Seismic Behavior Of CFST Arch Bridges Based On Existing Shaking Table Test

Concrete Filled Steel Tubular (CFST) Arch Bridges have been widely used throughout the world in recent years because of its light weight, high strength, good ductility and convenient construction procedure. Over 300 CFST arch bridges have been bulit in China, among which more than 200 CFST arch bridges have spans larger than 50m. China is an earthquake-prone country, most of CFST arch bridges have been built in high seismic intensity areas, thus the seismic research on CFST arch bridges is extremely important. In this dissertation, seismic behavior of single circular CFST arches has been investigated using Pushover method and Incremental Dynamic Analysis (IDA) method. The research work is as follows:Based on an existing shaking table test on a CFST arch bridge, this paper verifys the applicability of OpenSees in the analysis on seismic performance of CFST arch bridges. The failure process and failure mechanism of CFST arch bridges under severe earthquakes have also been studied. It is shown that under a series of earthquake actions whose peak accelerations gradually increased, the springs of the CFST arch bridges would firstly turn to plasticity due to the significant base shear force and overturning moment and eventually the internal force could not counterpoise the earthquake actions leading to dynamic buckling of the CFST arch bridges. The stress-strain development diagram obtained under the ultimate peak acceleration shows that, the CFST arches present favorable hysterestic behavior as well as good ductility and energy dissipation under the earthquake attacks.The IDA method has been used in the research on seismic performance of circular CFST arches. Two typical failure modes of circular CFST arches under earthquakes have been presented. In addition, the effect of slenderness ratio, axial compression ratio and included angle on the seismic performance of CFST arches are investigated. The ultimate peak acclerations and their mean value of circular CFST arches under 11 different ground motions for site condition 2 have been caculated to propose the formula of ultimate peak acclerations of circular CFST arches. Comapred with the results obtained from finite element analysis, the results obtained from the proposed formula are safer.The Pushover method has been used to investigate the seismic performance of circular CFST arches, and the influence of three typical lateral loading patterns on the seismic performance of circular CFST arches are studied, based on which the most suitable pattern is selected. The curves about the base shear force against the displacement have been caculated considering different paremeters, including the slenderness ratio, axial compression ratio and included angle. The paper also proposes the formula of out-of-plane paek displacement of circular CFST arches under severe earthquakes. Comapred with the results obtained from the finite element method, the results obtained from the proposed formula are safer.