. The science of railways . strains or loads the various members of abridge are subjected to; one is by platting theloads or strains and is called Graphical staticsor Graphical Method. The other method is a ^TAN^DAiiM oP oomTEUcfiom 249 > »- A *•■ c o- 0 ^ *•- y^ >> 0 \/\/\ s* /\y \/ \/ \/ \/ \/\ /\/\/ ff i e 0 C c O P /■ iiffj Fig. 155. DOUBLE LATTICE GIRDER-MODIFIED FORM OF WARREN TRUSS Where the length of the truss becomes too great to use the form shownby Fig. 154, this form can be used to support the intermediate pointsB B C on the lower chord and C C D on the upper chord, ABODEF
. The science of railways . strains or loads the various members of abridge are subjected to; one is by platting theloads or strains and is called Graphical staticsor Graphical Method. The other method is a ^TAN^DAiiM oP oomTEUcfiom 249 > »- A *•■ c o- 0 ^ *•- y^ >> 0 \/\/\ s* /\y \/ \/ \/ \/ \/\ /\/\/ ff i e 0 C c O P /■ iiffj Fig. 155. DOUBLE LATTICE GIRDER-MODIFIED FORM OF WARREN TRUSS Where the length of the truss becomes too great to use the form shownby Fig. 154, this form can be used to support the intermediate pointsB B C on the lower chord and C C D on the upper chord, ABODEF Q being the simple Warren truss with three others—A B C D. B C D, etc, A B C D, etc., added. e s £ e 6 e -fx \ ^ \/ \ r\. > Y /j >\ / Fig. 156. DECK BALTIMORE TRUSS—MODIFIED FORM OF PRATT TRUSS. This is Fig. 148 inverted to make a longer span for a deck bridge thanFis. 149 is suited for; the floor system is supported by the addition ofoblique members A B and A B and vertical members A C D E, 157. THROUGH BALTIMORE TRUSS—MODIFIED FORM OF PRATT TRUSS. This is another method of accomplishing what is done by the Whippletruss (Fig. 152.) The panels as A B C D have but one oblique D B, to this isadded the oblique C E and the vertical E F to support the floor system at F. Ji50 BUlLmNQ AND REPAtRIKO RAILWAYS. mathematical one, based on the laws of me-chanics.* The various members of a bridge must be sodesigned and connected that the strains will bein the direction of their axis; all strains tendingto buckle or shear the members must be avoidedin making the design, and in the erection caremust be taken that all members are placed asdesigned, no shortening or lengthening to beallowed, as this would tend to throw a greaterstrain on some members than they were designedto bear. The manufacture of steel has reachedsuch a high standard that the bridge designerknows definitely what duty it will perform, andbridge designing has become as near an exactscience a
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectrailroa, bookyear1900
