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应用软化拉压杆模型对钢筋混凝土框架节点核心区进行受剪承载力计算时,常常基于经验取柱截面宽度作为节点的有效宽度参与抗剪强度计算。但是,对于实际工程中含有现浇楼板的框架中节点,节点的有效宽度在核心区上下验算截面并不相同且随着作用外力的增加而逐步增大,直至软化拉压杆模型中结点域(nodal zone)混凝土达到其抗压强度后压溃而失效。本文对软化拉压杆模型中节点有效宽度的计算方法进行了改进,应用修正软化拉压杆模型(Modified Softened Strut-and-Tie,简称MSST)对国内外63个框架中节点试件的抗剪强度进行理论计算,并将受剪分析得到的峰值剪应力计算结果与现行规范建议方法及软化拉压杆模型方法的计算结果进行对比。结果表明:修正软化拉压杆模型计算得到的框架节点受剪承载力与软化拉压杆模型计算结果相比和试验结果吻合更好,与现行规范建议设计方法计算结果相当,该建议模型可较为合理地反映含现浇楼板框架节点的受力机理。
When calculating the shear strength of the core region of RC frame joints by using the softened tension-bar model, the width of the section of the RC column is often taken as the effective width of the joints to participate in the calculation of shear strength. However, for the nodes in the frame with cast-in-situ floor in the actual project, the effective widths of the nodes in the upper and lower core sections are not the same and increase gradually with the increase of external forces until the node domain in the softened tension-bar model (nodal zone) concrete reaches its compressive strength after collapse and failure. In this paper, the method to calculate the effective width of the node in the softened tension and compression rod model was improved. The modified Softened Strut-and-Tie (MSST) The theoretical calculation is carried out and the calculation results of the peak shear stress obtained by the shear analysis are compared with those of the current normative method and the softened tension-bar model. The results show that the calculated shear bearing capacity of the frame joints calculated by the modified softened tension-bar model is in good agreement with the experimental results and is in good agreement with the calculated results of the proposed design method. The proposed model can be more Reasonably reflect the stress mechanism of cast-in-site floor frame joints.