In order to study the differences in vertical component between onshore and offshore motions,the vertical-to-horizontal peak ground acceleration ratio(V/H PGA ratio) and vertical-to-horizontal response spectral ratio(...In order to study the differences in vertical component between onshore and offshore motions,the vertical-to-horizontal peak ground acceleration ratio(V/H PGA ratio) and vertical-to-horizontal response spectral ratio(V/H) were investigated using the ground motion recordings from the K-NET network and the seafloor earthquake measuring system(SEMS).The results indicate that the vertical component of offshore motions is lower than that of onshore motions.The V/H PGA ratio of acceleration time histories at offshore stations is about 50%of the ratio at onshore stations.The V/H for offshore ground motions is lower than that for onshore motions,especially for periods less than 0.8 s.Furthermore,based on the results in statistical analysis for offshore recordings in the K-NET,the simplified V/H design equations for offshore motions in minor and moderate earthquakes are proposed for seismic analysis of offshore structures.展开更多
This paper focuses on the seismic response of the curved and post-tensioned concrete box girder bridges. More specifically, it investigates how the curvature influences the response of a bridge subjected to earthquake...This paper focuses on the seismic response of the curved and post-tensioned concrete box girder bridges. More specifically, it investigates how the curvature influences the response of a bridge subjected to earthquake. Parametric analysis of different radius of curvature is performed and the internal forces, torsion moment, axial and shear along the bridge are calculated. Two types of connections are investigated, the monolithic connection and deck connection with bents and abutments with rubber bearing. The response spectrum seismic analysis was performed. The models were designed, according to the provisions of EC8-part 2, EC2 and the Greek regulations E39/99. Diagrams relating the curvature with the torsion moment have been obtained from the results of parametric analysis. These diagrams could be used by engineers for preliminary design of such kind of bridges.展开更多
Aiming at the seismic-resistant performance of cable-supported glass curtain walls,the methods for formulating nonlinear single degree of freedom system and calculating the nonlinear response spectrums are proposed. T...Aiming at the seismic-resistant performance of cable-supported glass curtain walls,the methods for formulating nonlinear single degree of freedom system and calculating the nonlinear response spectrums are proposed. Taking pretension effect in cables and geometrical nonlinearity into account,the nonlinear acceleration spectrums are calculated under given conditions,such as site and different seismic fortification intensities. The seismic design response spectrums are developed. During vibrating,varying period due to the influence of pretension effect in cables and geometrical nonlinearity drives the maximum period of plateau in nonlinear response spectrums to move towards the long period zone,and the maximum of seismic effect coefficient is larger than that of current seismic code. The theoretical analysis and the example demonstrate that using the nonlinear response spectrums is safe and economical.展开更多
Long-period acceleration spectra determined by seismic safety evaluation for project sites are generally lower than that given by relative code spectra.In this paper,we discuss the recurrence periods corresponding to ...Long-period acceleration spectra determined by seismic safety evaluation for project sites are generally lower than that given by relative code spectra.In this paper,we discuss the recurrence periods corresponding to the code spectra of different periods,by using ground motion attenuation laws for sites of types Ⅰ and Ⅲ.We show the results that the longer the periods of code spectra are commonly the more conservative the seismic level is.As for the project examples in this paper,when the periods are longer than 3.7 or 5.2 seconds for sites of types Ⅰ or Ⅲ,the recurrence periods corresponding to the code spectra are longer than 5000 years.We suggest that some problems need to be further discussed,including the reliability of the present attenuation laws,the performance of those project structures that suffer long period seismic waves and have been designed according to the conservative codes,and the effects of ground motion parameters such as velocity and displacement on seismic design.展开更多
According to the results of site seismic hazard analysis accomplished in the past decades, 96 site-related design spectra are selected as samples in this study. The result shows that the value of the corner period (T ...According to the results of site seismic hazard analysis accomplished in the past decades, 96 site-related design spectra are selected as samples in this study. The result shows that the value of the corner period (T g) of the design spectrum in GBJ11-89 (China Seismic Building Code, issued in 1989) is lower than the value obtained by site seismic hazard analysis. The same situation exists when we compare the design spectra of the Codes to the spectra according to the earthquake records. The value in current seismic design code, GBJ50011-2001 issued in 2001, is greater than that in GBJ11-89, but still less than the value obtained by site seismic hazard analysis. If we accept the value got by site seismic hazard analysis, we have a suspicion that 2/3 of buildings built according to GBJ11-89 will not be safe when an earthquake with 2% probability of exceedance in 50 years occurs.展开更多
基金Project(2011CB013605)supported by the National Basic Research Development Program of China(973 Program)Projects(51178071,51008041)supported by the National Natural Science Foundation of ChinaProject(NCET-12-0751)supported by the New Century Excellent Talents Program in University of Ministry of Education of China
文摘In order to study the differences in vertical component between onshore and offshore motions,the vertical-to-horizontal peak ground acceleration ratio(V/H PGA ratio) and vertical-to-horizontal response spectral ratio(V/H) were investigated using the ground motion recordings from the K-NET network and the seafloor earthquake measuring system(SEMS).The results indicate that the vertical component of offshore motions is lower than that of onshore motions.The V/H PGA ratio of acceleration time histories at offshore stations is about 50%of the ratio at onshore stations.The V/H for offshore ground motions is lower than that for onshore motions,especially for periods less than 0.8 s.Furthermore,based on the results in statistical analysis for offshore recordings in the K-NET,the simplified V/H design equations for offshore motions in minor and moderate earthquakes are proposed for seismic analysis of offshore structures.
文摘This paper focuses on the seismic response of the curved and post-tensioned concrete box girder bridges. More specifically, it investigates how the curvature influences the response of a bridge subjected to earthquake. Parametric analysis of different radius of curvature is performed and the internal forces, torsion moment, axial and shear along the bridge are calculated. Two types of connections are investigated, the monolithic connection and deck connection with bents and abutments with rubber bearing. The response spectrum seismic analysis was performed. The models were designed, according to the provisions of EC8-part 2, EC2 and the Greek regulations E39/99. Diagrams relating the curvature with the torsion moment have been obtained from the results of parametric analysis. These diagrams could be used by engineers for preliminary design of such kind of bridges.
基金the National Natural Science Foundation of China (Grant No. 50478028).
文摘Aiming at the seismic-resistant performance of cable-supported glass curtain walls,the methods for formulating nonlinear single degree of freedom system and calculating the nonlinear response spectrums are proposed. Taking pretension effect in cables and geometrical nonlinearity into account,the nonlinear acceleration spectrums are calculated under given conditions,such as site and different seismic fortification intensities. The seismic design response spectrums are developed. During vibrating,varying period due to the influence of pretension effect in cables and geometrical nonlinearity drives the maximum period of plateau in nonlinear response spectrums to move towards the long period zone,and the maximum of seismic effect coefficient is larger than that of current seismic code. The theoretical analysis and the example demonstrate that using the nonlinear response spectrums is safe and economical.
基金The project is sponsored under the Key Scientific Researchand Development Programof Zhejiang Province(2005C23075),China
文摘Long-period acceleration spectra determined by seismic safety evaluation for project sites are generally lower than that given by relative code spectra.In this paper,we discuss the recurrence periods corresponding to the code spectra of different periods,by using ground motion attenuation laws for sites of types Ⅰ and Ⅲ.We show the results that the longer the periods of code spectra are commonly the more conservative the seismic level is.As for the project examples in this paper,when the periods are longer than 3.7 or 5.2 seconds for sites of types Ⅰ or Ⅲ,the recurrence periods corresponding to the code spectra are longer than 5000 years.We suggest that some problems need to be further discussed,including the reliability of the present attenuation laws,the performance of those project structures that suffer long period seismic waves and have been designed according to the conservative codes,and the effects of ground motion parameters such as velocity and displacement on seismic design.
文摘According to the results of site seismic hazard analysis accomplished in the past decades, 96 site-related design spectra are selected as samples in this study. The result shows that the value of the corner period (T g) of the design spectrum in GBJ11-89 (China Seismic Building Code, issued in 1989) is lower than the value obtained by site seismic hazard analysis. The same situation exists when we compare the design spectra of the Codes to the spectra according to the earthquake records. The value in current seismic design code, GBJ50011-2001 issued in 2001, is greater than that in GBJ11-89, but still less than the value obtained by site seismic hazard analysis. If we accept the value got by site seismic hazard analysis, we have a suspicion that 2/3 of buildings built according to GBJ11-89 will not be safe when an earthquake with 2% probability of exceedance in 50 years occurs.
