Analyse On Seismic Behacior Of Concrete Filled Steel Tubular Arch Bridge

In recent years , as a new-type bridge, concrete-filled steel tubular(CFST) arch bridge has been deeply developed in our country's construction, for its own merits and can luckily make agreement with the factual situation of bridge engineering since the Sichuan Wangcang big bridge has been built in 1990.However, the study on design theories of CFST arch bridge gets relatively behind the engineering practice, and the search on dynamic performance of this structure get relatively behind the production on static feature of this structure. Presently, CFST arch bridges develop in the direction of large-span and lightweight style, accordingly, investigators and devisers should increasingly attach more importance to their dynamic behaviour, and some typical dynamic matter of bridges, such as seismic response, wind induced vibration, coupled dynamic vibration between bridge and vehicle should not be ignored.In this thesis, taking the example of some railroad CFST arch bridge (Nilesen bridge), with the help of ANSYS, one universal FEM software, author analyze its dynamic behaviors and abstract it as follows:1. Creating the FEM model of the whole bridge and analyzing its dynamical characteristic. Creating simplify model by the method of back and the solid model of the bridge and analyzing the bridge's dynamical characteristic, comparing and exploring the thoughts and methods of simplifying the bridge model. By comparing the simplify models we can find that, beam mode and shell mode are better simplified models for single-box and three-room bridge. The dynamical characteristic of this kind of bridge is analyzed basing on the calculation results and referring to the results of theoretics calculation and testing of other similar bridges. It is necessary to pay great attention to the dynamical problems of such big span bridge. In general, the out-plane stiffness is weaker than the in-plane stiffness for such type bridge, especially for small width-span ratio and heavy bearing bridge, so the cross direction vibration and stability are key problems for them.2. Applying the existing anti-seismic theory, the anti-seismic capability of this concrete arch bridge is analyzed by time-history analysis and response spectrum analysis. Basing on the results of time-history analysis, the structure form of this bridge has been optimized mainly centering on the style and number of the cross supports collocation, and the results can be reference for other bridges of the same type. From the results, it is easy to find that, the style andnumber of the cross supports collocation has big effect on the anti-seismic characteristic of arch bridge and the collocation location of K-shape supports and X-shape supports can also affect the anti-seismic characteristic of arch bridge. The good and sound collocation style of the cross supports can be confirmed and used to serve for the practical engineering only after considering their effect on the dynamical characteristic, stability and anti-seismic characteristic of the bridge.