Two parameters,block spectrum intensity Seq and spectrum shape factor a,which describe the characteristics of the loading block spectrum are defined,and the relationship between the parameters and fatigue crack propag...Two parameters,block spectrum intensity Seq and spectrum shape factor a,which describe the characteristics of the loading block spectrum are defined,and the relationship between the parameters and fatigue crack propagation behaviours is investigated.It is shown that the spectrum intensity is an 'average drive force' of fatigue crack propagation,and the variance of fatigue crack size at a given fatigue life is closely related to the spectrum shape factor α.展开更多
The present study is aimed to investigate the ability of different intensity measures （IMs）, including response spectral acceleration at the fundamental period of the structure, Sa（T1）, as a common scalar IM and t...The present study is aimed to investigate the ability of different intensity measures （IMs）, including response spectral acceleration at the fundamental period of the structure, Sa（T1）, as a common scalar IM and twelve vector-valued IMs for seismic collapse assessment of structures. The vector-valued IMs consist of two components, with S（T1） as the first component and different parameters that are ratios of scalar IMs, as well as the spectral shape proxies εSa and N, as the second component. After investigating the properties of an optimal IM, a new vector-valued IM that includes the ratio of Sa（T1） to the displacement spectrum intensity （DSI） as the second component is proposed. The new IM is more efficient than other IMs for predicting the collapse capacity of structures. It is also sufficient with respect to magnitude, source-to-site distance, and scale factor for collapse capacity prediction of structures. To satisfy the predictability criterion, a ground motion prediction equation （GMPE） is determined for Sa（T1）/DSI by using the existing GMPEs. Furthermore, an empirical equation is proposed for obtaining the correlation between the components of the proposed IM. The results of this study show that using the new vector-valued IM leads to a more reliable seismic collapse assessment of structures.展开更多
The determination of collapse margin ratio(CMR)of structure is influenced by many uncertain factors.Some factors that can affect the calculation of CMR,e.g.,the elongation of the structural fundamental period prior to...The determination of collapse margin ratio(CMR)of structure is influenced by many uncertain factors.Some factors that can affect the calculation of CMR,e.g.,the elongation of the structural fundamental period prior to collapse,the determination of earthquake intensity measure,the seismic hazard probability,and the difference of the spectral shapes between the median spectrum of the ground motions and the design spectrum,were discussed.Considering the elongation of the structural fundamental period,the intensity measure Sa(T1)should be replaced with *aS in the calculation of CMR for short-period and medium-period structures.The reasonable intensity measure should be determined by the correlation analysis between the earthquake intensity measure and the damage index of the structure.Otherwise,CMR should be adjusted according to the seismic hazard probability and the difference in the spectral shapes.For important long-period structures,CMR should be determined by the special site spectrum.The results indicate that both Sa(T1)and spectrum intensity(SI)could be used as intensity measures in the calculation of CMR for medium-period structures,but SI would be a better choice for long-period structures.Moreover,an adjusted CMR that reflects the actual seismic collapse safety of structures is provided.展开更多
文摘Two parameters,block spectrum intensity Seq and spectrum shape factor a,which describe the characteristics of the loading block spectrum are defined,and the relationship between the parameters and fatigue crack propagation behaviours is investigated.It is shown that the spectrum intensity is an 'average drive force' of fatigue crack propagation,and the variance of fatigue crack size at a given fatigue life is closely related to the spectrum shape factor α.
文摘The present study is aimed to investigate the ability of different intensity measures （IMs）, including response spectral acceleration at the fundamental period of the structure, Sa（T1）, as a common scalar IM and twelve vector-valued IMs for seismic collapse assessment of structures. The vector-valued IMs consist of two components, with S（T1） as the first component and different parameters that are ratios of scalar IMs, as well as the spectral shape proxies εSa and N, as the second component. After investigating the properties of an optimal IM, a new vector-valued IM that includes the ratio of Sa（T1） to the displacement spectrum intensity （DSI） as the second component is proposed. The new IM is more efficient than other IMs for predicting the collapse capacity of structures. It is also sufficient with respect to magnitude, source-to-site distance, and scale factor for collapse capacity prediction of structures. To satisfy the predictability criterion, a ground motion prediction equation （GMPE） is determined for Sa（T1）/DSI by using the existing GMPEs. Furthermore, an empirical equation is proposed for obtaining the correlation between the components of the proposed IM. The results of this study show that using the new vector-valued IM leads to a more reliable seismic collapse assessment of structures.
基金Projects(51161120359,90915005)supported by the National Natural Science Foundation of ChinaProject(NCET-08-0096)supported by the Program for New Century Excellent Talents in University of the Ministry of China
文摘The determination of collapse margin ratio(CMR)of structure is influenced by many uncertain factors.Some factors that can affect the calculation of CMR,e.g.,the elongation of the structural fundamental period prior to collapse,the determination of earthquake intensity measure,the seismic hazard probability,and the difference of the spectral shapes between the median spectrum of the ground motions and the design spectrum,were discussed.Considering the elongation of the structural fundamental period,the intensity measure Sa(T1)should be replaced with *aS in the calculation of CMR for short-period and medium-period structures.The reasonable intensity measure should be determined by the correlation analysis between the earthquake intensity measure and the damage index of the structure.Otherwise,CMR should be adjusted according to the seismic hazard probability and the difference in the spectral shapes.For important long-period structures,CMR should be determined by the special site spectrum.The results indicate that both Sa(T1)and spectrum intensity(SI)could be used as intensity measures in the calculation of CMR for medium-period structures,but SI would be a better choice for long-period structures.Moreover,an adjusted CMR that reflects the actual seismic collapse safety of structures is provided.
