Graphical method for the analysis of bridge trusses; extended to continuous girders and draw spans

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1875 Excerpt: ...mn. Next suppose that, instead of a rolling load from A to. G only, we first load B C throughout and then add the load from A to G as before. We must now use the curve G' M C, and the bending moment at the centre pier will be increased beyond the amount existing when only one span is loaded, so that the inclined lines will now meet the centre vertical between B'" and B'. Thus the two lines drawn from G' to the centre vertical are accounted for. Finding the supporting forces under the new condition of things, we shall have, in the diagram for shearing force, the lines aw, wu, uz, and a line between and parallel to ig and f d. We thus find a greater negative shear on A B under this load than under the former. Add a load on J. Draw J' M. The bending moment over the centre pier will be slightly increased, and we can construct, as we did from G', the two lines from J' to the centre vertical, and in the shearing diagram we shall find, when BC also is loaded, the hues ay,yv, etc., as before. A load added to L will, in the same way, determine the paint s. The curves starting from E', G', J', L' and A' represent the successive increments of rolling load on E, G, J, L andP, and, as combined with M C" or M C, apply to the cases where B C is unloaded or loaded. All the lines to the centre vertical are not drawn, but enough of them are shown to explain the action. The letters at the extremities of the curves are intended to indicate the last fully loaded point. A rolling load on B will be found not to alter the bending moment, hence the curve for P becomes the one from A'..54. As the load advances from A to B then, the span B C being fully loaded, we shall find that the ordinates for the maxima stresses in the successive panels occur immediately in front of th...