Study On PGA Amplification Factor Spectrum Of Mainshock Aftershocks

Earthquakes that have occurred show that a large number of aftershocks often occur after a strong earthquake,which will aggravate the damage of engineering structures,and affect the cost of post-earthquake relief,repair and reinforcement of structures.The aftershock has a significant influence on the seismic performance and failure state of the structure,which needs to be fully considered in the structural design stage.At present,China’s seismic design code only consider a seismic action in structural design,design code,does not incorporate the effect of aftershocks structure after the quake devastated tend to experience many aftershocks,it would further damage to the structure or structure collapse,leading to greater economic losses and casualties,and increase the risk of seismic secondary disasters,Therefore,it is necessary to study the seismic design method considering aftershocks in order to meet the structural behavior requirements under the action of mainshock aftershock ground motion.To solve this problem,a seismic design spectrum correction method considering the aftershock effect is proposed in this paper,which can be used for seismic design and seismic design of structures considering the aftershock effect.The main contents of this paper are as follows:(1)from the mainshock aftershock ground motion,the ground motion parameter characteristics and seismic response of set research status at home and abroad about the aftershocks are summarized,and introduces the common division of main earthquake aftershock sequence type standard,the number of access to a wide range of ground motion and under the premise of meet the engineering structure analysis,identified in this paper to establish the mainshock aftershock ground motion the principle of the ground motion data sets,Based on NGA-West2 strong earthquake record database,the mainshock aftershock ground motion data set is established,and the parameter characteristics of the data set are analyzed.(2)frame structure numerical model is established and different cycle of single degree of freedom system,the selection of ground motion as the input to the nonlinear dynamic time history analysis of structures,the maximum acceleration,maximum interlayer displacement Angle and hysteretic energy dissipation,the damage index as the structure parameters such as reaction index,study the response of the structure under the action of the aftershocks,The seismic parameters and the influence of site conditions are analyzed.(3)considering the effects of aftershocks design spectrum correction method is proposed,and expressed in PGA amplification coefficient correction coefficient,PGA amplification coefficient of different cycle order degree of freedom system carried out a statistical analysis,further study on the influence of random ground motion to the discrete,amplification coefficient prediction equation,is used for correcting the current specification design spectrum,Guide the seismic design of structures under the action of mainshock aftershock ground motion.Through the study in this paper,it is found that the impact of the mainshock aftershock sequence seismic vibration selected in this paper can not be ignored,and the aftershock has the greatest impact on the structure hysteretic energy consumption.In current seismic design code and does not consider aftershocks,therefore need to rethink the existing seismic design code,the influence of aftershocks in engineering structure design,this paper in order to achieve the targets of the PGA amplification coefficient spectrum to correct seismic design spectrum,the results show that the spectrum can provide target damage under design accurate adjustment coefficient.