Popular science monthly . deiXndableeNidcnccof the cause of the last disaster is undertwo hundrt>d feet of water, eye witnessesagree that, following a report like acannon, the south ui^stream cornerslipped olT its lifting girder and cork-screwed into till river. The most probable explanation of thefailure is that the steel rocker castingunder (he south upstream corner sudden-l\ crumpleii (see diagram page 732).Iiu- truss then dro|i|Hd on the \ing girder, kicking it out, or 748 Popular Science Monthly 729 turning it enough to let the corner ofthe truss slip off. Had the accidentha
Popular science monthly . deiXndableeNidcnccof the cause of the last disaster is undertwo hundrt>d feet of water, eye witnessesagree that, following a report like acannon, the south ui^stream cornerslipped olT its lifting girder and cork-screwed into till river. The most probable explanation of thefailure is that the steel rocker castingunder (he south upstream corner sudden-l\ crumpleii (see diagram page 732).Iiu- truss then dro|i|Hd on the \ing girder, kicking it out, or 748 Popular Science Monthly 729 turning it enough to let the corner ofthe truss slip off. Had the accidenthappened an hour earlier, many promi-nent engineers of the Inited Slates andCanada who were on the span witnessingthe lifting would have been lost. As lost. it was but aThe failureof the sunmierof 1907 cannothappen to thenew the lowei-chord of theold bridge wasbut four and ahalf feet squareand had sevenhundred andeighty-onesquare inchesof solid steel inits cross - sec-tion, the samechord of the dozen lives were. Diagram of the new Quebec Bridge. X marks thepoint where the bottom chord of the old structurecrumpled. The expansion of cantilever arm andsuspended span, due to temperature changes, istaken up by brake shoes at the connections, eachcapable of resisting a force of one hundred andtwenty-five tons. Even the difference of temperature,due to one side of the bridge being in the sun andthe other in shadow, was calculated with accuracy new bridge is seven feet two inches deepand ten feet four inches wide and has across-section of nineteen hundred andtwo square inches of steel—two and ahalf times the amount in the old familiar spring board at theswimming hole is agood example illustra-ting the principle ofcantilever constructionadopted for the Quebecbridge. The load iscarried by the project-ing portion, which issupported by a weightat the back end suffi-cient to keep it fromraising. The suspend-ed span is like the boystanding on the end ofthe spring boar
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectscience, bookyear1872
