Spalling is a typical tensile fracture phenomenon due to insufficient tensile strength of concrete. Concrete structure might experience severe spall damage at the rear surface of the structure owing to reflected tensile stress wave induced by impulsive load. In recent years, metaconcrete consisting of engineered aggregates has attracted attentions as metaconcrete exhibits extraordinary wave-filtering characteristics. Metaconcrete can be used to attenuate stress wave generated by impulsive load and hence possibly mitigate the spall damage. In this study, engineered aggregate is designed via the software COMSOL to have the frequency bandgap coincide with the dominant frequency band of stress wave propagating in the normal concrete (NC) specimen to reduce the stress wave propagation and hence spall damage. The wave propagation behaviors in metaconcrete specimen with periodically distributed engineered aggregates have been investigated in a previous study. This study establishes 3D meso-scale model of metaconcrete including mortar, randomly distributed natural aggregates and engineered aggregates to simulate spall behaviors of metaconcrete via the software LS-DYNA. The responses of metaconcrete composed of engineered aggregates with single bandgap and multiple bandgaps are studied. The results show that stress wave can be more effectively attenuated by using engineered aggregates with multiple bandgaps. It is found that although engineered aggregates mitigate stress wave propagation, the soft coating of the engineered aggregates reduces the concrete material strength, therefore spall damage of metaconcrete specimen is not necessarily less severe than the normal concrete, but has different damage mode. In addition, the influences of loading intensity and duration on stress wave, as well as the spall behaviors of metaconcrete specimen are also studied.

中文翻译：

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超混凝土的剥落行为：3D 中尺度建模

剥落是由于混凝土抗拉强度不足而引起的一种典型的拉伸断裂现象。由于冲击载荷引起的反射拉应力波，混凝土结构可能会在结构后表面遭受严重的剥落破坏。近年来，由工程骨料组成的超混凝土由于具有非凡的滤波特性而引起了人们的关注。超混凝土可用于衰减由冲击载荷产生的应力波，从而可能减轻剥落损坏。在这项研究中，工程骨料通过 COMSOL 软件设计，使其频带间隙与在普通混凝土 (NC) 试件中传播的应力波的主频带重合，以减少应力波的传播，从而减少剥落损伤。在先前的研究中已经研究了具有周期性分布的工程骨料的超混凝土试样中的波传播行为。本研究通过 LS-DYNA 软件建立了变混凝土的 3D 细观尺度模型，包括砂浆、随机分布的天然骨料和工程骨料，以模拟变混凝土的剥落行为。研究了由具有单带隙和多带隙的工程骨料组成的超混凝土的响应。结果表明，使用具有多个带隙的工程聚集体可以更有效地衰减应力波。研究发现，虽然工程骨料减轻了应力波的传播，但工程骨料的软涂层降低了混凝土材料的强度，因此超混凝土试件的剥落损伤不一定比普通混凝土严重，而是具有不同的损伤模式。此外，还研究了加载强度和持续时间对应力波的影响，以及超混凝土试件的剥落行为。