地面运动强度参数对RC桥梁地震需求的影响
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摘要
在基于性能的地震工程学(PBEE)中,建立概率地震需求模型(PSDM)时需要对桥梁结构的工程需求参数(EDP)进行概率估计。其中,强地面运动参数(IM)的选择对EDP的概率估计影响很大,因此需要正确选择IM。分别采用目前最广泛使用的结构第一模态周期弹性谱加速度(5%阻尼比)Sa(T1,5%)和峰值地面加速度PGA作为IM,选择实际地震波并进行合理的调值,对一座钢筋混凝土桥墩进行IDA分析,其计算结果表明:对于不同性质EDP的概率估计值,以PGA作为IM计算所得的结果明显偏于非保守,且离散度一般也更大。说明可以针对不同性质的EDP,根据地面运动强度的大小,选择不同的IM,通过合理的调值对EDP进行概率估计,可以更加精确、高效地建立PSDM。
Probabilistic seismic demand model(PSDM) necessitates the probabilistic evaluation of engineering demand parameters(EDP) in the performance-based earthquake engineering(PBEE) methodology.There is the significant influence of the selection of earthquake strong-motions intensity measures on the probabilistic evaluation of EDP so that the appropriate IMs should be selected.Incremental dynamic analysis of a RC column will be implemented using real accelerograms with reasonable scaling while the elastic spectral acceleration with 5% damping at the first period of the structure(Sa(T1,5%)) and peak ground acceleration(PGA) are selected as intensity measures(IMs),respectively.The analytic results reveal that the probabilistic estimators of different EDPs which are gained using PGA as IM are significantly nonconcervative and their dispersions are generally larger.It is shown that PSDM can be developed accurately and efficiently according to the changing of earthquake ground motions intensity and different EDPs obtained by selecting different IMs with reasonably scaling.
Probabilistic seismic demand model(PSDM) necessitates the probabilistic evaluation of engineering demand parameters(EDP) in the performance-based earthquake engineering(PBEE) methodology.There is the significant influence of the selection of earthquake strong-motions intensity measures on the probabilistic evaluation of EDP so that the appropriate IMs should be selected.Incremental dynamic analysis of a RC column will be implemented using real accelerograms with reasonable scaling while the elastic spectral acceleration with 5% damping at the first period of the structure(Sa(T1,5%)) and peak ground acceleration(PGA) are selected as intensity measures(IMs),respectively.The analytic results reveal that the probabilistic estimators of different EDPs which are gained using PGA as IM are significantly nonconcervative and their dispersions are generally larger.It is shown that PSDM can be developed accurately and efficiently according to the changing of earthquake ground motions intensity and different EDPs obtained by selecting different IMs with reasonably scaling.
引文
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[2]Lee T H,Khalid M,Mosalam.Probabilistic Seismic Evaluation of Reinforced Concrete Structural Components and Systems[R].Pacific Earth-quake Engineering Research Center,University of California,Berkeley,CA,2006.
[3]Opensees[EB/OL].http://opensees.berkeley.edu.
[4]PEER Strong Ground Motion Database[DB/OL].http://peer.berkeley.edu/NGA.
[5]Shome N,Cornell C A,Bazzurro P,et al,records and nonlinear responses[J].Earthquake Spectra,1998,14(3):469-500.
[6]Nielson B G,DesRoches R.Seismic fragility methodology for highway bridges using a component level approach[J].Earthquake Engng and Struct.Dyn.2007,36:323-839.
[7]Choi E,DesRoches R,Nielson B.Seismic fragility of typical bridges in moderate seismic zones[J].Engineering Structures,2004,26(2):187-199.
[8]Vamvatsikos D,C Allin Cornell.Developing efficient scalar and vector intensity measures for IDAcapacity estimation by incorporating elastic spec-tral shape information[J].Earthquake Engineering&Structural Dynamics,2005 34:(13):1573-1600.
[9]Shome N,Cornell C A,Bazzurro P,et al.Earthquakes,records and nonlinear responses[J].Earthquake Spectra,1998,14(3):469-500.
[10]Park Y J,Ang A HS.Mechanistic seismic damage model for reinforced concrete[J].Journal of Structural Division,ASCE.1985,111(4):722-739.
[11]Benjamin J R,Cornell C A.Probability,statistics and decision for civil engineers[M].New York:McGraw-Hill,Inc,1970.
[12]Vamvatsikosa D,Cornell C A.Applied incremental dynamic analysis[J].Earthquake Spectra,2004,20(2):523-553.
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