The Correlation Analysis Of Structural Response With The Duration Metrics

The damage of structures caused by earthquakes has always brought a huge threat to people’s lives and property.The damage is mainly determined by the characteristics of ground motion,the seismic performance of the structure,and the interaction between the ground motion and the structure.The characteristics of ground motion usually include three elements: amplitude,frequency spectrum and duration.In the current research and practical engineering application,the influence of duration on the structure is not well included in the seismic design code and seismic analysis,which still needs further study.The selection of duration index,the characteristics of structures,structural response parameters and how to decouple the duration index from the spectrum characteristics are the essencial contents of in-depth study.The different selection of duration indexes plays an important role in studying the influence of duration on structures,and the decoupling of duration and spectrum characteristics can better reflect the single factor influence of duration.Therefore,this paper uses artificial ground motions and spectrum matching ground motions to explore the correlation between different duration indexes and structural response,and quantitatively analyzes the impact of duration on each structure response.The main work is as follows:1.This paper summarizes the research status of the influence of duration on the structural response at home and abroad,analyzes the shortcomings of the research and the contents that need further research,and uses the method of artificial synthetic ground motion and the method of response spectrum matching to decouple the spectrum characteristics and duration characteristics,and obtains the ground motions with long or short duration,which are divided into two groups,artificial ground motion and natural ground motion.2.Several single degree of freedom systems are established by OPENSEES,including three hysteretic models,which respectively represent the slight degradation of stiffness(MC model),significant degradation of stiffness and strength(SSD model),and pinch effect with moderate degradation of stiffness and strength(p H model).Then,the artificial ground motion records and the natural ground motion records after spectrum matching are input into the three selected models respectively.Considering four yield strength reduction coefficients,the ductility demand,standard hysteretic energy consumption demand,damage index and other structural response measurement indexes are calculated.By calculating the correlation coefficient between each duration index and the response of different systems,the correlation under the records of artificial and actual ground motion is compared.Through the whole correlation analysis,it can be concluded that the uniform duration(Du)has the highest correlation with the structural response,so it is more suitable to be used as the duration index in the analysis of the influence of duration on the structural response.At the same time,through the correlation analysis,it can be seen that the ductility demand of the structure has a strong correlation with the models with stiffness and strength degradation or pinch effect in the short period,while for the model with no significant stiffness degradation,the correlation is low.3.In order to quantitatively analyze the influence of duration on the structural response,the recommended duration is used as the duration index,and the selected natural ground motion records are input into the models for calculation.According to the distribution of data,Du = 15 s is used as the boundary point of long-term and short-term ground motions.Then,the ductility demand and standard hysteretic energy consumption with stiffness and strength degradation,the pinch effect and different strength reduction coefficient under the long-term and short-term ground motions are discussed quantitatively.It is found that under the long-term ground motion,the ductility demand and standard hysteretic energy consumption are larger and more obvious in the short period;the models with significant stiffness and strength degradation have larger ductility demand than the model without considering degradation,while the standard hysteretic energy consumption is smaller;with the increase of strength reduction coefficient,the ductility demand and standard hysteretic energy consumption are larger.Finally,the empirical formulas of ductility demand and standard hysteretic energy consumption are given by regression analysis,and the empirical formulas of damage index can be deduced according to the empirical formulas of ductility demand and standard hysteretic energy consumption.