Influence of Frequency Ratio and Support Flexibility on the Seismic Response of Two-Segment Rockable Bridges

Rocking footing has been increasingly considered as a possibility for low-damage designed bridges. While most of the studies on rockable bridges have been conducted under a single-segment assumption, in real life poundings between adjacent bridge members are unavoidable during strong earthquakes. Only very limited research has been carried out on this topic, and none has investigated the effect of frequency ratio and support flexibility with pounding simultaneously. This paper presents the results of shake table experiments on two-segment rockable bridges subjected to simulated earthquake excitations. To better understand the pounding behaviour of rockable bridge systems, four different ratios of segment frequencies, i.e., 1.1, 1.2, 1.3 and 1.43, were considered. The effect of support condition was studied by comparing the result of rockable bridges on soil to the bridges allowed to rock on a rigid base and of bridges fixed to the base. The results revealed that the relationship between pounding and girder displacements highly depends on the support flexibility. With soil support, the maximum pounding force will not always increase with frequency ratios.