单层球壳结构强震下倒塌模式的构件截面优化

Cross-section optimization of the collapsing scenario for the single-layer spherical shells under severe earthquake excitations

以结构杆件重量最轻为优化目标,以杆件截面尺寸为优化变量,建立单层球壳结构倒塌模式优化模型。优化模型考虑长细比、挠度、杆件强度及稳定约束条件,保证优化后结构满足规范和规程要求,同时将构形度也作为约束条件,保证优化后结构在强震下呈现理想的、有征兆的强度破坏特征。针对遗传算法(GA)和模拟退火算法(SA)各自的优缺点,以遗传算法作为主体流程,将模拟退火算法的优化机制融入其中,建立遗传-模拟退火算法(GASA)。采用C++语言编写GASA计算程序,与APDL语言编写的有限元分析命令流相结合,得到GASA-ANSYS优化程序。采用该程序对跨度为70m的K6型单层球壳结构进行优化。通过对优化后结构进行构形易损性分析和地震动力时程分析,表明所提出的优化模型及优化程序能够解决大型单层球壳结构地震作用下倒塌模式的截面优化问题。

An optimal model representing the collapsing scenario of single-layer latticed shells is established.The optimal objective is to minimize the weight of the shell structure,and the optimal variables are the cross-sectional dimensions of members.The optimal model takes the slender ratio,deflection,strength and stability of members as constraint conditions to ensure the optimized structure meet the requirements of the related codes and standards.Meanwhile,the well-formedness is also taken as a constraint condition to guarantee the optimized structure present an ideal strength failure with clear failure characteristics under severe earthquake excitations.According to the respective advantages and disadvantages of genetic algorithms（GA）and simulated annealing algorithms（SA）,agenetic-simulated annealing algorithm（GASA）is proposed by taking the genetic algorithm as main process and integrating it with the simulated annealing mechanism.A GASA program is coded with C＋＋building language,and a GASA-ANSYS optimization program is obtained by combining the GASA program with a command stream of finite element analysis coded by APDL language.An optimization of a K6single-layer spherical shell with a 70 mspan is carried out.By performing form vulnerability analyses and dynamical time-history analyses to the optimized structure,it is concluded that the optimal model and program could be used to solve the collapsing scenario optimization of large-scale,single-layer spherical domes subjected to earthquake excitations.