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 tlie 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 liad to jjrocced in the 

 shadow of the giiastl\' catastrophe of its 

 predecessor which crumpled and fell, 

 carrying to deatli nearl\- a hundred men. 

 That tliis 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 



748 



