Structural Damage Research Of RC Frame Based On Dynamic Characteristics

An important basis for performance-based seismic design is to determine the reasonable index of structural seismic response, which can evaluate the structural performance under different level of earthquake. In addition, it can also be used to describe the degree of structural damage, and to make decisions for structural post-earthquake treatment.As the basic properties of the structure itself, the structural dynamic characteristics like frequencies and mode shape will change as the seismic action increase and the structure go into ela-plastic stage and damage occur in structural member. So the damage index based on structural dynamic characteristics will be discussed in this paper.The structural damage is assessed using the change of dynamic characteristics by Pushover the structure. The index based on frequency drawdown ratio, the index considering final frequency, and the index based on the frequency combined using relative mode mass is proposed in this paper. The IDARC program is modified to output the dynamic characteristic in every step of Pushover.A ten stories RC-frame building model is established and one frame is picked out to analysis. Using modified IDARC program, by gradually increasing the horizon distribution load, the varying of dynamic characteristic is observed, which indicts that the frequencies decrease a lot, while the mode shape change not much. The time-varying curve of damage index based on dynamic characteristic is drawn and compared with those index based on ductility or based on Park-Ang model. The result shows that the index based on dynamic characteristic can recognize the structural plastic stage and the structural fail stage.The frequency-based damage index can reflect the failure process of structure and recognize the different stage of structure. The combine-frequency-based damage index can take the contribution of preceding modes into the structural damage. By observing the changes of dynamic characteristic during Pushover process and calculating the corresponding frequency-based damage index, this paper provided a new way for overall structural damage assessment.