混凝土框架结构抗震设计的弯矩增大系数

Moment Magnification Factor in Anti-seismic Design of Concrete Frame Structure

基于结构的不同功能失效时对应的损失值不同这一基本事实,利用分枝限界法找出了框架结构在地震作用和竖向荷载共同作用下的主要失效模式和代表机构,通过引入基于失效概率的结构优化模型和结构失效损失期望值,并结合一个框架算例,对现行抗震设计规范的“强柱弱梁”弯矩增大系数的取值进行校核,优化分析得到了柱端弯矩增大系数的合理取值。计算结果表明,梁式失效机构的可靠指标为1.8,柱式失效机构的可靠指标为2.6,说明按照现行抗震设计规范设计的混凝土框架结构,可以满足“强柱弱梁”的要求。

Based on the fact that different failure modes have different loss values in a concrete frame structure under earthquake actions, the main failure modes and representative mechanisms of concrete frame structures under earthquake actions and vertical loads were found by the branch-bound method. Through introducing a structural optimization model based on the failure probability and a failure loss expectation of the structure, the values of the bending moment magnification factor of ＂ strong column-weak beam＂ in the code for anti-seismic design of buildings were calibrated with an example of concrete frame. The reasonable values of bending moment magnification factor were obtained by optimization analysis, and the reliable indexes of beam mechanism and column mechanism in the frame were respectively 1.8 and 2.6. It is shown that the concrete frame structure designed according to the anti-seismic code can meet the requirement of ＂strong column-weak beam＂.