RC梁冲击破坏机理试验研究与残余变形预测方法探讨

进行了3根剪跨比为3.58钢筋混凝土梁的落锤冲击试验和1个静力对比试验,重点研究钢筋混凝土梁在冲击荷载作用下的破坏机理和冲击能量对钢筋混凝土梁残余变形的影响规律.试验结果表明,在静力下发生弯曲破坏的梁在低速冲击下的裂缝形态以弯曲裂缝、弯剪裂缝为主,在高速冲击荷载作用下以腹剪裂缝为主.试验测试了冲击力、支座反力、跨中位移和跨中纵筋应变等动态时程曲线,通过分析其动态时程曲线结果,获得了钢筋混凝土梁的冲击破坏机理,即冲击作用下梁的破坏过程分为局部响应阶段和整体响应阶段.同时,还统计了国内外相关文献冲击试验结果,通过比较分析钢筋混凝土残余变形-冲击能量关系实验数据,探讨了冲击荷载作用下钢筋混凝土梁残余变形的经验公式的适用性和存在的问题.

Failure Mechanism of RC Beams under Impact Loading and Discussion on Prediction Methods of Residual Deflection

Tests of three RC beams under impact loading and one under static loadings were carried out with the shear pan ratio of 3.58. The failure mechanism and the influence of impact energy on residual deflection of the RC beams under impact loading were investigated. The test results showed that cracks of the flexural beams under static loading were mainly attributed by the bending-shear failure mode under low-velocity impact, while they changed to the shear failure mode under high-velocity impact. The time history of impact loading, support reaction force, mid-span deflection and reinforcement strain in mid-span were recorded and presented. Based on the analysis of the time history curves, the failure mechanism of RC beams was discussed. The failure process under impact loading can be divided into partial response phase and overall response phase. Moreover, the impact test results in the existing related papers were collected, and based on the comparison of the relationship between residual deflection and impact energy, the applicability of empirical formula to estimate residual deflection under impact loadings was discussed.