Lateral overturning process and failure mechanism of curved steel-concrete composite box-girder bridges under specific overloading vehicles

Abstract

Curved steel–concrete composite girders are regularly adopted for use in ramp bridges in urban overpasses. As such, it is important that the lateral overturning stability of girders supported by single-column piers is analyzed. In order to comprehensively evaluate the lateral overturning mechanism of girders, this paper carries out a full-range nonlinear analysis of the lateral overturning process of a three-span curved steel–concrete composite box girder based on the explicit dynamic finite element (FE) method. According to the FE analysis results and actual forces acting on the structure, a new method for analyzing overturning stability considering the corresponding limit state is proposed. The results show that the overturning process can be divided into three stages: (i) small girder rotation; (ii) large girder rotation; and (iii) lateral displacement and overturning. The mechanical behaviors, overturning processes and failure characteristics of curved steel–concrete composite girders are similar to those of typical concrete box girders. However, some distinct characteristics, including the crawling behavior of girders and buckling of bottom plates, only exist in composite girders. The proposed overturning stability checking method is found to be more appropriate for determining the bearing capacity of girders on the ultimate limit state than the current design method described in the specifications (JTG 3362-2018). Some measures – such as setting lateral movement limiting devices, setting pre-eccentricity of supports and increasing the distance between supports which can considerably improve the lateral overturning stability of steel–concrete composite girders – are highlighted.