The King Edward VII Bridge, Newcastle-On-Tyne.” by FRANKWILLIAM DAVIS and CYRILREGINALD SUTTON KIRK- PATRICK, Assoc

158 DAVIS AND KIRKPATRICK OK THE [MinuWs of

(Paper No. 3742.) ‘‘ The King Edward VII Bridge, Newcastle-on-Tyne.” By FRANKWILLIAM DAVIS and CYRILREGINALD SUTTON KIRK- PATRICK, Assoc. MM. Inst. C.E. THEmain line of the North Eastern Railway is carried across the River Tyne bp what is known as the Old High-Level Bridge. The people of Newcastle are justly proud of this picturesque structure, and also of theengineers who designedand constructed it, Messrs. Robert Stephenson and T. E. Harrison, Past-Presidents of TheInstitution. The bridge was formallyopened on the 15th August, ,1849, by the late Queen Victoria, amidst general rejoicings, for besides being the first railway-bridge over the Tyne, it was also the first high-level road-bridge connecting the Cityof Newcastle with Gateshead. The bridge was constructed for three lines of railway, and for nearly 60 years the whole of the enormous traffic of the districthad to be workedover thesethree lines. As thetrafic continued to increase, the directors of the North Eastern Ra,ilway Company decided toconstruct a newhigh-level bridge with four lines of railway, and parliamentarypowers for this undertaking were obtained in 1899. The position decided upon for the new bridge was 710 yards west of the old structure,and 260 yardseast of the Redheughroad- bridge (Fig.l). This position was chosen so that trains from London could enter the Central Station at one end and proceed northward fromthe opposite end, thus doing away with the objectionable arrangement previously existing, whereby trains had to enter and depzrt at thesame end of the station. The new bridge,now known as the King EdwardVI1 Bridge, was designed by Dr. Charles Ezrrison, M. Inst. C.E., Engineer to the

Northern Division of the North Eastern Railway, and it carries the railwayonly, without any accommodation for vehicles or foot- passengers.The contra.ct for the whole of theworks was let,on the6th March, 1902, tothe Cleveland Bridge and Engineering Company, of Darlington. Leaving the west end of the Central Station the railway bends to \ JESMOND NEWCASTLE

NEW BRlDGE S? ST”

REDHEUGH BRIM

Scale: I Inch - 4,000 Feet. FEET !3,000 tDa0 3,000 %p00 ,p00 0 5.000 FEET

the south on a curve of 10 chains radius, and crosses the river in rz straight line (Fig. 2, Plate 4). On the south side of the river four lines diverge on a 10-chain curve to the west, and join the existing Team Valley line, nearthe point whereit is crossed by the Redheugh Road, and two lines turn on a 7-chain curve to the east and join the Team Valley line near Gateshead statiob. A saving in distance of 682 yards is effected by the new route. The cost of the bridge and

Downloaded by [ La Trobe University] on [02/10/16]. Copyright © ICE Publishing, all rights reserved. 160 DAVIS ASD KIILKPATRICK ON THE [Xinuteu of approaches,exclusive of landand permanent way,was about g500,OOO. For the purpose of this description the work will be divided into six sections, namely- I. The Foundations. 11. The Korth Approach. 111. The Superstructure and its Erection. IV. The South Approach. V. The Cableway. VI. The Board-of-Trade Inspection and the Opening.

THE FOUNDATIONS. The contractors’ experience with electrical driving on other works having been very successful, it was decided to drive the plant used in the construction of this bridge as far as possible by electricity ; and in order to avoid any danger of breakdown while sinking the caissons, the generating-plant was duplicated. A generating-station was built on the Gateshead sideof the river, at the top of the bank, and sidings were laid down from a junction with the main line. Theplant consisted of foursemi-portable boilers of locomotive type, any two of which were capable of providing sufficient steam, at a pressure of l50 lbs. per square inch, to work the whole of the machinery.The generating-plant consisted of twosets of enclose- high-speed compound engines coupled direct to multipolar dynamos, each set beingcapable of giving an outputof 740 amperes at 240 volts, or about 240 HP. There were also three smaller sets for lighting at 110 volts. The main switchboard was arranged so that the two large sets couldbe used in parallel, if required. An electricity-meter, reading Board-of-Trade units, was placed on the main circuit, ancl also a recording ampere-meter reading up to 1,200 amperes. For supplyingcompressed-air tothe caissons three horizont,al compressors, havingcylinders 15 inches indiameter by 36 inches stroke, driven through steel spur-gearing by 125-HP. shunt multi- polarmotors, were laid down close tothe river. Each engine delivered about 740 cubic feet of free air per minute when running at 100 revolutions, and by means of a regulating resistance on the shunt-circuit of the motors, the speedcould beincreased to 110 revolutionsper minute. The air-cylinders had water-jackets for cooling, and a high-flash lubricating-oil was used, in order to keep the air as pure as possible. The valves were operated by Corliss gear and had a positive action, and were also governed by a compressed air piston which controlled the air-pressure as required within 5 lb.

Downloaded by [ La Trobe University] on [02/10/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] KING EDWhllD VI1 BRIDGE, BEWCASTLE. 161 The caissons (Figs. 3 and 4, Plate 4) wereconstructed of mild steel,the thickness of the outer plates of the shell rangingfrom inchto 4 inch.The area of allthree caissons was the same, namely, 3,361 square feet over the outside of the cutting edge ; but the height of the permanent part varied according to the level of the river-bed, the south caisson being 54 feet, the centre caisson 26 feet 6 inches, and the northcaisson 56 feet high. The total depth of the temporary and permanent caisson together was about 75 feet inall three cases. Thetemporary caisson was joinedto the permanent by a bolted joint, so that it could be disconnected by divers at about the level of the bed of the river. The cutting edge of the caisson, as shownin Fig. 4, was formed of threethicknesses of plate,the outermost being 6 inch thick. The shoe, which was carriedcontinuously round the caisson, was stiffenedby plate diaphragmsinch thick, 3 feetapart between centres,braced withangle-bars, theinner skin of the shoebeing composed of onethickness of plate, andthe outer skin of twothicknesses. The angle-bar at the bottom of the shoe was designed to act as a brake to the caisson during its descent through soft ground, and, together with the two wide-flanged girders, it proved to be of considerable assistance in keeping the caisson level. It will be noticed (Fig. 4) that the roof of the working-chamber was curved and had a headroom of 9 feet 6 inches at the highest point and 8 feet at the lowest. This was originally designed to be flat, with 7 feet headroom, but was altered by Dr. Harrison on the Authors’ suggestion. The object of the curved roof is to give more headroom to the men as they advance into the shaft, and also to make it easierto pack the concretetight against the roof when fillingup theworking-chamber. Subsequent experience during the progress of the workproved thealteration in the headroom to havebeen necessary, the cutting edge insoft ground being frequentlyconsiderably ahead of the digging.Another important addition to the caisson was made in putting the two large girders across the working-chamber between the shafts with wide bottom flanges 3 feet 6 inchesabove thecutting edge. Themain object of thesegirders was toprotect the men in case of soft ground being encountered which might cause the caisson to sink rapidly ; in this case the wide flanges would come in contact with theground and prevent further sinking. They were also very useful in keeping the caisson plumb and regulating its descent. At alltimes during the excavation a bank was leftunderneath each girder, and at high water,:when, owing to the increased air-pressure, theweight of the caisson was least, the tops of the bankswere [THE INST. C.E. VOL. CLSSIV.] M

Downloaded by [ La Trobe University] on [02/10/16]. Copyright © ICE Publishing, all rights reserved. 162 DAVZS AND KIRKPATRICK ON THE [Minutes of removed until there was about 9 inches clear between them and the bottom of the girders ; then as the tide wentback the caisson would graduallysink until it restedagain onthe banks. These large girders are shown by dotted lines (Fig. 4). Immediately above the working-chamber the caisson is spanned by girders 3 feet 6 inchesdeep and 3 feetapart. These c'arry the ceiling-plates and also form the floor upon which the weight of the concreterests during the process of sinking.The flooring was designed to carry a load of 1 ton per square foot distributed overthe whole area. The ceiling-plates of the working-chamber formed the

bottom flanges of these girders and were 22 inch thick. Above the top of the shoe the skin was one plate thick only, but above the tops of the flooring-girders it was stiffened by rolled joists 8 inchesdeep and 3 feetbetween centres placed vertically.This, portion of the caissonwas further stiffened by two belts, running continuously round it, formed of girders about 2 feet deep, m shown in section in Fig. 4, ancl braced by light lattice-girders and diagonally by channel-bars. The web and outside flange of the girder forming the topmost of these belts consisted of plates riveted together ; these plates acted as the top booms of the girder, of which the metal in the shoe formed the bottom boom, and had a sectional area in the centre such that, when resting onrock or other hard ground at each end and unsupported at the middle, the caisson was strong enough to support its own weight. Above 26 feet 6 inches from the cutting edge the caisson, whether temporary or permanent, consisted of a steel shell only, the strutting being of timber (Figs. 4 and 5, Plate 4), with about four light lattice girders in the length of the caisson and every 7 feet high, to act as ties and prevent the caisson from bulging outwards when left by water at low tide. Up to 26 feet 6 inches above the cutting edge the skin plates were vertical; above this theywere horizontal, in tiers of 3 feet and 3 feet 6 inches, ranging in thickness from 4 inch to 3 inch. The settings of timber were placed every 3 feet or 3 feet 6 inches according to the depth of the plates. The plates forming the permanent portion of the caisson were riveted together, but the temporary portion had bolted joints at every second or third plate forfacility of removal. The holes in thetemporary plates were punched square,and thebolts had square necksto prevent them from turning round. Thetotal weight of the lowest 26 feet 6 inches of permanent7 caisson was about 450 tons, and it was decided to build this on the staging in its properposition. For this purpose timber piles were driven round t'he site of the caisson, and the horizontal bwms whiclr

rested on the topsof the piles wereleft projecting inwards about3 feet. The steelwork was then built upon these overhanging beams, riveted togetherand caulkedwhere necessary. Verylittle caulkingwas done, as all plates before being joined together were thickly coated withbiturnastic solution, specially prepared; and so well did this answer that, in spite of the shape of the caissons, they were absolutely water-tight. Timber trestles were then fixed on the staging, and on these four steelbox girders were placed tospan across the caisson. Spaces uTere left in the flanges of these girders through which steel plates mere passed and connected to the ceiling-girders at eight points by rocking links. The steel plates had holes drilled in them 1 foot 6 inches apwt between centres,and steel pins 2 inches in diameter were inserted in these holes to rest upon small cast-iron saddles on the tops of the girders. A small crossgirder rested on the topof the rams, and when the rams werepumped up this girder came in contact with the pins, passing through the lifting-links and so lifted the caisson. Therams had a total lift of 2 feet.They were worked by two sets of four-throw hydraulic pumps, and were all connected together by piping, valves and pressure-gauges,being inserted at different points, so that the liftingor lowering of any two rams could becontrolled as required. When all was readythe rams were pumped up until the caisson was lifted about 2 inches clear of the staging. The overhanging portions of the timber headswere then cut off, leaving all clear underneath, and the pinsimmediately above the girders were removed. The valves mere now opened and the caisson wasallowed to descend 18 inches, until the pins, which had been re-insertedin the holesabove, restedon the girders.The rams were then again pumped up, and the process was repeated until the caissonwas lowered sufliciently for it to float in the water, which was generally about 17 feet below the level of the staging. Concrete was now putinto the interior of the caisson above the roof of the working-chamber, until the cuttingedge rested upon the bed of the river, andthen a furtherquantity was added of sufficientweight tocounteract the upward pressure of the compressed air. In the south caisson the weight of concrete put in before the commencement of the digging was about 4,500 tonsand at the finish 10,000 tons. Three shafts wereprovided for access to the working-chamber. In plan these shafts were shaped as shown in Figs. 3, Plate 4, in order to provide separate ways for men and for materials. The tie- bars were fixed to angle-cleats across the narrow part to form a M2

permanent ladder for the whole height, and a vertical angle-bar was fixed to the bars, so as to avoid any danger of the buckets catching, or swinging against the men’s fingers. On account of the height of the shafts, they could not be built up entirely at the start; steel doors were therefore provided to close them off one at a time at the level of the roof of the working-chamber, so that the air-locks could be removed, and the remaining lengths added to the shafts, without stoppingthe excavation or the air-compressors.These doors m-ere concreted in at thefinish. Theair-locks were fixed onthe tops of theshafts, and were designed by oneof the Authors(Mr. Davis) with the idea of removing the excavated material from the working-chamberof the caisson more rapidly than is possible with the ordinary type of air-lock. A plan, elevation, and section of the locks are shown in Figs. 7, Plate 4. Themain idea in the working of them was to remove the material from the insideof the caisson to the outside, and tipit into barges in one complete cycle of operations without any re-slinging and with a minimum loss of air. The main body of the lock, 8 feet 6 inches in diameter and 6 feet high, was constructed of $-inch steel plates, the roof-plate being flanged and domed. The bottom plate, whichwas flat, was 1 inch thick, and it was further stiffened by brackets attaching the plate to the sides of the shaft. An opening was cutin the plate to correspondwith theinside of theshaft. The material-lock was fixed in the roof-plate, and was 2 feet 11 inches in diameter by 5 feet 6 inches deep. This lock wasclosed on the inside by adished horizontal steel door with a rubber face and hingedon one side, the dooritself beinglifted by asteel rope passingover a small friction-drum on the shaft shown in Fig. 7. This shaft passed through a stufing-box in the roof of the main lock to theoutside, where it was driven through worm-gearingby a 2-HP. series-woundmotor fixed oniron brackets. A startingrheostat ampere-meter, and an automatic cut-out to prevent over-winding of the drum, were fixed in a damp-proof case inside the main lock. Thetop door of thematerial lock was dished and facedwith rubber. It was fastened on the outside as shown by means of four steel screws 2a inches in diameter, and four steel bolts, the latter being shot over the door after the screws had been tightened down. Two cylinders and pistons were fixed to the outside of the lock, and were connected to the inside by a small pipe. When the door was closed and compressed air was admittedto the lock, thepistons were forced out and tapered tongues would push home the bolts, if the attendant had forgotten to do this ay nand. This arrangement also prevented any possibility of the bolts being withdrawn as long

as there was any pressure in the lock. These bolts were themselves strongenough to hold the door against 40 1bs. persquare inch working-pressure, so that, with the four steel screws as well, there was not the slightest danger of any accident. The entrance-door for the men’s lock opened inwards, as shown in Fig. 7, sectional plan AA,and the lock itselfwas bolted tothe side of themain chamberwith a rubberjoint. Valves,worked fromthe outside, admitted air to this lock, and as soon as the pressure was equal to the pressureinside the caisson, the second door couldbe opened. About five mencould pass through a lock at a time. Pressure-gauges were fixed on the locks and the valves were worked by trained men on the outsideonly. Three 5-ton electric derrick cranes, one for each lock and working at a radius of 30 feet, were fixed on staging (Fig. 5, Plate 4), and from these a steel rope f inch in diameter passed through a stuffing box in the top door of the lock down to the centre of the material part of the shaft to theworking-chamber. The buckets employed were of special design, the object being to have as little clearance as possible between the outside of the bucket and the material-lock, and so reduce to a minimum the loss of air when discharging a lock. It was also necessary that they should be self-discharging with any kind of material, and with a very small amount of taper, Figs. S show theconstluction of thesebuckets, which worked satisfactorily. The signals for hoisting and lowering the bucketswere transmitted from a man in the air-lock to the electric crsnes, a,nd were given by means of two small switches and two glow-lamps, the latter being fixed in front of the crane-driver. One of these lamps was lit for “ hoist,” and the other for “ lower,” and both were turned out for stop.” The arrangement was found to work perfectly. Fig. 6, Plate 4, shows the power absorbed for a complete cycle of operations with one crane and one air-lock door-gear, the operations being the following. The empty bucketwas lowered into thematerial- lock, andthe top doorwas fastened down. A signal(two smart tapswith a hammer) was then givenby the outsideman to the inside man, and on receiving an answering signal back, he let the air into the material-lock by means of a ]&inch valve. The inside man t,hen lowered the horizontal door by means of his braked drum and signalled tothe crane-driver to lower the bucketdown the shaft. As soon as it reachgd the bottom it was disconnected from the rope, and a full bucketwas attached. The lock-man now signalledhoist ” and the bucketwas hoisted until it entered the material-lock,when the lock-man startedthe smallmotor which

Downloaded by [ La Trobe University] on [02/10/16]. Copyright © ICE Publishing, all rights reserved. 166 DAVIS AND IiIItIiPBTRICK ON THE [Minutes of closed the horizontal door. He then sign:tlled with his hammer to the outsideman, who immediately released the air from the material-lock by opening a l&-inch ralve. The pistons then fell by their own weight, and the screws and bolts were released. The top door was next hoisted out of the lock withthe bucket, and the Gutside men attachedthe tripping-chains, after which the,crane

Figs. 6.

shed round and discharged the contents (zlboat 25 cwt.) into the hoppers alongside the sta.ging. The hoppers used for taking the excavation were four in number, each of 250 tons capacity. Theyhad to be towed outto sea to discharge, the distance from tile work being a.bout 14 miles. The energy consumed in getting out each bucket was 0.38 unit,

andthe time taken was 4i minutes.The quantity of material that couldbe passed through one of these locks was governed by the speed of digging, and the height of the lift, the best day’s work through one lock being seventy-five buckets, or about 94 tons in l0 hours. Thesouth caissonwas begunon the7th January, 1903, and lowered on to the river-bed by the 30th May. Sinking was begun onthe 29th Juneand all excavationwas finished by the13th October.Concreting the working-chamber and filling theshafts (capacity 930 cubic yards) was completed by the 27th October, 1903. Thetotal quantity of excavation inthis caissonwas 7,228cubic yards, including 1,028 cubic yards of rock. Several thin seams of coal were passed through,and at times sulphuretted hydrogen from theseseams was present in the working- chamber,causing several cases of illness. Thefoundation was finished on a bed of compact grey shale, which was proved by boring inside the caisson to extend at least 30 feet deeper. In order to ensure the concrete beingsolid against the roof of the working-chamber, a 2-inch pipe was taken down each shaft and laid along close to the roof at itshighest point, with a series of slot-holes in it. Cementgrout was forceddown this pipeby air-pressure until it would take no more. The centre caisson was started on the 1st September, 1903, and lowered until it floated onthe 14th February, 1905. Fromthe 15th February to the 17th March, 4,500 tons of concrete were put in, and the caisson then finally rested on the bed of the river. The depth of water at the site of this pier is 25 feet at low water, and the average range of ordinary spring tides is 15 feet. When concreting started, the caisson, being afloat, was rising and falling with the tide. Excavation was started on the 17th April, andwas finished on the4th July, 1904.Concreting of the working-chamber and shafts was commenced immediately after, andcompleted on the 14th July. Work had to be suspended for 1 week within a foot of the bottom on account of the Newcastle races. The sinking of this caisson took longer on account of the depth of water. As there was not sufficient weight in the concrete to counter- act the air-pressure, the granite masonry had to be built to a height of 14 feet, givingan additional load of 2,000 tons, before the sinking could begin. After sinking 12 feet, workwas suspended inside,until 4,000 tons more granite had been set, after which the caisson was sunkto the requireddepth in greyshale, similar tothe south caisson. Thetotal quantity of excavation was 3,984cubic yards, including 743 cubic yards of rock.

Downloaded by [ La Trobe University] on [02/10/16]. Copyright © ICE Publishing, all rights reserved. 1% DAVIS AND KIRIiPATRICK ON THE [I\linutes of So much of the granite of the pier having been set before sinking, it was necessary to sink thecaisson absolutely level, and in its right position, and also to stop it exactly at a fixed point, so as not to have an unequal course of granite.This wasvery successfully accomplished withthe aid of the]large girders in the working- chamber. Thetotal load onthe foundationsis 8.5 tons persquare foot goss or 7 tonsper square foot allowing for water-displacement, but neglecting skin-friction. Thenorth caisson wasbegun on the1st March,1904. By the 28th October, 7,465 cubic yards of excavation had been removed,and a sandstonerock foundation obtained. Concreting the working- chamber andshafts was completed onthe 9th November, 1904. In all three caissons about 930 cubic yards of concrete were passed in and packed under air-pressure in 10 days. There was recently considerable correspondence in The Times in whichmuch was made of the dangers(attending men who work under compressed air, and stress was laid on the large number of deathsamong men engaged onthis class of work in America- Experience in England does not !accord withthese views, and it' seems apparentthat the deaths which have occurred in America have been due largely tocauses which are not a necessary nccompani- ment of compressed-air work. One of the Authors (Mr. Davis) has had experienceof compressed- air workextending over thelast 15 years with pressures up to 47 lbs. per square inch, and during this time he has had only one fatal and two serious cases of illness. The death and one of the ill- nesses occurred on the King EdwardVI1 Bridge. In both these cases the men suffered from paralysis of the loner limbs. In the one case the man was of good physique, and had been accustomed to working under compressed air for some years, and he isnow nearly recovered. In the fats1 case the man was of weak constitution and had only been at work a few hours ; the doctors assigned acute phthisis as the principal cause of death, aggravated by the paralysis brought on by compressed air.Generally speaking, smallwiry men have been found most suitable for the work. The following particulars of the men employed under compres>ed air will be interesting as tending toshow the small danger attaching to this work when it is efliciently managed. Of 169 men examined by the doctors, 7 men, equal to 4 per cent., were rejected as unfit. On each caisson 36men were employed under compressed air in theday shift, and 36 in thenight shift. Of these 72, 48 worked rightthrough the sinking of thethree caissons without being

Downloaded by [ La Trobe University] on [02/10/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] KING EDWARD VI1 BRIDGE, NEWCASTLE. 169 affected by compressed-airillness. Other 49 worked forshort periods of 1 or 2 months and 65 for periods less than 1 month. Out of the last 65, 29 men gave up through fear of bends, after a few days'work. Thelargest number of men off workthrough compressed-air illness occurred when the pressure was 24 to 30 lbs. per square inch. Up to 25 lbs. pressure the men worked in two shifts of 10%hours; from that to 30 lbs. they worked 9a hours, and above that pressure they worked in three shifts of 8 hours each, one hour being allowed for meals. The men were well looked after, having a large comfort- ableshed to go into,where hot coffee wasserved tothem after coming out of the caisson. They were also periodically examined by a resident medical man, and a medical lock was fitted up where men affected by bends could be treated. Both compression and deco'mpression (especially the latter) should be performed slowly, yet not so slowly as to run the risk of the men becoming chilled or getting nervous. Therule on this work was to allow 1 minute for every 5 lbs. of pressure, so that for 30 Ibs. 6 minutes would be taken;and this was foundto answer very well. Very divergent opinions are held as to the length of time to be taken in decompression, varying from 1 minute to 20 minutes for every 5 Ibs. of pressure, and although undoubtedly the possibility of bends or neuralgicpains inthe tissues couldbe lessenedby extending the time of decompression, the Authors' experience has been that there is great difficulty in keepingmen a longtime in the necessarily small air-locks ; and that, as only a small percentage of them suffer, the best plan is to keep a spare lock in readiness, in which menwho develop bends canbe at once recompressed, and then decompressed as slowly as wished. This lock can also be more readily warmed and ventilated, and a form can beprovided on which the men can lie. It is very important that the ventilation of the working-chamber and the shafts should begood. On the King Edward VI1 Bridge the air-pipes and valves were so arranged that if the air was being pumped into any two air-locks the valves on the third were opened slightly, and this caused the fresh air to descend the shafts, travel along the working-chamber, and ascend thethird shaft. This of course would not be necessary as long as the air had free egress underneath the cutting edge through gravel, but the centre caisson was the only one in which it was quite free. It was thought at one time that anexcess of carbon dioxide in the air in the caisson was one of the causes of bends, and therefore on

Downloaded by [ La Trobe University] on [02/10/16]. Copyright © ICE Publishing, all rights reserved. 170 DAVIS ASD IiIRKPATRICIi OK THE [Minutes of thenorth caisson arrangementswere made for analysing the air everyday. The fluctuation of CO, fromday to day is shown in Fig. 9, Plate 4, and was proved to bear no relation to the number of cases of illness. It willbe observed that whilstconcreting was in progress thepexentage of CO, fell below thepoint at which it stood during the week-ends when no men were inside. During meal-times two compressors were sometimes run together to clear theair, but at othertimes one compressoronly was used, pumping in about 22 cubic feet of freeair per man per minute.Some very interesting papers on the medicalaspect of compressed-airdiseases have been written by Professor Oliver :~ndDr. Parkin,2 for which data wereobtained by them on this work. In order to prevent blows underthe cutting edge,which on these large caissonswould have beenserious, rivets were omitted in thecutting edge every 2 feetand about 6 inches upfrom the bottom.These holes allowed thesurplus air to escape, and preventedthe pressure from accumulating sufficiently to cause a “ blow.” In all the caissons gelignite was usedwhen rock was reached, and singlecharges were fired by electricity from thetops of the shafts. Experimentswere made with eachcaisson todetermine the skin-frictionand the results obtained me given in the following Table :-

Sout,h Centre North Caisson. ___Caisson. Caisson. Weight,concrete ...... 9,200 4,231 8,430 ,, granite ...... 3,110 ,, steel ...... 600 600 timber,etc...... 200 so0 200 .. ~__---

Totaltons ....~ 10,000 8,241 9,230 --__---~----__ Air-pressure tohold caissons insuspension Lbs. i 25 30 25 Upwardreaction ...... 6,447 5,373 Arcaesposed to skin-friction ... 7,150 11,650 Weightsupported by skin-friction . . 1,794 3,858 Skin-friction ..... 5.0 6.62

Harheu Lectures on “Maladies Caused by the Air we Breathe,” 1906, by Professor Thomas Oliver, M.D., F.B.C.P., Newcastle-upon-Tyne. ? “Caisson Disease, including the Physiologicaland Pathological Effects of CompressedAir.” By AlfredParkin, M.D., F.R.C.S.,Northumberland and Durham Medical Journal, April, 1905. (Reprint in Libraq Inst. C.E.)

THE NORTIIAPPROACH. Thenew works commence upon the old bridgecrossing Forth Banks Road (Fig. 2, Plate 4), and it was intended to widen this bridge on both sides. There was no difficulty upon the south side, but on the north side the proposed widening involved lowering the road, and owing tothe severe gradientthis wouldhave been veryunsatisfactory. Powers were therefore obtained in 1903 to close Forth Banks Road, and to construct in its place an entirely new road under the existing Newcastle and Carlisle Railway, and alsounder the approach to the newbridge. As soon as the new road wasopened, the existingroad was closed except for a small subway for pipes. Bythis Act the RailwayCompany gained by being able to extend the station over Forth Banks, and the Corpora- tion of Newcastlegained a new thoroughfarefrom east to west. The new bridge is 40 feet wide on the square and allows a headway of 16 feet, the roadway being on a gradient of 1 in 40. The rails are carried on girders with flat floor-plates upon which an ordinary sleeper-road is laid. This bridge was difficult to construct, owing to the necessity of notinterfering with passenger-traffic. Thesteelwork was built upon the west side and drawn into position on several Sundays. In no case was the passenger-traffic interrupted, although the interval between trains on Sundays was only 4 hours. The railway then crosses the entrance to the Forths goods-ya,rd on three segmental brick arches of small span and three spans of steelwork supported on brick pillars. The railway passes through the Forthsgoods-warehouse on six steel spans averaging 48 feet each and supported on brick piers 5 feet wide. Rail-level is 19 feet 6 inches above the warehouse roadway, and a clear headway of 14 feet3 inches ispreserved, so that thetraffic below the newrailway can be carried on exactly as before the alterations. The roadway of the warehouse is supported by groined brick arches roofing over extensive cellarageat a lower level of about 15 feet 6 inches to which access is obtained from Pottery Lane. In order to geta foundation, thenew brick piers were carriedbelow the level of the cellar-floors, and this necessitated cutting through the groining and extensively supporting it by brick arching in cement. Above rail-level the old roof was removed and the gables were made good by means of glazed screens and steel trusses. Emerging from the warehouse the line crosses Pottery Lane by means of a skew steel bridge of 33 feet span, rail-level being 35 feet above the road.

The whole of the floor-plates of the ten steel spans referred to, after having been scraped and coated with bitumastic solution, have been covered with anaverage thickness of 13 inch of fine cement concrete in the proportion of 2 to 1, laid so as to give 2 inches of fall from the centreof each span to the gutters,which are parallel with, and immediately over, the brick piers below. Upon this has been laid bitumen sheeting, and above this another 14-inch layerof 2 to 1 cement concrete. The bottom layer of concretecovers flanges and rivets and makes a smooth surface for laying the sheeting, and the top layer is to prevent platelayers from damaging the bitumenwhen laying or maintaining the rails. The ballast is of clean gravel and the complicated junctions are carried by ordinary chaired rails and cross timbers. The south tangent-point of the 10-chain curve occurs on Pottery Lane Bridge. South of this bridge there is a straight stone viaduct withten semicirculararches of 25feet span. Southward from Pottery Lane the facework in the approaches is of red sandstone obtained from the New Cove quarries on the Caledonian Railway, 13 miles north of Carlisle. In order to form the north anchorage of the10-ton cableway, to be described later,the foundation of pier No. 3 waswidened to 12 feet and increased in depth by 4 feet ; and for the purpose of forming a suitable foundation for the cableway-tower the backing to the arches over pier No. 7 was made of ashlar built in cement, instead of rubble. The arching on the north side terminates in an abutment 28 feet wide on the top of the bank of the River Tyne, andthis abutment is built on cementconcrete, averaging 7 feet deep,stepped on a hard clay foundation 62 feet below rail-level, and 34 feet below ground-level. The masonry abutment was made 28 feet wide in order that the pilasters might be built to correspond with the main bridge. Five voids were left in the abutment to save material and to avoid unnecessary weight on the foundation.

THESUPERSTRUCTURE AND ITS ERECTION. Thereare three main piers in theriver. The north and south piers are 20 feet behind the frontage-line of the Tyne Improvement Commission ; but the third pier is in the centre of the river-channel. The north land-span is 231 feet; the two river-spans are 300 feet each, andthe south land-span,known as " Pipewellgate Span " ranges from 184 feet 6 inches to 205 feet.This varying width is duepartly to the span beingfan-shaped in plan,owing tothe divergence of the south-west and south-east approaches, and partly

Downloaded by [ La Trobe University] on [02/10/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] KING EDWARD VI1 BRIDGE, NEWCASTLE. 173 to the fact that the abutmentis at an angleof 80" with the centre line of the bridge. The headway of the two river-spans is 83 feet 6 inches above high water of ordinary spring-tides at the ends, and 84 feet in the centre. The cement concrete in the caissons, previously described, finished at river-bed level, and at this point granite masonry commenced. The overall dimensions of the piers at the bottom of the granite are 103 feet 6 inches by 30 feet 6 inches (footings excepted). At each endthere is a curvedcutwater 17 feet 6 incheslong, faced with granite and filled with cement concrete. At 5 feet 6 inches above highwater of ordinaryspring-tides the piers separate into three pillars ; the outerof these pillars are each21 feet 6 inches by 30 feet 6 inches with a void of 9 feet by 7 feet. The central pillar is 13 feet 6 inches by 30 feet 6 inches. These pillars are carried right down to the concrete and the spaces between the granite are filled with cement concrete. A series of intake courses reduces the dimensions of the pillars, and the spans between them are arched over by two stone arches 1 foot 6 inchesthick, thespringers being 64 feet 9 inchesabove highwater of ordinaryspring-tides. Above the relieving arches the pier is solid up to the girder-bed, which is 80 feet 6 inches above high water. Above and on each side of the girder-beds are pilasters, 36 feethigh and averaging 5 feet thick, of granitestiffened by rubblecounterforts. Below theintake courses allthe granite is rock-faced, each stone having about 2 inches of rock left on and the edges dressed to a true line with 1 inch margin drafts at all quoins. Above theintake courses thegranite is dressed to a smoothness known as '' single-axed." The staging around the caissons was in all cases used to build the stonework toabout 25 feetabove high-water level. For building above this height two 5-ton electric Scotch derricks were used, one at each end of the piers.They were placed so as toreduce to a minimum the risk of fouling the cableway. The centre of the cableway was 15 feet 9 inches west of the centre of the bridge. The jib of the west-end crane was therefore only 45 feet long, and lifted 5 tons at 30 feet radius, but the jib of the east crane was 70 feet long,and lifted 5 tons at 50 feetradius, or 2%tons at 60 feet. Stone was fed to these cranes by means of steam travelling cranes. For the purpose of discharging granite promptly a timber wharf was erected west of thesouth pier on the Tyne Improvement Commissioners' frontage-line, a berth 250 feet long being dredged so as to allow steamers drawing 15 feet to lie safely at low water. Theequipment of this wharfconsisted of two'?-ton steam

travelling cranes, and discharging was doneby day and night. There was direct access to the wharf from the railway and materials were transferredto the required positions either by the10-ton cableway or by means of floating craft. The total quantity of granite used was 546,257 cubic feet, and it was found that 13* 58 cubic feet weighed 1 ton. All the main girdersa,re of lattice design (Figs.10 and 11, Plate 5), the north land-span and the two central spans being similar, except that the actualsections vary on accountof the difference of the spans. The permanent wayconsists of a flat-bottomedrail 6,l, inches deep, fastened to a $-inch flat plate which distributes t.heweight uponwaybeams of kyanizedpitch-pine 18 inches wide, 10 inches deep at the centre and 16 inchesdeep at the ends. The width is obtained by bolting together two beams 9 inches wide. Each pair of rails runs in a longitudinal trough, and the actual rail-level is approximately the same as that of the top of the main girders at thecentre of the spans.Bulb-irons are fixed to the sides of the boom nearest to the parapets, to act as guard-rails. Thereare five maingirders to eachspan. In thetwo central spans each main girder is 308 feet long between the centres of the bearings, and 27 feet deep over the angles of the booms, the booms being 5 feet 6 incheswide and 3 feet deep. Thetops of the top booms are, however, only 4 feet 4 inches wide, as the out'side top angles are lowered so as to formshelves for the floor-plates. The bottom booms are stiffenedby lattice-bracing at every 11 feet 6 inches, and in addition there is diagonal bracing between the top and bottom booms. The south end of each girder is free to expand. The bottom member of the fixed bearing is a steel casting, 7 feet by 5 feet 5 inches, accurately bored at the top to receive a turned rocker-pin 9 inches in diameter. The bottom of the casting isplaned, and rests on a sheet of lead 2 inchthick, and is fastened to the granite by means of eight 1%-inchlewis-bolts run withcement grout. The top member is the same size, and is accuratelybored at the bottom to receive the rocker-pin, the top being planed where the girderrests upon it. The overall depth of the fixed bearing and pin is 3 feet. The expansion-bearing is the same depth overall, and consists of a rocker and saddleresting upon segments of rollers which arefree to travel on a roller-path.There are seven segmental rollers in a bearing, each being 12 inches high and 6 inches wide and turned to a radius of 6 inches, with a space of 1 inch between each roller, The Act of Parliament provided that one-half of the navigable waterway might be closed to traffic temporarily during construction.

Afterfull consideration of various schemes for erection, it was finally decided to erect timber staging in the river. As soon as two girders were built they were shed to one side to allow two more to be laid down. One of these was thenshed and the last girder. built.This method was fully approvedby Dr.Harrison, as it imposed no undue stresses upon the girders during erection. The south channel of the river was closed to traffic on the 10th April, 1905, and the staging was started immediately, all the piles being drivenfrom two floating craft.The piles were 14 inches square and 55 to 60 feet long, the depth driven in the river-bed being about 15 feet. Special blunt-nosed pile-shoes, weighing 56 lbs. each, were used to prevent the piles from being driven deeper thm absolutely necessary, so that they could be more easily drawn, and, if not damaged, used later in the northchannel. Each pile was driven until it sank fr inchwith n 12-foot drop of a l-ton ram, the greatest weight supported by any one pile being about25 tons. There weretwelve rows of verticals in elevation, the distancebetween thecentres of the rows being 23feet. In cross section there were four verticals 8 feet 8 inches apart between centres, the outside two being immediatelybelow the Goliath crane, the rails cf which were 26 feet apart. Raking struts half-way down increased the cross-sectional width to six piles at the base, which was 53 feet 2 inches over all. In addition to these raking struts a dolphin of four piles was driven on eitherside of the centreof the span, and two raking steel-wire guys, 1 inch in diameter, were fastened to the top in order to stiffen the stage. Exceptpiles, the all the verticals were 12 inches to 13 inches square. Upon the piles14-inch crossheads were fixed, ancl upon the crossheads were laid longitudinals. By the use of theselongitudinals the trestles were adjusted slightly for span, and so any small error in the driving of the piles was compensatedfor. Double diagonals formed of angle-bars were usedbetween highand low waterto brace each trestletogether. In cross section the outer piles were double braced by $-inch steel- wire ropes reaching to the river-bed level. The connection of these ropes below water was made before drivingthe piles, andthey were tightened bymeans of union screws above high-water level. Above the longitudinals the trestling was made in four tiers. The lower of these was 18 feet high, andthe three upper oneswere 19 feet high. All theforty-eight trestles were builtin the Skinnerburn yard on the Newcastle side and were laid out exactly totemplate. Cross bracing was fixed, bolt-holes werebored, and mgle fish-plates were attachedto the trestles beforeleaving the yard, so as to save as much labour as possible over the river.

Downloaded by [ La Trobe University] on [02/10/16]. Copyright © ICE Publishing, all rights reserved. 176 DdVIS AXD KIRKPATRICIi OX[Minutes THE of Each trestle, weighing about34 tons, was lifted from the building- ground by steama travelling crane and conveyed underthe cableway. The cablewa,y then lifted and lowered it to the required position, and held it until the bolts securing it to the vertical angle- plates had been driven home and temporary guys had been attached to thetop. As many as eighttrestles were fixed in 1 day of 10 hours by this method. Everypair of trestles was bracedtogether longitudinally, the outer verticalshaving double diagonals andhorizontals formed of half timbers, and the two inner verticals were braced by single half- timberdiagonals. The crossheads of thetop trestles projected 6 feet or- either side, andon these overhanging timber gangways were built, the outsides being protected by a light timber trussed fence. The girder-building platform was formed by laying fourteen longitudinal logs on the crossheads and decking with 3-inch close planking. The Goliath road was made of trussed beams resting on the crossheads,and calculated tocarry half theweight of the Goliath,namely, 10 tons,plus the whole of the winchweighing 5 tons, and the whole of the load of 15 tons, which was the weight of the heaviest piece of girder boom. The south channel was closed on the 9th April, 1905, and the first piece of trestling was erected on the 26th April, the last trestle being erected on the 16th May. The first piece of girder was fixed on the completed stage on the 14th June, and all five main girders were completed and on their bearings by the 19th September, 1905. The stage was inmediately dismantled, and the south channel was reopenedfor traffic on the29th October. The quantity of timber in the south-span staging was 26,885 cubic fect. Work in the north channelwas a repetition in all respects of that inthe south channel, except that the time occupied was slightly longer, owing to the north river-span and the north land-span being built at the same time. The north channel was closed to traffic on the 29th October, 1905, and reopened on the 26th May, 1906. The girders were made at the Cleveland Bridge Company’s girder- yard at Darlington, and were delivered to Gateshead in riveted sections not exceeding 15 tons in weight.A Goliath subsequently laid themin their proper places on building chocks about 3 feet above stage-level. Theface girders, including the small parapet fence, weigh 256 tons each, and the three central girders 3353 tons each. The total weight of one 300-foot span is 1,635 tons 12 cwt., or, inclusive of the bearings, 1,7 36 tons 12 cwt. The Goliath used was of steel construction, of 26 feet span, and 37 feet clear headway, with eight wheels, namely, two to each leg ;

Downloaded by [ La Trobe University] on [02/10/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] KIXG: EDWARD VI1 BRIDGE, NEWCASTLE. 177 the wheels on each leg being 7 feet 6 inches apart between centres with an overall wheel-base of 28 feet. The overhead girder was divided into two halves so that, the crab-winch could travel cross- ways. Each of the boomswas formed of channels, butto the top boom wereriveted flat plates andthese formed the rail- track.Electric current was picked up by a slipperfrom a wire conductor 15 feet above stage-level. The travelling motor was fixed at the top of the legs and drove :Lshaft across the full width. From this shaft power was transmitted by chain-belting to the travelling wheels on either side. As the staging was made only wide enough to build two girders at a time, it was builton the west side,'so as to beunder the c:lbleway and the two easterly girders were built first. These were then slued into their final position on the east side, and the west nrld central girders were laid down. As soon as the central girder WAS finished and slued out of the way, the girder between it and the west girder was built. Themethod of sluing was the following :-Upon acarefully levelled track was laid a continuousgirder, formed of a plate at top and bottom and four channels, all rivets in the top and bottom platesbeing countersunk. Uponthis track about forty mild-steel rollers were laidabout 6 inches apart,and upon the rollers was placed a bearing-girder similar in section to the track-girder. Side plates were bolted to the boom and end post of the main girders, and between these side plates heavy gussets were riveted, the two gussets being tied together by four angles and a flat bearing plate. On the outside of the side plates lifting brackets were riveted. As soon as the two east girders were built they were lifted by hydraulic rams, placed under the brackets, the temporary buildingchocks were removed, and the girders were lowered on to timber packing on the granite piers. When the track girders, rollers, and bearing girders werefixed in position, the main girders were againlifted, the packings on the piers were removed and the weight was placed upon the bearing-girders. At fist sluing was done by means of union screws, but this was foundtoo slow, the averagespeed being only 1 foot 6 inchesper hour.Wire-rope block and tackleworked by a hand-winch was therefore adopted, and a pull of about 5 tons at each end on this tackle was suecient to draw the two easterly girders into position, the weight being over 600 tons. The speed attained by this method was about 17 feet perhour, the distancetravelled being 34 feet 3 inches. Thecentral girder had only to betravelled 12 feet 3 inches and the tT5-o westerly girders 1 foot 3 inches each. [THE INST. C.E. VOL. CLXXIV.] N

All riveting after erection was done where possible by means of pueumaticpistol riveting-h,2lnmers, the rivets being heltl up by pneumatic dollies. Great care was taken that scraping and cleaning of the steel was donethoroughly, and that none butthe best paint was used.A trial was made of cleaning by means of compressed-air sand-blast. The work was found to be done perfectly, but certain serious dis- advantages prevented the method from being used on a large scale. These were :- (l) Great difficulty inmaking the men keep their helmetx on, and consequently danger to the lungs from flying sand. (2) After a sectionhas been cleaned and painted, no more cleaning could bedone within a radius of 50 feetuntil the portion painted was properly dried, as the sand stuck to the paint. (3) it was found to be three times as expensive as hand-labour. The following figures show the cost for a test extending over a period of 30 hours. 22 S. (l. Labour ...... 1 9 3 Sand,2.16 tons at 5s. 7d...... 10 O* Air (330 units at ad.) ...... 2 15 0

4 14 3&

Areacleaned ...... 640 sq. ft. Areacleaned per cubic foot of sand ....12.3 sq. ft. Do. per nozzle per hour ...... 21.3 sq. ft. Air-pressure at nozzle ...... 22.5 lbs. per sq. in. Cost persquare foot of surfacecleaned ...2.16d.

These costs areexclusive of dryingsand, scaffolding,depreciation or intereston plant, or engine-man’s time at the air-compressor. The cost of cleaning by hand was found to be 0.72d. per square foot. No paint was put on the steelwork before erection except at the joints. Two coats of pure red-lead paint were applied after erection, which were covered with two coats of green Torbay paint. A gangway, consisting of planks supported by the cross bracings at the bottom of the bottom booms runs between each pair of main girders,and isfenced by two galvanized tubes on each side. It enables the whole of the main girders to be inspected at all times. The tangent points of the south-west and the south-east curves occur upon the south pier. Four lines of way continue to the south- west, but only two lead to the south-east, and these join the two easterly tracks on the bridge. In consequence of the divergence of

Downloaded by [ La Trobe University] on [02/10/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] KING EDWARD VI1 BRIDGE, NEWCASTLE. 179 these curves in opposite directions, the south span of steelwork is fan-shaped on plan, and, owing to the points andcrossings, a different design was adopted. The face-girders are similar in elevation so a>s to make the design uniform, but the three inner girders 18are inches less in depth. Over these inner girders, and resting upon the shelf- angles on the top boom of the face-girders, is trough flooring filled with coke-breeze concrete and covered with bitumen sheeting. The bitumen sheeting is covered with 14 inch of fine cement concrete, above which ordinary ashes are used for ballast. The five girders for this span were built on a timber stage, and shed to their proper places in a manner simihr to the main spans, excepting that each girder had tto be shed separately on account of the divergence previous referred to. When the contract was let, it was intended that archesshould form the whole of the approaches south of the south main river- pier. Withthis intention a coffer-dam was startedto buildpier No. l in the river between the south river-pier and the old quay- wall. Before this was quite finished, the excavation of pier No. 2 was completed, and at a depth of 32 feet the foundation was found to be of a verytreacherous nature. Instead of being hard, level stone as the borings had indicated, it was composed of thin beds of hard rock, between each of which there was a bed of soft blue clay, and the whole was dipping at an angle of about 45" towards the river in a north-westerly direction. Trial bore-holes proved that the same state of affairs continued at least 20 feet lower. It was therefore decided that arches should be abandoned, and that a large span of steelworkshould be sub- stitutedfrom the south river-pier to Pipewellgate.Pipewellgate abutment therefore forms the abutment for the south span of steel girders, and it also forms the wing and abutment for the arches of the south-west and south-eastapproach curves.

THE SOUTHAPPROACHES. The whole of the facework is of red sandstone ashlar except the girder-beds and the main pilasters at each end, which are of granite to correspond with the main piers of the bridge. Thenew abutment is at an angle of 80" withthe centre line of the bridge, and the lengths of the concrete foundation vary from 162 feet at the front to 191 feet at the back, and the width of the concrete varies from 33 feet 6 inches at the centre to 71 feet at thewing. The masonry is lightened by several voids arched over. Thedepth of excavation within Pipewellgate abutment N2

varied from 50 feet at the highest point on the south-west wing to 20 feet below road-level. As there was aroadway between the abutment and the river, andall excavation had to be sentto sea, it was decided tosink threeshafts, each 6 feetsquare, inthe abutment. Two headings 6 feet square were driven into the abutment from the wharf-level, 7 feet 6 inches above high water, under the roadway to meet the shafts, and assoon as they were connected the excavated materialwas run through the headings to hoppers lying alongside in the river. About 27,750 cubic yards of excavation were thus dealt with. The foundation of this abutment needed very heavy timbering, the struts being in some. places 72 feetlong and 12 to 13 inches square. In additionto the ordinary weight of earththere was a very heavy surcharge owing to the rapidly rising ground, and the material on the east sidewas a mixture of sand and loam, which ran in wet weather. Concrete was brought into this foundation through the headings. In order to build the masonry for Pipewellgate abutment a timber stage was erected over the street, upon which was a &ton electric derrick with a 7O-foot jib which could be traversed from one end of the stage to the other as required. After the masonrywas completed, this stage was raisedto act as part of thestage for erecting the girders. During the sinking of the shaft at the west end, and just at the floor of theheading, an old coal-drift was metwith, whichwas explored andfound to extendseveral yards. It was therefore clearedout, and examined by Mr. HenryArmstrong, the mining expertto the North Eastern Railway Company, and orders were given to explore it further. Upon doing so it was found that under the whole of the remaining foundationsof both south-west and south- east approaches the ground was honeycombed with old pit-workings. Thedirectors therefore decided thatall the workings were to be thoroughly cleared out, and built up with brickwork in cement under every pier as far as 5 feet outside of the concrete. This work was proceeded withday and night as rapidly as possible, veryheavy timbering being necessary owing to the roof having fallen in, and in some places the headings were as much as 15 feet high, owing to hetvy falls. It was necessaryto provide mtificiad ventilationby means of an air-compressorwhich ran continuously.The amount of excavation taken outof these workings was 2,699 cubic yards, and a corresponding amount of brickwork in cement was put in. Great care was taken in wedging up tightly to the roof, and no subsidence has since occurred to anyof the piers.

Downloaded by [ La Trobe University] on [02/10/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] KING EDWARD VII BRIDGE, NEWCASTLE. 181 In the south-west curve, south of Pipewellgate abutment, there are three ashlar arches, each 50 feet wide in elevation with 22 feet 3 inchesrise. Two of these are segmental square arches, but the central one is 44 feet 6 inches upon the square with an elevation on the skew of 50 feet. This arch crosses the old RedheughIncline, connecting theDurham coal-field withTyne Dock. This incline is on a gradient of 1 in 23, and is usually worked by three North- Eastern six-coupled tank-locomotives. A new deviating railway has just been completed, so that the old incline can be abandoned. South of the arching the line continuesby means of a low embank- ment, and joins the Team Valley line at Redheugh Bridge Road. The south-east approach from Pipewellgate to Gateshead consists of three .%-foot semi-arches of ashlar and an ordinary girder span over the Redheugh Incline. The whole of the arches of thesouth-west and south-east approaches are of ashlar 2 feet 6 inches deep, excepting the quoins, which average 3 feet deep. The piers are also of ashlar,but the spandrels arebuilt of common rubblewith snecked face. The crown of the arches and the haunches are levelled up with a cement screed, and on this is laid a dry course of bricks with $-inch open joints.The joints are filled withasphalt, which also covers the bricks to the extent of 4 inch. The asphalt is sloped to manholes adjoining the spandrel walls and from these a 4-inch square pipe leads down each pier. THE CABLEWAY. The most important plant used was the 10-ton cableway of 1,520 feet clear span, which isillustrated in Figs.12, Plate 5. Thisis believed to be the largest yet constructed when both load and span are considered. Thetowers and anchorages of the cableway were designed by Mr. Max am Ende,M. Inst. C.E., whilst Mr. C. W. Hill, Assoc. M. Inst. C.E., designed the machinery and electrical gear. The north tower was built immediately above pier No. 7 of the north arching, the pivot at the foot being at the level of the soffit of thearching. This level corresponds withthe ground upon the south side,where the tower was placed immediately north of themain line. The main rope was 200 feet above highwater of ordinary spring-tides. The centre line of the ropeway was 15 feet 9 inches westward of the centre of the bridge. When this distance was decided upon, it was consideredprobable that twoparallel cableways would be required, the second being 15 feet 9 inches eastward of the centre- line,

Thesomewhat peculiar design of the towers in front elevation was caused by the necessity of makingprovision for two towers, theavailable length of the pier of thenorth arching being only 51 feet.The towers were of lightsteel construction. The base- pieces andpivots were built for two cableways, and a temporary raking strut or tie was fixed from the unused bases at the east ends toa point :xbont 32 feet upthe tower legs. Therewere four rocking-pins 6b inches indiameter at each pair of towers.These pins pmsed through castings securely strapped to the tower, andalso through castings securely anchored to concrete foundationssufficient to prevent overturning. The main rope was 96 feet above the pivots, and passed over a curved oak saddle at the top of the tower. It was fastened to the towers by a conical fastening invented by Mr. Max am Ende. Above the main ropes was a timber tower-head, used as a working-platform during the erection and for supporting some of the pulleys. Thetowers being on rockers, provision was made for adjusting the angle of the anchorage-ropes by means of a link formed of two plates each 2 feet 3 inches wide by g- inch.These plates were 15 feet long, and were attached to the steel tower by means of a 76-inch diameter pin. Between the plates at the other end of the link was a saddle casting curvecl to a radius of 1 foot 4 inches, and aroundthis saddle casting was thebight of theanchorage-ropes. Eight anchorage-ropes passed over thelink saddle casting. There were therefore sixteen ends, each terminating in an ordinary conical fastening. A sm411 flat plate was threaded on each end of each rope before the fastenings were made, and in these plateswere three holes, namely, one for the wire rope and two for attaching to the screwed rods whichwere embedded inthe anchorage, consisting of 200 tons of cementconcrete. There were, therefore,thirty-two anchorage-rods, and they were screwed for a length of about 9 feet each, so that ample room for adjustment was provided. Upon the north side of the river the anchorage-ropes passed through No. 4 arch to the foundation of pier No. 3, which formed the anchorage. Counter-anchorages were provided to prevent the towers from falling in the event of the main rope failing. The winch was driven electrically by a 100-HP. series motor and was placed upon the Gateshead side about 100 feet west of the tower. Hauling was done by an endless rope passing around pulleys on each towerand over a capstan-drum on the driving-winch. It was possible todrive the hoisting-drum singly or the hoisting- and travelling-drumtogether, a friction-clutch being provided for the purpose of compensating for any variation in the diameter of the

twodrums. Signalling was donewith flags, and in very foggy weather the cableway was not worked. The erection was a difficult matter. The Gateshead tower was so near the main line that it was necessary to put up a trestle staging over therailway to safeguard passenger-traffic against possible danger from the fall of any piece of the tower during erection. The toweron the Newcastle side, beingon the top of theviaduct to which there was no direct access, was nearly as difficult. The towers were built without scaffolding by means of derrick-poles carried up with the work, no piece lifted exceeding 2 tons in weight. The cableway itself crossed three main roads, the river, and two goods-lines, and the south anchorage crossed the main line between Newcastleand London. By far thegreatest obstruction to the erection of the ropes was the shipping in the River Tyne, and on this account they were mostly put up on Sunday, the traflic being then considerably less. A temporary i-inch wire was first laid out on the ground in two halves. When all river-traffic was clear the two halves were joined on the stage of the centre pier andwere drawn clear by the winding- engine at the Gateshead end. To the end of this wire was attached a $-inch diameter wire and then a 3-inch wire. To this &inch wire was attached the hauling-rope, inch in diameter, which was passed round the capstan-drum and the ends were temporarily joined. The process was then repeated from the &inch to the %-inch rope, but to the end of the latter a l+a-inch rope was fastened and drawn across. This was temporarilymade fast byscrew-nippers at each tower, and then permanently fastened by means of Niagara fasten- ingsto the foot of each tower.The sag for this rope and the hauling-rope was about 70 feet at this time. The l+$-inch rope was used solely for giving temporary support to the main rope during the process of drawing over. The main rope was 3Q inches in diameter and weighed upwards of 10 tons. It was wound on a drum and conveyed to the Newcastle end under the arch immediately at the foot of the tower, whence the end was passed to the top of the tower through a hole in the masonry. It was attached every 50 feet to small carriages formed of two pulley-wheels and triangularplates, and these carriages rested upon the l+g-inch rope. To the first and second of these carriages was fastened the hauling-rope, so that by hauling on the winding- engine the large rope was drawn across to Gateshead, every 50-foot lengthhanging in festoons between the carriages. It was then drawn as tightas was possible with the hauling-rope andmade secure to the two tQwers, The lig-inch temporary rope was next slacked

Downloaded by [ La Trobe University] on [02/10/16]. Copyright © ICE Publishing, all rights reserved. 184 DAVIS AND KIRKPATRICK ON THE [Minutes of and removed inthe reverse way to which it was erected. Then 40-ton wire-rope tackle was fixed on to theGateshead tower, and the main rope was pulled up to the required sag of 65 feet, oak struts being clamped to the rope to take up any length found necessary. These were inserted between the tower and the main rope fastening. The hntton-rope was then erected, the carriage was built, and the hoisting-rope was attached. When all was ready, a man was sent out in the carriage toremove the small erecting-carriages left suspended to the mainrope. The rope was working for nearly 2 years, and proved successful in every way. It materiallyhastened the completion of thebridge, anddealt with about 23,625 tons of material.The tonnage may not appear large, but when the levels of the ground are taken into account,and the difficulty and delay of transporting by other meansare fully considered, the expense was fullywarranted. It was constantly used for dismantling, removing, and building 7-ton steam-travellingcranes, fixing centres,transporting ashlar, lifting and setting granite (where too heavy for the 5-ton cranes to deal with), and lastly for putting up the river-staging. The first wire in the main ropebroke after carrying 19,160 tons, exclusive of the carriage, and this was highlysatisfactory. After the work was finished the main rope was used for the launch of the Cunard S.S. “ Mauretanirt.” Details of the cables, etc., are given in Appendix I.

BOARD-OF-TRADEINSPECTION AND OPENING. The girders were tested by the Board of Trade with a live loadof ten locomotives, coupled together in twosets of five each. At a given signal the two sets of locomotives travelled side by side over the bridge at a speed of 6 to 8 miles per hour, one set passing over the track on the east side of the girder to be tested, and the other set on the west sideof the same girder. Eachset was composed of five locomotives of two classes, two locomotives being of class S, and three of class T (North Eastern Railway classification). Particulars of these locomotives and of the deflections under test are given in Appendix 11. The maximumdeflection in the girders of spans Nos. 2 and 3 1 l was 2 inches = -of the spnn. In span No. 4 this ratio was ~ 1848 2781‘ In spans Nos. 2, 3 and 4 the tracks are straight and parallel to the girders, but in the case of span No. 1 over Pipewellgate the girders vary in length between the centres of the bearings.

Downloaded by [ La Trobe University] on [02/10/16]. Copyright © ICE Publishing, all rights reserved. Proceedings.] KING EDWARD V11 BRIDGE,NEWCASTLE. 185 The bridge was forndly opened by the King on the 10th July, 1906, and brought into use for general trafic on the 1st October, 1906. Mr. A. Cameron, Assoc. M. Inst. C.E., acted as Resident Engineer for the Railway Company, whilst the Authors supervised the work on behalf of the Contractors. They desire to record their thanks to Dr. Charles Harrisonfor permitting this Paper to be written by them.

The Paper is accompanied by drawings and tracings, from which the illustrations contained in Plates 4 and 5 and in the text have been sulected for reproduction.

[APPENDIXES.

APPENDIXES.

AITENDIXI.-DETaILS OF CABLES, ETC., OF CABLEWAY.

Main Rope.-Six strands,thirty-seven wires each;110-ton plough steel; breaking stress 350 tons. Weight per falhom 88 Ibs. Diameter of rope 3Q inches. Hauling Rope.-Six strands, nineteen wires each ; breaking stress 23.6 tons. Weightper fathom 7.2 lbs. Diameter of ropeinch. Hoisting Rope.-Six strands, nineteen wireseach ; breaking stress 152 tons. Weight per fathom 4.8 lbs. Diameter of rope $2 inch. Button Rope.-Six strands, seven wires each ; breaking stress 192 tons. Weight per fathom 5.9 Iha. Diameter of rope 3g inch. Anchorage Ropes.-No. 8 double ropes to each tower, seven strands, nineteen wires each ; breaking stress of each rope 61 tons. Weight per fathom 15.1 lbs. Diameter of rope 12 inch. Anchorage Rods.-No. 32 wrought-steel rods, 18 inch diameter, threaded with Whitworth threads. Counte~Ancltorage Rqes.-No. 2 double ropes to each tower, seven strands, nineteen wires each ; breaking stress of each rope 43.5 tons. Weight per fathom 10.6 lbs. Diameter of ropes @ inch. Main Rope 1,560feet 9 incheslong. Total weight l0a tons.Span from centreto centre of towerpivots 1,520 feet. Speed of travelling 400 feetper minute with &ton load. Speed of lifting (slow gear) 107 feet per minute with &ton load.Speed of lifting (quickgear) 158 feet per miuute with 5-ton load. Usualdip of ropesunloaded 65 feet. Grossload (with carriage) 10 tons. Net load (without carriage) 8 tons.

APPEXDIX II.-BOAIED-OF-TRADETESTS. Test-load Locomotives.

I Class. 1 Weight. 1 Length. Tons. Cwt. Feet.Inches. S 101 11 60 43 S 101 11 48 60 T 96 18 58 f T 96 18 58 f T 96 18 58 6

Dejections, Spans 2, 3 and 4.

Span 2. Span 3. Span 4. Over South Channel Over North Channel. Over 308 Feet between 308 Feet between 239 Feet between centres of Bearings. centres of Bearings. centres of Bearings. ~__.___-.--- Inch. Girder 1 West ...I If

,, 2 ,I .. l:&

,,3 ,I... 1;:

” It

,, 5 East” ...‘ . ’, 2 l

1 Length

~ betweencentres Deflection. ’ of Bearings. Inch. Girder 1 West ...... I Feet.213 H ,,a,, ...... 205 2

,,3,, ...... 119 ?K ,,4,, ...... 195 +B ,, 5 East ...... 193 I iJ

A .- -- A

1' - U SECTIO~ALELEVATION c c. -_ SECTION B E

I 1

R TYNE: c .- r PLAN OF TOP.

AIR-LOCKS FIOR CAISSON.

F 73: 9.

Y CROgSSECTION OF CENTRE PIER CAISSON

HALFSECTIONAL PLAN AA. HALF PLAN ON TOP.

-S C A L E S-

BEAM

HALF PLAN

NEWCASTLE Fy .' 10. GATESHEAD

GENERALARRANGEMENT OF CABLEWAY