. Practical structural design; a text and reference work for engineers, architects, builders, draftsmen and technical schools;. irders made of wrought iron orsteel, the latter material being generally used to-day, for it maybe used with a higher fiber stress, thereby reducing the rolled beams are not obtainable in a large enough size a GIRDERS AND TRUSSES 113 plate girder is used, provided a rolled beam cannot be made toserve, by attaching plates to the flanges. Tables of plate girdersare given in the steel handbooks, so the architect or builder findsit as easy to select a plate gi


. Practical structural design; a text and reference work for engineers, architects, builders, draftsmen and technical schools;. irders made of wrought iron orsteel, the latter material being generally used to-day, for it maybe used with a higher fiber stress, thereby reducing the rolled beams are not obtainable in a large enough size a GIRDERS AND TRUSSES 113 plate girder is used, provided a rolled beam cannot be made toserve, by attaching plates to the flanges. Tables of plate girdersare given in the steel handbooks, so the architect or builder findsit as easy to select a plate girder for much of his work as it is toselect a rolled I-beam or channel for light loads on shorter the load, or the span, either or both, make a plate girdertoo heavy, a trussed girder is used. Fig. 72 shows a plate girder. The thin vertical plate is knownas the web and is made thick enough to carry the shear. It actsalso as a long slender column, so must be safe against proportioned to carry the shear and the thickness is greaterthan ^V ^he depth between the rivets in the upper and lower flanges,. Fig. 72 — Plate Girder with Cover Plates and Stiffeners the plate is safe against cripphng. When designed to carry theshear and a thickness less than ^V the depth is obtained, it is neces-sary to use stiffeners spaced regularly at intervals equal to thedepth of the girder. Additional stiffeners are placed under con-centrated loads and at the ends. Intermediate stiffeners are some-times crimped over the flange angles, but it is as common to havefillers placed under them, the thickness of the fillers being equalto the thickness of the flange angle, so the stiffeners v/ill be straightand have the ends resting on the outstanding leg of the flangeangles. No scientific rules seem to be commonly accepted fordesigning intermediate stiffeners, the usual empirical methodbeing to have the outstanding leg equal in width to ^V the depthplus 2 in. ]End stiffeners act as


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