为了探讨在役预应力混凝土梁中现存预应力值，利用应力释放法对已经服役20年的预应力空心板梁进行切槽法试验。研究了不同的切割位置，切割缝间距对测点应力释放速度的影响；分析了切槽法释放混凝土工作应力随切槽深度、切割缝间距的变化规律，得到了梁体混凝土工作应力得以全部释放的切槽深度；利用数值分析软件建立切割深度与测点残余应力之间的拟合函数，从而推断出梁底表面的初始应力；根据推导的混凝土现存预应力的计算公式，将推导得到的初始应力代入计算公式，获得梁体现存预应力，通过这种方法实现对梁现存预应力的准确预估，以期对混凝土结构有效预应力的评估和桥梁结构评定方法提供一定的参考。%In order to study the extant pre⁃stressed force in the pre⁃stressed concrete beam, the stress⁃releasing meth⁃od on the pre⁃stressed hollow slab beam which had served for 20 years was used in the grooving test. The effects of different cutting positions and cutting gap spacing on the testing stress release rate are researched. The variation law of the release concrete working stress with the changing of the notch depth and gap spacing in the grooving test was ana⁃lyzed, achieving the depth of notch when the working stress of beam concrete was release completely. The fitting func⁃tion between the cutting depth and the measured residual stress was established using numerical analysis software, so as to deduce the surface initial stress of the beam bottom. According to the derived formula of existing pre⁃stress of concrete, the initial stress generated from the derivation was substituted into the calculation formula, so as to get ex⁃tant pre⁃stress of the beam. By this method the extant pre⁃stressed force of beam was accurately estimated. This paper provided reference to a certain extent for effective pre⁃stress evaluation and assessment of bridge structure.
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