Predicting through-thickness cone cracking of reinforced concrete slabs struck normally by flat-nosed projectiles
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摘要: 主要针对钢筋混凝土靶板在受到平头弹丸撞击下发生的厚度方向开裂的问题进行研究，并提出了一个弹丸低速撞击有限厚度板的二阶段模型。模型中第一阶段为侵彻阶段，弹丸受到混凝土介质的侵彻阻力由静阻力和速度效应引起的动阻力组成；模型中第二阶段为开裂阶段，钢筋混凝土靶板发生动态剪切破坏的最大承载力可以通过静态剪切破坏最大承载力乘以一个动态增强因子得到。该模型可以用来预测钢筋混凝土靶板发生厚度方向开裂破坏的临界能量。模型预测与实验结果吻合较好。Abstract: A two-stage model is proposed herein to predict the through-thickness cone cracking of a reinforced concrete slab struck transversely by a flat-ended projectile at relatively low velocities. The first stage is penetration, in which the resistive pressure from the concrete medium during the penetration process is composed of two parts: quasi-static resistive pressure and dynamic resistive pressure arising from velocity effect. The second stage is cone cracking, in which the dynamic resistive load is obtained through the punch shear strength for the concrete slab loaded quasi-statically by introducing a dynamic enhancement factor. A semi-analytical equation is derived for predicting the critical impact energy that causes the through-thickness cone cracking of the reinforced concrete slab subjected to impact by the flat-nosed projectile. It transpires that the present model predictions are in good agreement with available test data.
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图 1 二阶段破坏模型示意图
Figure 1. Schematic diagram of the two-stage model (penetration + cone cracking)
表 1 破坏模式转换临界值
Table 1. Critical values for the transition of different failure modes
编号 m/kg H/d $f_{\text{c}}^{'}$/MPa V0/(m·s-1) Hc/d 破坏模式 模型预测 实验观察[9] 55 401 1.0 25.1 6.32 3.00 CC CC 71 404 1.8 33.2 6.80 3.30 CC CC 66 396 2.7 36.3 5.07 3.53 CC CC 61 407 4.0 32.7 6.83 3.90 P+CC P+CC 77 399 6.0 32.0 14.35 4.20 P+CC P+CC 注：P为侵彻；CC为厚度方向开裂破坏。 
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