Lateral-torsional buckling of shallow-arched steel girders under pure bending

This study develops a theoretical framework to assess the stability resistance of shallow-arched steel girders under pure bending. It focuses on beams with a specific curvature radius and span length, subjected to constant bending moments under simply supported conditions. Existing theories have gaps in predicting instability resistance beyond the elastic range. To address this, a revised formula for calculating the critical bending moment of vertically curved steel girders is proposed and verified through linear and non-linear finite-element analyses. A pilot bridge built with shallow-arched steel girders was simulated to capture its actual structural behaviour, accounting for material non-linearity and large deformations. The simulation results closely match the American Association of State Highway and Transportation Officials load and resistance factor design curves for straight girders. Field data from the pilot bridge confirmed minimal lateral displacements and acceptable vertical deflections, validating the proposed approach for girders with a radius-to-span ratio of 3.2 or higher. This research highlights the need to extend current theories to include post-elastic behaviour and to consider different load conditions. The findings provide crucial insights for improving design standards and promoting the use of shallow-arched steel girders in future bridge projects, particularly in the Mekong Delta of Vietnam.