. Iron truss bridges for railroads. Methods of calculating strains, with a comparison of the most prominent truss bridges, and new formulas for bridge computations; . utments are inversely as tnehorizontal distances of the weight from the abutments. Instead of the very simple combination in Figure 6, suppose the point A, and theweight thereto suspended to be connectedwith B by the combination A EB F. Itis manifest that the change makes no dif-ference in the amount and line of directionof the portion of the weight to be trans-mitted to B. It will as before be Af, andits line of direction will b
. Iron truss bridges for railroads. Methods of calculating strains, with a comparison of the most prominent truss bridges, and new formulas for bridge computations; . utments are inversely as tnehorizontal distances of the weight from the abutments. Instead of the very simple combination in Figure 6, suppose the point A, and theweight thereto suspended to be connectedwith B by the combination A EB F. Itis manifest that the change makes no dif-ference in the amount and line of directionof the portion of the weight to be trans-mitted to B. It will as before be Af, andits line of direction will be the theoreticalline A B. There being no tie or othermeans of transmitting the force directly toB, thereby conforming to the general lawof mechanics that forces always travel bythe most direct route, this force is mechan-ically resolved into two components, one ofwhich travels through A E, and the otherthrough A F. The component A h, that goes through A E, at E, is resolved into EG^=i w, that goesdirectly to the fixed point, and^s that at i*^ becomes F v, one of the componentsthat generates Fu. The force A a, transmitted to F where it is Ft, is the other com-. 16 IRON TRUSS BRIDGES FOR RAILROADS. pouent of Fit, which at B becomes Bg, there being resolved into B i and B h. Theresult then is that Af, the original component of Ad to be transmitted to B, becomesby this mode of transmission B w acting horizontally, and B h acting vertically. ButB w, the horizontal force that reaches B, should be equal to ef, the horizontal force tobe transmitted, which it is ; and B h should be equal to A e, which is likewise the may therefore conclude that the transmission of forces has been correctly simple inspection at once gives the strains on all the parts of the combination. Strains of Extension an A C is An or Gj) on AE is Ab ox Em on E B is Ec or Iw on AF is A a or Ft on F £ is Fu ox B g Strains of Compressionon E F is Es ox Fv The tendency to pull out the supporting p
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Keywords: ., bookcentury1800, bookdecade1870, bookpublishernewyo, bookyear1870
