Inelastic Analysis and Behavior of Steel I-Beams Curved in Plan

Abstract

An I-beam curved in plan and subjected to vertical loading experiences primary bending and nonuniform torsion actions. Because of this, the vertical deflections are coupled with twist rotations. These primary actions and deformations couple together to produce second-order bending actions about the minor axis. The interactions between these actions can grow rapidly, produce early nonlinear behavior and yielding, and lead to significant reductions of the ultimate load-carrying capacities. This paper develops a curved beam finite-element model for the geometric and material nonlinear analysis of I-beams curved in plan. Comparisons with existing results show that the finite-element model is accurate, effective, and economical. The numerical results show that when the initial curvature of a curved beam is small, bending is the major action and the nonlinear inelastic behavior is similar to the inelastic flexural-torsional buckling of a straight beam. However, if this initial curvature is not small, both nonuniform torsion and bending are dominant and nonlinear inelastic behavior develops very early. The behavior differs markedly from the inelastic flexural-torsional buckling behavior of a straight beam.