FINITE STRIP METHOD FOR GIRDER BRIDGES

Abstract

A girder bridge consists of two structural systems, namely transverse medium and longitudinal medium. The transverse medium by• way of slab and cross-beams transfer the imposed load on the deck to the main girders which in turn transmit them to the supports. Various methods of analysis aim at finding the distributions of imposed loads amongst the girders. Of these methods, Finite Strip Method is used for the analysis of simply supported girder bridge decks of constant width. In this method, the stiffness matrix of a beam is derived and is coupled with that of a strip. In deriving the stiffness matrix of a beam, harmonic functions which fitted the simply-supported end conditions in one direction are used in conjunction with polynomials for the other direction and thus, a simple beam-type stiffness matrix for a strip is derived. Finite Strip Method requires the operation on narrow-band matrices of small order which can be easily carried out on a small capacity computer. An effort has been made in this dissertation to compare the results for girder bending moments and deflections obtained by Finite Strip Method with those of Orthotropic Plate Theory, Harmonics Method, Stiffness Method and Semi-Continuum Method. For this, two 4-Girder right bridge systems having 2-Lane and 4-Lane have been analysed for critical positions of LRC Class-A and 70R loadings respectively and certain conclusions arrived at.