PC梁加固前后使用性态差异性试验研究

摘要

通过模型梁加固试验,研究桥梁正常使用阶段,主梁开裂前后及加固前后力学性能以及主梁开裂后的加固效果.试验结果表明:在降低主梁应力、挠度和裂缝等关键力学指标上,总体上呈现主被动结合加固法＞主动加固法＞被动加固法的规律.在不同等级荷载作用的全过程中,开裂截面的中性轴高度和抗弯刚度随荷载增加均呈非线性变化,以往相关文献中按分段线性考虑不能反映结构真实的截面特性和受力状态变化规律,同时对已经开裂和损伤的旧桥进行加固试验时,计算模型中应考虑运营桥梁损伤的现实状态,否则可能出现部分开裂截面加固后即使在第一级加载作用下,其开裂截面的校验系数(特别是受拉区钢筋应力校验系数)仍不能降低到1.0以内.研究成果可为今后类似工程的加固设计和检测评估,以及有关规范的完善提供参考.%Through the model beam reinforcement test,the variation of the mechanical properties of the main girder before and after the beam cracking and reinforcement during the normal use of the bridge was studied.The reinforcement effect after the crack of the main girder was studied.Test results show that,better performance of the active and passive combined reinforcement method than the active reinforcement method,and better performance of the active reinforcement method than the passive reinforcement method,in terms of reduction of the key mechanical indexes such as stress,deflection and crack of the main girder.In the whole process of different levels of load,the neutral axis height and bending stiffness of the cracked section show nonlinear changes with the increase of the load.The section properties and the stress state of the cracked structure cannot be reflected in the piecewise linear consideration in related literature.At the same time,the actual condition of the bridge damage should be considered in the calculation model when the reinforcement test is conducted on the cracked and damaged old bridge.Otherwise,the calibration coefficient of the cracked section cannot be reduced to less than 1.0,after the reinforcement of the cracked section (even if under the first level load).These results could present as an example for the safety assessment and reinforcement design of similar projects and the improvement of relevant norms.