冲击作用下钢筋混凝土深梁动力性能试验研究

为了探讨在冲击荷载作用下钢筋混凝土深梁的动力性能,利用大型落锤试验机对两组具有不同静载破坏特性的简支钢筋混凝土深梁进行了不同冲击速度下的动力性能试验研究,并考虑了二次冲击的影响。通过对高速摄像机所记录的各试件在冲击过程中裂缝的发生、发展直至试件破坏的全过程进行分析和不同荷载下裂缝形态差异的对比分析,表明不同的冲击速度下试件裂缝的发生、发展过程及裂缝形态表现出明显的差异,二次冲击下的主要裂缝基本遵循一次冲击产生的裂缝路径发展。详细分析了冲击力和跨中位移时程曲线以及冲击力-跨中位移曲线的特征,发现冲击力峰值与冲击速度、最大跨中位移和跨中残余位移与冲击速度在不发生严重剪切破坏时均满足近似线性关系。分析还表明,具有较好延性的深梁具有更好的抗冲击性能。最后,通过对比分析冲击力、支座反力和惯性力时程曲线,得出采用冲击力峰值和支座反力峰值作为深梁的抗冲击承载力均不准确的结论。

Tests for dynamic behaviors of deep RC beams under impact loadings

In order to understand the dynamic behaviors of deep reinforced concrete (RC) beams under impact loadings, falling-weight impact tests on two groups of simply-supported deep RC beams with different static behaviors were carried out and the effects of impact velocity and the second impact on the impact-resistant behavior of deep RC beams are investigated. By analyzing the crack initiation, propagation and the failure process of the specimens recorded using a high-speed video camera and comparing the crack patterns of specimens under different loadings, it is found that the crack initiation, propagation, the failure process and crack patterns are affected obviously by impact velocity and the major crack development under the second impact mainly follows the crack path induced by the first impact loading. The characteristics of time histories of impact force and mid-span displacement and impact force versus mid-span displacement curves are described in details and that the maximum impact force, the maximum mid-span deflection, the residual mid-span deflection change approximately linearly with impact velocity for specimens without serious shear failure is observed. Moreover, the specimens with better ductility have better impact-resistant behaviors. Finally, by analysis of the time histories of impact force, supported reaction force and inertia force, it is deduced that taking the maximum impact force or the maximum support force as the impact-resistant loading capacity is irrational.