73^2 



Popular Science Monthly 



If the reader will pause a uioinent to 

 look at the acxoiiipan\in^ photograph of 

 the bridge, he will note a series of 

 perfectly good cajjital K's made up of 

 vertical steel posts and diagonal rods. 

 This picture shows also the traveler, 

 which is nothing more or less than a 

 great steel tower 

 carrying gigantic 

 movable cranes on 

 top to handle the 

 heavy pieces of 

 steel, some weigh- 

 ing one hundred 

 tons. By examin- 

 ing the diagram of 

 the bridge, it will 

 be seen that both 

 north and south 

 sections of tlu- 

 bridge, symmetric- 

 al about the main 

 piers, are made u|) 

 of a series of K's. 

 The "K" system 

 has a number of 



Cast-steel rocKer 

 which probably 

 foiled Pirst. 



f- Vtfoter 



How did the disaster occur? Probably the steel 

 rocker casting under the south upstream comer 

 suddenly crumpled. The truss then dropped on 

 the carrying girder, kicking it out or turning it 

 enough to let the corner of the truss slip off 



advantages for a bridge of great size. 

 Chief of these is tliat during erection of 

 the cantilever arms, each panel or "K" 

 can be completed without temporary 

 supports and the traveler moved out to 

 the end. It will be remembered that 

 conditions at this bridge site made 

 temporary supports out of the question. 



The top chords of the arms are in 

 tension; that is, the forces acting upon 

 them tend to stretch them. So, they 

 are made up of great e>-ebars, thirty-two 

 of them on either side of the main posts 

 having a cross-section of eight feet of 

 solid steel. The bottom chords are in 

 compression; that is, the forces acting 

 (»n them tend to shorten them. 



The great post over the main ])ier is 

 three hundred and ten feet high and 

 weighs fifteen hundn-d tons. It is 

 compcj.sed of four posts latticed together 

 into a rectangular lower nine feet by 

 ten feet. The shcje under the main post 

 has a bearing on the stone pier of twenty- 

 two feet by tAventy-six feet and is 

 nineteen feet high, and weighs four 

 hundred tons. Like some other parts of 

 the bridge, it was shipped in pieces, 

 each weighing one hun(ir<-(l ions. An- 

 other measure of the ni.igiiiludc- of this 

 modern wonder of the worlcl is the jiin 



connecting the slK)e and tower. It is two 

 and a half feet wide and weighs six tons. 

 Two sets of massive steel temporary 

 \iaduct were built under each anchor 

 arm, one set to carry the floor system, 

 which in turn carried the traveler; the 

 other to support the lower chords. 

 During the winter 

 of two years ago, 

 the traveler, weigh- 

 ing a thousand 

 tons, was built on 

 the north shore. In 

 the spring it was 

 moved to the main 

 pier and the shoes 

 placed. The tra\el- 

 er then nu)\ed back 

 front the main pier, 

 placing the lower 

 ciiorcls t)n the 

 t e m p o r a r y \- i a - 

 ducts. It was 

 luovetl out to the 

 main pieragain and 

 on the way back 

 the trusses erectcxl up to the point where 

 the vertical and diagonal legs of the "K" 

 intersect. Arriving at the anchor pier, 

 it began to erect above the iiitersection 

 of the legs t)f the "K." 



Thus the anchor arms were erected. 

 But when the traveler reached the 

 main pier, it naturall>- had to erect the 

 cantilever arm in front of it, panel by 

 panel. A "flving liritlge," projecting 

 forward from the finishe<l work, carrietl 

 the periuaiu'iit work ol the panel until 

 it was rixeti'd u]). The iKing bridge was 

 coniposcxl of pieces of steel with one end 

 fastencKl to the coiui)leted work, the 

 other projecting out into space and held 

 up by susjjension rods. 



The suspended span was assemiiled 

 in a sliallnw cove some three miles below 

 the bridge' at the same time the .south 

 cantile\er arm was being erected. Six 

 l)argi-s thirty-two feet wide by one 

 huniheil and lift\- feet long were placed 

 untler as many panel points. When 

 the tide came in the span was afloat and 

 w.is towed by tugs to the bridge, where 

 it was aiu'horeil to the h.mging trusses 

 and coupled to the hanger slabs. The 

 plans wi-re to raise it to its liii.il ])()sition 

 in a few hours by eight oni- tiinus.ind-ton 

 lu<lraulic jacks, two .it e.ich <i)rner. 



