基于拉压杆模型的预应力深梁抗剪承载力

为了给中国桥梁工程中的深梁抗剪设计提供理论依据，针对深梁应变分布不符合平截面假定，在结构设计中属于力流紊乱区的问题，借助拉压杆模型理论对预应力作用下的混凝土深梁极限抗剪承载力展开试验与数值研究。首先利用通用有限元分析软件ANSYS并结合Tcl/tk语言联合开发插件程序，以图形用户界面的方式实现深梁拉压杆模型的自动构形。然后，借助生成的拉压杆模型，按改进的破坏准则推导考虑预应力效应的深梁极限抗剪承载力公式，并通过12组数值试验确定主拉应力沿深梁拉压杆模型压杆分布的不均匀系数表达式。最后，通过有黏结与无黏结预应力混凝土深梁试验对推导的预应力深梁极限抗剪承载力公式的有效性进行验证。研究结果表明：对于有黏结预应力混凝土深梁试验，试验结果与Tan教授预测结果的比值均大于与本文计算结果的比值，前者平均值为1.27，后者为1.10；对于无黏结预应力混凝土深梁试验，试验结果与Tan教授预测结果之比的平均值为1.13，与本文计算结果之比的平均值为1.10；相对于已有预测值，计算结果与试验结果更加吻合，并且偏于安全，说明该公式可以较可靠地预测深梁的实际承载力，具有一定的理论价值和实用意义。

Shear-carrying Capacity of Prestressed Concrete Deep Beams Based on the Strut-and-tie Model

Deep beams are generally classified as a discontinuity region (D-region), where the conventional plane bending theory does not apply. To provide a theoretical foundation for deep beams design in bridge structures, both experiments and numerical simulations were conducted to investigate the shear-carrying capacity of prestressed concrete deep beams by means of the strut-and-tie model theory. First, a practical program was developed to automatically generate the strut-and-tie model of prestressed deep beams using a combination of the finite element analysis software ANSYS and Tcl/tk language. Second, the shear strength formula of prestressed deep beams was derived with the aid of the strut-and-tie model according to a modified failure criterion. At the same time, expressions for two key coefficients in the formula were derived using 12 sets of numerical simulations. Finally, two tests were conducted to verify the effectiveness of the formula for predicting the shear strength of prestressed deep beams. In the first test, the average ratio of the test results to results obtained by Professor Tan was 1.27, which was larger than the ratio of the test results to the author's prediction results (i.e., 1.10). In the second test, the former ratio was 1.13, while the latter ratio was 1.10. A comparison of the results indicate that the predicted values in this study shows better agreement with the experimental values than existing solutions, and these prediction values stand on the conservative side. It indicates that the shear strength formula derived in this study can predict the actual bearing capacity of deep beams, which has some theoretical value and practical significance.