大悬臂PC盖梁根部受力性能试验与分析

Experiment and analysis on mechanical behavior at root of large cantilever PC bent cap

摘要:

大悬臂预应力混凝土盖梁（以下简称大悬臂PC盖梁）通常会在悬臂根部设置折线段来保证结构的受力性能,但尚未有合理的折线段尺寸设计依据。为此,通过将附加折线段等效为弧线段,提出了折线段大悬臂PC盖梁的剪应力计算理论；针对大悬臂PC盖梁的折线段尺寸设计问题进行了1∶4的缩尺模型试验,分析了折线段对悬臂根部剪应力分布及受力性能的影响；并根据结构弯剪受力强度要求,给出了不同盖梁悬臂长度、受压边倾角及预应力水平等设计参数下的最小折线段长度比计算公式。结果表明:所提出的折线段变截面梁剪应力计算理论能较好地反映折线段设置对剪应力纵向分布带来的影响,顶缘最不利受力位置由悬臂根部转变为变受压边倾角处,随着折线段长度比的增加,盖梁顶底缘应力峰值均有所降低,需要通过控制折线段尺寸来保证结构受压边底缘的强度要求。所给出的最小折线段长度比计算公式对不同设计参数的大悬臂PC盖梁均能保证其有效精度,具有一定的实用性。

Abstract:

Large cantilever prestressed concrete bent caps (hereinafter referred to large cantilever PC bent caps) typically incorporate corbels at the root of the cantilever to ensure the mechanical behavior. However, there is currently a lack of a rational framework for determining the appropriate size of these corbels. In this paper, the shear stress calculation theory of large cantilever PC bent caps with corbels is proposed by equating the corbels to arc segments; a 1∶4 scaled model experiment is carried out to analyze the influence of corbels on the shear stress distribution and stress performance of the cantilever root; The formula for calculating the minimum corbel length ratio under different design parameters of compression edge inclination, cantilever lengths and prestressing level is given according to the bending and shear strength requirements. The findings indicate that the shear stress calculation theory proposed in this study for variable cross-section beams with corbels provides a more accurate representation of the impact of corbels on the longitudinal distribution of shear stress. Additionally, the most critical location for shear stress has shifted from the cantilever root to the changing position of bottom inclination. Furthermore, as the corbel length ratio increases, the stress peaks at the upper and bottom edges of the beams decrease. Therefore, it is essential to control the size of the corbel to ensure the strength of the compression edges. The formula for the minimum corbel length ratio, as presented in this paper, ensures its effective accuracy when applied to large cantilever PC bent caps with varying parameters. This formula demonstrates practicality in construction applications.