单层柱面网壳在强震下的破坏机理研究

Failure mechanism of single-layer latticed cylindrical shells subjected to strong earthquake

柱面网壳的结构形式、受力特性与其他网壳结构不同,造成其在强震下破坏机理的特殊性。采用基于结构响应的全过程分析方法,利用软件Abaqus,综合宏观、微观响应指标,对单层柱面网壳进行大规模的参数分析,探求其在强震下的破坏机理。通过典型算例的分析比较,确定了单层柱面网壳的破坏模式及其特征,总结了临界荷载的确定方法。在大量计算数据统计的基础上,提出了单层柱面网壳实用的动力破坏判别准则。单层柱面网壳在强震下可能出现的动力失稳破坏突然,破坏时塑性发展浅,结构刚度几乎没有削弱,结构位移小。单层柱面网壳在强震下强度破坏也可能出现,情况与前不同,其中强度破坏包括强度破坏Ⅰ和强度破坏Ⅱ,强度破坏Ⅱ有明显失稳现象而强度破坏Ⅰ没有。动力实用判别准则以最大节点位移和8p比例为参考指标,用来确定强度破坏Ⅰ和强度破坏Ⅱ极限荷载。对考虑损伤的柱壳破坏机理进行了初步探讨,损伤对不同的结构影响不同,给出了工程设计中损伤降低系数的建议值。

The characteristics of latticed cylindrical shells are different from those of other latticed shells, which make some particularity on failure mechanism. Based on the structural response analysis method in Abaqus, considering multi-indexes responses from macroscopic and microscopic levels, a large number of parameter analyses for single-layer latticed cylindrical shells have been done, which can be used for exploring the failure mechanism under strong earthquakes. After the analysis of some typical cases the failure modes and some characteristics have been determined. According to a great number of analytical calculated data a practical dynamic failure criteria of single-layer latticed cylindrical shells is given. Under strong earthquakes, the dynamic instability of single-layer latticed cylindrical shells may appear suddenly, and when it happens, the plastic deformation is very limited, the structural stiffness is almost as same as before and the displacements are not considerable. The strength failure of single-layer latticed cylindrical shells may also happen. It seems quite different. The strength failure includes strength failure mode Ⅰ and strength failure mode Ⅱ. Strength failure mode Ⅱ has obvious similar phenomena as those in dynamic instability, while strength failure mode Ⅰ has not. Using maximum displacement and the ratio of whole-section yield elements （8p） as reference indexes the practical failure criteria can be used for determining the ultimate loads of strength failure mode Ⅰ and mode Ⅱ. In this paper the preliminary study on failure mechanism of damaged single-layer latticed cylindrical shells subjected to strong earthquake motion is also studied, a reduced damage coefficient for engineering design is given.