This study discusses the effects of local sites and hazard amplification on the seismic vulnerability assessment of existing masonry buildings.In this context,a rapid seismic evaluation procedure was implemented on an...This study discusses the effects of local sites and hazard amplification on the seismic vulnerability assessment of existing masonry buildings.In this context,a rapid seismic evaluation procedure was implemented on an old masonry building stock in the historical center Galata,located inİstanbul,to determine the seismic risk priority of the built heritage.Damage scenarios were generated for all soil classes,different moment magnitudes,and source-to-site distances to obtain more accurate results for the seismic vulnerability assessment of the studied building stock.Consequently,damage distributions estimated under nine different scenarios with/without site effects were compared and illustrated in maps to discuss changes in vulnerability owing to amplification effects.In this study,by re-examining the rapid seismic evaluation procedure by including geo-hazard-based assessment,the importance of site effects on the vulnerability and risk assessment of built heritage was underlined.The proposed framework integrating field data and local site effects is believed to advance the current applications for vulnerability assessment of masonry buildings and provide an improvement in the application of rapid seismic assessment procedures with more reliable results.展开更多
Collapses of transmission towers were often observed in previous large earthquakes such as the Chi-Chi earthquake in Taiwan and Wenchuan earthquake in Sichuan,China. These collapses were partially caused by the pullin...Collapses of transmission towers were often observed in previous large earthquakes such as the Chi-Chi earthquake in Taiwan and Wenchuan earthquake in Sichuan,China. These collapses were partially caused by the pulling forces from the transmission lines generated from out-of-phase responses of the adjacent towers owing to spatially varying earthquake ground motions. In this paper,a 3D finite element model of the transmission tower-line system is established considering the geometric nonlinearity of transmission lines. The nonlinear responses of the structural system at a canyon site are analyzed subjected to spatially varying ground motions. The spatial variations of ground motion associated with the wave passage,coherency loss,and local site effects are given. The spatially varying ground motions are simulated stochastically based on an empirical coherency loss function and a filtered Tajimi-Kanai power spectral density function. The site effect is considered by a transfer function derived from 1D wave propagation theory. Compared with structural responses calculated using the uniform ground motion and delayed excitations,numerical results indicate that seismic responses of transmission towers and power lines are amplified when considering spatially varying ground motions including site effects. Each factor of ground motion spatial variations has a significant effect on the seismic response of the structure,especially for the local site effect. Therefore,neglecting the earthquake ground motion spatial variations may lead to a substantial underestimation of the response of transmission tower-line system during strong earthquakes. Each effect of ground motion spatial variations should be incorporated in seismic analysis of the structural system.展开更多
基于2008—2015年龙门山地区的强震动记录,采用广义线性反演法计算了龙门山地区的震源参数、品质因子以及83个强震动台站的局部场地放大系数。结果显示:芦山地震发生之前,汶川地震余震的应力降随时间的增加而逐渐增大;芦山地震发生之后...基于2008—2015年龙门山地区的强震动记录,采用广义线性反演法计算了龙门山地区的震源参数、品质因子以及83个强震动台站的局部场地放大系数。结果显示:芦山地震发生之前,汶川地震余震的应力降随时间的增加而逐渐增大;芦山地震发生之后,龙门山断裂带上余震的应力降明显减小,并在之后随时间呈缓慢增大的趋势;部分M_S≥4.7余震事件的加速度震源谱中出现明显的高频衰减现象。通过对应力降随时间变化规律的分析认为,这种高频衰减现象可能与震级大小和震源破裂滑动的最大速率有关。此外,反演得到了山区和盆地地区的品质因子分别为Q(f)=264 f 0.75和Q(f)=223 f 1.01;同时获取了龙门山地区83个强震动台站的局部场地放大系数,并计算了基于NGA场地分类标准的A类、B类和C类场地的平均场地放大系数。结果显示,以上3类场地的平均场地放大系数具有相似的峰值,但是随着场地趋于软弱,峰值平台区向低频部分发育。展开更多
文摘This study discusses the effects of local sites and hazard amplification on the seismic vulnerability assessment of existing masonry buildings.In this context,a rapid seismic evaluation procedure was implemented on an old masonry building stock in the historical center Galata,located inİstanbul,to determine the seismic risk priority of the built heritage.Damage scenarios were generated for all soil classes,different moment magnitudes,and source-to-site distances to obtain more accurate results for the seismic vulnerability assessment of the studied building stock.Consequently,damage distributions estimated under nine different scenarios with/without site effects were compared and illustrated in maps to discuss changes in vulnerability owing to amplification effects.In this study,by re-examining the rapid seismic evaluation procedure by including geo-hazard-based assessment,the importance of site effects on the vulnerability and risk assessment of built heritage was underlined.The proposed framework integrating field data and local site effects is believed to advance the current applications for vulnerability assessment of masonry buildings and provide an improvement in the application of rapid seismic assessment procedures with more reliable results.
基金Project supported by the National Natural Science Foundation of China (No. 50638010)the Specialized Research Fund for the Doctoral Program of Higher Education of China (No. 20070141036)
文摘Collapses of transmission towers were often observed in previous large earthquakes such as the Chi-Chi earthquake in Taiwan and Wenchuan earthquake in Sichuan,China. These collapses were partially caused by the pulling forces from the transmission lines generated from out-of-phase responses of the adjacent towers owing to spatially varying earthquake ground motions. In this paper,a 3D finite element model of the transmission tower-line system is established considering the geometric nonlinearity of transmission lines. The nonlinear responses of the structural system at a canyon site are analyzed subjected to spatially varying ground motions. The spatial variations of ground motion associated with the wave passage,coherency loss,and local site effects are given. The spatially varying ground motions are simulated stochastically based on an empirical coherency loss function and a filtered Tajimi-Kanai power spectral density function. The site effect is considered by a transfer function derived from 1D wave propagation theory. Compared with structural responses calculated using the uniform ground motion and delayed excitations,numerical results indicate that seismic responses of transmission towers and power lines are amplified when considering spatially varying ground motions including site effects. Each factor of ground motion spatial variations has a significant effect on the seismic response of the structure,especially for the local site effect. Therefore,neglecting the earthquake ground motion spatial variations may lead to a substantial underestimation of the response of transmission tower-line system during strong earthquakes. Each effect of ground motion spatial variations should be incorporated in seismic analysis of the structural system.
文摘基于2008—2015年龙门山地区的强震动记录,采用广义线性反演法计算了龙门山地区的震源参数、品质因子以及83个强震动台站的局部场地放大系数。结果显示:芦山地震发生之前,汶川地震余震的应力降随时间的增加而逐渐增大;芦山地震发生之后,龙门山断裂带上余震的应力降明显减小,并在之后随时间呈缓慢增大的趋势;部分M_S≥4.7余震事件的加速度震源谱中出现明显的高频衰减现象。通过对应力降随时间变化规律的分析认为,这种高频衰减现象可能与震级大小和震源破裂滑动的最大速率有关。此外,反演得到了山区和盆地地区的品质因子分别为Q(f)=264 f 0.75和Q(f)=223 f 1.01;同时获取了龙门山地区83个强震动台站的局部场地放大系数,并计算了基于NGA场地分类标准的A类、B类和C类场地的平均场地放大系数。结果显示,以上3类场地的平均场地放大系数具有相似的峰值,但是随着场地趋于软弱,峰值平台区向低频部分发育。
