钢框架体系作为一种应用广泛的结构体系，如何准确、安全、经济、快速地进行结构优化设计，一直是结构工程界仍未突破的瓶颈。本项目以半刚性钢框架结构为研究对象，提出多阶段体系优化方法。从结构失效的演化规律及不同失效模式的物理机制出发，研究不同失效模式快速判别的合理准则。基于结构易损性分析，提出不同破坏等级的合理划分依据，探究结构成本与体系可靠度的内在联系，建立表征结构从施工至后维护的多阶段成本模型。在此基础上，对优化参数、固定参数和可变参数进行合理区分，建立结构体系优化所需的基础参数数据库；深入分析不同优化参数与目标函数、约束条件的内在联系，提出优化模型的简化表达。对体系可靠度计算的积分进行降维处理，结合改进遗传算法，完成基于整体可靠度的半刚性钢框架结构体系多阶段优化研究。本研究通过考虑传统优化所缺少的体系可靠度及全生命周期成本进行优化分析，对促进钢结构优化领域的发展具有重要理论意义和应用价值。

Steel frames are widely used around the world. How to precisely, safely, economically and quickly obtain the optimal design of steel frames, has always been a complicated issue in structural engineering. Semi-rigid steel frame is studied in this project to get an optimization method based on system reliability and multi-stage cost. Based on the failure evolution law and the physical mechanism of different failure modes, reasonable criteria for rapid identification on different failure modes are purposed. Based on the structural vulnerability analysis, the reasonable criteria for different damage levels are proposed, the internal relationship between structural cost and system reliability is explored, and a multi-stage cost model representing the structure from construction to post-maintenance is established. Based on fragility analysis, different damage levels are purposed, the internal relationship between structural cost and system reliability is explored, and a multi-stage cost model representing the structure from construction to post-maintenance is established. Then the classification of optimization parameters, fixed parameters and variable parameters are conduct. And the internal relationship among different optimization parameters, constraints and objective function is studied, a simplified optimization model is purposed. This project has theoretical significance and profound application value on the development of steel structure optimization by considering the system reliability and the multi-stage cost of structure.