基于软化拉-压杆模型的钢筋混凝土框架节点受剪分析

Shear strength of reinforced concrete frame joints using softened strut and tie model

软化拉-压杆模型是基于经典桁架模型理论而发展起来的一种模型,主要用于混凝土结构中应力紊乱区的受剪设计。以包含钢筋混凝土变梁中节点在内的各类框架节点为研究对象,建立框架节点等效核心区在剪、压复合荷载作用下的计算模型,应用软化拉-压杆模型对节点等效核心区进行受力分析,推导框架节点的受剪承载力计算公式,并通过国内外110个钢筋混凝土框架节点试件峰值剪应力试验结果与软化拉-压杆模型计算结果进行对比。结果表明:试验值与软化拉-压杆模型计算得到的节点受剪承载力的平均比值为1.169,方差为0.208,吻合较好。与现行混凝土结构设计规范中框架节点受剪承载力的半经验计算方法相比,软化拉-压杆模型方法有明确的力学计算模型,合理地反映框架节点的受力机理。

The softened strut and tie model is a new simplified method which originates from the classical truss theory,and can be used for determining the shear strength of discontinuity regions failed in diagonal compressions of reinforced concrete strut.An analytical model of the equivalent core of frame joints including interior joints with different depth beams of different depths under the combined action of axial load and shear was established,the softened strut and tie model was used for the shear analysis of reinforced concrete frame joints.In addition,a simplified formula for calculating the shear strength of the equivalent core of frame joint was proposed.Furthermore,the suggested analytical model was verified using 110 test data of reinforced concrete beam-column joints.Good agreement between test results and prediction results was achieved with an average ratio of test results to results of 1.169 and a variance of 0.208.Comparing with the semi-empirical formulas of joint shear strength suggested by the current concrete structures design code,the softened strut and tie model has definite mechanical model and can reasonably reveal failure mechanism of beam-column joint.