Effect Of Earthquake Duration On Seismic Response Of Structures

Earthquake damage to building structures seriously threatens the safety of people’s lives and property.Structural damage during earthquake is largely determined by the characteristics of earthquake ground motion and seismic performance of structures.The characteristics of ground motion are generally determined by the three elements of ground motion,frequency spectrum,amplitude and duration,which affect the seismic response of structures.The research on frequency spectrum and amplitude in the field of seismic engineering has always been a hot research topic.The corresponding research results are also reflected in the seismic design codes of various countries,however,the effect of duration on seismic response of structures has not been explicitly considered by seismic design codes.It is a hot topic to study the effect of duration on structural response at home and abroad recently.There are four difficulties in this subject: one is to select appropriate duration index,the other is to eliminate the effect of frequency spectrum and amplitude,the third is to select appropriate structural model and structural response index,and the fourth is to quantify the effect of time-holding on structural response.Considering the above four points,this paper studies the effect of duration on seismic response of structures,aiming at providing reference for seismic design of engineering structures.Specific research contents are as follows:1.Introduce the commonly used duration index of earthquake motion in engineering,and select the important duration Ds5-75 as the duration index parameter of analysis,further introduce the spectrally equivalent method which can eliminate the effect of frequency spectrum and amplitude of earthquake ground motion,and 114 pairs of long and short duration ground motion records with the same spectrum and amplitude but different duration are obtained by screening and matching.2.For SDOF structures,three hysteretic constitutive relations and three structural response parameters,ductility,hysteretic dissipation energy and damage index,are selected to calculate the ductility spectrum,standard hysteretic dissipation energy spectrum and damage spectrum under long and short duration ground motions.The effect of duration on seismic response of structures is quantified in the form of ratio spectrum,and the effect of duration on structural yield strength,nominal ductility and stiffness of softening section are analyzed.It is found that the influence of duration on structural response is largely determined by the selected constitutive model and type of structural response,and is greatly affected by structural yield strength,nominal ductility and stiffness of softening section also has a certain impact.3.In order to facilitate the practical application of engineering,a statistical regression analysis method is used to quantitatively analyze the effect of duration on the structural ductility,hysteretic energy dissipation and damage index,considering the yield strength,nominal ductility and softening stiffness of three constitutive models.A prediction method is obtained which can be used to estimate the corresponding structural response changes of when the significant duration of ground motion changes.The method can provide reference for seismic design of engineering structures.