Cross-Sectional Moment Capacity Prediction of Steel Box Girders Based on the CSM

Abstract

The objective of this paper is to propose the prediction method of the cross-sectional moment capacity for continuous steel box girder bridges based on the continuous strength method (CSM). First, the critical buckling strain of the compressed members in box girders is determined using the base curve in the CSM, with which the elastoplastic cross-sectional analysis is conducted to derive the ultimate bending moment of steel box girders under sagging and hogging bending states. Then, a large number of applicable cross sections of steel box girders are designed, and their cross-sectional moment capacities based on the CSM and the elastic and plastic analyzing methods are calculated. Based on an analysis of the mutual relationship of these three moment capacities, the linear and quadratic prediction equations are proposed for both the positive and the negative moment capacities of steel box cross sections. The proposed equations are adopted to predict the cross-sectional bending capacities of some steel box girders in experiments, and the predicting results agree well with the experimental ones. Lastly, the proposed equations are applied to predict the cross-sectional moment capacities of the main girder in Xiamen Second East Passage as a case study. Compared with their elastic moment capacities, the analysis results show that using the proposed linear prediction equations, the cross-sectional moment capacities presented a 5.2% increase for cross sections with a nominal width-to-thickness ratio of 39.2 at support and a 22.2% increase for cross sections with a nominal width-to-thickness ratio of 37.6 at midspan. The linear and quadratic interpolation equations can well predict the cross-sectional moment capacity of the steel box girder.