Natural Vibration Feature And Seismic Response Analysis Of Long Span Concrete Filled Steel Tube Arch Bridge

In recent years, with the continuous improvement on the theory of concrete filled steel tube (CFST), the application of CFST arch bridge has a great development, but the anti-seismic analysis for CFST arch bridge with large span is still a problem which needs to be studied deep. At present, there is no clear description about anti-seismic problem of CFST arch bridge in Chinese code. With reference to papers about anti-seismic problem of bridge, studies on seismic response of CFST arch bridge is still very few. Aiming to natural vibration characteristic and seismic response of CFST arch bridge with large span, the following several aspects are studied in the paper.1. Taking Nanning Bridge (CFST arch bridge with the span of 338m) as an example, establish finite element model for seismic response analysis by general finite element software ANSYS. Natural frequency of this bridge is calculated as the basis of dynamic calculation with taking the influence of horizontal bracing stiffness, arch rib stiffness and suspenders into account.2. According to geological condition of Nanning Bridge and combining with norm seismic response spectrum, draw spectrum curve and calculate the bridge's response under the impact of longitudinal, transversal and vertical seismic load respectively. Working status of bridge structures is also researched under the most adverse seismic load combination. From the analysis, the influence of vertical seismic load on structures can not be ignored.3. Seismic response of the bridge under uniform excitation and traveling wave effect is analyzed by making use of time history analysis method. The maximum and the place of the maximum of arch bridge seismic response is different. During seismic analysis, seismic response will become large if vertical seismic load and traveling wave effect is considered. Therefore it is very necessary to consider vertical seismic load and traveling wave effect.4. Constitutive relations of CFST are established according to the analysis of bridge nonlinear factors as well as related codes. Based on the seismic response analysis of Nanning Bridge with considering material nonlinear factors, geometry nonlinear factors and the combination of above two nonlinear factors, it indicates that: material nonlinear factors have little effect on bridge seismic response because combined material of CFST is under elastical condition; while geometry nonlinear factors have much effect on bridge seismic response because CFST arch bridge is flexible structure where nonlinear performance of arch rib and suspender of is notable.