| With the rapid development of structural nonlinear dynamic analysis and accumulation of NSMONS ground motion data since 2008,the earthquake ground motion selection plays more and more important role in engineering practice.To meet the different earthquake fortification demands in China,different levels of the ground motion selection methods are studied in this paper.This paper focuses on three objects of ground motion selection:normal structures in design code,important key structures considering the local seismic hazard,and for application in performance based earthquake engineering.The corresponding ground motion selection methods studied in this paper includes matching the design code spectrum,construction of CMS,CS and GCIM which considers the hazard consistency and parameter sufficiency.A relatively comprehensive ground motion selection system is established in this paper which could be utilized for estimation of structural response median value and the whole distribution.The main contents of this paper are as follows:(1)The whole procedure of records selection matching Chin seismic design spectrum is proposed including the earthquake,site parameters and scaling factor range based on the ground motion data including U.S.PPER NGA-West1 dataset and China National Strong Motion Observation Network System(2007 to 2015 year)dataset.A new method was proposed to improve the performance of whole period range matching method by modification of the weight function based on its own error function.The selected ground motion recordings for design spectrum in Chinese seismic code were provided for reference.Then the maximum inter-story drift ratios(MIDRs)of one 12-storiy and one 3-story 2D RC frame were simulated and compared with the results using different recording selection methods and high-end prediction values.The method in this paper performs better than other methods in predicting the median structural response and does not rely on the accuracy of selected structural nature period.(2)The influence of the number of strong motion records and record-to-record variation on structural time-history analysis results in China seismic code is then discussed.The cumulative probability distribution of Mont Carlo simulated structural response indicated that the expectation of results distribution using just three recordings is much higher than the true median structural response and the safety assurance rate are significantly affected by the record-to-record variation.A 10-story RC frame of numerical simulation results confirmed the above conclusions.Finally,it is suggested that using the empirical equation to compute the required 84th percentile value.And the applicability of the empirical equation for Chinese seismic code is verified using structural time-history dynamic analysis.(3).This paper then aims at implementing the use of Conditional Mean Spectrum(CMS)and Condition Spectrum(CS)as the main input parameter in the practice of seismic safety evaluation in China.For this purpose,a procedure for M-R-epsilon-?seismic hazard deaggregation in China was first developed considering the magnitude,source-to-site distance,epsilon,and the long and short axis of typical attenuation relationship in China.Then the correlation coefficients based on earthquake records from China is developed using a dataset based on a newly developed GMPE.For illustration purpose,two different typical sites in China were considered as examples to carry out seismic hazard deaggregation and illustrate the construction procedure of CMS and CS.Ground motions records were selected correspond to the target CMS and CS including the mean and variance.(4)Spectral hazard consistency of the selected records matching CS distribution for the studied examples was evaluated and validated by computing the annual exceedance probability rate of the response spectra of the selected ground motions and comparing the results to the hazard curve corresponding to each site of concern at different periods.The tools developed in this work and their illustrative application to specific case studies in China are a first step towards the adoption of CMS and CS into the practice of Seismic Safety Evaluation in this country and could be used in engineering practice.(5)Because only the spectral acceleration is considered as intensity measure(IM)in the CMS or CS method,the generalized conditional intensity measure(GCIM)is utilized considering the earthquake parameter sufficiency in this paper including 23IMs:PGA,PGV,Sa,D_s,SI and ASI.Firstly,the correlation coefficients for these IMs were computed one by one based on the ground motion in NSMONS dataset.The GCIM distribution is constructed using new proposed method considering contribution weight of each potential earthquake scenarios.Using the same safety evaluation examples in the context for illustration,the GCIM is constructed and matched which could be used for a wide range estimation of structural response related to any intersected IM rather than the Sa only.(6)For the demand of new perprformance based earthquake engineering,a new earthquake demand hazard curve(EDHC)computation method is proposed based on traditional multiple stripe method using the ground motion results considering the hazard consistency and parameter sufficiency.This method could be closely linkedwith the PSHA results in safety evaluation work in China and reduce the computation cost.One 10-story RC frame was used as example for SDHC computation using cloud method and proposed method using CMS method,CS method and GCIM method for ground motion selection.A good agreement within different records selection methods used in this paper verified the applicability and stability of proposed methods.On the other hand,the cloud method significantly overestimated the SDHC results due to its hypothesis is not always reasonable in practice especially considering the seismic hazard of target site.Finally,SHDC consistency of the selected CS records for the studied sites was assessed and validated by changing the conditional period. |
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