Queen Alexandra Bridge Over the River Wear, Sunderland." by FRANCISCHARLES BUSCARLET, Assoc

Proceec1ings.1 BUSCAKLET ASU HUNTXR OK BRIDGE OVER WEAR. 59

(Papev No. 3824.)

" The Queen Alexandra Bridge over the River Wear, Sunderland." By FRANCISCHARLES BUSCARLET, Assoc. M. Inst. C.E., and ADAMHUNTER, M. Inst. C.E. THE bridge and approaches which arethe subject of thisPaper convey both a road and a double line of railway across the River Wear, at a point about 29 miles from the entrance to Sunderlmd harbour. Previous to 1899 the necessity for a road-bridge over the river in the neighbourhood of the new bridge was realized, and rough plans and estimates were prepared, but it was not until 1899 that theNorth Eastern Railway Company finally came toan agreement with the Corporation of Sunderland. It was then decided to construct a jointbridge across the river on the presentsite, and parliamentary powers for the undertaking were obtained in 1900. The general design of the main bridge will be readily understood from Plate 3. It consists of three 200-foot (clear) land spans, one on the southand twoon thenorth side of the river, and of a 330-foot (clear) span over the river, this lastgiving a clear headway of 85feet above high-water level of spring-tides.The massive abutments andpiers which support these spam are builtof Norwegian rock-faced granite in cement.

SITE AND APPROACHES. Therailway (Fig. 1, Plate 3) extends from a point (A), about 160 yards west of Millfield station on the Penshaw branch railway, to R point (B), opposite to the Hylton colliery on the Hylton, South-

wick and Monkwearmouth branch railway ; a total distance of about 1 mile 59 chains. It is built primarily to enable the large mineral- traffic from the coal-fields, in the district between Washington and Annfield Plain,to be brought, if required,to the South Dock, Sunderland,without the tworeversals that are now necessary at Washingtonand Penshaw. The aggregate output fromthese collieries is upwards of 6 million tons per annum. Ultimately, the new bridge and railwa,y will be used t'o develop passenger-trafiic in the district. The roadway extends below the railway from Havannah Street (C)on thesouth side of theriver to the point D on thenorth side, where it leaves the railway and, crossing Camden Street, leads up to Mary Street bridge; this being the proposed route for the tramways thatare eventuallyto be laidacross the newbridge. The building of the roadway from point D to Mary Street bridge, and the widening of this bridge to suit future requirements, was carried out by the Southwick District Council. When laid, the tramway will connect the system which has its terminus at '' The Green," Southwick, onthe north side of the river, with that which, on the south side, extendswestwards from the Central station, Sunderland,along the Hylton Road and pastMillfield station. The new road-bridge will also be of great valuefor foot- passengersbetween theindustrial districts of Sunderlandand Southwick, andfor the heavy tractionand other traffic between Sunderland and Newcastle, as the only other means of cornmunica- tion between the banks of the river in the immediateneighbourhood is a road-bridge crossing the river at a point about 1 mile 3 furlongs farther down.Lastly, the new bridge is made use of to carry important water- and gas-mainsacross the river. Approach-Railmap.-Starting from the south side of the river at its junction (A) with the Penshaw branch, the railway (Figs. 1 to 3, Plate 3) is laid on an embankment in which are two small girder- bridges, one over a proposed road and the other over the Lambton railway (a colliery-line). From this point it is carried on retaining- walls as far as :I girder-bridge overNew Road, and beyond this again on brick arching, until a girder-bridge over Havannah Street is reached at which point (C) the south roadway-a,pproach to the main bridge commences. Frompoint (E) on thenorth side of the river the railway is carriedon brick arching asfar as twogirder-bridges over Wear Street and Camden Street, then on an embankment as far as the skew girder-bridge over the Hylton,Southwick and Monkwearmouth branchrailway, andthe adjoining road; and lastly, beyond that

againon an embankment which tailsout at (B), opposite to the Hylton colliery. Owing to the high level of the railway, a great dealof the masonry in connection with this part of the work is of massive character ; it is built of local stone, faced withred sandstone from the Locherbriggs quarry, near Dumfries. It waspossible to get blocks of stone from this quarry of almost any size ; its fine colour and thefact that it is easily worked,though hardening considerably on exposure, render the stone valuable for building purposes, from both an architectural and an engineering point of view. A block of this stone, 6 inches cube, was submitted to a crushing-test and with- stood a weight of 90 tons (i.e., 360 tons per square foot), the edges only being slightly split. The embankments are made up mostlyof material from the spoil- bank at the Wearmouth colliery. There is nothing of particular interest from an engineering point of view in connection with this part of the railway, except the skew girder-bridgereferred to. This bridge is built at the exceptional angle of 18", the skew andsquare clear spansbeing respectively 212 feet and 65 feet. The steelwork of the superstructure weighs 743 tons. South Approach.-At HavannahStreet bridgebegins thesouth approach-road, which is 346 feet long and rises towards the main bridge at a gradient of about 1 in 44. It consists of a short length of retaining-walls and severalbrick arches, the latter being built on solid ashlar piers which taperto a width of 5 feet below the springers (Figs. 3 and 4, Plate 3). The piers, arch-quoins, parapet- walls and facework are built of the redsandstone previously referred to. Owing to the depth of made ground it was found necessary to carry the foundations below the level originally intended, and 6-to-l cementconcrete wasused wherenecessary below the ashlar foot- ings, all the foundationsbeing taken down to good clay. Inside theretaining-walls, and behind the 3 feet of masonry above the arching, a. backing of 6-to-1 cementconcrete, respectively 10 feet and 11 feet 3 incheswide, is builtup ; this also formsa solid foundationfor the granite blocks that act as bases for the steel columns supporting the railway superstructure. These steel columns are placed 12 feet 6 inches apart longitudinally and are made up of twochannels with lattice bracing.They are anchored tothe bedstones by bolts and washer-plates, rtnd are securedlongitudi- nally to each &her by lattice girders 4 feethigh at the level of the f@otways, These girdersact also as a handrailingbetweer

the roadway and footways. The bases of the columns are strengthened with gusset-plates andangles, and are surrounded with bitumen concrete composed of pure pitch and oil, and coke breeze. All the st.eelwork with which the bitumen concrete was to come in contactwas carefully dried before the concretingwas allowed to proceed, and the cokebreeze was thoroughlyheated in a special drier. It was then laid on the steelwoTk in 2-inch to 3-inch layers andthoroughly grouted up with a mixture of hotpitch and oil. This bitumen concrete upon a %-inch layer of rock asphalt was also used instead of cement concrete on the roadway and footways over the mainbridge; it was considered to afford a better protection against damp, andwas also considerably lighter than cement concrete, the respective weights being89 lbs. and 140 lbs. per cubic foot. This modification reduced the weight of the superstructure over the river and land spans by 104 tons and 67 tons respectively, or by 6 cwt. per lineal foot, The superstructure which carries the railway is arranged to give a clear headway of 18 feet above the finished road (Figs. 4, Plate 3). It consists of cross girdersriveted tothe columns bymeans of brackets, with $-inch floor-plates in between ; there are longitudinal rail-bearers under each rail, and rail-guards and anglecleats are provided for thepermanent way. Thelattice-work parapets are 6 feethigh, being placed 28 feetapart between centres. 'l'hc columns at theirtops are braced togetherlongitudinally with lattice-work.They are also braced togethertransversely where possible above the headway, and longitudinally at the ends and at twointermediate bays, by a system of channels and tee-bars to stiffen the superstructure.Provision is made for expansion over these two intermediate ba.ys. Thetotal weight of steel inthe superstructure of the south approach is 453 tons. The drainage of the railway superstructure is led into cast-iron gutters, which run below the rail-bearers and alongside every alternate cross girder ; they empty into down-comers which deliver into gullies on each side of the roadway. The roadwayhas a camber of 3 inches and consists of beechwood blocks laid on 8 inches of cementconcrete with a cushion of sand,The footways, which are formed of 3-inch cement concrete on broken bricks, hwe a fall of 2 inchestowards the roadway. North Approach.-On the north side of the river therailway turns out (Fig. 2, Plate 3) in a westerly direction with a 194-chain curve ; while the roadwaybranches off inthe opposite direction, at %D

Downloaded by [ York University] on [17/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] QUEEX ALEXANDKA BRIDGE OVER THE WEAR. 63 angle of about 8" withthe centre-line of the bridge. The construction of this approach is similar to that on the south side, and the total weight of steel in the superstructure is 280 tons.

FOUNDATIONSOF RIVER PIERS. The north and south abutments, andpier No. 3 on the north side of the river, are founded on good stiff clay, with 6 feet to 7 feet of concrete below the granitefootings. The excavation of the foundationsfor pier No. 1 necessitated the building of a coffer-dam; but as the riverside of the pier was approximately on the line of the existing quay-wall, it was only necessary to build the coffer-da.m on that side, with short return ends carried back to the solid ground (Figs. 5, p. 64). The coffer- dam was of special construction as it was built upon a rock bottorn. The bed of theriver on the south sidebeing limestone under a foot or two of mud, the piles had practically no foothold, and the dam had to be kept in position by connection to the struts inside and by means of wire ropes placed outside and secured to the ground behind. Theother three sides of thefoundations were supported by 3-inch sheeting, that on the land sidebeing kept up by long raking struts which were carried down to the rock inside the dam onthe river side. The placing of these struts was animportant matter, as before they could be fixed permanently a certain amount of excavation had to be done, and until the struts were in position nothing was secure. The risks were that the dam would be pushed out into the river either from the fall of the tide orfrom a rush of water, which threatened to come over the sides of the coffer-dam whenships were beinglaunched fromthe adjoining yards. The foundations were carried down to 20 feet below high-water level, a perfectly sound and almost level bed of limestone being reached at this depth. The limestone was first met with at about 8 feet below high-water level ; its surface,which consisted of softrock very muchfissured, was loosened bymeans of picks andbars and, as the rock became harder, by means of blasting, while the last foot or two was quaryied out so as not to disturb the underlying strata. The rock at the bottom of the foundations was left with an uneven surface, so as to form a bond with the concrete above. Many of the blocks of stonequarried out, being of large size and having level beds,were used as backing in the masonryretaining-walls. Before thequarrying-out was stopped, bore-holes were driven another 16 feet into therock by meansof steam-drills, thus ensuring that the foundations were perfectly sound.

Figs. 5.

scale: I lnch - 20 Feet. rem5 , 0 f to, 17 10 U JOFEEl

An average of 44 feet of concrete was then laid over the whole area,and on this the grnnite masonry was built. The struts and rakers had to be removed in building up the granite, and the sides weresupported from the masonry.These temporary struts and rakers were shifted up as each course was completed and the course above became sufficiently advanced to support them. Although limestone was found on the south side of the river at 8 feet below high-water level, this bed extended only about half-way across the river, and practically no stone was met with on the north side untila depth of75 feethad been reached. Thefoundations of pier No, 2 on the north side of the river, therefore, were carried down to the redsandstone, or 78 feet 6 inches below high-water level. The excavation of the foundations for pier No. 2 necessitated the sinking of a rectangular caisson. It was at first intended to use a temporary caisson above the permanent shoe, inside of which the masonry was to be built up in theusual way ; but at the request of the contractor and on conditions laid down by the Chief Engineer, thetemporary caissonwas dispensedwith, andthe sinking was carried out by superimposed load. The conditions under which this was allowed were, that no payment was to be made until the caisson had been satisfactorily sunk on to a good foundation and the superstructure of granite had been brought up to high-water level. The caisson (Figs. 6, Plate 3), as constructed for these altered conditions, measured 63 feet 3 inches by 35 feet 3 inches over the cutting edge ; it was 44 feet deep and weighed about 340 tons. The shoe (Figs. 7, Plate 3) consisted of $-inch shell-plates, to the inside of which were riveted triangular brackets. The &-inch plates whichformed the roof and sloping sides of the working-chamber were attached to the top and sides of the brackets. Manholes and smaller holes for concreting were provided in the roof-plate, over each pocket formed by the brackets. The cutting edge of the shoewas formed by strengthening the shell-plates on the outside by two$-inch plates, respectively 22 inches and 14 inches deep ; and on the inside by a l-inch plate bent to suit the base of the shoe-brackets, with a 6-inch by 6-inch by;-inch angle above it. Cover-plates and angles are provided at the shell-plate joints. Above the shoe, the shell-platesare 2- inchthick, and are connected to cross girders, which rest on the brackets at the two sides of the caisson. These cross girdersare strengthened and braced together by angle stiffeners and diaphragms. Above the cross girders, the caisson isbuilt up of five &rakes [THE IJST. C.E. VOL. CLXXXII.] F

Downloaded by [ York University] on [17/09/16]. Copyright © ICE Publishing, all rights reserved. 66 BUSCARLET AND HUNTER ON THE [Minutes of of $-inch shell-plates and one top strake of &inch shell-plates, the longitudinaljoints being 3 inchesdeep. Each strake overlaps the oneabove, andthe caisson is thus reduced inlength and breadth at every strake, whichgives the requiredtaper. The caisson is stiffened by angles and cross girders as shown in Figs. 6. Two openings for 38-inch shafts were allowed for in the roof of the working-chamber, but eventually only one at the east end was used. The first threestrakes of shell-platewere built up ontimber staging 12 feet above the river-bed, that is, about 4 feet above highwater. Aftergrouting up the bottom of the pockets above thecutting edge with 6 inches of l-to-lPortland cement and sand, the caissonwas lowered, by four hydraulic jacks, on to the bed of the river, which had been levelled over the required area. The pockets and the space between the girders forming the sides and roof of the working-chamber were then filled in with concrete, commencing at the north side of the caisson, which was the higher. Special care was taken to see that this was properly done. At first the concrete was brought up level to within 6 inches or so of the deck-plates, and after it had been well rammed, the remaining space was packedwith fine concrete by means of grafting-tools and ironbars. This was found to be unsatisfactory, as the concretegot jammed in underthe deck-plates, andprevented the pockets from being thoroughly filled. The method then adopted was to bring theconcrete in the pockets to within a few inches of the top, a.nd to pack in through the manholes until it rose to the top of the two smaller holes. In additionto this, the cornerpockets, which weremore difficult to pack, were grouted up with cement. From this point the sinking was carriedout in the usual way by superimposed load, which consisted of the concrete filling of the caisson together with the granite. The top of the caisson, and after- wards the courses of granite, were kept sufficiently far ahead of the sinking to ensure that the top of the building would always be a few feet above high-water level ; and to do this the concreting had often to be carried on day and night. Particulars of the sinking of the caisson are given in Appendix I. Excavation was carriedon without interruptionduring the sinking, except at thechange of shifts or when the air-pressure had to be cut off. Themethod adopted throughout was to excavate fromthe centre towards the ends and sides, leavinga dumpling sloping up to theroof of the working-chamber either round thesides, or at both ends, or at one end only, according to the lie of the strata and the level of the caisson at the time. By this means the caisson \vas kept so fully under control that it could be brought almost to a

' level position, if required, and couldbe so guided as to be kept exactly on the centre-line. During the sinking of the caisson various strata were met with. After passing through 19 feetof mud and yellowish sand, and 12 feet of sandy clay, the north and west cutting edges came on to stiff grey clay which fell in a south-easterly direction and at a slope of about 1 in 5 for two-thirds of the length of the caisson ; it then dipped down at a verysteep slope of approximately 2 to 1. Thesouth side and east end of the caisson were thus on sand, while the north side and west end were on clay. As the caisson sankfar more easily in the latter, this side and end had to be kept well ba,nked up until the composite strata, which extended to a depth of about 23 feet, had been pierced ; so much was this the case that at one time the bank extended from the west end to beyond the line of the opening into the unused shaft. Had that shaft been kept open, as was originally intendedfor hurrying forward the excavation, it couldseldom have been used duringthis period of the sinking. The caisson next passed through 5 feet of clayextending over the whole area of the cutting edge, and from that time the tendency was for it to travel faster at the east end, consequently tha,t end had to be banked up. After the day came yellow sand with lumps of half-formed sandstone, extending a fewfeet inside the north cutting edge, and with gravel over the remaining area. This continued for a depth of about 6 feet, the area of yellow sand graduallyincreasing, and that of the gravel decreasing,until grey seggar(fire-clay) was met with. When about 3 feet 6 inches of this seggar had been passed through, astratum of 12 inches of hardgrey sandstone was encountered. This was at a depth of about 76 feet below high-water level, and it was decided to take off the air-pressure gradually, tosee how far the caisson would travel. The superimposed weight was then 9,890 tons (neglecting friction). This was done, and no movement was noticed until the pressure had been reduced to 12 lbs. per square inch, when the caisson began to descend ; and when the pressure had been reduced to zero it had sunk7 inches. On restoringthe air-pressure it was found that the strata of grey sandstone had broken and tipped upunder the weight of the caisson, leaving thecutting edge resting onhard, red, laminated sandstone. About 18 inches of thissandstone waspassed through,and the cutting edge of the caisson was then 78 feet below high-water level. Beforedeciding to stop at thisdepth, trial holeswere dug to satisfy the resident engineers as to the condition of the underlying strata. This being satisfactory, the air-pressure, which at this point reached a maximumof 39 lbs. per square inch, was taken off gradually, F2

Downloaded by [ York University] on [17/09/16]. Copyright © ICE Publishing, all rights reserved. GS BUSCARLET AND HUNTER ON TTIE [Minutes of causing the caisson to sink a further 2 inches into the sandstone. With regard to level, taking 0 as the level of the highest corner, the caisson at this stage stood as follows : north-east corner, 0 ; South- eastcorner, $ inch down;north-west corner, 1 inch down;and south-west corner, 3 inch down. The air-pressurewas again restored, and the concretewas filledinto the working-chamber, commencing at the west end and working out towards the east shaft, untilit extended to within afew inchesof the roof. The remaining space was then packed as tightly as possible by ramming in the concrete. When this had been done, neat cement grout waspoured intothe working-chamberthrough a3-inch pipe, which extendedfrom the air-lock, down the eastshaft and across the caisson. Thepipe was suspendedfrom the roofof the working-chamber as far as the unused shaft at the west end, and rose a few inches up it. The grout was poured down this pipe until it rose in the shaft 2 inches above the roof of the working-chamber, n.nd when it remained at this level thegrouting was stopped. Altogether about 1 tm of cement was used. When the cutting edge hadbeen sealed, an escape-valve was providedon theshaft and the compressor was run slowly, so as to prevent the air-pressure from rising any higher than 33 lbs. per square inch, which was the pressure used during this final grouting.When the grouting had been completedthe air-pressure was finally taken off, and the air-lock and sha.fts wereremoved, the holesoccupied by thelatter being filled with concrete. The total weight on the foundations at the close of these operations was 9,890 tons (neglectingfriction). During this concreting the caissoncontinued to descend for a few days,sinking a total of 6 inches, when it stopped at 78 feet 6 inches below high-water level of spring-tides. The working-chamber was then a little over one-third full of concrete, and the levels were as follows : north-east corner, 3 inch down ; south-eastcorner, inch down ; north-west corner, 0; andsouth-west corner, 0. No subsequentchange of level, even after the pier was built to its full height, was observed. All the granite was built in 3-to-1 cement mortar, and great care was taken with the grouting of the joints. Theoutside joints of each coursewere first plasteredwith cement mortar, andthe inside joints were then well filled with a very liquid cement grout that was swept intothem until they were full, after which the grout wasallowed tosettle, This was donerepeatedly untilthe joints were quitefull, and no furthersettlement beingdetected, the next course of granite wascommenced. Thegranite masonry in the piers, apart from the relieving arches, is solid throughout,

Downloaded by [ York University] on [17/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] QUEEN ALEXANDRA BRIDGE OYER THE WEAR. 69 while the abutments have a central and two side pockets measuring 16 feet by 12 feet and 8 feet by 74 feet respectively. Thefoundations, embankments and masonry werecommenced in February, 1905, and were practically completed by July, 1907 ; the amount of material used was as follows :- Granite ...... 496,000 cubic feet. Ashlar ...... 222,000 ,, ,, Rubble ...... 19,000 .. yards. Concrete ...... 13,000 ,, ,, Brickwork ...... 6,000 ,, ,, Earthwork ...... 330,000 ,, ,, This work, with the exception of the sinking of the caisson by the contractors, Sir William Arrol andCompany, was carried out by the sub-contractors, Messrs. MitchellBrothers, of Glasgow. Taking into consideration thefact that there was unavoidabledelay at the beginning, owing to a large portion of the site for the work not being available, and later by the stopping of the supply of granite fromNorway owing tothe frost, the progress was distinctly satisfactory. SUPERSTRUCTURE. Land Spans.-Each of the three land spans (Fig. 3, Plate 3) consists of two parallel main girders of the Linville type, 224 feet long and 30 feet deep,placed 32 feet apart from centre to centre. The roadway floor is carried from the bottom booms, and the double-line railway-track is placed between the main girders above the roadway, allowing 18 feet of clear headroom. The main girders are sufficiently braced together by the railway cross girders, and do not require any special bracing-girders or wind-bracing. The generalconstruction is similar to that of the river span described later. The total weight of steelwork in each land span is about 1,000 tons, and the total dead weight including permanent way is abont 1,400 tons. Riaer Span.-The main or river span(Figs. 10, Plate 4) consists of twocurved-top girders of the Linvilletype, 3532 feetlong over end-plates ; they are 30 feet deep over angles at the ends, rising to 42 feet over angles at the centre, and are placed 32 feet apart from centre to centre. The booms are of trough section and are composed of web-plates (two side and one centre) and flange-plates, connected together by means of angles and stiffened by vertical diaphragm- plates placed at thecentre of each bay. The side plates are 42 inches deep, andthe flange-plates are 68 inches wide inthe top and 56 inches wide in the bottom booms.

Downloaded by [ York University] on [17/09/16]. Copyright © ICE Publishing, all rights reserved. 70 BUSCARLET AND HUNTER ON THE [Minutes of The end posts, which measure 9 feet by 4 feet 2 inches overplates, are built up with a centre plate and four outside plates, connected together by angles and stiffened by three horizontal diaphragms. The vertical posts are 12 feet apart between centres, and consist of aweb-plate andeight channels.They are designed to saddle over the centre web-plate of the bottom boom, and to receive that of the top boom. The diagonal ties, with the exception of the four end ones which extend across the posts and one bay, extend over two bays and consist of flat bars in pairs ; and towards the centre, where the stresses are liable to be reversed owing to the moving load, they are braced togetherwith lattice bars. Theycontinue beyond the centre as counter-ties ; and are connected by gusset-plates to both booms. The top booms are connected by six overhead bracing-girders at 24 feet intervals, these being used only towards the centre of the span, where the headroom for the trains permits of them. The main girders rest at one end on roller bearings, and at the otherend on fixed bearings (Figs. 9, Plate 3) ; provision for expansion is thus made at one end of the span. The roadway is carried on cross girders which are suspended from the bottom booms of the main girders by suspender angles(Figs. 10, Plate 4). These are sptLced 3 feet on each side of the vertical posts and G feet between centres, and they project as cantilevers about 13 feet 6 inches beyond the main girders on each side to carry the footways, ancl, outside of these, the gas- and water-mains. These cross girdersare 64 feetlong over all, andare 2 feet 9 inches deep over angles between the main girders. Longitudinal stringers 5 feet apart are riveted to the webs of the cross girders, and inverted buckled plates 8 inch thick are riveted to the cross girders and stringers to form a decking for the roadway. Instead of being in separate plates, the decking was made in lengths with severalbuckles in eachlength. On the projecting cantilevers, longitudinal troughing is laid to carry the footways.Outside the footways, which have a lattice-work parapet 4 feet 6 inches high, steel chocks are fixed to support thegas- and water-mains. A bulb-tee is placed at the extreme end of the cantilevers to carry a permanent travelling gantry, which is hinged to pass the piers. The roadway has a clear width of 26 feet, and is formed of 5-inch beechwood blocks laid diagonally, with a $-inch cushion of sand, upon bitumen concrete, this being filled into the buckled plates and above them. The concrete variesin thickness from8 inches at thecentre to 5 inches at the sides of the road, thus giving the required 3-inch camber. Before laying the bitumen concrete the buckled plates were covered

Downloaded by [ York University] on [17/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] QUEENALEXANDRA BRIDGE OVER THE WEAR. 71 with 2 inch of rockasphalt, whichwas increased to 1 inch over the top of the cross girders and stringers to protect the rivet-heads; it was carried 12 inches up the main girder web-plate, to form a fillet on either side of the roadway. Cast-iron troughing lined with rock asphalt is laid on each side of the roadway for drainage purposes, the space between it and the asphalt filleting being filled with bitumen concrete. In the centre of the roadway 12-inch by 6-inch waybeams are laid over the two centre stringers to carry a single line of tramway, and are held in position by angle cleats riveted to each moss girder. The inside of the lower booms is lined at the bottom with rock asphalt, which averages 2 inch in thickness and slopes towards 14-inch holes providedin each bay for drainage. The footways, which are 7 feet wide and have a slope of 2 inches towards the parapets, are formed of a 2-inch layer of 440-1 gravel and cement, with a l-inch layer of 2-to-l granite chips and cement on top. This cement concrete is laid upon bitumen concrete, which was filled into andover the troughs afterthese hadbeen covered with 3 inch of rock asphalt. There was some difficulty at first in getting the rock asphalt, which was tried of various consistencies, to adhere to the steelwork, even when the latter was perfectly clean ; but a satisfactory result was ultimately obtained by covering the cleaned steelwork with athin coating of creosote oil, well rubbed in and then left to dry thoroughly before the rock asphalt was laid over it. The railway (Figs. 10, cross section) is carried on cross girders 12 feet apart from centre to centre, and resting on brackets; both cross girders and brackets being riveted to each other and to the end posts and verticals. The cross girders are 2 feet 9 inches deep over angles, and they are arranged at a similar height to those in the land spans. Longi- tudinal rail-bearers areriveted to the webs of the cross girders. Flat plates # inch thick are riveted to the cross girders and rail- bearersand form the floor of the railway,being covered with inch of ‘‘ Mastico ” bituminous enamel. The permanent way is similar over the whole bridge and south approaoh, and is composed of 95-lb. BritishStandard steel rails with specially-rolled continuous fishplates (Figs. 11, Plate 4) ; these rest onkyanized timber waybeams,which are scarfed and bolted togetherevery 36 feet or so. Bracketssupport therail-guards, which consist of S-inch by 34-inch channel-bars placed so that their top is 2 inches above rail-level. As the rails do not rest on chairs, the necessary cant is given to them by the waybeams,which are sawn to the required slope. Provision for expansion is made in the

continuous fishplates as shown in the Figure. The north approach, being on a curve, the continuous fishplates could not well be used, and the permanent way here consists of steel rails with ordinary chairs and fishplates. The total weight of steelwork in the river span is 2,600 tons, or 74 tons per lineal foot, and each main girder weighs 954 tons. The total deadweight, including permanent way, etc., is 3,200 tons, which is equal to 9 tons per lineal foot. The weight of the river span is not exceeded by any existing bridge of the same length. The steelwork inthe bridge and approaches was designed to carry the following live loads : l&ton per lineal foot on each railway track ; an equally,distributed load of 1 cwt. per square foot on the whole area of the roadway and 100 lbs. per square foot on the footways, or a concentratedload of 40 tons onfour wheels on the roadway floor-girders. Themaximum working-stress allowedwas 6$ tons persquare inch on the net section. Theriveting throughout the whole bridge was doneby means of hydraulicand pneumatic long-stroke riveters. The hydraulic riveters were of two types, hingedand fixed, the formerbeing used for the flange- andthe latter for the web-plates of the booms. Therivets were usually heated inthe ordinary way, but at times, especially for the hydraulic riveters, which require a more uniform supply of rivets, a heating-furnace with an electric blower was used. Mccnufactwe.-All the steelwork in the contract is of mild steel, specified to have an ultimate tensile strength of not less than 27 tons andnot more than 31 tons persquare inch, with an elongation equal to at least 16 per cent. on a length of 8 inches before fracture. The girders were drawn down full size on the mould-loft floor, from which templates of well-seasonedyellow pine were made. These templates were applied to the straightened plates and bars, which were marked off to enable them to be planed to shape and chilled. Afterthe plates and barswere planecl to shape, tho component parts of the flange or webs of a. boom were assembled, cl:t.mped together and marked from t,lla templates ; all Ides were tlrilled t,heir full size through thetotal tllickness of metal, thus onsuring that they wouldcome togethercorrectly after the parts had been taken apart and cleaned. The three land spans, being exactly similar, were marked off and drilled from the sametemplates. One spanonly (thelast one required at thesite) was erected inthe yard, to " prove " the correctness of the nlannfncture, the remaining two spdns being sent

Downloaded by [ York University] on [17/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] QUEEN ALEXANDRABRIDGE OVER THE WEAR. 73 direct to the site. As the river span is symmetrical, only one half was erected in the yard previous to inspection and dispatch. Before leaving the manufacturer’s yard the steelwork received a coat of boiled oil, and whenerected and properlyscraped and cleaned,one coat of redlead and two of best ‘‘ Torbay ” paint ; excepting the underside of the spans, the ends of themain girders, and the inside of the top and bottom booms,which were painted with two coats of Brigg’s solution. The railway deck of the mainspan and approaches, and of allgirder-bridges notto be ballasted, were covered withinch of “ Mastic0 ” bituminous enamel.

ERECTIONOF THE LANDSPANS. The land spans were erected in their permanent positionupon staging formed of three timber frestles ; these supported temporary girders to form a platform about 4 feet below the bottom booms of the main girders. The highest trestle was72 feet from ground to deck level ; it was formed of two piers, 11 feet square, which were placed 32 feet apartbetween centres, and braced together and strutted on the outsides to give a tritnsverse width of 64 feet at the base. Each pier was formed of four vertical timbers, 12 inches square and braced together on the four sides ; excepting, however, at the front of the pier next the 653-foot spnn, where two timbers were used under each longitudinal staging girder, the load being limited to a maximum of 24 tons on each vertical timber. In the three smaller spans of the staging the permanent roadwaycross girders of the river span were used as temporary staging girders. The staging was taken down and re-erected for the two remaining land spans. The cross girders of the roadwaywere first laid down on the platform and wedged up to suit the building-camber. When this had been done the bottom flange-plates were laid on them, and the centre and side webs were placed in position. Theend posts and the verticals were next erected, and simultaneously with the latter the diagonal ties and the top booms. Themain girders were erected with the building-camber of 4 inches at the centre of the spa11, this falling to about 24 inches under the full ded load. Theerection of thethree land spans was commenced ill April,1907, and practically completed by March,1908, those adjoining ‘the river spanbeing finished fist. Thequantit,y of temporarywork inthe staging,per ton of permanent steelwork erected, amounted to, 10 cubic feet of timber in the trestles and platforms, 5 cubic feet of timber in the blocking,

Downloaded by [ York University] on [17/09/16]. Copyright © ICE Publishing, all rights reserved. 74 BUSCARLETHUNTER AND ON THE [Minutes of gangways,riveting-platforms and painting-stages, and 1 68 cwt. of steelwork in the staging-girders, which includes the permanent cross girders used inthe twosmall spans. As thisstaging was taken down and re-erected for the otherland spans, thenet quantitiesare one-third of theseamounts and compare very favourablywith the amounts used in the erection of largespans of other bridges.

ERECTION OF TEE RIVERSPAN. The shipbuilding yards on both sides of the river extend close up to the bridge, and new vessels are launched directly under it. This condition, as well as the necessity for keeping the navigable water- way always open for the passage of vessels, led to the insertion in the North EasternRailway Act of 1900 of a clause for the protection of the River Wear Commissioners. The clause required that the bridge should be constructed with only one arch or span over the river, of not less than 321 feet on the square, between the bases of the piers, and with a headway of not less than 85 feet above high- water level of spring-tides. Further, during the time of erection, the Company should keep the navigation of the river, at and about the bridge, free and clear, subject, however, to provisions allowing coffer-dams, piling, etc., to be temporarily placed where necessary for the erection of the bridge-piers. Upon this understanding, the Act was passed authorizing the constructionof the bridge. Thecontract specification, framedon these requirements, sug- gested two alternative schemes by which the river span might be built, namely :- (l) By using temporary towers and suspension members attached to the bottom booms and anehored to the land spane. (2) By using the land-span girders cantilevered over the river, struttedout from thepiers and anchoredfirmly tothe shore, supporting a platform upon which the main girders might be erected. The contractor was not bound to any of these methods of erection, if he could propose any other scheme which should be approved by the Chief Engineer. Before the contractor decided on the method of erection, com- parativeestimates were made of the cost of different schemes. Building the main girders back on the land spans and rolling them forward was considered, as well as building them upon brackets or fan-like staging supported upon the river piers ; consideration was also given to a scheme for erecting across the opening temporary

Downloaded by [ York University] on [17/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] QUEEN ALEXANDRA BRIDGE OVER THE WEAR. 75 girders to which the permanentroadway cross girders wouldbe socured, forming a platform upon which to build the main girders. The great weight to be dealt with rendered all these schemes very costly, so that it was finally decided to convert the main girders temporarilyinto cantilevers anchored back tothe adjacent land spans, and to build them by overhang from each side of the river.. From the weights previously given it will be seen that this is the heaviest independent span yet erected by overhang. The general scheme of the erection of the river span ia shown in Figs. 13 and 14, Plate 4. The adjacent land spans had been entirely completed previously, and the temporary gussets for the lower end of the back anchor-ties had been riveted up to the side plates at the far end of the bottom booms. A 10-ton steam-crane was placed on the railway floor on each side of the river, and moved forward as the erection proceeded. Stage 1.-After setting the bearings for the river span upon the piers the first length of the bottom boomwas placed in position, and temporarily held back to the end posts of the land span while the end posts and first diagonal ties of the river span were erected and riveted. The temporary tie used for this is shown dotted in Fig. 13. Thegirder was now adjustedto the correct alignment, and to a suitable inclination to allow for de5ection during building, by means of the long temporary bolts at the top of the end posts. Solid steel thrust-blocks were placed between the end posts of the two spans at the level of the bottom booms, to transmit the thrust from the river span to the bottom booms of the land spans. These thrust-blocks were 60 inches wide by 45 inches deep, and were made up of four thicknesses of machined slabs having a total thickness of about 12 inches. When the booms and end posts were completely riveted the ends of the bottom booms of both land and river spans werecarefully chipped and surfaced, using the abutting slabs as surface plates, so as toobtain an evenbearing over the whole section. Three of the slabs were fitted into position, leaving a gap of about l$ inch, to which a slight taper of about t inch in plan was given. Thefourth slab which was machined to gauge and made in three horizontal sections of the full width, was forced into the gap by hydraulic power. These closing sectionswere grooved to contain a heavy lubricant of plumbago and oil, in order to permit of easy vertical motion during the future operations of raising the projecting ends of the girders. The expansion-bearings under the river span were then locked to prevent any motion, and the bolts wereremoved from the upper eastings of the fixed bearings at the far end of the land spans, thus

Downloaded by [ York University] on [17/09/16]. Copyright © ICE Publishing, all rights reserved. 76 BCSCARLET AND HUNTER ON THE [Minutes of allowing themain girders to slide on the top of the cast-steel bearings, which had been prepared with oil-grooves and lubricated. Provision was also made at this end of the land spans to prevent any lateral motion. The fist vertical post and a lengthof the top boom were now put into position, and a temporary flange-tie and side web-ties at the tops of the land-span end posts were connected tothe top flange and web-plates of theriver span (Fig. 13, Plate 4). Thetemporary side ties were each formed of two short plates, 24 inches wide by f inch in thickness and of varying lengths, rivetedto theweb-plates on each side of the main girders. The horizontal flange-tie, shown by the thickened line in Fig. 13, was 63 inches wide by 3 inch in thickness. The side web-tieswere of sufficient strengthto amy the whole load due to theoverhanging weight, but it was considered that their short length would prevent them from accommodating the small variations due to the necessary lateral adjustments of the main girdem during building. These adjustments would, probably, have thrown a greater tensile stress on the temporary ties on one side of the main girders than could safely be permitted, and the horizontalflange tie therefore was added as aprecaution against this condition. To provide for an even distribution of the shearing stressover the rivets connecting the temporary ties to the main girders, the followingprocedure was adopted: The steelwork was erected up to the first joint in both booms and included the vertical posts, ties, and cross girders, as shown in Fig. 13. This was supported by the timber blocking at the frontof the masonry pier, and by the tie-bolts near the topof the end posts. At this stageone-half of the holes (shown blackened) connecting the temporary horizontal side ties to each main girder were drilled and riveted, and the temporary tie-bolts and timber packings were removed. An additional length of the booms, with the posts, ties and cross girders, was added, 60 that the average shearing stress on these rivets from the overhanging weight was about 12 ton per square inch. The remainder of the connecting holes in the temporary side ties were now drilled and riveted as well as those in the horizontal flange-ties. The span was then bdt out to complete the second stage (Figs. 14, Plate 4). Sfagc %--During the progress of building this stage, temporary steel towers 70 feet high were erected upon the end posts of the river span, being bolted down to the main girders. The holes in the bases of the towers had been drilled to a template taken from the girders, and after placing the lower length of the towers in position these holes wererimered. All thejoints in the towers and the attachment of thelarge gussets atthe topswere connected by

Downloaded by [ York University] on [17/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] QUEEN ALEXANDRA BRIDGE OVER THE WEAR. 77 turned andfitted steel bolts in holes rimered after erection, the bolts themselves being turned to gauge to an absolute driving fit. Each tower was formed of two plate-girder sections 54 inches deep, placed transversely across the booms and braced together in elevation as shown in Figs. 8, Plate 3. The towers were 9 feet wide at thebase, taperingto 34 feet at the top, and each had a sectionalarea of 190 square inches. Suitablediagonal bracing wasfixed betweon the towers, to transmit the wind-stresses to the piers. In view of the heavy load that would come on to each tower, about 760 tons, it was considered desirable to distribute this weight evenly upon the whole section of the end post, without placing any reliance upon sideriveting. Toattain this end the bottom of each tower and the top ends of the plates and angles of the end posts were chipped flush, afterthe verticalside plates had been riveted to them. The anchor-ties were erected from the top of the towers towards the lower ends, being supportedon timber trestles placed about 30 feet apart. The lower end of each tie next the gusseton the land spans was left as ,z closing joint to be drilled atthe site. Before drilling this joint, thewhole of the operations in connection with the building of the remainder of the river span were reviewed. It was necessary, for reasons to be given later, to lift the projecting ends of the river span when the first inclined front ties were fixed, and again when a second set of front ties had been attached to the main girders. Each of these operations would rock the base of the towers backwa.rds, though the deflection of the main girders during building would again move them forward to some extent ; further, the tops of the towers would move steadily forward,due to theelonga- tion of the anchor-ties, to the shortening of the bottom boom of the land spans, and to compression of the towers themselves. If the towers were started with aneven bearing upon the end posts and in line with them, the various motions referred to would have thrown the whole of the stress upon the front limb of the towers when they were carrying their maximum load, and would have induced heavy shearing stresses in the diagonal bracing between the limbs. From these considerations it was evident that the towers should be so set originally that when cmrying their full load they would be sitting evenly upon their bases,n.nd be freefrom any bending stresses. After careful calculations had been made of the various motions, it was decided to pull over the top of each tower 4 inches towards the land span, and as the anchor-ties had an unavoidable waviness in plan, to allow an additional 4 inchfor them straightening out, making 43 inches in all. AS the bolts connecting the base

Downloaded by [ York University] on [17/09/16]. Copyright © ICE Publishing, all rights reserved. 78 BUSCARLET AND HGNTER ON THE [Minutes of of the towers to the main girders were incapable of resisting the tensile stresses due to the rocking of the towers, one-third of them at the front and back had the nuts slackened back (A on Fig. 13), leavingonly thebolts through the central 3 feetfirmly screwed down (B). In this way the base of the tower was given comparative freedom for a.ny pivot action, and the tower was relieved of consider- able bending stresses, while the full strength of the bolts in shear was maintainedfor the connection of the temporaryhorizontal fiange-tie to the main girders. A force of about 7 tons, applied by union screws at the closing joints, was required to pull each tower over to the full extent. The bases of all the towers opened $ inch at the front edge, tapering back for 3 feet to where the bolts were hmly screwed down ; there was no apparent distortion of the vertical side plates of the towers, beyond a slight permanent curvature of the bottom edge. On the completion of stage 2 of the erection, each of the lower lengths of the first inclined ties was connected to a large gusset riveted to the side plates of the bottom boom of a main girder (Figs. 8, Plate 3) ; they projected several feet above the top booms, leaving a gap of about 18 inches to the upper lengths, which had been erected downwards from the gussets at the topof the towers. At this point it was necessary totake the wholeload from the overhanging portion of the spanon tothe inclined ties, andto relieve the temporary ties at the end posts of all stresses to enable them to be cutout. The removal of thesetemporary ties gave the requisite freedom for the tops of the end posts to move backwards, since the projecting ends of the main girders had to be raised to a sufficient height to allow fortheir further deflection in buildingthem to the centre of the span. As the temporaryties atthe endposts were comparatively short and stiff, the process of lifting the ends of the main girders the requisite amountwould have thrown them into compression, and with the locked bearings at the bottom, it would have been necessary to bend or deflect the entire girder upwards to get therequired lift at the projecting ends. The calculsted deflections of the main girders during buildingindicated that theprojecting ends should be raised 4 inches at this point, in orderto have the required camber when completed,and the liftwas made in two stages. In the first stage it amounted to l&inch, being made by meansof a special hydraulicgear acting on the inclined ties at the gap. A force of 200 tons on each pair was estimated as sufficient to relieve the end- post ties of all stress. The ties werenow severed by first cutting out all rivets connecting the temporary horizontal ties to the flange- plates of the land spans, and then by drilling through each of the

Downloaded by [ York University] on [17/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] QUEEN ALEXANDRA BRIDGE OVER THE WEAR. 79 vertical side tie-plates in two lines close tothe endposts of both spans. From careful measurementsmade before andafter cutting out the ties, it was found that the tops of the end posts came together between 0 02 and 0 * 04 inch and that the end posts of the river spandropped inch below those of theland spans.This drop in the end posts was observed to take place after the majority of the holes had been drilled, and indicated that the ties had been carrying a large shearing stress either from the buildingor lifting operations. The outer ends of the main girders were now raised 3 inches, and the cover-plates at the gap in the inclined ties were drilled and bolted on. During this lift the top of the endposts of the river span moved backwards between 1 12 inch and 1* 15 inch, and the top of the towers moved forward between 3 inch and 4 inch. The opening between the flange-plate and at the front of the base of each tower practically closed up, leaving the latter sitting fairly evenly upon the girder.The steel packing-blocks at the bottom of the end posts showed a total vertical motion of & inch at the lubricated surfaces, and opened 0.036 inch at the lower edges. Stage 3.-When the third stage of the erection was completed, the second temporary ties were built in place and a gap was left at the tie-joint as before. The actual deflection at this point agreed exactly with the estimated amount of 2.2 inches in all cases, and was accepted as aconfirmation of the calculations. The hydraulic stressing-gear was fixed at the gap, and the ends of the main girders wereraised l+: inchby a force of 380 tons acting on each pair of ties, which was just sufficient to relieve the first inclined ties of all direct stress. It was computed that if these first ties were just relieved of stress, the elongatior, of the second temporaryties, duringthe building of theremainder of thespan to the centre, would again cause them to carry a part of the load, notwithstanding the slighthogging of the main girders. The second inclined ties were designed to take the whole weight, as the original intention was to cut out the first ties after the second set had been erected and stressed. Further consideration, however, showed that nothing was tobe gained by removingthese tiesand that, by simply relievingthem of stressand allowing them to come intoaction again, the deflection of the girders at the centre would be materially reduced.The actual maximum deflection of the maingirders at the junction of the second ties to the bottom booms,when the girders were built to the centre, was +P inch less than the amount calculated on the assumption thatthe first inclinedties were removed.

Downloaded by [ York University] on [17/09/16]. Copyright © ICE Publishing, all rights reserved. so BUSCARLBT AND HUBTER OX THE [Minutes of Iluring the third stage the opening at the bottom of the thrust- blocks closed up and transmitted the thrust evenly over the section of thebottom booms, andthe base of each towerwas observed to have eased slightly at its front edge. Theobservations made afterthe lift was completed at the second ties showed, that the verticalmotion atthe lubricatedsurfaces of the thrust-blocks was -& inch, and that they hadagain opened up at the bottom edges between 0.025 inch and 0.03 inch. Thetop of theend postshad moved backwardsabout 0.36 inch and the top of the towershad moved forward another inch,making 2g inches since they were set. Singe 4.-The fourth stage of the erection (Figs. 14, Plate 4) pip to the closing joint in the main girders was rapidly completed. The length of the plates and angle-bars of the closing pieces varied from 8 feet to 20 feet according to their position, and the measurements for them were made by rods of yellow pine, 14 inch square. These were marked off on the cextre of the plate or bar and cut to the exact length, one rod being used for each plate or bar. Duringthe progress of the erection the variationsdue to temperature were recorded, as it was anticipated that large move- mentsboth vertically and horizontally would take place at the projectingends of the girders, dueto the rapid absorption and radiation of heat by the longplate-ties. These observations were made for guidance in drawing up the programme of operations for putting in the closing lengths of themain girders. When these girders had been built outto thecentre closing-length, the maximum movements from a temperature-range of 10" F. in the shade, and of 17" F. in thesun, were inchvertically and l>:-inch laterally, of which Iiirch was up-stream or westwards from the morning sun, and 4- inchdown-stream from thesun in theafternoon. The average movements, however, on a dullday were inchvertically, and 2, inch laterally from a shade temperature-range of S" F., and theS-foot gap at the centre closed about $ inch in the bottom boom and inch in thetop boom. The maximum expansion occurred between 2 p.m. and 3 p.m., and the girders moved laterally awayfrom the sun. From theseobservations it was evident that the measurementsfor the closing-lengths would have to be taken when the temperature was a little above the mean of the previous days, to given reasonable opportunity for erectingthe closing-lengths while the girders were contracted. The measurements were taken about midday on a dull day when the temperature was 59" F., the time occupied being about 4 hour. The length-rods were despatched to the works in Glasgow, where

Downloaded by [ York University] on [17/09/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] QUEEN ALEXANDRA BRIDGE OVER THE WEAR. 81 wooden templates were made of each bar and plate in the closing- lengths.Accurate template models hadbeen kept of the closing- joints, and these enabled the separate angles and plates of the booms to be cut to the exact size, and all holes in them to be drilled to correspondwith the holes inthe joints at thesite. The closing- lengths of the bottom boomswere made 4 inchshorter than the measured lengths, to ensure the sections of the top booms butting at the closing-joints before those in the bottom booms. An interval of 5 working-days elapsed from the time the measurements were taken until the closing-lengths were completely erectedin place, the method being to bolt up one end ready for drawing together and bolting the closing-joint. The10-ton crane on thenorth side was dismantled before the closing-lengths werebuilt on thathalf of the main girders, but the crane on the south side of the joint was left to complete the erection, andto equalizeas far as possible the weights and deflections of each half of the bridge.The levels of the correspondinghalves of thegirders agreedwithin 4 inch, andthe centre lines coincided exactly. Theends of the flange-plates on the completed-lengths of the girders projected over the vertical webs of the closing lengths,and were loosely bolted andsprung back from the meb-platesnear the closing-joints, allowingfor any unequal vertical motion of the correspondinghalves from temperature. Wheneverything was readyno delay occurred in the closing- operations,as the temperatureconditions were favourable. The early-morning temperature was 49" F., and the abutting faces at the closing-jointwere 4 inchopen inthe top booms. By noon the temperature had risen to 61" F., and the top-boom joints were butting hard on each other, while the closing-joints of the bottom boomswere aboutinch open. This practically correspondedwith the amount by which they had been made shorter in length. The closing-joints in the bottom booms were first secured. Barrel drifts, having a maximum diameter of 9 inch, were inserted into the holes atthe joints,and each drift was hammered upin succession, graduallydrawing the joint together until 3-inch bolts couldbe inserted in the holes. The drifts wererapidly replacedby others of 1g6 inch maximum diameter, the full size of the holes, and each was hammered up in succession until the joint was drawn up tight andall the holeshad beenfilled with full-sized bolts. Thetop- boom joints were then bolted up and secured without any difficulty. Theriveting of the angles andvertical web-joints followed immediately upon these operations, which occupied about an hour. Provision had been made to push the girders forward or draw them [THE INST. C.E. VOL. CLXXXII.] a

Downloaded by [ York University] on [17/09/16]. Copyright © ICE Publishing, all rights reserved. 82 BUSCARLET AND HUNTER ON THE [Minutes of backwards, and to raise or lower them, if the movementsdue to temperature did not act as desired. As the river span wasnow continuous with the two land spans at eachend, anew provision for temperature-movements was required. In deciding the positions of the fixed andexpansion bearings under the different girders on the river piers, this point had been kept in view, and the permanent expansion-bearings were placed underboth land and river spans on thenorth river pier. Thesebearings, which hadbeen locked in position duringthe erection of the river spa.n, were now released, and the girders were rendered free to move longitudinally over this pier andalso over the middle pier under the two north land spans. The falling temperature during the night caused a longitudinal motion of ?% inch at the end of the land span on this middle pier. The total suspended weight at thetime of closing the centre joint was 2,780 tons,including the temporary work and cranes. Such permanent work as could safely be omitted during the erection was left out, thus reducing theweight to be supported by the temporary ties. All the longitudinal stringers and floor-plates on the railway- Boor wereomitted, and all the longitudinalstringers, the floor- plates, and each alternate cross girder of the roadway-floor after the first 40 feet from the pier. Thefootway troughingand parapets were left out for thewhole length of the span. At the time of making the junction at the centre, the top of the towers had moved forward an additional f inch, or 29 inches in all, since the original setting. Temporary Reinforcement of Permanent Work.-Temporary diagonal bracing, to transmit thewind-stresses to thepiers, was placed between the bottom booms where the roadway-floorplating was omitted. This bracing was made & inch shorter than the required length and was drifted up tight in order to put an initial tension on it, and to ensure efficient support being given to the bottom booms while they were temporarily acting as compression members. The bottom booms were further reinforced for several bays at the end posts of both river and land spans. During the erection of the river span the diagonal andvertical web memberswere subjected tolarge reversals of stress, and all the diagonal ties, which were of flat bars, were reinforced and suitably braced to act as struts, as shown by the thick lines in Figs. 14, Plate 4. The riveting of the permanent steelwork followed rapidlyon the erection,and before anything was done to the temporary ties all the erectedsteelwork back to the pier was completely riveted up. Bolting TemporaryTies.-The largegussets for the temporary

tie connections were placed so as to intercept the shear from the two web-systems of the main girders, and were riveted to the side plates of the bottom booms ; but all joints in the temporary ties themselves were made with turned steel bolts l& inch in diameter. These bolts, of which about 20,000 were used, were turned togauge to suit theholes and made a hard driving fit. Parallel rimerswere passed through all the holes in the joints after the ties were erected, and the bolts were fitted by skilled mechanics. The workmanship and fit of these bolts w‘w equal to thebest engine-work. Previous to deciding to bolt the joints, two tests of riveted and bolted joints were made under conditions similar to those obtaining at thesite. In the first Table of Appendix I1 are recorded the comparative tests carried outon a hydraulically riveted joint andone made with turned steel bolts of a driving fit. The holes were drilled the full size through the flats, and the rivets were put in under similar conditions to the ordinary shop-work. The steel bolts were taken at random from the heap. The holes for the bolts and rivets were not rimered out, but the bars were taken apart and cleaned in the usual way, The flats were of mild steeland the rivets and bolts of “ rivet steel.” In the two tests made the two end bolts sheared almost simultaneously, and the thirdbolt had the upper section displaced 2%inch beyond the lower section, being on the point of shearing. The end rivet in both tests had the upper section displaced about 2%inch beyond the lower section, and hac1 practically failed when the bolts sheared. No slip was observed at the bolted joint until the shearing stress exceeded 7 tons per square inch, nor at the riveted joint until the stress exceeded 11 tons per square inch. A third test wasmade in whichblack wrought-iron bolts were used inch smaller in diameter than the holes. Theresult of this test is given in thesecond Table of Appendix 11. In this case no slip at the bolted joint was observed until the shearing stress exceeded 6 tons per square inch. These tests demonstrated the high eficiency of a bolted joint made in the manner described, and showed that a riveted joint had little advantage in strength, while the bolted joint had the great advantage of being more rapidly dismantled when the temporary work was being removed. There was, further,the certainty that all bolts were filling the holes and doing theirfull share of the work, in a better manner than would rivets which had been put in under the conditions obtaining at the site. The small superiority in strength of theriveted joint was, no doubt,due tothe greater frictional adhesion between theplates a2

Downloaded by [ York University] on [17/09/16]. Copyright © ICE Publishing, all rights reserved. 84 BUSCARLET AXD HUNTER ON THE [Minutes of from the contraction of the rivets in cooling, and emphasizes the importance in a bolted joint of having all bolts screwed up as hard as possible. The tests indicate that underordinary workingcon- ditions the bolts or rivets in a joint are not called upon to resist shearingstress. Tosee how farthis was true in the actualties, some of the bolts were taken out while the tie had the maximum stress in it ; these bolts were easily hammered outand hadno indication of any distortion or marks due to shear. Hydraulic Stressing-Bear.-The generalarrangement of the hydraulicstressing-gear for each pair of maintemporary ties is shown in.Fig. 12, Plate 4. A lower cross girder was securely bolted to the two main ties about 4 feet below the gap in the closing joint, and an upper cross girder wasfixed about 7 feet above the gap. Two plate ties, each formed of four plates, lO$ inches by 2 inch, rivetedtogether, were placed between andriveted at their lower ends to the webs of the lower cross girder ; then passing between the webs and through the flanges of the upper cross girder, were riveted at their upper ends to a crosshead girder, which was free to move between the twomain ties. On account of the relatively great thickness (3 inches) of these two side ties, it was considered advisable toarrange for ensuring an evendistribution of the stress on each plate and for avoiding a bending stress on the connecting rivets;they weretherefore made to project beyond the twogirders at each end and wereriveted together outside their connections to the webs of thesegirders. The upper cross girder formed a seatingfor two hydraulic screw-jacks, which were placed between it andthe crosshead girder. On therams being brought into action, the crosshead girde.r was pushed upwards, and by means of the connecting ties pulled up the lower cross girder, and so raised the maingirders of the bridge.The jacks were coupled togetheron the same hand-pump so thatthe hydraulic pressure in each wouldbe equal. Thesehydraulic jacks are of special design, andare shown in Figs. 25. Therams were of forged steel, 148 inches in diameter,and upon them was cut a screwed thread, which engaged in a nut where they projected throughthe cylinder. As the pressureforced outthe rams the nuts weregradually screwedback, andkept continuallybearing upon thetop of the cylinders, so thatin the event of any failure of the hydraulicpressure there was no possibility of the rams running back, and further the rams could be securely held in any desired position. Thisstressing-gear was perfectly safe and reliable in its action, and enabled the operations of raising the ends of the m&ingirders to be perfarmed in satisfactorymapner. The

Downloaded by [ York University] on [17/09/16]. Copyright © ICE Publishing, all rights reserved. PraCeedi11gs.l QUEEN ALEXAN'DIEA BRIDGE OVER THE? WEAR. S5 screw device on the rams rigidly maintained the gap in the main temporary ties, until the closing-pieces had been drilled and securely bolted on. After this was done an additional force of about 18 tons on each jack was required to release the pressure on the nut, and allow the rams to be run back for removal of the gear. By means

Figs. 15. i...... i:2%''...... *

ELEVATION

i ...... 2,. 7"...... p

=I Foot -

PLAN DETAILSOF HYDRAULICJACK.

of this gear the calculated stress on the temporary ties could be confirmed at each operation of raising the girders. Relieving Temporary Ties.-After the closing joint in the booms at thecentre of the spanwas made, the remainder of the permanent steelwork in the floors was erected andriveted. The final operations in connection with the release of the temporary tieswere then

Downloaded by [ York University] on [17/09/16]. Copyright © ICE Publishing, all rights reserved. 86 BUSCARLET AND HUNTER ON THE [Minutes of undertaken. Two of thehydraulic screw-jacks,which had been used in the stressing-gear, were placed under each main girder of the landspans at theends of theanchor-ties. The end of each span was then raised 11 inches by a force of about 720 tons. The centre of the river span lowered 2$ inches when the lift of the end of theland spans was 10 inches. Theadditional lift of 1 inch entirely relieved the temporary ties of all stress, which was clearly indicatedby their assuming the original waviness in plan that they had on erection, and by no further deflection taking place in the riverspan. The bolts inthe lowest jointin eachanchor-tie were then taken out, and the ends of the land spans were lowered back on totheir bearings.The steel thrust-blocks between the bottom booms of the endposts were immediately removed, and the whole of the temporarywork was rapidly dismantled.The distancebetween the lowerend of an anchor-tieand the gusset connecting it with the bottom boom of the land span was measured after the span was back on its bearings, and the gapwas found to be 5 inches. The top of each tower had moved forwards about 3 inches or a total of 54 inches from the original setting. The large temporary gussets for the attachment of the temporary ties to thebottom booms of the main girders were not removed, but were cut off flush with the tops of the side webs by means of the oxy-acetylene blow-pipe. The time taken to burn through a plate 14 feet wide by 13 inch in thickness was 50 minutes. Dejlectionsand Stremes during Erection.-The deflections were computed by the principle of work, checked graphically by dis- placement diagrams. The modulus of elasticity was assumed to be 12,000 tonsper square inch, anda reduction inthe calculated deflection was madefor the stiffness of the riveted joints, covers and gussets, amounting to 20 per cent. of the deflection contributed by the main girders, and to 10 per cent. of that contributed by the temporary ties. The agreement between the actual and calculated deflections confirmed these assumed values. The maximumpermissible unit stresses in the permanentand temporarywork during erection were carefully considered before elaboratingthe scheme, and it wasdecided in consultationwith Mr. C. A. Harrison, the engineer for the bridge, that the stresses should not exceed one-fourth of theultimate strength under the dead load, and that under a wind-pressure of B0 lbs. per square foot the combined stresses from the dead and windloads should not exceed one-half of the elastic limit. These values are low for direct stresses in temporary work, but it must be remembered that there are many accidental secondary

stresses which it is impossible to foresee and to provide for, and a relatively small amount of additional material is required to make the work quite safe. Thecalculations for the loads and stresses during thevarious stages of the erection are shown in Appendix 111. Considerablecare was manifested throughoutto avoidlarge secondary stresses ineither the temporary or the permanent work. The towers andtemporary ties were set out at suchin- clinations that they should be, as far as possible, in the direct line of stress when subjected tothe maximum load, and the observations made duringthe operations confirmed the originalassumptions. The adoption of pin connections or their equivalent, at the ends of the temporary ties and at the base of the towers, would no doubt have removed any anxiety from this cause ; but the success which attended the operations throughout leaves this point open to doubt. About 700 tons of steelwork, 4,500 cubic feet of timber in the trestles, and 3,900 cubic feet in the platforms and gangways, was used in thetemporary work ; or approximately 5 -4cwt. of steelwork and 33 cubic feet of timber per ton of permanent work erected in the river span. Thetotal amount of steelwork inthe whole contract was 8,440 tons. When the closing joints in the riverspan were riveted up, all the permanent work omitted during the erection was put in place and permanentlyriveted, the temporarywork being dismantled. This was practically completed by the end of December, 1908, and the roadway andpermanent waywas finished early in 1909. The erection of the river span took 10 months. Thebridge was tested byColonel Von Donop, acting for the Board of Trade,on the 3rd June, 1909. Twelvelocomotives, having a total weight of 1,190 tons (3.34 tons per lineal foot on the double track), were run over the bridge.The maximum deflections of the main girders of the land and river spans were, respectively, 3 inch and +Q inch. The whole contract took about 4 years to complete, and the total cost for the bridge and approach-railways was about 2325,000. Thebridge was openedby the Earl of Durham, E.G., on the 10th June, 1909, and by the gracious permission of Her Majesty the Queen it was named the Queen Alexandra Bridge. The bridge and approach-lines were carried out from the designs and under thesupervision of Mr. C.A. Harrison, D.Sc., M. Inst. C.E., Chief Engineerto the North Eastern Railway, whose Resident Engineerswere Mr. P. Bulmer, M. Inst. C.E., and Mr. F. C. Buscarlet, Assoc. M. Inst. C.E. Thesuperstructure of themain

Downloaded by [ York University] on [17/09/16]. Copyright © ICE Publishing, all rights reserved. 88 BUSCARLET AND HUNTER ON THE [Minutes of bridge was designed by Mr. C. E. Procter, and the 212-foot skew bridgeby Mr. G. F. Jackson, Assoc. M. Inst. C.E., both of the Company’s engineering staff: The contract for the whole of the work was undertaken by Sir WilliamArrol and Company, of Glasgow, underthe personal supervision of Mr. A. S. Biggart, Assoc. M. Inst. C.E. Mr. R. C. McDonald was the contractors’ agent at the site for the steelwork. Messrs. Mitchell Brothers were the sub-contractors for the masonry and earthwork. Mr. J. Mitchell Moncrieff, M. Inst. C.E., acted as ConsultingEngineer to the contractors,and Mr. Adam Hunter, M. Inst. C.E.,prepared and supervised the scheme of erection for them.

The Paper is accompanied by twenty-two sheets of drawings and three Tables, from whichPlates 3 and 4,the Figures in the text, and the Appendixeshave been prepared.There is also a portfolio of photographs.

[APPENDIXES.

m 10 ?c 00 m N +W mu3.. '0. W. mm.. -S 00 0 0 00 0

am r-0" 5 3 fi

......

APPENDIX 11.

COMPARATIVETESTS ON THE SHEARING STRENGTHOF STEEL RIVETS AND TURNEDSTEEL BOLTS. (Fig. 16.) Three bolts llLg inch diameter in drilled holes I& inch diameter. Three rivets l& inch diameter hydraulically riveted in drilled holes l& inch diameter. Shearing area of rivets and bolts, 2.66 square inches.

To measure the slip centre-punch marks were placed on each side of the joints, and measurements were taken by dividers at each load given and measured on a finely divided scale.

T- Slip (in inches).

Total Load. Ihearing Stress. Rivets. Remarks

Tons. Pons per Sq. In. 14.8 5.6 No slip. 19.7 7.4 24.6 9-3

29.5 1 11.1 34.4 12.9 39.3 14.8 44.2 16.6 49.2 18.5 52.8 Bolts 19.9 sheared

N.B.-In a former test thebolts sheared at 19.4 tons per square inch.

TEST ON THE SHEARINQSTRENQTH OF BLACKWROUQHT-IRON BOLTS. (Fig. 17.)

Three bolts 1 inch diameter in drilled holes l& inch diameter. Shearing area of bolts, 2.36 square inches. Fig. 17.

Slip (in inches). Total Load. Shearing Stress Remarks. on Bolts. I --- At*. i btB. Tons. Tons per Sq. In. 4.9 2.1 , . No slip. 9.9 4.2 .. No slip.

14.8 6.3 3% $3

19.7 8.4 3% :c 24.6 10-4 c5 ZZ 29.6 12.6 8% 8% 34.4 14.6 .. 39.3 16-7 .. , .. Boltssheared. I

APPENDIX 111.

CALCULATIONSFOR LOADSAND STRESSESDURING ERECTIONOF RIVER SPAN,

In all the calculations wind-pressure hasbeen considered as acting on the bridge at an angle producing a horizontal component of 50 lbs. per square foot, and a downwardvertical component of 5 lbs. persquare foot of exposed area. The exposed area, of the windward girder has been increased by 50 per cent. to make allowance for the leeward girder ; and in the case of the temporary ties and tower by 100 per cent. Stage 2 (Figs. 14, Plate 2).-In thin is shown the 6rst portion of the 330-foot spanerected and supported by ties at the top boom of the main girder; the Figure also shows the tempo-ry work in position prepamtory to the erection of the second portion of the span.

Downloaded by [ York University] on [17/09/16]. Copyright © ICE Publishing, all rights reserved. 92 BUSCARLET AND HUNTER ON TflR [Minutes d D ead load Dead ...... = 747 tons. Moment about end bearings 747 tons X 34.6 feet = 25,846 foot-tons. Dead load on supporting tiesat the topboom- Fortwo main girders 25,846 + 27 feet . . - 958 tons. Maximum load on supporting ties (for one girder onlyt 958 Deadload = ...... - 479 ,, 2 - Windload vertical component .....- 4 7, Windload horizontal component ....= 51 ,, __ Total = -534 ,, Section of supporting ties (one girder)- Four plates 24 inches X $ inch - 6r ...= 63.0 sq. ins.(net). One plate 68 inches X 2 inch - 1Or ...- 42.5 ,, ,, ,, Total = 105.5 ,, ,, ,,

Deadloadstress = 479+105.5 .....= 4.6 tonsper sq. in. Maximumstress = 534 + 105.5 .....= 5.1 ,, ,, ,, ,, Stage 3.-Shows the first and second portions erected and supported by ties A and C ; the Figure also shows tie B erected preparatory to building the third portion of the span. Deadload (total) ...... = 1,126 tons. Moment aboutend bearings ...... = 63,844 foot-tons. Maximum load on tie A (one girder)- Deadload ...... = 557 tons. - Windload vertical ...... - 6 9, Wind load horizontal (transferred) ....- 113 ,, - Total = -676 ,, Section of tie A- Four plates 24 inches X $ inch - 21. ...= 76.5 sq. ins.(net). Dead load atress ...... = 7.3 tonsper sq. in, Maximum stress ...... - 8.9 ,, ,, ,,,, Stage 4.-Shows the 380-foot span erected to the centre and supported by ties A, B and C.' Deadload (total) ...... = 1,391 tons Momentabout end bearings ...... = 108,219 foot-tons, Maximum load ontie B (one girder)- Dead load ...... = 715 tons. Windload vertical ...... - 17 >> Wind load horizontal (transferred) ....- 124 ,, - Total = -856 ,, Section of tie B- Eight plates 24 inches X 8 inch - 2r ...- 110 sq. ins.(net). Dead load stress ...... - 6.5 tonsper sq. in. Maximum stress ...... - 7.8 ,, 9, 9, 7, ___~~~~~. In calculating the load on tie B it is assumed that tie A is entirely relieved of stress.

Tower.-Masimum load for one girder only- Deadload ...... - Weight of tower ...... - Wind load ...... - Total =

Section of tower ...... - Dead load Dead stress ...... - Maximum stress ...... - Steel Packinq Blocks at Bottom Boon~s.--Il.laximurn boom of main girder- Deadload ...... - 550 tons.. W ind stresses Wind ...... - 145 ,, - Total = -895 ,, Tie C.--l\laxinlum lo~lfor one girller only- D ead load Dead ...... - Wind load ...... -

r3lotal =

Section of tie C- Four plates 30 inches X ;inch - 2r ...- D ead load Dead stress ...... - Maximum stress ...... - 200-foot Land Spu.n.--Total weight,, complete . = Load on each girder bearing 1,484 + 4 ...- Upward pullfrom tie C, dead loadonly ...- Difference =

P'iy!? 4 .

I ts r ph ~ ~ ~~ ~~

PART SECTION L =MD VIEW. ELEVATION. EXPANSION - BEAR1 NG.

YOWKWlARYOUfll

SUNDERLAND l'

MAP OF SiTE.

SECTIOMAL ELEVATIOW hA. u HALF SECTIONAL HALF SECTIONAL PLAN. GENERAL PLAN. ELEVATION. DETAIL aF SHOE. CAISSON SECTION AT C C PLAN FIG? 6. ON OF PLAN. PLAN- FIXED BEARlNO. CAST-STEEL EEARiNGs OF RIVER SPAN.

3 Q

A.. .. PierIp a. C.S. OF W'TTOM IWY STAGE 3 , . . 8MOWlYG DllCHluwS DEVELO$UENT OF INSIDE FLAWCE-PLATES [ BOTTOM SOON ) L 0

ARRANGEMENT 0.F HYDRAULIC GEA,R FQR STRESSING TlL,S-,l.US,lD)f, ELEVATlDl. DETAIL AT C {FigsJO)