Show I Y C r w 5 y j. j i I I Ii IiI V X r r r. r a ad f y y f t s' s y d I Ih Mr fh I j sq Mf d ss i Boa n nonn win C Great Quebec bridge photographed when the central span had been hoisted about half way Into place between the THE BRIDGE Overcoming Extraordinary A QUEBEC J UJ J L With the Worlds World's Greatest ONE NE of the greatest engineering feats in history the history the bridging of the St. St Lawrence Ricer Riper at Quebec was Quebec was accomplished on Sept 20 T Two tOO previous precious attempts had ended in disaster but hut had taught lessons by hy which the engineers profited profiled to make this his a success The problem they had to solve was teas to throw a bridge strong enough to carry the main line of a track double track railroad across a river nearly a mile Wide flowing eight miles an hour feet fed deep with a tide of sixteen feet the banks hank of which rise more than feet above abode the water and to do it With wilh a single span A single span was necessary because the channel channa is so broad and so deep that supporting supporting sup sup- porting piers could not be he built huilt in it and because in the springtime it is a raging avalanche of blocks Macks of ice rushing down to the sea cl J 4 By Arthur Benington OW great the St. St Lawrence is at Quebec can be e understood only by remembering that all the waters of Lakes Superior Huron OW Michigan Erie and Ontario with all the rivers that drain into I j D' D them from a half dozen States and a vast territory in in Canada all all' the waters of the labyrinth of lakes from which the Ottawa River springs and d all the territory that it drains and all the waters of Lake George and Lake Champlain flow between its wooded banks hanks To fo go from Levis on the south bank to the City of Quebec on the north one must either take a ferry boat or go all the way around by Montreal miles distant for until now there has been no bridge across the St. St Lawrence below Montreal The railroads of which there are eight run up and down the river on each side but have been een unable to cross In the summer it is easy enough t to take a ferryboat and in the depth of winter one can drive across on the ice But there are long m months in the autumn and in ht the spring when the river is too full of ice for the ferries and not frozen hard enough for sleighs What this bridge means to railroad travellers can be appreciated from the fact that when the trains begin to run across it the time between Halifax and will be cut down half halfa a day It was necessary sary to build a bridge over which heavy freight trains could go and under which the largest ocean steamers could pass For Montreal is the terminal port of the Canadian transatlantic lin lines except in winter when these run to Halifax or to Portland Me r t THE project of a bridge at Quebec is almost l as old as railroading in Canada The first bridge was almost completed ten years ago when it collapsed For that the engineers had selected the cantilever type type that that is is two cantilevers built one from each end and a central truss built out from the ends of the cantilever arms A cantilever is really a huge sea saw its weight resting on a central mass of masonry and its arms balancing each other The shore arms are fastened to the land and if these be made slightly heavier than the outward extending arms it is easy to see how the latter will support a great weight especially when this weight is distributed between two of them That first bridge was nearing completion when the bottom chord of the shore arm OJ on the south side buckled under the load of tons which was thrown upon it it crumpled up and collapsed crushing or drowning eight eight- two workmen A SPECIAL board of engineers studied this disaster and concluded that a bridge to be built successfully would have to be much heavier and stronger A new design was drawn up which called for cantilevers built out from shore as 1 central truss trues built separately and hoisted into place when con COlT work was finished in September of last year But while they the central truss into place one corner of it slipped off i i 1 which it was supported the whole truss collapsed and went t of the St. St Lawrence La The engineers were so confident that this second disaster was dt di in their plans that they immediately announced they would reb reI and have it in place within a year And they have kept their woid word details details' HE SCIENTIFIC AMERICAN gives the following details a a T THE o structure The Quebec Bridge has the distinction of containing the long long 1800 feet of any existing bridge the next longest spans being being 1710 feet in length of the Forth Bridge Scotland The centre sp spar span feet deep and feet in length was built in the shallow wate wat the Quebec side of the river a few miles west of that city and a af fethe fe fethe the bridge site 1 The span was floated into position on Sunday Sept 16 16 and anding andl andling ing Thursday had reached its final level feet above the river river J ir irin J Jin in place The span was erected upon six large scows which were placed end panel points at each end of the span and the ton into place beneath the centre of the bridge by several powerful tugs tugs' span in exact position a mooring truss' truss had been built at each end ends end lever and by means of powerful tackles the span was brought i ii bridge and vertically below it The span was lifted by m mew mea 4 q 3 S i I I II I I i 1 X f fi fg i i g I II II II I x k kI I I ill illI I I Ii x rw I f i t n One of the two foundation n piers on which the cantilevers rest An idea of the enormous size can be gathered from the sentinel on guard below the steel lattice work on the right chains attached to the four strings of massive steel links link's links At their lower ends these chains to girders ate atea truss truss truss-or or four in all and Upon th it span rested while it was being being r rl in tion At their upper ends the lint li lif ti il made fast to similar supporting gi in in pairs on the ends of the cantil cantile cantile r the other with a pair of 1000 1000 lifting jacks interposed Each operation of the jac jacks jacks two feet During the lifting 12 the lif lifting ting chain through 1 built in the upper jacking girders girder f inch p i ns were the diaphragms in the lower j jackin ackin rs accomplished the jacks and upp lowered and the jacks were t through another foot 2 lift 9 THE success of the lifting op opera opera ra JL on the weather On Satur when the span was to have beer bce storm made all work impossible impossible ton structure would have swa permit accurate hoisting If the the abated within five days the en 1 have waited till the next high tide the month and if the raising had n then it would have been necessary 1 year The span was towed int into day the hoisting began on Month Mond on Thursday afternoon I years and cost to paint tl two masonry piers that support contain cubic feet of i of the cantilever arms extends 58 feet above the river iver and th the the the he bridge from shore to shor h |