Dynamic Time-history Analysis And Cumulative Damage Assessment Of Concrete-filled Steel Tube Columns

Earthquake is an unpredictable natural disaster, which will cause damage in different degrees to structure, and endanger people’s lives and property safety seriously. The action of earthquake is a cyclical process. Even if the structure does not have a great response throughout the process, but the cumulative damage under reciprocating action may cause structural damage. Concrete filled steel tubular(CFT) columns have been widely used in high rise buildings, industrial buildings and bridge structures because of their many advantages. At present, most of the seismic performance evaluations of CFT columns are based on the characteristics of ductility, bearing capacity, hysteretic energy dissipation and so on, and effects of cumulative damage are seldom considered. There is little research on the application of damage model in the actual earthquake damage assessment. The response of structure under different earthquake action is different because of the randomness of earthquake. In this paper, the dynamic time history analysis of CFT columns under different ground motion intensity is carried out, and the seismic damage of CFT columns is studied systematically from the angle of probability.An incremental dynamic analysis of a CFT bridge pier example under 18 strong ground motion records was carried out by Perform-3D, and the characteristics of displacement response, moment-curvature relationship and energy dissipation of the column under different earthquake were analyzed in detail. The results show that the CFT column can resist strong earthquake, and has good seismic performance.Different damage models were compared and analyzed, and a seismic damage assessment method based on damage index was put forward, the vulnerability analysis of CFT column was carried out at the same time. The results show that for the CFT pier with a fortification intensity of 7, the pier is in perfect condition under 7-degree E1 earthquake action,and the probability of serious damage and failure is zero under 7-degree E2 earthquake action, and the probability of failure under two ultra rare earthquakes is small, which indicate that the bridge pier can satisfy the target of seismic fortification. The research can provide reference for the performance-based seismic design and post-earthquake restoration of CFT columns.Through the analysis of 7 different models, the effects of the length to thickness ratio, diameter to thickness ratio and axial compression ratio on the seismic response and cumulative damage of CFT columns were investigated. The results show that the influences of the 3 parameters on the seismic behavior and cumulative damage of CFT columns are significant, and different parameters have different effects.