Abstract
The cross-sea bridges play an important role to promote the development of regional economy. These bridges located in earthquake-prone areas may be subjected to severe earthquakes during their lifetime. Group pile foundations have been widely used in cross-sea bridges due to their structural efficiency, ease of construction, and low cost. This paper investigates the seismic performance of bridge pile foundation based on the seismic fragility analysis. Based on the analysis platform OpenSees, the three-dimensional finite model of the bridge pile foundation is developed, where the pile-water interaction is replaced by the added mass method, nonlinear p-y, t-z, and q-z elements are used to simulate pile-soil interaction, and the displacement of the surface ground motion due to seismic excitations is applied on all spring supports. The seismic fragility curves of the bridge pile foundation are generated by using the earthquake records recommended by FEMA P695 as input motions. The curvature ductility based fragility curves are obtained using seismic responses for different peak ground accelerations. The effects of pile-water interaction, soil conditions, and different types of ground motions on the bridge pier fragilities are studied and discussed. Seismic fragility of the pier-group pile system shows that Sec C (the bottom section of the pier) is the most vulnerable section in the example fluid-structure-soil interaction (FSSI) system for all four damage LSs. The seismic responses of Sec E (a pile section located at the interface of the soil layer and water layer) are much lower than other sections. The parameter analysis shows that pile-water interaction has slight influence (less than 5%) on the fragility curves of the bridge pier. For the bridge group pile foundations considering the fluid-pile-soil interaction, PNF may induce larger seismic response than far-field (FF) and no-pulse near field (NNF). The bridge pile foundation in stiff soil is most vulnerable to seismic damage than soft condition.
Highlights
With the development of economy and advancement of technology, more and more cross-sea bridges have been constructed around the world in recent decades. e crosssea bridges located in earthquake-prone areas, such as the eastern coast of China or the western coast of the USA, may be subjected to earthquake action. e strong ground motion can destruct the cross-sea bridges, which will cause great economic loss and confusion of society. erefore, seismic design of cross-sea bridges has become an urgent research topic
E earthquake-induced hydrodynamic forces on a single cylinder [11,12,13] and the seismic responses of cylinder surrounded by water [14,15,16] have been investigated widely in recent decades. e results indicated that effect of free surface waves on the earthquake-induced hydrodynamic force can be neglected and effect of water compressibility is quite important when the dimensionless frequency is greater than unity
A three-dimensional finite model is developed to reliably assess the seismic fragilities of the bridge pile foundation system considering fluid-structure-soil interaction (FSSI), where effects of hydrodynamic added mass, soil conditions, and different types of ground motions on the fragilities are comprehensively taken into account
Summary
With the development of economy and advancement of technology, more and more cross-sea bridges have been constructed around the world in recent decades. e crosssea bridges located in earthquake-prone areas, such as the eastern coast of China or the western coast of the USA, may be subjected to earthquake action. e strong ground motion can destruct the cross-sea bridges, which will cause great economic loss and confusion of society. erefore, seismic design of cross-sea bridges has become an urgent research topic. E experiment conducted by Wei et al [5] indicated that fluid-structure interaction had significant effects on the dynamic response of bridge pile foundations submerged in water. It is important to evaluate the seismic responses of cross-sea bridges considering SSI. Shock and Vibration seismic responses of bridge pile group foundation considering fluid-structure-soil interaction (FSSI). Wang et al [29] developed an accurate finite element model to evaluate the earthquake-induced hydrodynamic forces on multiple cylinders. A few studies have been carried out to analyze the seismic response of cross-sea bridges considering FSSI. E main objective of this study is to obtain fragility curves for a typical bridge pile group foundation considering FSSI. E effects of water, soil, and different kinds of ground motions on the seismic behavior of the bridge pile group foundation are quantitatively analyzed. Concrete 01 from the material library in
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