EFFECT OF CROSS SECTIONAL DIMENSION ON DEFORMATION OF DOUBLE SPINE MONO-SYMMETRIC BOX GIRDER DUE TO TORSIONAL-DISTORTIONAL LOADS

Abstract

The differential equations for torsional-distortional analysis of a double spine mono-symmetric box girder section were obtained following Vlasov’s theory. The evaluation of Vlasov’s coefficient of the governing differential equations formed a major part of this work. This involved the valuation of the various strain mode diagrams for the box section and an assessment of the strain mode interaction to ascertain the relevant strain modes that affect torsional and distortional displacements. Vlasov’s coefficient for the governing equations of equilibrium were obtained using Morh’s integral for displacement computations diagram multiplication of the strain modes diagram. By substituting the coefficients into the governing equilibrium equation, a set of coupled fourth order differential equations of equilibrium were obtained. The solution of these equations by method of Fourier sine series gave the torsional and distortional displacements of the 20m simply supported box girder section. A Matlab computer program was developed for this work and used to verify the result obtained by manual analysis and the maximum values for torsional and distortional displacement were 2.975mm and 8.763mm respectively. The width of the box girder was varied from 10.3m to 12.3m and again increased to 14.7m. The maximum distortional displacement varied from 8.763mm for 10.3m width to 15.575mm for 12.3m width and 18.911mm for 14.7m width

KEYWORDS: Box girder, Distortion, Double spine, Mono-symmetric