Analysis On Structural Vulnerability Of High-Rise RC Frame Core Tube Under The Action Of Near-Field Main Aftershock Sequence

The main earthquake is often accompanied by multiple aftershocks in a relatively short period of time.Multiple aftershocks often occur in a relatively short period of time after the main earthquake.After the main earthquake action,the plastic deformation of the structure increases,and the stiffness and bearing capacity is reduced,causing serious damage to the structure and even collapsing.However,current codes for seismic design in most countries only the case of a single main seismic effect and ignore the additional cumulative effects of aftershocks.Therefore,it is of great significance to study the damage increment generated by the main aftershock sequence on the structure and to evaluate the seismic performance of the structure.Recently,Seismic vulnerability analysis based on incremental dynamic method has been widely used in the evaluation of seismic performance of structures.The main research work is as follows:1.This paper reviews the incremental dynamic analysis method,the current research status of seismic vulnerability and the characteristics of near-site vibration.2.In this paper,a high-rise RC frame core tube structure is simplified.Then a geometric model is established by using ETABS.The structure period,interlayer displacement angle,and interlayer shear force all meet the current codes,ensuring the rationality and accuracy of the elastoplastic analysis model.Finally,this paper introduces several direct integration methods commonly used in structural dynamic elastoplastic time history analysis.3.Based on the incremental dynamic analysis method,the PGA of 10 main-aftershock records were modulated from 0.1g to 0.8g.The HHT direct integration method is used to analyze the finite element model of high-rise RC frame core tube structure for 120 times.The results show that aftershocks significantly increase base reaction,maximum vertex displacement,displacement angle,and inelastic energy consumption of the structure.However,there are certain differences between different damage indicators.4.Based on the calculation results of the incremental dynamic analysis,PGA is selected as the seismic intensity parameter and the maximum interlayer displacement is used as the structural damage index.Then,structural seismic susceptibility curves are plotted.The results show that the final structural failure under the action of the near-field main aftershock sequence is related to the structural damage state after the main earthquake.Moreover,it is difficult to meet the three-level seismic fortification target.