The Artizan . of contrary flexure; andinto two end parts, each of which is in the same condition as a girder fixedat one end and free at the other, loaded equally, and also having a weightequal to half the weight of the load on the central part, suspended from itsend. This state of affairs is what we should naturally expect, and suchis actually the case; hence the determination of the distance of the pointsof contrary flexure becomes the desideratum. In any continuous girder the moment of strain over the pier will be amaximum when the two spans only which meet at that pier are loaded,and the g
The Artizan . of contrary flexure; andinto two end parts, each of which is in the same condition as a girder fixedat one end and free at the other, loaded equally, and also having a weightequal to half the weight of the load on the central part, suspended from itsend. This state of affairs is what we should naturally expect, and suchis actually the case; hence the determination of the distance of the pointsof contrary flexure becomes the desideratum. In any continuous girder the moment of strain over the pier will be amaximum when the two spans only which meet at that pier are loaded,and the greatest moment of strain on the central part of any span will beobtained when that span only is loaded. We will now apply our process to various practical cases, first illus-trating its general nature by its application to a single girder, firmly fixedat both ends, which represents a case occasionally occurring in continuousgirders. If A B, Fig. 1, represents the position of a girder fixed at both ends, of WW. which the points of contrary flexure are situated at e and d, in the para-bolic curve e eg d It, the ordinates of which represent the moment of strainfor every point in the girder; thus, for instance, f g shows the momentof strain at the centre, drawn to a given scale, and A e, B h those over thepiers to the same scale. As it is necessary that the moments of strain and resistance must atevery point in the girder be equal, in order to satisfy the conditions ofequilibrium, and the moment of resistance depends upon the area of thesection when the depth is constant, and also as the weight of the girderdepends upon its bulk, which is made up of these sections, which them-selves depend upon the ordinates to the curve, it follows that, the webbeing left to bear the shearing load (of which we shall presently treat), theweight of the flanges will vary as the area of the curve. The manner inwhich the girder resists the action of the load will be such, that the strainson all parts o
Size: 2786px × 897px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1840, booksubje, booksubjecttechnology
