Nonlinear postbuckling analysis of frames with varying cross-section columns

A nonlinear static analysis is performed on an imperfect elastically supported two bar frame, which is subjected to a concentrated vertical load eccentrically at its joint. The column has a variable cross-section whereas the girder has a uniform cross-section. The variation ratio of the column cross- section is extensively investigated in combination with other geometric parameters (ratios of lengths and moments of inertia between column and girder) as well as loading parameters (loading eccentricity). Following a simplified procedure where the horizontal stiffness of the frame is modeled by a spring at the joint of the frame, it has been found that the developed axial force in the girder can be neglected (insignificant deviation of the exact results). Nonlinear finite element analysis is performed to verify the analytical results.