Comparative analysis of seismic performance of 122-meter long concrete-filled steel tube arched chord truss bridge before and after reinforcement

Abstract

Finite element analysis of a 122-meter concrete-filled steel tube arched chord truss bridge was performed using ANSYS to obtain the natural vibration characteristics of the bridge, both before and after reinforcement. In addition, the response spectrum and dynamic time history methods were used to analyze and compare its seismic performance. The results show that the transverse stiffness of the bridge’s main truss was relatively low. After the reinforcement, the vertical and the torsional frequencies of the bridge significantly increased by 24% and 32%, respectively. under the same condition, the axial force at the fixed end of the top chord of the strengthened bridge was reduced by roughly 29%, and the transverse and the vertical displacement at the middle of the top chord span were reduced by roughly 10% and 20%, respectively. Thus, the reinforcement measures significantly improved the vertical stiffness of the bridge. For this bridge, the dynamic time history analysis played a more controlling role in the seismic design. Among the three types of seismic waves, the El Centro wave yielded the largest transverse displacement result and hence, should preferably be used to assess the deflections.