Research On Intensity Measures Of Near-fault Ground Motions For High-rise Aseismic Structures And Isolated Structures

As one of the key research topics of earthquake engineering all around the word,the ground motion intensity measures?IMs?are used to connect the seismic hazard analysis and structural probabilistic seismic demand analysis.So,it is of great significance for seismic analysis of structures in the near-fault regions.However,there are few studies on near-fault ground motions related to long-period high-rise aseismic structures and isolated structures.Therefore,two kinds of high-rise building structures are designed in this paper and 100 strong earthquake records?50 impulsive records and 50 non-pulse records?from Chi-Chi earthquake in Tai wan are selected as input to calculate the dynamic responses of two kinds of high-rise building structures.Furthermore,the statistical methods are used to study the ground motion IMs and seismic response of high-rise building structures.The aim is to obtain the general laws that characterize the efficiency,practicality,proficiency,sufficiency and hazard computability of ground motion IMs through statistical analysis.Seismic demand fragility curves and seismic demand hazard curves related to IMs are also discussed.Firstly,the engineering demand parameters?EDPs?of 11-story and 14-story reinforced concrete frame structures under Chi-Chi earthquake are calculated and new IMs?AP and AS?are proposed in the construction of probabilistic seismic demand model?PSDM?.Then,according to five criteria,the influences of EDPs on IMs selected are analyzed.The results show that,the efficiency,proficiency and sufficiency of structure-specific IMs for floor displacement and inter-story drift ratio are better than non-structure-specific IMs and IMs related to average inter-story drift ratio perform much better than IMs related to maximum inter-story drift ratio;In terms of inter-story drift ratio,the optimal IMs related to impulsive ground motions are easily obtained from the pseudo velocity response spectrum S_pv and the optimal IMs related to non-pulse ground motions are easily obtained from the velocity response spectrum S_v.In addition,the optimal IMs for long-period aseismic structures considered are selected.Secondly,the EDPs of 10-story reinforced concrete frame structure isolated at the base under Chi-Chi earthquake are further calculated.Besides,the influences of EDP under different yield displacement on the performance of IMs are examined.The numerical results indicate that,with the increasing of yield displacement,the better IMs are being related to S_pvv and S_v gradually;Two IMs?AP and AS?proposed show better performance and can effectively improve the PSDMs.What's more,the optimal IMs for base-isolated structures considered are suggested.Finally,the efficiency of optimal IMs on hazard computability is discussed by using seismic demand hazard curves obtained indirectly.It is shown that,seismic demand hazard curves obtained indirectly are good for aseismic structures and are not good for base-isolated structures;Optimal IMs suitable for base-isolated structures should obtain the source site's seismic hazard curves directly.