下击暴流作用下单层球面网壳倒塌破坏研究

Research on Progressive Collapse of Single-layer Spherical Reticulated Shells Subjected to Downbursts

针对大跨空间结构在下击暴流作用下破坏规律尚不明确的问题,本研究分析了下击暴流作用下K8型单层球面网壳结构的破坏模式与失效规律。基于确定性-随机性混合模型模拟了下击暴流风场,其中平均风的模拟采用Wood竖向风剖面模型和Holmes经验模型,脉动风的模拟则采用自回归模型。基于向量式有限元分析方法,考虑结构的几何非线性、材料非线性及构件断裂准则,对下击暴流作用下不同矢跨比的网壳结构进行弹塑性时程分析及连续倒塌过程模拟。通过研究矢跨比分别为1/3、1/5与1/7时,结构节点位移幅值的变化及下击暴流平均风荷载与总风荷载对结构破坏模式的影响,探究单层球面网壳结构在下击暴流作用下的失效规律。研究结果表明:下击暴流作用下单层球面网壳结构的失效主要是由结构杆件屈曲所致,且平均风的影响占主导地位,决定着结构的破坏模式,而脉动风则使得结构响应加剧,破坏时间提前。此外,随着结构矢跨比的增大,结构的体型系数与受风面积随之变化,进而影响结构的破坏模式,使其由局部杆件渐进式屈曲失效的模式向结构整体瞬时失效的模式转变。研究成果可为大跨空间结构的抗下击暴流设计提供参考。

Aiming at the problem that the failure law of large-span spatial structures subjected to downbursts is not clear,the destruction mode and failure law of the K8 single-layer spherical reticulated shell structure under a downburst are analyzed.Based on the deterministic-stochastic hybrid model,the downburst wind field is simulated.The mean wind is simulated by the Wood vertical wind profile model and Holmes empirical model,while the fluctuating wind is generated according to the autoregressive model.Considering the geometrical nonlinearity,material nonlinearity and element failure criterion of the structure,the elastic-plastic time-history analysis and progressive collapse process simulation of reticulated shell structures with different rise-span ratios subjected to downbursts are carried out using the vector form intrinsic finite element method.The failure law of the single-layer spherical reticulated shell is explored by studying the variation of the maximum nodal displacement and the influence of the mean and total wind load of a downburst on the structural failure mode when the rise-span ratios are 1/3,1/5 and 1/7,respectively.The results show that the failure of the single-layer spherical reticulated shell structure under the action of a downburst is mainly caused by the buckling of structural elements.The influence of the mean wind plays a dominant role,determining the failure mode of the structure,while the fluctuating wind intensifies the structural response and makes the failure time advanced.In addition,with the increase of the rise-span ratio,the shape coefficient and wind area of the structure change,which will affect the structural failure mode,namely the structural failure mode changes from the gradual buckling failure mode of the local elements to the instantaneous failure mode of the whole structure.The research results of this study can provide references for the downburst-resistant design of large-span spatial structures.