矩形截面梁后张锚固区劈裂力计算的拉压杆模型法

Strut-and-tie Model Method for Bursting Force Calculation of Post-tensioned Anchorage Zone in Rectangular Beam

针对矩形截面梁端部承受一个水平或倾斜锚固力的工况,根据主应力迹线构建出后张锚固区的拉压杆模型。在此基础上,利用拉压杆模型中节点力的平衡条件以及模型中的几何关系,推导出后张锚固区劈裂力大小的计算式。同时,利用有限元数值分析结果,拟合出劈裂应力合力重心位置的计算公式。在锚垫板宽度、锚固偏心距及力筋倾角变化的情况下,通过对比本文计算方法、美国AASHTO规范公式、欧洲FIP99建议公式的计算值以及有限元结果,表明所提出的劈裂力计算方法能够较好地反映锚垫板宽度、锚固偏心距以及力筋倾角对劈裂力大小以及劈裂应力合力重心位置的影响规律。与现有规范建议的计算公式相比,考虑的影响因素更为全面,计算精度更高。

Based on the trajectories of principal stress obtained from finite element analysis, the strut-and-tie model （STM） for the post-tensioned anchorage zone of rectangular beam subjected to a horizontal or inclined force at beam end was developed. The formulae for calculating the magnitude of bursting force in the post-tensioned anchorage zone was derived on the basis of the force equilibrium conditions of the nodes in this STM formation and its intrinsic geometrical relationship. At the same time the equation for determining the cg location of the resultant bursting stress was regressed based on the results of FEA. To evaluate the preciseness of different methods for bursting force, a comparison was drawn among the results of this paper, AASHTO code, CEB- FIP99 recommendations and the numerical solution from FEM. It indicates that the proposed method can well reflect the laws that the influence of width of the anchor device, the eccentricity and the inclination of the tendon on the magnitude of bursting force and the cg location of the resultant bursting stress. Compared with the design formulas recommended by the existing codes, the influence factors considered by the proposed methods are more comprehensive and the calculation accuracy is higher.