As a high-performance building material, fiber-reinforced concrete (FRC) has attracted garnered significant interest in practical engineering construction. However, the effect of coupled static-dynamic loading on the dynamic response of FRC remains far from understood, which seriously limits its wide application. In this study, a series of coupled static-dynamic loading tests are conducted on four types of FRC specimens using the modified split Hopkinson pressure bar (SHPB) system, and the influences of static pre-stress and strain rate on the mechanical performance of FRC under coupled static-dynamic loading are systematically analyzed. The experimental results indicate that static pre-stress generally reduces the dynamic strength and energy dissipation density, but increases the total strength and fragmentation degree of FRC. As the pre-stress ratio increases from 0 to 0.6, the dynamic strength of FRC decreases ranging from 12 to 25 %, and the total strength increases ranging from 12 to 34 %. The failure features of FRC specimens changes from tensile failure mechanism to tensile-shear mixed mechanism with increasing the static pre-stress. Combining the scanning electron microscope (SEM) and mercury intrusion porosimetry (MIP) techniques, the microscopic structure and fracture mechanisms of FRC specimens are revealed, and the underlying influencing mechanisms of the static pre-stress, strain rate and fibers are further discussed. The axial pre-stress exerts a dual effect on FRC: enhancement by compacting primary voids as well as attenuation by stimulating secondary microcracks. The strain rate dominates the mechanical performance of FRC under coupled static-dynamic loading, and the influence of pre-stress is diminished by higher strain rates. In addition, the fiber incorporation strengthens the concrete pore structure by bridging action and crack inhibition, resulting in superior mechanical performance compared to normal concrete under coupled static-dynamic loading conditions.

中文翻译：

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动压耦合作用下纤维型对纤维增强混凝土力学性能及断裂机理的影响


纤维增强混凝土 （FRC） 作为一种高性能建筑材料，在实际工程施工中引起了极大的兴趣。然而，动静耦合载荷对FRC动态响应的影响仍未得到充分认识，严重限制了其广泛应用。本研究采用改进的分体式霍普金森压力杆 （SHPB） 系统对 4 种类型的 FRC 试件进行了一系列静-动载荷耦合试验，系统分析了静-动载荷耦合作用下静态预应力和应变速率对 FRC 力学性能的影响。实验结果表明，静态预应力通常会降低FRC的动态强度和耗能密度，但会增加FRC的总强度和断裂程度。随着预应力比从 0 增加到 0.6，FRC 的动态强度下降了 12 到 25 %，总强度增加了 12 到 34 %。随着静态预应力的增加，FRC 试件的破坏特征由拉伸破坏机制转变为拉剪混合机制。结合扫描电子显微镜 （SEM） 和汞侵入孔隙度测定 （MIP） 技术，揭示了 FRC 样品的微观结构和断裂机制，并进一步讨论了静态预应力、应变速率和纤维的潜在影响机制。轴向预应力对 FRC 产生双重影响：通过压缩初级空隙来增强，以及通过刺激次生微裂纹来衰减。在静动耦合载荷下，应变率主导 FRC 的力学性能，较高的应变率会减弱预应力的影响。 此外，纤维掺入通过桥接作用和裂缝抑制增强了混凝土孔隙结构，在静动耦合载荷条件下，与普通混凝土相比，具有优异的机械性能。