An Evaluation on the Effect of Cross-Frame Spacing Limit on Buckling Strength of Horizontally Curved Multi-Girder Systems under Uniform Bending

Abstract

This study provides an evaluation on the effect of existing cross-frame spacing limit on buckling strength of horizontally curved girder systems. Since current design specifications only consider individual buckling between cross-frames for multi-girder systems, this study utilizes global lateral torsional vertical buckling strength of such girder systems. Elastic eigen value analysis was conducted using the finite element program, ABAQUS. Models with varying degrees of curvature, flange width-to-thickness ratio of 12, 10 and 8 and span length-to-depth ratio of 16, 20 and 24 were generated and their respective maximum cross-frame spacing was computed. These models were then subjected to uniform bending in order to obtain the buckling strength and different buckling modes from the analysis. Finally, critical buckling capacity ratio (Mcurved/Mstraight) was used to establish the effect of the existing cross-frame spacing limit on the buckling strength of horizontally curved multi-girder systems. Using comparative analysis, the results showed that the existing cross-frame spacing limit gave conservative critical buckling capacity ratio for models with high degree of curvature. However, for models that yielded the maximum cross-frame spacing equal to 0.25L and low degree of curvature, the critical capacity ratio decreased significantly. A suggestion was developed based on the results of the finite element analysis to provide a better guide on the design of cross-frame spacing limit.