海水干湿循环对初始损伤RC梁力学性能的影响

沿海环境下的钢筋混凝土(RC)结构处于荷载作用和环境作用同时存在的工作状态且在正常条件下会出现不同程度的荷载损伤。为了在实验室内模拟其工作状态,对RC梁试件施加幅值分别为0.3P_u、0.4P_u、0.5P_u、0.6P_u和0.7P_u(P_u为单调加载梁的极限荷载)的初始荷载造成不同程度的损伤,经历120次海水干湿循环作用后,进行单调加载试验测试剩余力学性能,并对梁试件钻芯取样测试不同位置及深度处混凝土的氯离子含量。试验结果表明,不同程度初始损伤RC梁经历120次海水干湿循环后,其屈服荷载、极限荷载和延性均随初始荷载幅值的增加而降低;与无损伤梁试件相比,当初始损伤荷载为0.4P_u时,梁试件的屈服荷载和极限荷载降幅分别为10.4%和7.9%,随着初始荷载增大,屈服荷载和极限荷载快速下降,当初始损伤荷载为0.7P_u时,屈服荷载和极限荷载降幅分别达33.7%和32.4%。氯离子含量测试结果表明,梁试件混凝土受拉区氯离子含量均大于受压区氯离子含量;当初始损伤荷载小于0.5P_u时,受拉钢筋表面混凝土的氯离子含量差别不大且小于0.1%,当初始损伤荷载为0.7P_u时,钢筋表面氯离子含量最大达到0.14%。可见,初始荷载损伤与海水干湿循环综合作用对RC梁力学性能及耐久性劣化影响显著。

Effect of seawater wet-dry cycles on mechanical performance of RC beams with initial damage

The working condition of reinforced concrete (RC) structures in coastal chloride environment combined load effects and environmental effects and there would be a different degree of damage due to load effects in normal conditions.In order to simulated that working condition in laboratory,different loads of 0.3Pu,0.4Pu,0.5Pu,0.6Pu and 0.7Pu (Pu is the ultimate load of beam under monotonic loading) were applied on RC beam specimens to induce varying degrees of damage.Subsequently,beam specimens were placed in an automatic sprinkler device to simulate seawater wet-dry cycles.After 120 wet-dry cycles,monotonic loading test and chloride concentration test were conducted on RC beams.The test results show that the yield load,ultimate load and ductility of specimens decrease with the increase of initial damage load amplitude.When the initial load is 0.4Pu,the decrease of yield load and ultimate load is 10.4％ and 7.9％ respectively,compared with control group.With the damage increasing,the yield load and ultimate load decrease constantly.When the initial load is 0.7Pu,a great degeneration of mechanical performance occurs and the decrease of yield load and ultimate load is 33.7％ and 32.4％ respectively.The results of chloride concentration test show that the chloride ion content of concrete in tension area is higher than that in compression area.When the initial load is below 0.5Pu,the chloride ion content in steel position is below 0.1％ and has no significant changes.When the initial load is 0.7Pu,the chloride ion content increases significantly and the maximum value is up to 0.14％.Thus,the initial damage combined with seawater wet-dry cycles has a great impact on degradation of mechanical performance and durability of RC beams.