中柱失效时组合框架压拱效应力学模型分析

钢-混凝土组合梁在正弯矩下的转动中心通常要高于其在负弯矩作用下的转动中心，因此在中柱失效工况下，组合框架中存在压拱效应．针对两榀分别采用了焊接连接和平齐式端板连接的钢-混凝土组合框架进行了拆除中柱的试验研究，记录并详细分析了压拱效应．分析结果表明，无论采取何种梁柱节点形式，组合框架中均存在压拱效应；常规压杆模型无法准确描述压拱效应的效果．提出了一种考虑钢梁下翼缘及部分腹板受拉的桁架弹簧模型，并对该模型的竖向荷载-位移公式和水平位移-竖向位移公式进行了推导，公式结果与试验结果吻合良好．本文提出的桁架弹簧模型及相应变形公式可以很好地预测压拱效应对于整体结构承载力和变形的贡献，为抗连续倒塌工况下组合框架的设计提供了参考．

Analysis on Mechanical Model of Arch Action in Composite Frames under Middle-Column Loss

The rotation center of steel-concrete composite beams under sagging moment is normally higher than that under hogging. In that case, arch action occurs in composite frames under middle-column removal. In this paper, two one-story composite frames with four spans under middle-column removal were tested. Fully welded rigid joints and flush endplate semi-rigid joints were adopted respectively in the specimens. Arch action was recorded and analyzed in detail. The analysis results show that arch action exists in composite frames, regardless of joint configuration. Traditional compressive strut model cannot reflect the arch action. A new truss-spring model is proposed which considers the bottom flange and partial web of steel beam in tension. The vertical load-deflection and horizontal displacement-vertical deflection formulas are deduced. The calculation results and experimental results match well. The truss-spring model and the responding deformation formulas could predict the contribution of arch action to the resistance and deformation of the frames and provide reference for the anti-collapse design of composite frame.