Nonlinear seismic properties of the Second Saikai Bridge: A concrete filled tubular (CFT) arch bridge

The technology of concrete filled tube (CFT) arch bridges has developed rapidly in China since 1990. More than one hundred CFT arch bridges have been built or are now under construction. However, since the weight of a CFT arch rib is greater than that of a steel rib and the arch action is not effective in the out-of-plane direction, the seismic safety of CFT bridges should be evaluated. This paper examines nonlinear seismic responses of the Second Saikai Bridge, which is the first highway bridge in Japan to be a CFT arch bridge. This bridge has a main span length of 240 m. The natural vibration characteristics of this bridge are discussed using a three-dimensional FE model. A nonlinear seismic analysis is performed using the strong ground motions observed in the Hyogo-ken Nanbu Earthquake of Japan. The nonlinear seismic characteristics and seismic safety of this bridge are examined in detail by subjecting the bridge to earthquakes in the out-of-plane direction, longitudinal direction and combined out-of-plane and longitudinal directions. It is found that the analysis should consider the combined out-of-plane and longitudinal excitations.