落锤冲击作用下钢筋混凝土梁的动态响应

为研究钢筋混凝土梁在不同冲击速度下的动态变形规律，利用落锤冲击试验装置和二维数字图像相关系统，对12根钢筋混凝土梁的冲击力时程、平均跨中位移变化过程、跨中钢筋的平均应变时程以及裂缝的形成与扩展过程进行分析，重点讨论了梁的变形破坏模式及动态响应过程。研究发现：不同于静态三点弯曲试验的弯曲型破坏，钢筋混凝土梁的动态破坏形态主要表现为弯剪型破坏；冲击力峰值明显大于静态加载的承载力峰值，在恒定冲击质量的条件下与冲击高度正相关；钢筋混凝土梁的位移响应过程明显滞后于冲击力的响应时程，挠曲变形所持续的时长约为冲击力作用时长的40~60倍，位移响应表现出明显的滞后性；钢筋是否进入屈服阶段以及维持时长显著影响梁的最大位移以及残余位移。

DYNAMIC RESPONSE OF REINFORCED CONCRETE BEAM UNDER DROP HAMMER IMPACT

In order to study the dynamic deformation law of reinforced concrete beams under different impact speeds, the drop hammer impact test device and two-dimensional digital image correlation system was used to investigate the impact force time history, average mid span displacement change process, average stress time history of mid span reinforcement and the formation and expansion process of cracks of 12 reinforced concrete beams, and the deformation failure mode and dynamic response process of beams were emphatically discussed. The results show that the dynamic failure mode of reinforced concrete beams is mainly bending shear failure, which is different from the bending failure mode of static three-point bending test; The peak value of impact force is obviously larger than that of static loading, and is positively correlated with the impact height under the condition of constant impact mass; The displacement response process of reinforced concrete beam obviously lags behind the response time history of impact force. The duration of flexural deformation is about 40 ~ 60 times that of impact force, and the displacement response shows obvious lag; Whether the reinforcement enters the yield stage and the maintenance time significantly affect the maximum displacement and residual displacement of the beam.