基于多目标最优钢桁架拱桥体系的结构优化设计

目的研究钢桁架拱体系桥梁的结构优化设计方法.方法建立以桁架拱片的体系效率和总用钢量为综合目标的多目标优化模型.以上下弦拱顶竖直间距及构件截面尺寸作为设计变量,建立设计变量与满足结构强度、刚度及稳定性要求的状态变量之间的约束关系.并采用多目标最优化的一阶分析法来进行桁架拱桥的形状控制及构件尺寸确定.结果得到了设计中的中承式钢桁架梁拱组合体系桥的优化方案;桁架拱片形状的控制是重要的,随着拱顶高差增大,结构用钢量下降,但当拱顶高差超过一定高度后,用钢量反而上升.结论将体系效率与多目标最优化计算理论引入桁架拱体系桥的整体优化是可行的,结果也是合理的;体系效率的增加并不能确保用钢量的减少,因而结构体系效率的高低并不能完全反应经济性能的优劣.

Analysis of Steel Truss Arch Bridge Based on Multi-Objective Optimization

This paper researches into the analysis method about steel truss arch bridge based on multi-objective optimization.It suggests system efficiency as an important index to show mechanical property of truss arch bridge.We built up the multi-objective optimization model,taking system efficiency and total steel weight as integrated objection.Taking distance between upper arch's top and lower arch's top and section size of components as design variables,we built restrain relation between design variable and state variable meeting condition of structure's strength and stiffness and stability.The first order optimization method is used to do rational shape control and determine the size of components of truss arch system.This method is used to determine the rational shape of truss arch and the size of components of one steel truss arch bridge.Truss arch's shape control is important:when the distance between upper arch's top and lower arch's top is up,gross steel weight is down,but when it is bigger than certain distance,gross steel weight is up.The result shows that suggesting system efficiency and using multi-objective optimization theory to optimize truss arch bridge as a whole is feasible and reasonable.But high system efficiency doesn't ensure good economic performance.