能力谱法中等效阻尼比的误差分析及假设检验
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摘要
通过一单自由度和一多自由度算例,对考虑等效阻尼比的传统能力谱法和采用弹塑性反应谱的改进方法进行比较,并和非线性动力分析对比。为验证等效阻尼比的假定,构造了能产生完整、对称滞回环的特殊地震动。结果表明:采用等效线性体系考虑附加阻尼的传统方法低估了结构响应,有较大误差;同时说明结构的塑性滞回耗能与等效阻尼比并无直接联系,即等效阻尼比的假设并不准确;而采用弹塑性需求曲线的改进方法和真实反应吻合较好。
Numerical examples are performed for a single-degree-of-freedom system and a multi-degree-of-freedom system by the traditional capacity spectrum method(CSM) which considers the structural non-linear behavior as the additional damping and the improved method which uses the inelastic response spectrum directly.The results are compared with each other and those from the non-linear dynamic analysis,respectively.In order to verify the concept assumption of the equivalent damping ratio,a special ground motion which makes a structure form a complete and symmetrical hysteretic loop is constructed.The results show that the traditional CSM which uses the equivalent linear system and the additional damping underestimates the response of structures,indicating the structural hysteretic energy dissipation has no direct relationship with the equivalent damping ratio,as the assumption of it is proved incorrect.The improved method which uses the inelastic demand curve generates more accurate results,which is close to the actual response.
Numerical examples are performed for a single-degree-of-freedom system and a multi-degree-of-freedom system by the traditional capacity spectrum method(CSM) which considers the structural non-linear behavior as the additional damping and the improved method which uses the inelastic response spectrum directly.The results are compared with each other and those from the non-linear dynamic analysis,respectively.In order to verify the concept assumption of the equivalent damping ratio,a special ground motion which makes a structure form a complete and symmetrical hysteretic loop is constructed.The results show that the traditional CSM which uses the equivalent linear system and the additional damping underestimates the response of structures,indicating the structural hysteretic energy dissipation has no direct relationship with the equivalent damping ratio,as the assumption of it is proved incorrect.The improved method which uses the inelastic demand curve generates more accurate results,which is close to the actual response.
引文
[1]A pplied Technology Council.Guidelines for seismicperformance assessment of buildings,ATC-58 50%draft[R.]ATC,Redwood City,CA,2009
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[12]丁建国.弹塑性反应谱及其在抗震设计中的应用[J.]南京理工大学学报,2007,31(6):780-783(Ding Jianguo.Elasto-plastic response spectrum and its applications inaseismatic design[J.]Journal of Nanjing University ofScience and Technology,2007,31(6):780-783(inChinese))
[2]FEMA-445 Next-generation performance-based seismicdesign guidelines program plan for new and existingbuildings[S.]FEMA,Washington DC,2006
[3]ATC-40.Seismic evaluation and retrofit ofconcrete buildings[R.]ATC,Redwood City,CA,1996
[4]FEMA-273 NEHRP guidelines for the seismic rehabilitationof buildings[S.]FEMA,Washington DC,1997
[5]Fajfar P,Gaspersic P.The N2 method for the seismic damageanalysis of RC buildings[J.]Earthquake Engineering andStructural Dynamics,1996,25:31-46
[6]Chopra A K,Geol R K.Capacity-demand-diagram methodsfor estimating seismic deformation of inelastic structures:SDF systems[R.]PEER,University of California,Berkeley,CA,1999
[7]Krawinkler H.New trends in seismic design methodology[C/]/Proceedings of 10th European Conference onEarthquake Engineering.Rotterdam.Netherlands,1995
[8]Fajfar P.Capacity spectrum method based on inelasticdemand spectra[J.]Earthquake Engineering and StructualDynamics,1999,28(9):979-993
[9]Newmark N M,Hall W J.Earthquake spectra and design[R.]Earthquake Engineering Research Institute,Berkeley,CA,1982
[10]Vidic T,Fajfar P.Consistent inelastic design spectra:strength and displacement[J].Earthquake Engineeringand Structural Dynamics,1994,23:507-521
[11]Miranda E.Site-dependent strength-reduction factors[J.]Journal of Structural Engineering,1993,119(12):3503-3519
[12]丁建国.弹塑性反应谱及其在抗震设计中的应用[J.]南京理工大学学报,2007,31(6):780-783(Ding Jianguo.Elasto-plastic response spectrum and its applications inaseismatic design[J.]Journal of Nanjing University ofScience and Technology,2007,31(6):780-783(inChinese))
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