杆件初始缺陷对单层凯威特球面网壳地震响应影响研究

为研究杆件初始缺陷对单层凯威特球面网壳地震响应的影响，利用OpenSEES有限元程序，采用多段梁法模拟杆件初始缺陷，给出了OpenSEES模拟空间网格结构圆管杆件滞回的多段梁法建模参数合理取值，基于GB 50017—2003《钢结构设计规范》中压杆稳定系数拟合了圆管等效偏心率和正则化长细比的关系式。考虑杆件初弯曲方向随机分布，建立了不同参数单层凯威特球面网壳模型，对网壳增量动力分析的最大位移进行了比较。结果表明：当网壳处于弹性状态时，杆件缺陷对其地震响应的影响可以忽略；当网壳进入塑性状态后，杆件缺陷对其地震响应的影响不可忽略，不同杆件初弯曲方向的网壳地震响应离散程度随地震动强度提高基本呈增大趋势；地震动强度较大时，考虑杆件缺陷和结构整体缺陷的单层网壳地震响应和仅考虑整体缺陷的单层网壳地震响应差异较大，两者最大位移的相对大小并无规律性，其关键影响因素为地震作用下塑性杆件分布的离散程度。

Research on influence of member initial imperfections on seismic response of single-layer Kewitt latticed domes

To study the influence of member initial imperfections on seismic response of single-layer Kewitt latticed domes, a multiple beam elements method was used to model the member initial imperfections with OpenSEES. Appropriate parameters for the multiple beam elements method in modeling the hysteresis of circular pipes in spatial grid structures were presented, and equations describing the relationship between equivalent eccentric ratio and normalized slenderness ratio were derived by fitting the stability coefficients in GB 50017—2003. In consideration of stochastic distribution of initial member bending directions, single-layer Kewitt latticed dome models with different parameters were created, and the maximum displacements obtained from incremental dynamic analyses were compared. The results show that the influence of member initial imperfections on the seismic response can be neglected when the domes are in the elastic stage, whereas the influence cannot be neglected when the domes are in the inelastic stage. The dispersion level of the maximum displacements of the domes with different member bending directions basically increases with an increase of seismic intensity. The difference of response between the domes incorporating both structural and member geometric imperfections and those only consider member imperfections can be significant, and uncertainties exist in the prediction of the maximum displacement of the domes with the two cases of imperfection. The key influential factor is related to the dispersion level of the distribution of yielded members under earthquakes.