Strong Ground Motion Selected For Structural Analysis Under Seldom Occurred Earthquake

In 1910's ,Earthquake Engineering separated from Structure Engineering ,formed a new domain. There has been almost a hundred years up to now. In this development process , all kinds of new theories and methods have been used into structure design .Now ,the time history method has been widely used in the design of tall buildings and important buildings .Strong ground motion ,as a special kind of load ,is a major reason to structural damage and collapse. During seismic design, analysis and research ,the strong ground motion records usually should be selected to simulate the earthquake load .Because of the strong randomicity and complexity in earthquake ,there are thousands of motion records have been accumulated .Facing so many records ,how to choose the best one to the design structure often make the structural designer at loose ends .This difficulty also limits the time history analysis/method widely and effectively used.Facing this kind of condition, a lot of work has been done by our country's scholars, they have put forward several selecting methods to satisfy the Code demand .But these researches all established on the stage of elasticity analysis, the same characteristic period of response spectrum was used for the stage of elasto-plastic analysis .The selecting waves' response spectra should be in accordance with the Code's design response spectrum .The maximum of seismic influence coefficient and the characteristic period of response spectrum are the two major parameters to establish the design response spectrum .As the strong ground motions increase ,it has been recognized that the characteristic period of response spectrum moves backward as the increase of the peak ground acceleration .This result doesn't been incorporated in the current Code ,so lengthen the characteristic period of response spectrum is a good way to tackle this condition .In the strong earthquake ,soil ,being a kind of special structure ,may be damaged ,so the fundamental period may be lengthened.The deformation analysis was made to a 12 storey reinforcement concrete structure, building in site condition II,earthquake fortification level 8, by a program IDARC-2D which is put forward by the State University of New York at Buffalo .The strong ground motion records obtained from PacificEarthquake Engineering Research (PEER)Stiong Ground Motion Database .Thirty-eight waves were selected from the database by sorting the site condition and peak ground acceleration A comparison was made to the thirty-eight records' response spectra and the Design Response Spectrum .Thirteen waves were selected to the deformation analysis ,El-centro wave and Taft Wave were added as a comparison .The result of computation shows that the selected waves damaged the structure severely than the El-centro wave and Taft wave. Storey drift and damage index were the two criteria to evaluate the severe level .The example confirmed the accuracy of the method put forward in this paper, the method can be applied to the actual structural design.