Study On Methods Of Selecting The Most Unfavorable Earthquakes For Long Period Super High-rise Building Structures

Owing to the complexity and extreme uncertainty of earthquake events, now it is still difficult to forcast the earthquakes that may happen in the future precisely, so building structures may be attacked by earthquakes far more severer than design earthquakes. Therefore, for the zones with high seismic hazard or building structures with great importantance, it must evaluate seismic damge with the most unfavorable earthquakes. Now there are some methods to select the most unfavorable earthquakes, however, it is lacking in systematic study and comparation on the accuracy and application scope of these methods. Besides, the research objects at present stage are mostly short or middle period RC frame structures, studies on selecting the most unfavorable earthquakes for long period super high-rise building structures are few. Super high-rise building structures have long period and the reponses are quite different with other structures under earthquake actions; and because of containing a lot of people, equiments and property, the structures must be good in seismic capacity. So it is quite important to study the method of selecting the most unfavorable earthquakes for long period super high-rise building structures.Aiming at these problems, the research of this paper includes three aspects as following:(1) For systematically comparing the accuracy of three common methods of selecting most unfavorable earthquakes, which are deterministic method, probabilistic method and ground motion damage potential comprehensive evaluating method, select 50 earthquake records of different types, use these three methods to calculate the unfavorable degree indices of earthquakes, and implement the correlation analyses between these indices and elastic response spectra values as well as Park-Ang damage indices of elastic perfectly-plastic SDOF systems. The results show that it is not highly correlated between these unfavorable degree indices and structure seismic responses, so these methods cannot ensure the selection of the most unfavorable earthquakes.(2) Analyse and summary the limitations of these three methods of selecting the most unfavorable earthquakes, and aiming at the existing problems of ground motion damage potential comprehensive evaluating method, improve this method without considering the effect of structure types. For verifying the rationality of this improved method and the applicability to long period structures, take a long period frame core-tube super high-rise building structure as an example, implement the dynamic elastic-plastic time-history analyses and compare the accuracy of the presented method and other three methods based on structure seismic responses. The results show that the presented method have the highest accuracy, and there are at least three earthquake records which is selected by this method as the most unfavorable earthquakes in the five most severest earthquake records to the structure, so it is applicable to selecting the most unfavorable earthquakes of long period super high-rise building structures in real engineering.(3) For considering the effect of structure types on selecting the most unfavorable earthquakes, take long period frame core-tube super high-rise building structure system as the analysis objective and take three structure numerical examples as analysis models, and then determine the parameter vector that is most suitable to present the ground motion damage potential to this kind of structure system by correlation analyses, which can provide reference for selecting the most unfavorable earthquakes of this kind of structure system.