Strength design of steel I-section beams curved in plan

When a steel I-section beam that is curved in plan is subjected to vertical (or transverse) loading, its primary actions are bending about its major a xis and torsion. Secondary torsion and minor axis bending actions are usual ly significant in steel I-section beams curved in plan under combined bendi ng and torsion. However, the common circular interaction equation used in p ractice for rectangular solid or hollow section curved beams does not accou nt for these significant effects and so may overestimate the interaction st rength of steel I-section beams curved in plan under bending and torsion. T his paper investigates the nonlinear elastic-plastic behavior of steel I-se ction beams curved in plan under vertical loading and proposes straightforw ard formulas for their design against combined bending and torsion actions. Comparisons with rational finite-element results and existing experimental results show that the proposed interaction equations provide a good lower bound for the design of steel I-section beams curved in plan against combin ed bending and torsion. The proposed interaction equations are simple and c onsistent with existing codified design rules.