DESIGN OF COMPOSITE BEAM-COLUMNS UNDER BIAXIAL BENDING

Abstract

The thesis is divided into two parts as given below: - Part I: Analysis of the composite column. The finite element method is introduced to solve the problem of composite beam-columns under biaxial bending. The incremental loading procedure is applied to take into account the material and geometric nonlinearities. Necessary modifications are introduced to the classic derivation of the stiffness matrices to be applicable for beam elements with unsymmetric cross-sections. A parametric study has been performed to consider the effect of concrete strength, steel grade and steel profile on the composite-columns. Contour lines are provided to determine the capacity of the column for different models having different slenderness ratios. Simple formulas are deduced to describe the relation between the moments and each of the concrete strength or steel grade under a specified axial load. A complete computer program has been developed to solve the problem of composite-columns under biaxial bending having any slenderness ratio. - Part II: Optimization The optimal criteria is adopted to achieve the composite column having the least cost.