Torsional-Distortional Performance of Multi-Cell Trapezoidal Box Girder with All Inclined Web Members

In this study, the torsional and distortional performance of a three triangular cell trapezoidal box girder section\ud was studied using Vlasov’s theory of thin walled structures. The potential energy of a system under equilibrium\ud was used to obtain the governing differential equations of equilibrium for torsionl-distortional analysis of the\ud box structure. The strain modes diagrams representing torsional and distortional interactions of the box girder\ud structure were obtained as well as the distortional bending moment diagram for the box girder structure. These\ud were used to compute Vlasov’s coefficients contained in the differential equations of equilibrium. The fourth\ud order differential equations obtained were solved using method of trigonometric series with accelerated\ud convergence to obtain the distortional and torsional deformations which were compared with torsional and\ud distortional deformations of a single cell mono symmetric box girder section of similar overall dimensions and\ud plates thicknesses. The maximum distortional deformation was found to be 168% lower than that of a single cell\ud mono-symmetric box girder section of the same size and dimensions. The inclined internal web members,\ud which also act as diaphragms, brought about increase in the pure torsional and distortional components of the\ud applied torsional load, resulting to marginal increase in the torsional deformation but major decrease in the\ud distortional deformation