concrete Products Industry have estab• aesthetics. It is difficult to put a figure to the prone to trouble on this score. In other lished sound reputations. However, it is amount one is prepared to spend to maintain cases the preferred water flow patterns necessary to repeat that the advice given a particular appearance. result from the surface texture rather than its carries only a moral responsibility, not a legal The relevance of all this to the subject of this shape. A nominally flat surface will not be so one. A reputation for sound advice is impor• flat that water will wash uniformly over it. seminar lies in the fact that observation shows Fig. 6 tant to most organizations, but in the end the The maxim is that flat concrete is streaky that both the material and the way it is detailed North west pier. architect has the responsibility for the design concrete. The use of textured surfaces, at present do not result in maintenance-free Drilling ducts for reinforcement and specification. particularly exposed aggregate types, is partly surfaces. Yet despite this, and despite the fact through foundations designed to disperse the water flow and so that the detailing principles required to limit (Photo: copyright Water flow on surfaces give uniform colour change The trouble is staining are widely known, designers often Shepherd Building Group) 20 talk as if they believe concrete to be a material In considering the effects of water flow on the that this degree of texture is often not enough. changing appearance of concrete surfaces. A more extreme texturing is currently very inspections of samples of all components popular. This is deep ribbing, either with or 4 green stains from copper, flashings, permanently wet. but this, of course, can be Fig. 2 throughout the production period. Some without broken tips. Although it has been in bronze fixing devices, bronze sculptures an advantage. Once again the life expectancy North west pier. initial tests were done on the strength of the use for a relatively short time only, the results 5 black bituminous stains from badly made of the materials is variable, and depends to Foundation layout assembled rods, couplers and anchorages to are looking quite good. roof trim details, from accidental spillage some extent on how complete a seal is ensure that the strength of the individual Of course, the traditional technique of of waterproofing compounds on site, obtained in the first instance. The existence of items was fully realized in the assembly. dispersing water down a facade by using from bleeding of material from joint pinholes through the coating can allow water cornices, is still valid today. Current ideas for to penetrate and blistering may occur later. Drilling fillers of the impregnated fibre or cork the design of buildings usually do not accept types One trouble is that with rough concrete Right from the outset it was obvious that the this particular trick, but it has to be recognized surfaces it is difficult to obtain a complete film. 6 stains from spillage of structural jointing success of the whole foundation proposal as a valid weapon in the architects' efforts to It is interesting to reflect on the fact that when materials such as epoxy or polyester depended on the drilling operation. The drill control weathering. By throwing the water off concrete is painted, the necessity for main• resins, or from more mundane materials Existing Norman walls and footing Prestressed shots varied in length from 6.4 m (21 ft.) to the facade, one does not remove it from the tenance is generally accepted. When clear such as grout concrete 16 m (50 ft.) through 11th century masonry building. However, the wind tends to spread it treatments are applied they are expected to be foundations of doubtful quality. Although the contractor out on the surface below, so that uniformity 7 oily staining from the bleeding of con• maintenance-free. Yet it is more difficult to had had wide experience in rock drilling, no of weathering is obtained. This principle stituents of poor mastics and sealants develop a durable clear varnish than one one had any knowledge of the problems of should be used much more than it is at present. into the pores of the concrete containing pigments. accurate drilling through this type of material. Another detail currently in use for controlling 8 oil and grease stains from site plant, The whole problem centred on obtaining the weathering, is to collect the water in channels particularly cranes The use of applied surface finishes does required drilling accuracy, which was deter• enable the weathering of concrete to be at every level and pipe it away. Cost considera• 9 dirty smears around windows caused by mined by the alternate layers of rods being controlled in another way (i.e. other than by tions usually dictate against complete plumb• careless window cleaning under difficult only 230 mm (9 in.) apart vertically. the careful detailing approach outlined above). ing of facades, but some buildings have been conditions It must be recognized that when they are / An accuracy of 25 mm (1 in.) off line in the erected in which the water is piped through 10 miscellaneous stains caused by inter• concrete cladding panels and discharged into used, a maintenance cost will be incurred (or above length of shot is easily achieved when action between the surface and vandals, their effectiveness will diminish) and this must drilling in a homogeneous medium such as open-drained joints. The water is most sprayed paint being the current favourite frequently collected below the windows so be examined in the light of other claims on HMl Pier solid rock or good concrete, but this is not so 11 mould growth resulting from interaction that dirt settling on the glass is not transferred resources. in ancient masonry. Some preliminary drill with the environment in general shots carried out before concreting had begun to the concrete below Obviously the deliber• Quality control 12 finally, deposition of salts on the surface were encouraging, indicating accuracies of the ate channelling of water into joints puts a Some of the construction problems involved due to numerous possible interactions, order of 25 mm (1 in.) in a length of 6 or 7 m greater strain on the waterproofing system, in the use of exposed concrete have been with adjacent brickwork, cracks within \ (19 ft. 6 in. or 23 ft.). Also, during work and if it is less than perfect the leakage can be mentioned above under staining. There are the concrete itself, cracks within adjacent already completed on the superstructure, 46 spectacular. Other problems arise from many others. The main one to be discussed concrete, proximity to areas treated with drill shots about 20 m (67 ft.) long had been blockage of the plastic drainage tubes in the here is quality control. concrete panels. This detail is probably quite de-icing salts, and contact with the put through the walls of the 15th century The requirements for quality of a concrete unsuitable for use on a building near trees, ground central tower. These had indicated that surface are difficult to specify. Yet. unless the unless regular rodding out is done when the The list is depressingly long and contains a sufficient accuracy could be obtained provided attributes considered to be important by the windows are cleaned. If blockages are not mixture of problems arising during construc• all voids in the masonry were well grouted. architect are clearly described, the contractor removed, severe damage due to the freezing tion, and problems arising subsequently. will have some difficulty knowing just what The drilling in the superstructure was carried of trapped water could result. With many of the very expensive concrete is wanted. These attributes may include NAVE out with a rotary-percussive tungsten-tipped The overall staining of a concrete panel may surfaces being used today, elaborate protec• freedom from blowholes, sharp arrises, low pneumatic drill rigidly mounted on a special also be influenced by the type of jointing tion procedures have to be employed. Most permeability of surfaces, a particular texture cradle. Unfortunately, when work really started between panels, regardless of whether the of the long-term stains can be avoided at the and uniformity of texture, certain dimensional on the foundation drilling, this drill proved to water is drained into the joints or not. With design and specification stage. However, tolerances, the absence of crazing or cracks, be too inaccurate, at least under the NW pier. filled joints the water is kept on the surface, their avoidance requires a degree of attention and uniformity of colour both within one unit The two chief factors contributing to this were but with open drained types it is allowed in to detail that it is often not possible to give. and between one and another. In some cases firstly, the poor mortar in the 11th century and then expelled Current detailing of these There will be many more examples of staining sub-contracts for the supply of precast masonry due to a very low lime content, and joints encourages the water to flow forward like those green concrete roof edge beams at concrete cladding are let on extremely T secondly, the presence of a grid of large oak to the face by means of 'wash-boarding' Churchill College, Cambridge. minimal documents. At worst these consist of S baulks used by the Norman masons to rein• grooves and by turning the bottom of each drawings showing the units required and a force their footings. Both these factors baffle strip forward. The effect of discharging Applied finishes general statement of the type of concrete detracted from the homogeneity of the the water in this way is to encourage differen• The search for an invisible surface sealant (i.e. exposed 19 mm (% in.) Cornish granite masonry. The attempt to solidify the masonry tial weathering between the edge of the that may be applied to concrete has sometimes aggregate with white cement matrix). After by preliminary grouting had not been as panel and the remainder. taken on the character of a search for the approval of a sample panel for appearance, beneficial as desired. The problem of differential water absorption philosopher's stone. Who will find the key casting commences. between panels and joint fillers (where these for transmuting the base absorbent concrete After many rather dismal weeks of attempts are of mortar) is well known and need only surface into a noble impermeable one, The difficulties of contractors in guessing with rotary-percussion drilling, the first be noted here for completeness. Jointing resistant to the ravages of time? Must we what standard of finish is expected obviously really consistent success was achieved using mortars are usually more permeable, thus forever use the controversial rejuvenation affects their pricing of tenders. They may a diamond-studded coring drill, with only i collecting more dirt than the surrounding drug procaine (i.e. silicone) to alleviate the often price for 'normal' fair-faced concrete rotary and no percussive action. While this concrete. symptoms of ageing, subjecting the subject only to find later that the architect's idea of system was being used to keep the job going (concrete surface) to regular courses of the this corresponds more to the contractors' 'high further experimentation was carried out with a material in order to maintain the efficiency of quality' category of finish. It is essential for different rotary-percussive technique, and Interactions with other materials the treatment ? designers to recognize that there are no / eventually a vole hammer drill proved to have Concrete surfaces are relatively sensitive to ^20-0 Silicones act by lining the pores of the con• absolute standards in this matter. Various about the same accuracy as the coring staining from contact with other materials. crete, altering their surface tensions and categories may be identified and compared machine in this material. This was a most The comparison is particularly marked when making them water-repellent rather than with one another, and in general the same important development as the overall speed they are compared to brick. The normal water-absorbent. The surface remains clean units will cost different amounts depending of the vole hammer was three or four times variation between individual bricks obscures because the dirt does not penetrate. The on the quality category. that of the corer and its overall operational many stains that may occur on a wall. How• 7 period of effectiveness of this treatment is The shortcomings of the cube test as a quality cost was corresponding much less. ever, this sensitivity is not so great that real N. W.Pier variable, but there do seem to have been control test for fair-faced concrete are widely difficulties are experienced in using the All the drilling equipment was supplied by some advances recently. Some materials recognized. Unfortunately visual observation material adjacent to others. It is merely Holman Brothers Ltd. and the very latest appear to work for only 3-5 years, while of the surface is also not enough. For good sufficient to require fairly careful attention to innovations in techniques were applied. At others are claiming lives of about 12 years. weathering on a well detailed building, a be paid to detailing. the time of going to press there was still much The period varies with the concrete being concrete surface of uniform (and usually low) drilling to be done and further improvements The list of materials causing staining on used, and with the environment. permeability is required. A technique has been 2 nd Pour may still be effected. concrete is quite long, even when the dis- Some other proprietary formulations are developed by the Research Committee of the colorations arising from interactions with available which claim to act in a similar way Cast Stone and Concrete Products Industry5 Acknowledgements i formwork and release agents are not con• to silicones, but have a longer life. Claims of which enables quality to be assessed by the The above works were executed for the Dean sidered. The following notes illustrate the this type are very difficult to evaluate owing initial surface water absorption. The rate at ;o-6 and Chapter of York Minster by the following : sources of the main problems, and serve to to a lack of accelerated tests. Their effective• which water penetrates the surface is emphasize further the necessity of seeing any ;-6" Architect: B. M. Feilden, Norwich. ness in the short-term may be checked, and measured, and compared both with other concrete surface within the context of the one should not be too surprised if some of readings on the same concrete and with Consulting Engineers: Ove Arup & Partners. overall building. these materials fail to perform at all. readings that have been obtained on a wide Contractor: Shepherd Construction Ltd. 1 brown rust stains from pyrites in aggre• The other main way of trying to modify the range of concrete surfaces. York. gates surface performance without completely The visual requirements are most usually obliterating the appearance is to use a clear 2 rust from scaffolding, starter bars, struc• controlled by the use of an agreed sample varnish. A few products are available based tural steel, badly treated bolts, tying wire panel. For large projects this usually consists The Carlton Centre and York Minster articles on methyl methacrylate. The idea with these of full size panels or assemblies of panels. left in shutters, misplaced reinforcement Fig. 3 I 1 are reproduced with the permission of the is to form a complete skin of varnish over the For smaller ones, a more limited specimen 3 rust stains from the soluble compounds North west pier Cement and Concrete Association and the surface, blocking all the pores in the process. will be used. Whatever the job, the sample in the early patina on cladding made from Foundation prestressing layout Concrete Society. They tend to make the surface appear should include all the features that the 21 weathering steels Norman walls (c. 1070 AD) were in turn (1 25 lbf./in.2). The resulting stress regime can (1% in.) rods used on site. The rods were This series of photographs has been supported by strip footings, the tops of which be considered as one of 'partial prestressing'. continuously threaded which maximized their selected to illustrate some of the points made were about 2 m (6 ft. 6 in.) below the present In order to provide prestressing ducts through bond characteristics. in the article. It is deliberately biased floor. The Norman footings were either 4 m the foundations, it was necessary to drill An initial prestress of 540 N/mm2 (35 tonsf./ towards defects and failures in order to (1 2.5 ft.) or 6.5 m (21 ft.) wide, and were about 75 mm (3 in.) diameter holes through the in.2) was used. Prestress losses proved emphasise the point that it is possible to 2 m (6 ft. 6 in.) thick, apparently having been ancient masonry. The following is a simplified negligible on bars which were restressed learn from experience. It is extremely rare to well founded on the virgin clay or on the very summary of the construction procedure : several weeks after installation which is find the seamier side of weathering deeply founded Roman footings. Each of the probably not surprising considering the discussed openly and illustrated in this way. 1 the first pour of concrete was cast including four corners of the tower was treated separately comparatively low levels of stress in the rods Most buildings only get into print when steel duct-tubes on the drilling side but similarly, so it will be convenient in the in the foundation. Nevertheless it would they are new and unweathered. following discussion to refer mainly to the NW 2 the upper concrete collar was cast and the appear that the relaxation properties of this pier. It was desired to make the effective whole masonry footing was pressure-grouted Unfortunately black and white photographs stainless steel were favourable for prestressing foundation area about twice what it had been in an attempt to fill any voids and cracks do not show all the subtleties of concrete purposes, but unfortunately no laboratory as well as to stabilize the cracked areas. As the As the new areas of concrete footing initially weathering as changes of colour are figures were available for relaxation at any main pier load was extremely high, and as the supported only their own weight, it was important. stress levels. masonry was in a rather delicate condition, it necessary to induce artificially their full load Couplers was necessary to find a method of strengthen• capacity. For this purpose 'compression pads' Fig. 1 ing which would incur the least disturbance were cast below the main foundations. After The maximum length of rod that could be Uniformity of weathering is achieved to the existing footings. horizontal prestressing of the whole founda• readily manufactured was 5.5 m (18 ft.), and through uniform exposure and uniform tion, the flat-jacks between the compression in certain places on site it was necessary to use absorbency of surface. The in situ board- After studying various strengthening schemes, pads and the main foundation will be inflated, shorter rods because of limited clearance for marked concrete is contrasted with the it was finally decided to encase the Norman thereby vertically stressing the new founda• insertion into the ducts. Purpose-made precast exposed aggregate panels. The light footings in concrete, incorporating the NW tion-bearing area; this second post-stressing couplers were used to join the rod. tapers streak is due to the cleansing effect of a pier and the adjacent nave and transept action transfers the desired amount of load being provided to facilitate threading the water discharge. The colour of the wider columns on one huge footing about 14.5 m from the existing masonry to the new footings. coupled rods through the masonry which was cylinder has changed from grey to (48 ft.) square. This would utilize all the (At the time of writing this process had not subject to partial blockage with chips yellow-brown as the cement has been cracked masonry footings as well as providing been carried out) loosened by the drilling. The couplers were leached away exposing the sand. (About some completely new areas of footing in 44 mm (1% in.) diameter and were made of seven years) concrete. The total effect would be to spread the same steel as the rods. Materials and techniques the load from the columns over a much larger Anchorages Fig. 2 Prestressing tendons area of clay. The new average bearing pressure The rods were anchored with a nut and an White in situ board-marked concrete fares 2 on the clay would be about 290 kN/m Because the whole strengthening work anchorage plate which were made of FV520B no better in city atmospheres. (About 2 (2.7 tonsf./ft. ) improving the safety factor clearly had to be a once-for-all conservation eight years) and AISI 304 stainless steel respectively. The against shear failure in the clay from about operation with a life expectancy of hundreds rods and nuts had UNS threads, and the nut 1.3 to 2.5. of years, it was decided to make the prestress• Fig. 3 was the heavy duty size All the above ing hardware of stainless steel. The rods were This is another example of the superior stainless steel items were fabricated by The new concrete and the ancient masonry made from a high-strength alloy manufactured Frederick Mountford (Birmingham) Ltd. weathering of precast exposed aggregate were unified by prestressing them together. by Firth-Vickers Stainless Steels Ltd. and Jacking panels. (About three years) There are four layers of main prestressing rods, designated FV520B. It was a precipitation- two layers in each orthogonal direction hardened stainless steel which had been over- The rods were stressed using a Macalloy Fig. 4 passing right under the main pier, thus pro• aged in a temperature of 550°C (1022°F) for Mark 10 jack with a modified attachment to One technique for overcoming this viding the tensile reinforcement necessary in two hours, a guaranteed minimum 0.1% suit the UNS cut thread. The jack was very problem is to paint the in situ concrete with the bottom of this large spread footing. This proof stress of 800 N/mm2 (52 tonsf./in 2) was reliable and simple to use. concrete coloured paint. Of course, this main part of the new foundation is 2.1 m agreed for this project. The ultimate strength Laboratory tests looks unsightly when it begins to break 2 2 (7 ft.) deep with an average compression due averaged over 920 N/mm (60 tonsf./in. ). An independent authority was commissioned down. Note the mould growth on the 2 to the prestress of only 0.86 N/mm These properties were achieved for the 32 mm to carry out strength tests and tolerance plinth where the detailing provides a water trap. (About four years)

Fig. 5 With older concrete the quality may be such that the erosion of the surface through acidic rainwater attack may outpace dirt deposition. The surface is self cleansing, but the appearance is still not satisfactory. (About eight years)

Fig. 6 The black and white photograph does not \ZA Norman foundations adequately show that the retaining wall and Norman walling bridge have turned green with mould, whilst the wall of the building has turned brown due to exposure of the sand. The difference o o is attributable to the moisture content difference between walls of heated and Th% Present M/nst+r I unheated spaces. (About forty years) ri n n n n n _n n n n Fig. 7 Prestnt NW. Pier Smooth white permeable concrete weathers so badly in cities, that the appearance may be disfigured before the building is o o 17 finished. (New) IE

Fig. 8 I Own It is nearly impossible to patch concrete in I such a way that the patch weathers uniformly with the rest of the concrete. The roof edge concrete is turning green with mould. Note also the tell-tale signs of Fig.3 f rs reinforcement corrosion on one transom. (About seven years) u u U—u—u—u—u—u 5

! 5 o Ur u ^ to K> 20 JO m

Fig. 1 Norman foundations in central tower area The grid was cast on to grid piles and installed architect considers relevant to the quality of Cracks present an even more intractable factory nature of this situation will be when the excavated level was about 9 m the particular surfaces. It is surprising that problem and, until the day arrives when non- apparent to all designers and clients. (30 ft.) below ground. this procedure is not used more often for in shrinking cements are available and widely The question of defects in exposed concrete After completion of the grid, precast props situ concrete work, where quality finishes used, this problem will loom large in all work is very depressing. Once a defect is were erected against the perimeter piles on the are sometimes more difficult to achieve. With concrete jobs. In situ concrete usually gives there, it is nearly impossible to restore the two deeper sides, while the bracing on the any work there is an initial learning phase more trouble than precast work, due to the concrete to what was originally intended. A other two sides was achieved by casting the ft while difficulties are ironed out and opera• sizes of continuous concrete members substandard product is obtained. This really grid directly against the piles. Before pro• tives become familiar with the procedures. involved and the way they are restrained. is a subject in which the cliche 'preservation ceeding with further excavation, the grid was How often has this learning taken place at Cracks from thermal movements or structural is better than cure' applies entirely. prestressed and external forces were applied low levels in the building (for example the deflections will always be a problem. main entrance area) where appearance was through jacks placed between the props and The question 'How can I fill this crack?' Conclusions most important? By the time the roof is normally receives the answer 'Why do you the grid. The discussion in this paper has ranged quite reached the quality is approaching what the want to fill it?' as the answer to this condi• The bracing grid represents an unusual usage widely over design, construction and main• architect wanted. tions the repair method to be used. The few of prestressed concrete in that the majority of tenance problems with concrete surfaces. reasons why cracks may have to be sealed the axial load was applied by external jacking With in situ concrete work there is usually a Mention has been made of the vast store of are as follows: forces. The grid was analysed under the clerk of works around to keep an eye on information standing around us, in the form anticipated loading conditions from earth things, if not a resident engineer. If the 1 to obscure them of examples of different degrees of weather• pressure together with unbalanced loading former understands the problems of making ing on a wide range of concrete surfaces, good fair-faced concrete, so much the better. 2 to prevent them becoming visually exag• applied over short lengths of the perimeter, in i i gerated by weathering detailed in a variety of ways. It is tempting to order to check the sensitivity of the design to With precast work, this continuous super• think that this source can be easily tapped and 3 to prevent water penetration into a building abnormal conditions. & vision is lacking. The product is presented to the information used in future designs. In the designer for acceptance. Visual checks are 4 to prevent water leaching lime out, giving The stress conditions in the grid were complex reality this will be very difficult to achieve. made and the unit incorporated in the build• white deposits and longitudinal cables were added in order to The most effective feed-back procedure is for ing. Concealed defects like badly positioned 5 to prevent corrosion of reinforcement each architect to use his eyes and learn for control peak stresses in the members and to —- reinforcement only become apparent later to increase the ultimate load strength of the grid. 6 to restore structural continuity himself He must then develop a recall system the consternation of all concerned. Cover in his mind so that his observations may be Prestressing was also applied transversely in Four main types of repair may be con• meter checks on precast concrete units should used in his design thinking. Too often, the order to resist the bending from vertical loads be a matter of routine, even if they are only templated : as well as to increase the factor of safety 11 observations are made, but not recalled when done on a sample of say 25% of the total. i cut a chase along line and fill with flexible it comes to a design problem. against beam shear failure. The grid was F or rigid sealant On a more formal basis, there is a need for a designed to be used as part of the con• Rectification of defects struction access roadway to the site and was ii rub cement + polymer emulsion into sur• new text book, probably backed by C & CA also used for the majority of storage areas and One of the most depressing things about fair- face and the Concrete Society, covering the faced concrete work is the difficulty of making principles of design to achieve various site offices. An important advantage of the in trickle in polymer or latex emulsion sealers repairs that will both look the same initially effects and including many examples of design was the easy access for maintenance Fig. 2 iv pump in epoxy or polyester resin sealer and will weather the same It is certainly actual buildings. Of course, one problem and adjustment of the jacks. Artist's impression of the completed Carlton Centre Before doing any of these things, it is neces• easier to do the former than the latter, but that bedevils this kind of work is that the The grid was prestressed using 26 mm (1 in.) sary to be reasonably sure why the cracks even so. the result is often disappointing to newsworthy items are those where some• Dyckerhoff rods and, in general, unbonded have formed, and to decide whether they are all concerned. The main types of defects are thing has gone wrong, but the architects cables were used to permit easy removal prior Hydraulic oil was used as the pressure likely to continue moving. If they will move, steel for a number of reasons. Although cracks (from whatever cause), damaged or responsible are understandably reluctant to to demolition of the grid. the only procedure is (i) using a flexible filler, medium in the jacks. The forces in the jacks demolition would have been easier with steel, honeycombed arrises and corners, and mis• have their design mistakes highlighted. prestressed concrete was markedly more and accept the damage to the appearance. The design horizontal earth loads on the together with the change in thermal condi• placed reinforcement. Perhaps seminars of this type will help to 2 tions of the grid were monitored regularly and economic, and in addition, the forming of the If structural continuity is required, method (iv) grids were of the order of 4300 kN/m With corners and arrises, the main problem change their attitudes. 2 the jacks adjusted to suit changing conditions. connections in steel with the very large loads should be used, provided that checks are (40 tons/ft. ). The axial loads in the members with making good is to ensure that the patch The jacks were loaded to % of the full design involved would have created difficult engineer• made to ensure that the properties of the were very large and gave rise to elastic sticks and remains sticking indefinitely. The load and increased to nearly full design load in ing problems. material really will give what is required, and References deformations of approximately 100 mm trouble is that the materials that stick well those areas where the ground movements that the degree of filling likely to be achieved (4 in.) across the site. Similar movements of Although the grid represented a major (e.g. resins) weather in a quite different 1 STONE, P. A. The economics of main• approached certain danger marks. (often quite low) will be enough. Obscuring the order of approximately 50 mm (2 in.) were engineering structure, its total cost, including manner from the surrounding concrete due tenance. Conference report on main• Stability of the basement in its final condition the cracks can be done by method (ii), but the anticipated from temperature effects. In order demolition, was no more than 1 V?% of the to their different absorption characteristics tenance of buildings. MPBW, 1965. durability of the filling is questionable as very to control movements of the supported earth was provided by the permanent floor slabs of total cost of the complex, and the saving in and occasionally problems of colour stability. 2 STONE. P. A. Building design evaluation: little penetration is obtained. It would easily face. 400 kN (400 ton) Freyssinet flat jacks the building. As these slabs were constructed, contract time afforded by the use of this With some concrete finishes it is difficult to costs-in-use. Spon. 1967. were built into the seatings of the inclined the load in the grid was adjusted to transfer the temporary prestressed structure fully justified fall out if movement occurred. If it is going match the appearance in a patch. This is 3 WHITE, R. B. The changing appearance precast props against the grid. Similarly, jacks loads to the permanent structure. After com• this cost. to stay in it must have similar weathering particularly true with exposed aggregate or of buildings HMSO. 1967. were placed against each pile on the other pletion of the slabs, the grid was demolished Skidmore, Owings 6- Merrill and Rhodes- tooled finishes. characteristics to the surrounding concrete. 4 PARTRIDGE. J. The weathering of St. two sides of the site, and, by placing a number with the help of explosives. Harrison, Hoffe 6- Partners are the architects Misplaced reinforcement presents a different Polymer or latex emulsion sealers have been Anne's College. Oxford. (In: Concrete of jacks in series, it was possible to allow for a Prestressed concrete was chosen for this and the contractors are Murray & Roberts type of problem. It may be misplaced from quite widely used for trickling into cracks. Quarterly No. 82. pp. 20-25. July-Sept. maximum movement of 150 mm (6 in.). temporary grid in preference to structural Holdings Ltd. the position shown on the drawing; but still They are sold as flexible crack sealers. Figures 1969) are not available for their success rate, but it be 20-25 mm (% in.-1 in.) below the surface. 5 LEVITT, M. An assessment of the durability is probably very low. Much of the trouble The question arises in precast concrete work of concrete by the initial surface absorb- comes from their use in cracks subject to as to whether the unit should be rejected, tion test RILEM. Symposium on durability movement, but with an extension/compres• have one section broken out and recast or be of concrete. Vol. 1, Academia. Prague, deformation of the superstructure. The basic After a good deal of investigation, including accepted without modification. The latter sion capability of less than 10%. very small 1 969. The use of trouble was that the area of the foundations extensive exploratory excavation, it was alternative may depend upon the contractural absolute movements at cracks are required was too small for the stratum of clay imme• discovered that the effective area of the relationships, on the quality of the concrete to fail them. prestressing in diately underlying the building which had footings was such that the factor of safety in the region of the defective cover to rein• Defects that only appear after a time can be lead to excessive differential settlements and against shear failure in the clay was possibly forcement and on the exposure conditions foundation rotations. as low as 1.3. Also the masonry below floor very troublesome for a different reason. On once the unit is on the building. It is rare to one job in London some 3000 similar There were three principal zones of damage : level was found to be badly deformed in accept recasting of parts of precast concrete strengthening at bending and cracked in shear. The main cladding units were installed. . After three 1 the central tower area units, as this presents great difficulties with years, four of them failed due to corrosion of problem was to strengthen the foundations of the types of sections normally involved. With York Minster 2 the western towers the four main piers supporting the central reinforcement. This was traced to excessive in situ work, the larger members often enable calcium chloride coupled with very per• 3 the east end tower. A number of different strengthening breaking out. re-positioning the steel by schemes was studied, the one finally chosen meable concrete. The problem was how At the east end. the whole of the east wall was bending, and recasting to be done. Obviously having prestressing as its essential element. many other units would show defects in time. David Dowrick slowly but surely rotating outwards due to it depends on the amount involved. The problem of the western towers was A number of samples were taken from two yielding of the clay under the toe of the In cases where the position of steel only similar to that for the central tower founda• areas of the building and analysed for chloride. footing. The structural solution was to replace varies slightly from where it should be. the tions, and required a similar if simpler solution The two areas showed differentcharacteristics. Summary the existing foundation with a new concrete question is frequently asked. 'Is there any• suggesting variability in batches of units. to that used for the central tower. Only the thing with which I can coat the surface to York Minster is one of England's great mediae• one twice the size, but, as no prestressing was They also showed that the chances of having latter will be considered in the following make good the deficiency?'. As will be val cathedrals. It is about 1 58 m (51 5 ft.) long used, this will not be further discussed in the further defective units were fairly high, but discussion. apparent from the section on surface finishes, and 75 m (245 ft.) wide across the transepts. present paper. that the total number of these would not be this magic substance is not yet available. In Its present superstructure was built between In the central tower area, however, the The central tower foundation scheme all that large. Of course, the actual units that certain cases, where the cover has been only 1225 AD and 1472 AD. and it stands on the greatest danger was not from continuing The great weight of the central tower is will give trouble can only be found by 10-1 5 mm (% in.-% in.) the concrete over the site of former Roman buildings which were foundation movement. The cracking of the carried mostly by the four main piers, each of sampling every unit. The client is therefore bars has been removed and replaced by an followed by a series of Saxon and Norman superstructure had been caused by differential which carries a vertical load of about faced with the fact that he has a building on impermeable resin mortar. This procedure is churches. At the time of writing the Minster settlement of the tower with respect to the 38.500 kN (3.850 tons) at floor level, while which he knows he probably has a small alright for concealed concrete or concrete was undergoing extensive restoration to a adjacent structure, but little further settlement the smaller columns adjacent carry about proportion of defective units, but that to find that is to be painted, but it has serious short• total expected cost of about £2 m. A large part was likely. Thus although some superstructural 3,000 kN (300 tons) each. Exploratory these before they actually fail will be very comings for exposed fair-faced concrete for of this expenditure is due to underpinning and control of the cracks was necessary, the excavations revealed that the columns were costly. All he can do is to institute a regular the same reasons as given for patching strengthening of the existing foundations, the cracking was important largely in that it pro• built on the remnants of the walls of the (annual) inspection procedure and wait for corners with this type of material. inadequacy of which had caused substantial voked a study of the foundations. previous Romanesque-style Minster. These them to show up. The exceedingly unsatis• British Consultants Bureau. Roger Kemp is to could have been made of the opportunities Prague was a beautiful venue for an inter• be congratulated for his organization of the offered by the site to create a striking modern national congress, but also a sad one. The Beecham display of ourwork which included Gateshead bridge in a city which once knew how to build people speak surprisingly openly about their Viaduct, Sydney Opera House, Standard beautifully. One point of technical interest, political troubles, and no-one likes the Research Bank, Glasgow Airport and Lusaka Aircraft however, was the use of its cross-section intervention of a foreign power in the manage• Dry pack under Concrete stitch Column above truss Hangers among other jobs. which was of the single box girder type. The ment of their affairs. Ken, Duncan, and I had Laboratories: deck is to be used for road traffic while under• the pleasure of visiting the most hospitable 2N*r H Continuity rods at eoch Insltu slab to rails Technical visits ground trains will run inside the box. families of two of our London colleagues and an exercise support threaded under links cast after erection Levelling bolts nuts S. of cladding bearing washers Arrangements had been made with the Czechs of helping, we hope, in some way to span the in simplicity for visits to various building sites around Social events gap that divides them. Prague, most involving prestressed concrete. Thanks are due to the FIP committee who 2'Woodwool Some of us chose a trip which took us to a managed to arrange an evening of free Alan Hart Sealing strip warehouse and a bridge. The former was a entertainment for delegates who could choose Conclusion very large storehouse for motor vehicle spare between the State Opera at the National Although the very poor translation service was parts just out of Prague. The superstructure Concrete f Theatre, the Czech Philharmonic at the disappointing and diminished what we could slilctl At llilch. was entirely precast, including columns, Smetana Concert Hall and the Symphony get out of the Congress, there nevertheless prestressed trusses and roof slabs, while the Orchestra of Czech Radio at the Dvorak Hall. was much that was stimulating, technically walls were clad with Siporex slabs made Those of us who went to hear the Philhar• and otherwise. We all have many more friends Introduction locally under licence. monic playing Dvorak voted it a superb in the industry, and the proceedings, when Set in the Surrey countryside, facing the Dry pock Grouting to be D completed before asbestos shim Although the roof trusses incorporated some performance. published, will be a useful document. southern slopes of Box Hill, near Dorking, is concrete stitch Asbestos shim nice design ideas, their construction left much Another evening we went to see the Magic Finally I would suggest that, as well as the Brockham Park, a large country mansion Sxf to be desired, the members varying wildly in Lantern which has to be seen to be believed— papers we presented, other Arup work was acquired shortly after the last war by the thickness and the reinforcement cage often an extremely imaginative combination of worth recording at the Congress in some way. Beecham Group. Installed in this idyllic setting bereft of any cover. One can only presume films, puppets and live actors. Then on Friday James Sutherland actually had difficulty get• are research scientists regarded somewhat that the present political troubles have night all delegates and wives attended a ting enough material for his summary of warily by local residents in the fear that a new Celng panels affected the morale and incentive of the men slap-up reception at the beautiful Cernin British prestressed concrete developments. An Frankenstein is being created. on mortar producing these goods. Palace (of Maseryk suicide fame). Oldrich example of valuable experience which has not been properly published is John Nutt's It was here, in an area where one would We then visited the Nusle bridge, a major Cernik was our official host but didn't appear account of grouting difficulties on Sydney expect to see thatching straw rather than construction of several large spans across a for reasons which have since become clear. Opera House roof. Who else is sitting on Siporex planks, that a new research laboratory deep valley in Prague. The bridge was of As an ally of Dubcek he has been obliged to Dowel bars between knowledge worth sharing ? was required. The actual position in the merlocking loops orthodox style and one felt that a lot more relinquish his post. grounds was originally the stables and an old walled garden. More recently the stables have housed the scientists and their complex equipment. The contract for the new labora• tories is worth approximately £1 m, of which In order to control the deterioration of the give rise to appreciable movements and one third represents the cost of the structure. The earth face and to allow for a simple propping provision must be made to absorb these Originally planned as a phased operation procedure, 1.1 m (3 ft. 6 in.) diameter cast-in movements. allowing rehousing of the scientists as the Carlton Centre situ piles were installed at approximately 2.3 m In addition, the problems associated with project proceeded, the building work went (7 ft. 6 in.) centres along the perimeter of the constructing a building around a maze of ahead in one phase and temporary accommo• site. These piles were, in general, carried down supporting props are very real. The design, dation was provided by the erection of below the lowest basement level. Later in the therefore, aimed at an open and relatively Portakabins. Ron Heydenrych contract, gunite arches were formed between simple bracing structure, but nevertheless The requirement was for a building of the piles to complete a continuous permanent having facilities for incorporating sophisti• approximately 5630 m2 (66.000 ft.2) provid• retaining wall. cated control devices. The Carlton Centre, which is situated in the ing office accommodation and heavily serviced The bending strength of the piles allowed bulk Becauseof the fall of theground. 6.1 m (20ft.). business district of Johannesburg, is one of laboratories. To minimize interference to the excavation to proceed without further prop• the piles of two sides required propping at the largest central city complexes in Africa. occupants, services had to be easily acces• ping to a depth of excavation against the piles two intermediate levels, but on the other two The development comprises a 50-storey office sible. of 10.7 m (35 ft ). This depth was the maxi• sides a single prop at approximately % height tower, a 600-bed hotel and 4.05 hectares mum clear height to which the piles could act was satisfactory. (10 acres) of shopping. Parking facilities are The structural concept as cantilever bulkheads. provided for 2,500 cars. In order to maintain The bracing structure took the form of a Working closely with the architect, William open areas at street level, the majority of the The 29.5 m (97 ft.) depth and extent of the temporary rectangular prestressed concrete Holford & Partners (Canterbury office), the shopping, parking and servicing facilities are excavation made conventional inclined or grid. While the principal structural behaviour project gradually evolved as a structure situated in a seven-level basement. The flying shores impractical, but an essential of the grid was as a compression ring it was similar in principle to that adopted by Arup basement extends over an area of 165 m requirement in all central city developments necessary to ensure full stability with un• Associates at Loughborough: a highly (540 ft.) by 1 38 m (450 ft.) with the general is the careful control of ground movements. balanced loading conditions and. for this modular structure of precast components. The level of the lowest basement varying between Normal elastic shortening and temperature reason, the additional struts across the site 1 tartan grid chosen was based on a module of E2 Jtitch 23.5 m (77 ft.) and 29.5 m (97 ft.) below the variations on any bracing structure of this size were added. 0.9 m (3 ft.) and 230 mm (9 in.) while the surrounding streets. The variation in depth main structural grid is 10.3 m x 10.3 m occurs because of a 6.1 m (20 ft.) cross-slope (33 ft. 9 in. x 33 ft. 9 in.). The building con• on the surrounding streets. Fig. 1 sists of two separate, two-storey blocks with The site geology comprises residual soils from The excavation for the Carlton Centre an intermediate link block. Although basically basement Fig. 1 deeply weathered strata of various igneous a two-storey building there are basements in (Photo: A. A. Gordon. Johannesburg) Typical first floor jointing details and metamorphic rocks. A feature of the each block housing plant and materials. To geology is the great variation in the con• reduce excavation to a minimum, a system of sistency of the materials. The greatest design shallow basements or undercrofts was hazard, however, was the extreme fissuring of developed with deep basements where the parent rock. Generally, the natural water required. The relative areas of deep basement where the geometry of the block dictated holes cast through to allow pipes to pass down table was about 12 m (40 ft.) below the are 10% in the larger block and 70% in the otherwise, each truss spans 10.3 m (33 ft. the re-entrant angles of the column. To carry surface. smaller block. All undercrofts are deep enough 9 in.) and carries the loads from precast the fascia, side and corner columns were cast to permit movement within them to check concrete deck panels on the top boom and with cantilever fins which support an L-sec- Studies of the economic viability of the pipe runs. The substructure is entirely of in precast concrete ceiling panels on the bottom tion precast concrete waling beam, spanning project indicated that the earliest possible situ reinforced concrete. The structure sup• boom. At first floor level the depth of the 10.3 m (33 ft. 9 in.). The fascia of each block start on construction was vital. Consequently, porting the ground floor deck is generally truss is 1.7 m (5 ft. 8 in.) and its weight is consists of ribbed precast concrete panels it was decided to proceed with a preliminary brick sleeper walls with reinforced concrete 6 tons. The depth reduces at roof level to 3.4 m (11 ft. 3 in.) long, weighing 3.5 tons, contract aimed at excavating and stabilizing beams over basement areas. In the South 1.4 m (4 ft. 6 in.) and the weight decreases with the aggregate exposed, and storey the basement. During the 12 months' Block, 2323 m2 (25,000 ft.2) columns are proportionally. Primary trusses generally span height, smoked glazing. At first floor level a contract period allowed for this work, the carried individually on pad footings, but in between columns and carry the loads from narrow balcony is provided and precast detailed design and documentation on the the North Block. 13.252 m2 (35,000 ft.2) two secondary trusses. concrete handrails are positioned in upstands main contract was completed. where columns are grouped, one footing The precast concrete columns are cruciform cast onto the fascia panels. Two problems existed in ensuring the safety serves each group. The sub-soil on the site section, 530 mm x 530 mm (1 ft. 9 in. x A coffered profile was chosen for deck and of the excavation; firstly, some form of is mainly fissured Weald Clay. 1 ft. 9 in.) overall, with a fair-faced finish. The ceiling panels which are approximately strutting was needed to control the deteriora• Since complete flexibility of structure was length of each column was determined by the 3.3 m x 3.3 m (11 ft. x 11 ft.) and weigh tion of the earth face and, secondly, a system required, an arrangement of precast concrete clear height required and the depth of truss 3.25 tons. Although the basic shape of each of props was required to control the overall primary trusses on the main structural grid supported, and each column weighs approxi• unit remained unchanged, corner details movement of the sides of the excavation. was adopted. The basic grid is sub-divided mately 2.5 tons. In order to carry the vertical varied and six basic shapes for each type of Before any work was carried out on the site, into areas 10.3 m x 3.4 m (33 ft. 9 in. x loading from the trusses, columns were cast panel emerged. By precasting we were able to the water table was lowered by means of a 11 ft. 3 in.) by secondary trusses. Except with cruciform shaped corbels. All corbels had anticipate the service engineer's requirements ring of well points surrounding the site. for holes by indicating on individual unit Member group reports International recommendations for the drawings the size and location of hole Pre-stressed design and construction of concrete Various countries presented group reports on required. From six basic shapes over 400 * 5 structures recent major works under the three headings variations were obtained! The 1.7 m (5 ft. concrete congress, Something of a landmark in engineering of Bridges, Buildings and Other Structures. 6 in.) deep void between ceiling and deck is affairs was witnessed with the presentation of The British report on bridges was delivered by easily accessible and the service engineer was Prague, June 1970 these recommendations jointly agreed by the D. Lee of Maunsell & Partners, and included presented with a large area with few con• Ey3L' CEB and FIP. This new document is a step the Western Avenue extension and the Calder straints. River bridge, but, I thought, was not very well forward on the 1966 draft recommendations, There is a second, less heavily serviced void illustrated. In fact, it was striking how much incorporating many amendments and addi• between the ceiling to the first floor and the more interesting the German and Italian bridge tions to the original text. roof. Access between floors is provided by an David Dowrick reports were than those of other countries. One important facet of the document is the oil-draulic lift in the South Block and stairs in J. Sutherland presented the British report on adoption of SI units and it struck me as still both blocks formed of in situ concrete spine buildings and. despite apologising for a lack rather strange to see Newtons rather than Kgf beams with precast terrazzo treads. In the link of material, gave an outstanding talk which in an international document. It is significant, block there is a spiral staircase, approximately incidentally mentioned several Arup jobs. Ron however, that concrete stresses are quoted in 2.4 m (7 ft. 9 in.) diameter, formed entirely of 2 2 Heydenrych presented the South African The 6th congress of the Federation Inter• N/cm rather than N/mm . allowing an easier precast terrazzo units. 2 group report on buildings which included ®— nationale de la Precontrainte was held in comparison with the European Kgf/cm . mention of our Standard Bank and Carlton • Prague and attracted 2300 delegates from at International co-operation is certainly not at Manufacture of components • Centre projects in Johannesburg. His des• ! least 49 countries including Kuwait and its best regarding what one might have hoped 1 cription of the latter follows this article. All the precast components were manufac• Monaco but excluding China. About 80 would be the simple, quantitative issue of tured at the Southampton works of Reema British delegates attended including Arupians units. It is apparent that confusion will reign Construction Ltd., who were also the L Individual technical contributions Povl Ahm, Duncan Michael. Ken Shaw. over this subject for many years to come. nominated sub-contractor for the erection. Keith Ranawake and myself. The Arup con• Another point of comparison with intended This FIP Congress saw the innovation of Units were transported to the site by road and, tingent was swelled by the presence of our British practice is the terminology for design technical contributions by individuals as with the exception of deck and ceiling panels, South African colleagues, Ron Heydenrych limit states. The CEB/FIP document prefers distinct from group and commission reports. no special arrangements had to be made. The M and Ian Scott who brought their wives, as did 'ultimate limit state' to 'limit state of local These were divided into English, German and dimensions of the latter were such that they K Povl Ahm and Keith Ranawake. Most of the damage'. I personally prefer the CEB/FIP French language sessions (without translation were classified as a wide load and required a British delegation stayed at the International terms, the word 'ultimate' being widely used services) which were held concurrently in the police escort for sections of the route The Hotel, a vast pile of a place, massive bureau• internationally, and 'serviceability' being more Technical University. Thusthese sessions were consequent delays on site were reduced cratic architecture with primitive plumbing on a pleasantly human scale in terms of both t meaningful than 'local damage'. The proposed towards the end of construction by stock• KEY PLAN and non-automatic lifts—all very Russian. Try British unified concrete code will take enough lecture hall and audience size, compared with piling units. the Park Hotel if you go to Prague. the impersonality of the vast Congress Hall. getting used to without such new terms as In order to accommodate the vast numbers- Despite the shortness of time allowed for the Few problems were encountered in casting well as all the other changes. the congress was held mainly in the Julius presentation of these papers, they generally the various units although the geometry of An interesting inclusion is the recommenda• Fig. 2 Fucik Hall with some smaller meetings in the proved interesting, covering a wide range of some was complex. To standardize the tions for dimensioning of punching shear First floor layout Technical University. The congress timetable subjects such as ground anchors and the pre• manufacture as much as possible, similar reinforcement in flat slabs. was very crowded, taking five and a half days stressing of cylindrical wine reservoirs with members in different trusses were made from 9 a.m. until 6 p.m. and included lectures, heated cables. One of the more valuable dimensionally the same. The trusses were Commission reports cast on their side on a steel palate which could reports, technical papers and some visits to papers dealt with a prestressed folded plate i local building sites. It is hoped that the Several FIP Commissions presented reports on hangar by S. Firnkas (USA). This roof has a be rotated to a vertical plane. The weight of following account will give a reasonable idea subjects ranging from fire resistance to pre- free span of 77 m (252 ft.) which is believed trusses was such that they had to be cast of the wide ranging nature of the material fabrication. Each commission has an inter• by its designers to be the longest free span outdoors and lifted from the mould by a presented. national membership and does much to draw folded plate ever constructed. It is certainly track-mounted tower crane. With two moulds tjEH experience from widely differing sources and the longest I have heard of. The vertical in operation the production was a continuous increase the chances of general acceptance of structural depth of the folded plates is 4.27 m process involving a 24-hour cycle. As the Lectures • the recommendations. (14 ft.) Of interest is the means of dealing with units were cast outdoors it was not possible to B. Gerwick (USA) opened the proceedings the considerable horizontal and vertical have a refined curing procedure, but it was with a fascinating if sometimes rather possible to withdraw the steel formers after 3 On durability movements in such a large roof, due to futuristic lecture on floating or submerged prestressing and gravity loads, shrinkage, only a few hours and to lift the finished truss This to me was one of the most significant structures in prestressed concrete, his subjects creep and temperature effects. The whole roof from the palate the day after casting. Only one reports as it brought an encouraging rebuttal ranging from ships to undersea oil tanks and sites on four spherical bearings situated on truss presented any problem—a primary truss to those doubting Thomases who keep pre• undersea nuclear power stations. With the flexible corner columns. Full data on pre• with a corbel, capable of carrying a secondary : I dicting that all our prestressed structures will latter two types of project the problems of dicted and final cambers was given. truss, on each face. In this case it was neces• have short lives due to insidious dangers such • controlling cracking must become onerous Three of the papers in the technical contribu• sary to leave out the concrete round the area Of as corrosion of tendons, creep, relaxation, etc. indeed on we poor designers, not to mention tions sessions were about Arup jobs. Duncan of the corbels and to form them when the truss A world-wide survey has been carried out the contractors. Michael presented one on the suspended had been lifted from the mould. With some which examined the state of 200,000 complex reinforcement details in the trusses, 33-9 11-3 33—9 11-3 33-9 Y. Guyon (France) discussed composite frame of the Standard Bank, Johannesburg, prestressed structures and has shown an steel fixing provided some problems during structures of steel and prestressed concrete, a and I presented two papers, one on the extremely low proportion of cases causing the first castings but as production proceeded combination of materials with which I was Sydney Opera House roof and the other on the 3 concern. Most of the damage was repairable it became possible to form the complete unfamiliar. He drew a number of examples new foundations of York Minster. It was and the maiority of reported accidents date reinforcement cage and position it in the from France and Belgium, and claimed that gratifying to hear Mr. Burr Bennett (USA) from the early days of prestressing techniques mould as a single unit. Due to a combination of some advantages could be found for the make very complimentary remarks about all and many of the causes are unlikely to be hot weather, a hot steel palate and warm system on certain projects. The idea apparently three of these projects during his summary of repeated owing to the advantages of concrete, it was found that the top boom of Fig. 3 is to combine the constructional advantages the technical contributions to the full congress experience. Certain types of high alumina the trusses was susceptible to cracking. To Typical cross sections E-E and F-F of North Block of steelwork and the stress advantages of on the final day. As no Arup paper on the York cement are banned, and the grouting of cable some extent this was controlled by adding prestressed concrete. When questioned on Minster works has been in print before, we ducts is fully discussed and recommendations extra reinforcement, but the problem was not economics, M. Guyon hedged his bets even are reproducing the Prague paper on page 6 made. considered critical. Lifting sockets were cast more than we usually do in engineering. of this issue. into the top boom above the penultimate Unfortunately M. Guyon spoke far too quickly mould. To obtain the desired appearance on were made before the architect chose a vertical members. and most of his message was lost. Report on seismic structures the underside, ceiling panels were cast in a sea-dredged gravel aggregate. The exhibition R. Baus lectured on fatigue and breakdown This report consists mainly of design recom• With the exception of those columns with fibre glass mould, whereas deck panels were The question of tolerances being so critical it of prestressed concrete and presented so much mendations prepared since the last congress A most impressive display of technical cantilevered fins, the casting of the cruciform cast in timber. To standardize panels in the was necessary for us to examine thoroughly detail that he completely failed to communi• and should be read in conjunction with the expertise was given in the Congress Exhibition section was quite straightforward. We had event of services being added or subtracted, all the moulds before the first units were cast. cate to such a huge audience, especially via existing FIP/CEB document Practical recom• on behalf of 29 organizations from France. assumed that the cantilever truss would be each ceiling panel had conduit cast in In this way a standard was set and the translators. The only reason I mention his mendations for the design and construction of Germany, Italy. Switzerland, the UK and quite separate but at the suggestion of the vertically at the rib intersections and each necessity to check individual components lecture is to make the point that speaking to a prestressed concrete structures. There are Czechoslavakia. Designers, contractors and manufacturer it was made integral with the deck panel had Uni-struts cast into the was eliminated. Occasional spot checks were large international audience requires a special some useful comments on ductility and the suppliers of prestressing steels and stressing columns to reduce erection times. Columns underside of the ribs. made by us to ensure uniformity. Although the approach and anyone intending to do so design of columns and connections. systems were represented. were cast on their sides in a steel mould. Lifting eyes were cast into the top side of the specification called for certain dimensional should consult a few past audience members It was most interesting to observe how the Those columns with a fin were cast with the units at the four corners and burnt off on site. tolerances, a proviso was added that in the first ! The report on prefabrication German stressing systems are generally fin flat and where two fins were required the Production of these units was fast since their event of units being outside these tolerances promoted by the bigger contractors, in con• second was added when the concrete had size meant that they could be cast indoors and they would be accepted if the tolerances were The rules are: This was discussed at some length and trast to the British systems which are supply gone off and it was possible to rotate the not cumulative or the efficiency of the mentioned the stressing together of precast the reinforcement in them was simple. 1 speak slowly (and fix) only. There would almost certainly column through 90°. The arrangement of structure was unimpaired. units, in particular Coventry Cathedral, Architecturally the fascia panels are one of the 2 use simple language as far as possible for be more prestressing done in this country if holes for lifting purposes was such as to Glasgow Airport, and the Sydney Opera more important components and it was these All the structural components were in your theme allow the column to be lifted vertically. 2 2 House in relation to the use of epoxy glued there was a similar technical commitment to units that required extensive post-casting 41.4 N/mm (6000 lb./in. ) concrete. Where Although the deck and ceiling panels were 3 any slides must be extremely clear and joints. Of interest were the splicing of long prestressing amongst our contractors. It is no treatment. They were cast face down in it was necessary to cast units outdoors it was basically similar with 150 mm (6 in.) wide varied with very few words which must be piles (over 30 m (100 ft.) long), and a new accident that PSC and CCL are being forced timber moulds with a ribbed fibreglass base. found more practical to use an independent ribs in two directions at 1.1 m (3 ft. 9 in ) printed as large as possible system of tolerance control developed in East into more and more site operations. After striking they were grit blasted and the ready-mixed concrete supplier than the centres, they were not cast from the same 4 avoid using complex equations Germany. Of interest to Arupians was the stand of the ribs knapped. Several preliminary castings factory's own mixing plant. the requirements and asbestos shims were functions vary, from those which are easily and the people actually using the buildings. familiar with the means of execution and used to carry all temporary loads. Asbestos defined but difficult to fulfil, for instance to They felt it as a duty to help in formulating the their cost. It is a fallacy to believe that more packs were prelevelled centrally in each slot build a bridge over a gorge, to others which are brief, a task which grew more and more com• accountancy and cost planning will in them• before the column was lifted into position. easy enough to fulfil if only we could manage plicated, and which demanded the expertise selves make building more efficient. These This eliminated the lengthy process of to define them. A teaching hospital, involving of architects and engineers. The field of obviously have their use but chopping some• adjusting the level of the column by crane several authorities and a large number of architecture was widened to include housing, thing off a design by lowering standards does and required only that the length of the doctors all with their different and often schools, hospitals—and gradually all struc• not create anything. For that you must go column remained constant. Each column was conflicting demands, and which moreover tures which clutter up our environment, for back to the drawing board and make a better r held in position with four push-pull props may very likely become obsolete before it is their architectural quality concerns us all. design. To get the right materials in the right enabling adjustment for verticality. place is what gets building costs down. 1 finished, owing to changing demands, At the same time engineering technology also belongs to the latter category. invaded the whole field of building and Design is creative accountancy. 1 By virtue of their size and weight, trusses I proved slow to erect. Asbestos shims 25 mm They must also all last well—that is, they must construction. In fact the realization of The future (1 in.) thick were placed on the front edge of be stable and able to withstand wear and tear architects' dreams depended on engineering To use our resources efficiently there are two the corbel receiving the truss. The four main by natural forces or imposed loads. But this knowledge. The whole way of building has kinds of question we have to make up our ! trusses on the grid were placed in position may be a simple or a very complicated matter changed—it will soon all be engineering. minds about: what to build, and how to build, and clamped to the column with ply side- —the latter a characteristic of daring needs and means, more or less! Of course The need for co-operation shutters and clamps. The next stage was to engineering structure. they are intertwined in various ways, for what This demands collaboration of architects and ensure that the trusses were square to one They should also all look well—they create we decide to build depends largely on what engineers, a topic which has been discussed I another and vertical. The narrow gap between our man-made environment which is of we can afford to build, and this depends 0 ad nauseam these last 30 or 40 years. the end of the truss and the face of the concern to us all. But again the emphasis again on the means available or employed. To begin with, the civil engineering consul• column was mortared up and the in situ varies widely—between, for instance, a So that those who decide what to build must tants, the heirs of Telford and Brunei, were concrete stitch made. Once the stitch had retaining wall and a cathedral. be advised by those who know how to build reluctant to enter the field of ordinary gone off, the two secondary trusses within And finally they should all cost as little as But I think this distinction can help us to throw the main frame were erected using the same possible, but again, the need for economy building—there wasn't much engineering in some light on the role of engineers and procedure. When the stitching had been varies. Economy is a matter of devising a it, it was fiddly, unremunerative work and they architects in building. were certainly not prepared to act as mere completed the frame was stable and a dry sensible way of building the structure, and How to build will more and more become a assistants to architects—they didn't think pack mortar (1 :1) was packed firmly around even the richest client doesn't want to spend matter of engineering, it will at least have to much of them anyhow. V2 the spigot at the foot of the column and under more than necessary. employ engineering methods and will need an * ,»•.•*. . ' the full area of the cruciform. Attempts to Roughly speaking engineering structures are The architects, on their side, naturally wanted attitude of mind mostly found among consolidate the dry pack with a Kango those which have an easily defined and to retain complete control over the design— engineers. That the designers must be hammer proved unsuccessful and packing undisputed function and which present you have to, when you are producing a thoroughly familiar with the means of con• was done by hand with a hammer and a piece structural problems of some intricacy, whereas masterpiece, you cannot tolerate interference struction and their cost has already been Fig. 4 of steel. A similar process was used for the those where aesthetic and functional prob• from people who know nothing about the mentioned—as I have said so often, designing North Block : layout of trusses below first floor level 25 mm (1 in.) gap between corbel and truss, lems dominate are classed as architecture. finer points of architectural composition—or means indicating a sensible way of building. (Photo: Beecham Research Laboratories) but in this case the operation was made easier Or we could say that the first are those where for that matter, from those who do. But a new The engineer, however, is used to working to by the position and nature of the gap. The dry a civil engineer is in charge and responsible proletariat in the form of structural engineers a definite brief. What he has to achieve is pack takes all vertical loads and the wet stitch grew up, somewhat more narrowly based than i for the design, whereas the second are fairly easily defined—to span a river, to store provides continuity and frame action. We designed by architects. civil engineers, but with a deeper knowledge of grain, etc. He is dealing with the art of / assumed that the asbestos packs carried none engineering structure, and willing to offer directing the Great Sources of Power in of the final vertical loads. The two professions their help under the architect's direction—the I i Nature for the use and convenience of man— 1 These two ways of classifying structure lead normal process of specialization. And many 1 Erection of ceiling panels was almost as swift but he does not give so much thought to to more or less the same result, and correspond other kinds of engineers and experts are as deck panels but more care was needed to whether it will in fact benefit man. He will to the difference in training and background coming into the picture. Buildings nowadays ensure that the finish on the underside was see to it that the thing functions well, last of the two professions. At least this was the are full of services and gadgets which account not damaged. The nominal 10 mm (% in.) gap well and costs little, provided somebody tells case before the drastic changes brought about for a greater and greater part of the total cost. between the panels and the bottom boom of him what the function is going to be. And the by the modern movement in architecture and All these changes have brought about a pretty the truss was mortared up and pointed, 'looks well' part is not always his strong suit. the technological advance since then. En• chaotic state of affairs. People, old habits, producing an air-tight seal. He has both feet on the ground, not given to gineers built bridges, railways, harbours, old ways of thinking, do not change so rapidly. dabbling in airy-fairy aesthetic notions, or so Before placing the first floor deck panels, dams, tunnels, factories—in fact all the utility There are powerful personal interests at stake. it is generally assumed. 1 lengths of reinforcement were slotted through structures called into being by the industrial New ways of building demand larger jobs to The modern architect, on the other hand, is the links projecting from the top boom of the revolution, whereas architects were con• be tackled by larger organizations, different endeavouring to design an environment for trusses and through the cruciform slot in the cerned exclusively with 'fine' buildings, with financial arrangements, collaboration of differ• people to live in and work in and enjoy—a very head of the column. Full continuity was Building as an art. an art which could trace ent departments not in the habit of speaking to different and very much more complex obtained when the gap between deck panels its origins back to antiquity. Ordinary houses each other, in fact a complete reorganization business—for we humans enjoy so many r. was concreted up. In the vicinity of the were at that time, and are still to some extent, of the whole building industry. At the moment different things. column heads the level of the in situ stitch the province of builders. Architecture was every possible combination of new and old was left 76 mm (3 in.) low to enable the next confined to mansions or important public methods and attitudes is in evidence. A house is a machine to live in—Corbusier's lift of columns to be placed. buildings and these were designed by archi• It would take far too long to sort out this dictum, which has loomed large in the public tects on quite different principles. The image of modern architects, has perhaps not As erection of the fascia was not structurally complicated situation now—and I am just as architect then had a client who knew, or always been rightly interpreted, as Joe I f important, this was erected last in the lost as anybody else anyhow. But one thing thought he knew, what he wanted, and a Chamberlin pointed out in his lecture to the sequence. The waling beams were positioned is obvious—what we build is always a whole, well-established tradition of buildings based RIBA in 1 969. The machine part is largely the Fig. 5 Fig. 6 on asbestos packs on the cantilever fins of the an entity—a building, a precinct, a town with on a few materials and supported by crafts• engineer's business—but to live in is not a Connection detail between corner column Typical connection detail prior to columns and a wet stitch and dry pack roads, etc.—and all these entities interact men who knew their job and were proud of it. simple matter. Man lives not by bread alone. and precast truss. Side shutters for concreting of truss completed their fixing. Projecting bolts on the and influence each other. If you split the He could therefore concentrate on creating Man needs life and company as well as calm in situ concrete stitch being fixed to cruciform section column waling beams enabled each fascia panel to be design of these entities amongst a number of architectural masterpieces according to the and privacy, he needs the sun and air and (Photo: Beecham Research Laboratories) (Photo: Beecham Research Laboratories) located in position. To prevent the panel specialist designers each acting more or less prevailing rules of the game. In fact the green plants and birds singing as well as the rotating outwards two adjustable props tied it independently, you won't get an entity, but a highlights of architectural achievement were excitement of the metropolis, he needs work back to the deck until an in situ stitch could be hotch-potch. There must be co-ordination, felt to lie in the past rather than in the future. and play and relaxation—he wants to be able made. Although an in situ balcony was integration, a proper assessment of priorities Engineers looked the other way. to drive his car anywhere—but he doesn't poured later the connection at each end of the based on the true interest of the community. It was in part the great engineering achieve• At the moment we are far from achieving this want his peace disturbed by other cars. And Erection procedure with a 38 mm (1% in.) thick floor screed, waling beam was designed to resist the full ments in the last century which triggered off a integration. We are just about drowning in his needs tend to grow faster than our means tolerances were reasonably liberal. Each overturning force imposed by the panels. Having established firmly the principle that change in architectural philosophy. The specialization. It is perhaps the biggest to satisfy them. Man is quite a problem. panel was bedded on 1.6 mm ( Via in.) thick the simpler the components, the quicker a The second phase, from first floor level to Bauhaus. the whole Modern Movement, problem we have to face. Architects have long been grappling with this shims of Hyload placed under all the rib project is completed, the erection of the two roof, was erected by the same method with accepted the new structural materials and the It means much more than the much discussed problem. It cannot be solved by computers seatings. To reduce any live feeling in the blocks has been incredibly swift. Had it not the exception that 610 mm (2 ft.) wide, technological advance with enthusiasm and collaboration of the design team. Design or technology—it is a question of sensitivity, panels, an in situ concrete stitch was made been for a recurrent fault in the tower crane, 1 50 mm (6 in.) Siporex planks span between dreamt about building a new and better decisions are taken by all sorts of authorities, of understanding the deeper needs of along the top of the supporting beam. Erec• erection would have been completed without trusses in place of deck panels. world. It partly misfired, for enthusiasm for the financiers, etc., outside the design team human nature. tion of these panels was dependent on their hitch. visual manifestations of technology was not proper. It means, for instance, that the Ministry availability on site, but as many as 40 were The main contractor, James Longley & Co. Amongst these experts the architects should enough to effect a radical change in architec• Basically the completed structure can be 2 2 of Transport must collaborate with local erected per day 41 8 m (4500 ft. ). Ltd., started work on site in May 1 969 and the play a decisive role, for it is their task to compared to a table standing on top of first precast components were placed in mid- tural thinking—the Modern Movement in planning authorities, that city architects must ensure the artistic quality, the character, the another table, i.e. the continuity at the foot The original complex detail for fixing precast September. The South Block was completed many cases amounted to no more than a new work hand in hand with city engineers and visual harmony of our environment. of the columns is negligible while the joint columns involved ducts cast in, projecting in 1 6 weeks including a 5-week delay due to style. But one radical change in outlook took extend the other hand to those who frame our For me, then, everything we build is architec• at the top produces complete continuity. So dowel bars and grouting up. The final detail crane breakdown. The North Block was com• place which changed the way we look at bye-laws and building regulations and to ture—different kinds of architecture, even much of the design load is dead weight that required simply a cruciform shaped spigot cast pleted by the beginning of May 1970 in 15 architecture today. Architects acquired a government on a local and national level. And when the structural problems dominate. An we were not too concerned with this concept. on the base of the column and a 76 mm weeks. These figures represent the time spent social conscience, they were no longer con• it means further that the gap between design engineering structure is not a good structure On completion of the substructure a thorough (3 in.) deep cruciform slot in the head of the on erection of the precast units only and do tent to cater for the whims of rich clients, they and execution which is such an ingrained if it is not also a pleasant thing to look at. dreamt of a better world where technology check was made of the compatibility of the column below. Prior to erection, tests were not include construction of basements, semi• feature of the building industry must be And a piece of architecture is not perfect if the could make everybody share in the good life. in situ work to accept the first precast made on the suitability of several materials for basements or stairs. The total length of bridged somehow. For the designer must be structure is second-rate, if the roof leaks and The client was therefore society as a whole. 26 elements. Since all deck panels are finished use as shims. It was found that asbestos met contract is for 21 months. the heating fails. Vol. 5 No. 3 September 1 970 Contents Conclusion Published by Ove Arup & Partners Consulting Engineers By close collaboration with the architect and Arup Associates Architects and Engineers the precast manufacturer, we set out to THEARUP 1 3 Fitzroy Street. London. W1 P 6BQ isolate as many problems as possible and solve them before erection on site began. In Editor: Peter Hoggett this way erection was controlled by produc• Art Editor: Desmond Wyeth MSIA tion. To ensure that components were avail• JOURNAL Editorial Assistant: David Brown able when required entailed a detailed study An engineer looks at architecture. 2 of the components, the erection technique by Ove Arup and not least, the time allowed. Had it been possible to produce only basic shapes for Prestressed concrete congress, 4 deck and ceiling panels the overall time for Prague. June 1 970, production and erection might have been by D. Dowrick significantly reduced but it would have meant additional, noisy work on site cutting holes. The Carlton Centre, 5 The short time for erection of the shell has by R. Heydenrych given finishing trades and service engineers a The use of prestressing 6 dry and spacious surrounding in which to foundation strengthening at work. York Minster, A rigorous cost analysis has shown that by D. Dowrick certain items proved uneconomic since they serve no primary function. One must realize St. Katharine Docks. 10 that the cost per item for erection, within by M. Tucker limits, is constant regardless of size of com• The changing face of concrete, 20 ponent. Brockham Park now has, in addition by T. O'Brien to its other amenities, a building that blends perfectly with its surroundings and that is a Beecham Research Laboratories : 24 Fig. 7 radical departure from the stables ! an exercise in simplicity, North Block during erection of the frame (Photo : Beecham Research Laboratories) by A. Hart Average cost of the precast frame superstructure per ft2. - Fig. 8 excluding fascia In situ concrete link block between North & South Blocks Item North Block South Block Fascia panels are precast as for the main blocks (Photo: Beecham Research Laboratories) Supply

Front cover: I warehouse, St.Katharine dock, seen from the new Dock House (Photo: Henk Snoek) 1) Trusses 14/1 12/6

Back cover: Cameo of Thomas Telford (Reproduced with the permission of Mrs. N. S. Telford) 2) Columns 2/6 3/2

3) Deck Panels 1/11 1/11 architecture from the many tangible proofs of engineering. Here there is steady progress in An engineer looks its existence encompass such acknowledged the achievement of engineering aims, and a 4) Ceiling 7/4 7/4 landmarks as Vitruvius's De Architectura. and very much greater agreement about what is 5) Siporex 3/1 * 3/1 * at architecture Norberg-Sciiulz's latter day Intentions in good and bad engineering. architecture, many less systematic but more What is the reason for this difference, and Erect Ove Arup impassioned pleadings by actual and would- how can it be maintained in view of the fact be architectural practitioners, and the weekly that there is no clear border line between 1) Trusses 3/6 4/2 outpourings of esoteric critics in architectural engineering and architectural structures. 2/4 journals whose claim to fame rests on their Whether you call a bridge architecture or 2) Columns 1/10 This paper was given at being incomprehensible, or so it appears to a engineering is optional—if we attach the Leicester University Arts Festival on 3) Deck Panels 2/6 2/6 mere engineer. normal vague meaning to these words it is 11 February, 1969 4) Ceiling 5/- 5/- What all these have in common is: both. And that in fact applies to all man-made structures—they are both structures—i.e. Introduction 1 that they are all different, if that isn't too 5) Siporex • • engineering structures and pieces of architec• The title for my talk is An engineer looks at Irish ture, in different proportions, if you like. ~;.' JZZv^ ' ZL ~7 •til ': * Total 29/5 29/8 architecture. The engineer is me, of course, and 2 that they deal almost exclusively with The question arises, can one separate the (excluding the only reason for bringing him into the title aesthetic considerations of order, balance, structural from the architectural part? Can a ceiling panels) is to indicate that I am only an engineer, and space, form, light and shade, textures—in structure be a bad engineering structure and cannot claim to be an expert on architectural short, the visual organization of the material, •Supply & Erect good architecture or vice versa? That is a theory, so what I say about architecture may and are less concerned with function or very important question, which I will return not meet with the approval of the pundits. But economy to later, when I have dealt with my first I have had a great deal of experience in helping 3 that although they may be a very valuable query. architects to design buildings and other aid to the understanding of different architec• structures, and I have tried my hand at the tural viewpoints, they are too vague to be a The reason for the difference between the latter myself, and it was always the intention guide to architectural creation. What I mean architectural and engineering 'climate', so to that the result should rank as architecture, is, you cannot look up in a book on architec• speak, is very complex. It is partly a matter of preferably good architecture. Unfortunately ture where to draw the next line on a drawing terminology, partly a matter of historical that doesn't mean that I can give you any board, as the engineer can if he has forgotten accident, and the consequent training of satisfactory or generally accepted definition the formula for analysing the strength of a architects and engineers, and mostly a matter of the term, and I doubt whether anybody else beam. Books and drawings may enable an of what is commonly supposed to be the can. I can only give you my own point of architect to produce a building in the Gothic difference in content or context—architecture view. or even Miesian style, but that is not nowadays being concerned with producing works of t'^Mlll II III' mi '^l A building can be a piece of architecture. But considered an acceptable substitute for true art; engineering with utility structures. of another building, some might say that it and original architecture—whatever that may isn't architecture. In other words, buildings are mean Structural requirements architecture only if they fulfil certain condi• No, the architect nowadays is definitely on If we continue to use the word structure in its tions. Which conditions?—general confu• his own. in an ocean of complete permissive• widest sense, in which it can mean a building, sion. ness and an almost infinite choice of means. a silo, a bridge, dam or road, in fact anything Architecture can also mean a discipline, like It can be a relief, therefore, if his choice is built by man which stays put—for a time at philosophy, medicine, law. building science, limited by impossible site conditions and a least—so as to avoid 'static hardware' or some sociology or Art—with a capital A. In fact shortage of materials or technical resources. such concoction—we have seen that to call architecture was once considered the mother A corollary, or in any case in keeping with some of them architecture and othersengineer- of arts, a valid art form like painting, poetry or this chaotic state of affairs, is the fact that ing structures is rather arbitrary. drama, and many attempts have been made, architecture cannot be said to have progressed We demand of all of them that they should and are still being made, to produce a theory from old times till now. Few would argue that function well, last well, look well and cost of architecture which will enable us to modern architecture is a marked improve• little, but if we survey the whole field of distinguish architecture from mere building, ment on the architecture of earlier epochs, possible structures, the emphasis placed on good from bad architecture, and which will be that our great architects are greater than their these four demands differs widely. Fig. 9 a guide to the creation of architecture. ancient confreres. Perhaps such a comparison They must all fulfil their particular function, North Block on completion of the structural frame (Photo: Beecham Research Laboratories) 2 These attempts to distil the volatile essence of is meaningless. But look at the contrast in for that is the reason for building them. But the THE ARUP JOURNAL

SEPTEMBER 1970

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