近场地震下评估单层网壳响应的地震动强度参数分析

为了选取近场地震动作用下适于评估单层网壳结构响应的地震动强度参数,以3个矢跨比不同的单层球面网壳和5个矢跨比、长宽比不同的单层柱面网壳为模型,从相关性、有效性及充分性3个方面对多个地震动强度参数进行分析评价。结果表明,对于单层球面网壳结构,水平向的相关系数大于竖向的相关系数.加速度反应谱值S_a(T_1)和S_a(T_2)为近场地震动作用下适于评估单层球面网壳结构响应的地震动强度参数;对于单层柱面网壳结构,跨度方向的相关系数大于长度方向和竖向的相关系数,近场地震动作用下适于评估单层柱面网壳结构响应的地震动强度参数为S_a(T)、速度反应谱值S_v(T)和位移反应谱值S_d(T),当单层柱面网壳的长宽比和矢跨比较大时,T应取第一阶振型的自振周期T_1,当单层柱面网壳的长宽比和矢跨比较小时,T应取第二、三阶振型的自振周期T_2和T_3。

Ground Motion Intensity Measures for the Evaluation of Effects of Near-faultGround Motions on the Response of Single-layer Reticulated Shells

In recent years, near fault ground motions were found in several large earthquakes, causing severe damage to many structures. However, the analysis of structures subjected to near fault ground motions was mostly about bridges, and few relevant studies were conducted to single layer reticulated shells. To identify ground motion intensity measures for use in the seismic response evaluation of single-layer reticulated shells, three single-layer spherical reticulated shells with different rise-span ratio and five single-layer cylindrical reticulated shells with different rise-span ratio or length-width ratio were designed. Then to have a better understanding of their dynamic features, both modal analysis and harmonic response analysis were conducted to them. After that, several commonly used ground motion intensity measures were evaluated in terms of correlation, efficiency, and sufficiency. Results show that for any particular ground motion intensity measure, the measure along the span has stronger correlation compared with that in the vertical direction, when single-layer spherical reticulated shells were set as models; and that values of acceleration response spectra S_a(T₁) and S_a(T₂) are the proper intensity measures for the evaluation of the response of single-layer spherical reticulated shells. Moreover, when single-layer cylindrical reticulated shells were set as models, for any particular ground motion intensity measure, the measure along the span has stronger correlation compared with those in the vertical direction and the direction along the length; and the value the value of acceleration response spectra S_a(T), the value of velocity response spectra S_v(T) and the value of displacement response spectra S_d(T) are the proper intensity measures. When the rise-span ratio or the length-width ratio are large, the basic period T₁ should be chosen as the parameter T, otherwise the second or third natural period (T₂ or T₃) of the structure should be chosen as the parameter T.