预应力T梁多裂缝特征参数演化规律模型试验研究

Model Test Study on Characteristic Parameters Evolution of Prestressed T Beams with Multiple Cracks

为研究预应力T梁桥在破坏过程中裂缝高度、宽度及密度信息的扩展规律,对7片预应力混凝土T梁模型进行了加载破坏试验,同时为模拟梁桥中预应力筋的腐蚀影响,采用电化学加速腐蚀的方法对JZL-3~JZL-7进行通电腐蚀。加载试验显示,腐蚀梁中JZL-7表现出明显的腐蚀影响,结合加载过程中观测到各模型梁梁体裂缝的高度、宽度、间距等参数特征的发展变化,总结了多裂缝特征参数演化规律和腐蚀影响规律。试验研究表明:1)梁体裂缝高度和间距在损伤积累先期发展较快,并随着损伤积累会逐步趋于稳定直至破坏,裂缝宽度则一直呈快速增长趋6倍、裂缝平均间距达梁净跨径的1/375、裂缝最大宽度达1 mm时,梁3,梁体濒临破坏;当钢绞线腐蚀率达到5%时,梁体承载力明显削弱,使得梁体提前破4 mm是预应力混凝土T梁承载能力不足的一个重要拐点。研究结果可为同类工程设计、检测、评估和事故分析参考。

In order to study the propagation law of crack height,width and density during the failure process of prestressed T-beam bridge,the loading failure test was carried out on seven prestressed concrete T-beam models.Meanwhile,the electrochemical accelerated corrosion method was used to conduct electrocorrosion on JZL-3~JZL-7 in order to simulate the corrosion of prestressed tendons of girder bridge.The loading test shows that JZL-7 in the corroded beam shows obvious corrosion effect.Combining with the development and change of the parameters of the height,width and spacing of cracks in each model beam body observed in the loading process,the evolution law of multi-crack characteristic parameters and the law of corrosion effect are summarized.The experimental results show that:1)the height and spacing of cracks in beams develop rapidly in the early stage of damage accumulation,and gradually stabilize until failure with damage accumulation,while the width of cracks increases rapidly all the time;2)in the pure bending section,when the average crack height is 0.6 times of the beam height,the average crack spacing is 1/37.5 of the net span of the beam.When the maximum crack width is 1mm,the stiffness reduction coefficient of the beam decreases to about 0.3,and the beam is on the verge of failure;When the corrosion rate of steel strand reaches 5%,the bearing capacity of the beam is obviously weakened and the beam is destroyed in advance;3)the maximum crack width of pure bending section is 0.4 mm,which is an important inflection point for the insufficient bearing capacity of prestressed concrete T beams.The research results can be used as a reference for similar engineering design,detection,evaluation and accident analysis.