Seismic behavior of long-span concrete-filled steel tubular arch bridge subjected to near-fault fling-step motions

Abstract

Special characteristics of earthquakes in the near-fault regions, mainly fling-step and forward-directivity effects, may result in the significant damage to long-span bridge. In this paper, investigations are performed to analyze the seismic behaviors of the long-span concrete-filled steel tubular arch bridge called Zangmu Bridge under fling-step motions. Firstly, a three-dimensional finite-element model for the bridge is constructed with proper consideration of the material and geometric nonlinearities; secondly, three kinds of seismic loadings are comprehensively illustrated including recorded ground motions, idealized pulse models and residual components; then, comparative analysis and parametric analysis are conducted to gain insight into the effect of different components in fling-step motions on the seismic response; finally, the potentially dangerous locations of the CFST arch are estimated by taking the strain index as performance evaluation standard. Findings from the studies reveal that fling-step motions consist of static and dynamic pulses, both of which possess significant influence on the seismic response and performance state; the seismic demands depend on both pulse period and pulse amplitude; and the 'narrow band' effect for different members appears at different pulse periods related to the mode contribution.