Page:Popular Science Monthly Volume 89.djvu/742

 Quebec's Disastrous Bridge

How the principle of a diver's spring board is ap- plied in the building of the biggest cantilever bridge

Bv C. E. Dravc r

���One of the cantilever arm-compression diagonals being placed in position. Like the opera- tions of an army in the field, the work of erection has a dash of danger and romance. As the success of the army in action is due to the output and character of the shops behind the lines, so the speed of erection of a structure is due to the excellence of the shop work

��TniC new Quebec cantikner bridge ranks among the most important and lirilliant of all construction. The boldness of a great general in war pales by the side of the courage of its builders, wiio had little precedent to follow in some of its vital and most difficult features of design and erection. Besides, they had to jjrocced in the shadow of the giiastl\' catastrophe of its predecessor which crumpled and fell, carrying to deatli nearl\- a hundred men. That this siiadow was not an imagin- ary one is cviticnced by the recent disaster when the suspended span fell from fifteen feel above the water while being hoisted tf) position. The l>est engineers in American erred not in design, l)ut, if at all, in failing to

��be superliuman. The latest failure can dela\- for but a short time the finishing of the great structure. \'ery .soon the successful ijlacing of a new span will be recordetl.

It all happened in about live seconds. While jiractically all deiX'ndableeNidcncc of the cause of the last disaster is under two hundrt>d feet of water, eye witnesses agree that, following a report like a cannon, the south ui^stream corner slipped olT its lifting girder and cork- screwed into till' river.

The most probable explanation of the failure is that the steel rocker casting under (he south upstream corner sudden- l\ crumpleii (see diagram page 732). I'iu- truss then dro|i|H'd on the siiort c.irr\ing girder, kicking it out, or

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