强震下单层柱面网壳损伤及失效机理研究

基于结构损伤理论,对单层柱面网壳在强震下的失效机理进行研究。单层柱面网壳在强震下不仅会发生动力失稳,也可能由于过度塑性发展导致动力强度破坏的模式。对于动力强度失效的研究,应当在分析中考虑材料损伤累积以及断裂效应的影响。为在有限元分析中包含这一影响因素,编制了基于通用有限元软件ABAQUS的用户材料子程序,具有较高的计算精度和较好的收敛性。应用其对单层柱面网壳在强震下的响应进行参数研究,并与基于理想弹塑性材料时的响应对比,讨论考虑材料损伤对网壳失效特征的影响。将单层柱面网壳在强震下失效时刻的多项特征响应进行统计分析,拟合了能够表征网壳损伤程度的损伤模型,建立单层柱面网壳在强震下的失效判别准则。针对实际工程抗震设计中采用损伤累积本构模型计算的困难,提出网壳结构失效极限的简化判别方法。

Failure and damage of single-layer reticulated cylindrical shells under earthquakes

The failure mechanism of single-layer reticulated shells subjected to earthquakes is addressed on the basis of the structural damage theory. Dynamic instability collapse of single-layer reticulated cylindrical shells subjected to severe earthquakes is not the only form of dynamic failure, strength failure resulted from excessive development of plastic deformation may also occur. The effect of material damage accumulation and fraction should be considered in the analysis of dynamic strength failure of reticulated shells. The user material subroutine in ABAQUS is compiled for analyzing reticulated shells subjected to dynamic loads with the consideration of damage accumulation, and the user subroutine is validated and proved be excellent in convergence. Using this subroutine, the failure characteristics of single-layer reticulated cylindrical shells under severe earthquakes is studied with parameterization, and the influence of damage accumulation is discussed. According to the characteristic responses of single-layer reticulated cylindrical shells at failure state, the damage mode indicating the damage level of the reticulated shells is fitted, and the strength failure criterion is proposed for distinguishing the ultimate load of earthquake failure. A simplified method for obtaining the ultimate load is proposed, because it is difficult to calculate structural damage index with the consideration of damage accumulation in anti-seismic design.