Stability analysis and bracing for system buckling in twin I-girder bridges

Abstract

Twin I-girder structural systems are often encountered in practice on pedestrian bridges, railroad bridges, and temporary conditions during multi-girder bridge erection and demolition. The current paper is based on an in-depth stability analysis and bracing design conducted on a twin I-girder pedestrian bridge recently constructed in Minnesota. This work demonstrates that the strength of non-composite twin-girder systems without lateral bracing can be controlled by the limit state of ‘system’ or ‘global’ buckling, however the existing literature and governing design specifications do not adequately address this limit state. For twin-girder systems with partially braced spans and/or non-prismatic cross-sectional properties, a complete 3-D finite element (FE) buckling analysis should be considered for quantifying buckling strength and associated bracing forces; either linearized eigenvalue analysis or complete non-linear incremental collapse analysis. These FE stability analysis models can be verified effectively by checking the vertical, lateral, and torsional stiffness against results provided by classical solution techniques.