Nonlinear behaviour and failure analysis of multicell reinforced concrete box girder bridges

Abstract

A numerical method of analysis is developed to trace the nonlinear response of multicell reinforced concrete (RC) box girder bridges under stepwise increasing static loads. The nonlinearities considered are material nonlinearities inherent in reinforced concrete structural members, such as cracking of the concrete and yielding of the reinforcement due to flexure, shear, and torsion. The analytical model, based on a three-dimensional grillage, is developed for multicellular structures of arbitrary plan geometry and constant height. The analytical method can trace the complex nonlinear behaviour of the bridge beyond the working stress range up to ultimate failure and collapse of the structure. Collapse mechanisms and failure loads can both be determined. The proposed analytical scheme, which is based on a mixed model formulation, is demonstrated and tested on two numerical examples. The results are compared with experimental results obtained from large-scale tests on RC box girder bridge models and indicate excellent agreement. The behaviour of these bridge models under increasing overloads is discussed. Key words: box girder bridges, bridge design, multicell structures, reinforced concrete, analytical model, nonlinear analysis, mixed model, ultimate strength, failure modes.