冲击荷载作用下钢纤维混凝土配筋梁性能试验

Experiment on Behavior of Reinforced Concrete Beams with Steel Fiber Under Impact Load

为探讨冲击荷载作用下掺有端钩型钢纤维的配筋混凝土梁的抗冲击性能,对6根简支的有不同钢纤维体积掺量和不同配箍率的试件进行了落锤冲击试验,冲击点为跨中.分析了不同钢纤维体积掺量和不同配箍率对钢筋混凝土梁的抗冲击能力的影响,并采用高速摄像机记录了各试件的开裂形态.详细分析了试件的开裂形态、跨中位移时程曲线、试件中纵筋和箍筋应变时程曲线的特征.结果表明:在相同冲击荷载作用下,配箍率较高的试件中钢筋发生屈服乃至失效的几率相对较小,随着配箍率的增加,试件承受冲击荷载时产生的最大裂缝宽度减小;在冲击荷载作用下,提高钢纤维体积掺量对构件混凝土基体强度的影响相对不大,但对于试件刚度的影响较为明显;同时,钢纤维含量的增加,会减少梁中箍筋的应变,使得钢筋混凝土梁中钢筋发挥更好的作用;钢纤维体积掺量的增加,可以明显减少试件在冲击荷载作用下裂纹的发生与开展,并改变梁本身的开裂形态,使得裂缝发生的区域相对集中,形成主要集中在试件跨中的竖直裂纹,而支座附近裂纹相对减少.

The purpose of this research is to understand the impact-resistant behavior of reinforced concrete（RC）beams with hooked-end steel fibers. A series of 6,simply-supported concrete beams with different volume fractions of steel fibers and different shear reinforcement ratios were tested under free-falling drop-weights,impacting the specimens at the mid-span. An analysis was made of the effects of different shear reinforcement ratios and different volume fractions of steel fibers on the impact-resistant behavior of RC beams. The crack patterns of the specimens were recorded using a high speed video camera. The strains of longitudinal and transverse steels were recorded,and the time histories of mid-span displacement were described in detail. The results obtained are as follows：under the same impact load and with the increase of stirrup ratio,the reinforced steel shows a less frequent occurrence in yield and failure,and the maximum crack width decreases under impact load;Under impact load,improving the volume fractions of steel fibers only has negligible effect on the concrete matrix strength,but for the whole stiffness of the specimens the effect is more obvious. Meanwhile increasing steel fiber content will reduce the strain of stirrups,making specimen reinforcement play a better role;The increase of volume fractions of steel fibers can significantly reduce the occurrence and development of cracks in specimens. Changes in the crack pattern of the beam occur at the same time,making the area of crack occurring relatively concentrated on the mid-span in the form of vertical cracks,while reducing the cracks near the support.