无腹筋钢筋混凝土梁抗冲击行为试验研究

Experimental study on the impact-resistant behavior of RC beams without shear-resistant rebar

为了深入了解冲击下钢筋混凝土梁的抗剪性能,对六根无腹筋简支钢筋混凝土梁进行落锤冲击试验研究,对试验结果进行详细描述和分析。分析冲击锤重、冲击速度和冲击能量对梁抗冲击行为的影响,测量混凝土以及钢筋的应变时程和冲击力时程,并通过高速摄像机记录了试件在冲击荷载下裂缝的发生、发展和破坏全过程。获得梁的裂缝分布图和典型的破坏模式,并与相关梁抗冲击试验的破坏模式进行比较分析。分析通过应变片测得的数据发现,在冲击开始时,跨内靠近支座附近和半跨跨中位置处梁截面上部出现受拉应变,下部出现受压应变。当这些应变达到应变峰值后,拉压应变状态朝反向转变,反映出冲击开始时在梁跨内产生了明显负弯矩,惯性效应明显。最后对冲击过程中梁弯矩分布的特点进行分析,并对相关的梁抗冲击计算方法进行讨论。

In order to further understand the shear-resistant behavior of reinforced concrete （RC） beams under impact load, falling-weight impact tests on six simply-supported RC beams without shear-resistant rebar were carried out and the experimental results were described and analyzed in detail. Parameters including weight of impact mass, impact velocity and impact energy were considered as variables and their effects on the behavior of the RC beams were analyzed. Time histories of the strain of concrete and longitudinal rebar and the impact force were recorded, and the crack initiation, propagation and the failure process of the specimens were recorded using a high-speed video camera. Crack distribution on the side surface of the beams was sketched and comparison of crack patterns between the specimens under different impact tests in this study and another tests reported in related literature was conducted. From the strain measurement, it is shown that, at the beginning of the impact process, the upper fibers of the cross section of the specimen close to the supports and in the half-span were in tension, while the opposite Iower fibers were in compression. After those strains reached their peak values, they developed in reverse directions. Thus it can be inferred that the negative moment was induced by the inertia effect at the beginning of impact process. The characteristics of moment distribution along the beams during the impact process were obained and methods of analyzing the behaviors of RC beams subjected to impact load were discussed.