Friday, September 27, 2013

Several Point Loads acting on a Girder- max Bending Moment and Shear Forces

There are some live examples which you see everyday when a several point loads act on a single girder. On a bridge there are a numbers of wheel loads which act simultaneously and results in the induction of the bending and shear stresses, for design of such structures, it becomes important to find out the magnitude of location of stresses induced.
MAX. B.M. On a Girder when several point loads move from one end of the girder to another end of it.
There are following two important propositions regarding the B.M. on a girder where several point loads act on the girder:
Proposition 1. :  The maximum bending moment(B.M.) for a given point load among the several point loads occurs at the point of action of the load when the distance between the line of action of the load and the equivalent load of the whole load assembly is divided into equal half by the center of the span of the girder.
Proposition 2.  : The maximum bending moment for an assembly of several loads occur at the section which divided the load assembly in such a manner that the average load on either side of the section is same or equal.

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