. The Americana; a universal reference library, comprising the arts and sciences, literature, history, biography, geography, commerce, etc., of the world. H^n^er lotver OiorJ- rie/?0(/ enc//i>sf^ Tension Memders ^^^^^ Compresson Members. Fig. I.— Simple Truss. simple bridge truss with its several membersdesignated as struts, ties or tie-rods, etc., ac-cording to the character of the stresses devel-oped in them by the combined action of thedead and live loads. BRIDGE CONSTRUCTION In the struts the stresses are compressive;in the ties* tensile. The upper and lowerchords* are placed in compres
. The Americana; a universal reference library, comprising the arts and sciences, literature, history, biography, geography, commerce, etc., of the world. H^n^er lotver OiorJ- rie/?0(/ enc//i>sf^ Tension Memders ^^^^^ Compresson Members. Fig. I.— Simple Truss. simple bridge truss with its several membersdesignated as struts, ties or tie-rods, etc., ac-cording to the character of the stresses devel-oped in them by the combined action of thedead and live loads. BRIDGE CONSTRUCTION In the struts the stresses are compressive;in the ties* tensile. The upper and lowerchords* are placed in compression or tensionaccording to the direction of action of the ex-ternal forces applied to the structure. In atruss supported at the ends and bearing a down-ward acting load, the upper chord is always incompression, and the lower chord always in ten-sion. Counlerbraccs are designed to resist both structure, provided all the members are properlydesigned to carry their respective loads. The economy and the efficiency of the trusslies in the panel or quadrilateral system. shows its development from the triangular. tensile and compressive strains alternately, asthey may be applied by the changing positions ofthe load. No truss-member can act simulta-neously in full tension and compression, but maydo so partially, since the stress developed in anymember by the strains of two or more externalforces is equal to and of the same sign as thealgebraic sum of all those forces. Thus a tiemay resist a compressive strain without be-coming a counterbrace, or a strut may resist atensile strain without becoming a tie, so longas the contrary strains are smaller than thosefor which the member is designed, and whichcontinue to act at the same time. Fig. 2 shows the action of a truss. As al-ready stated, a truss acts as a beam, and a loadapplied at (h) will be carried to the abut-ments at (a) and (v) along the several mem-bers as indicated by the arrows, leaving thepost (hi), the ties (ij) (kl)
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectencyclo, bookyear1908
