To fully understand the fracture behaviour of concrete after low-cycle reciprocating loading, a series of experiments are carried out using compact tension specimens. An improved wedge splitting device for adaptive loading is proposed to relieve the brittle unloading process during the concrete fracture tests. Due to the additional springs, the complete stress–strain curves representing concrete fracture are measured and recorded, including the evolution of micro-cracks, damage accumulation, and ultimate fracture stages. Moreover, a group of specimens is designed to split directly under quasi-static loading for comparison. Both the measured load–strain curves and load-CMOD curves are given and analysed to determine the fracture toughness and fracture energy with the double-K fracture model. The results show that the reciprocating loading changes the failure pattern and that more failures occur around the coarse aggregates, causing the relative ratio up to over 160%. When subjected to a limited number of low-cycle reciprocating loadings, concrete generates more micro-cracks or damage that result in an earlier crack initiation and a lower critical force, as well as a smaller fracture energy. Meanwhile, the measured values of the initiation force, the initiation toughness and the unstable toughness increase slightly because the weaker bond zones have accomplished fracture, and the rest performance of concrete specimen is mainly determined by the properties of coarse aggregates. The results indicate that the bearing capacity of concrete decreases and the deformation becomes more brittle as concrete undergoes reciprocating loading.

为了充分了解低周往复载荷后混凝土的断裂行为，使用紧凑的拉伸试样进行了一系列实验。提出了一种改进的楔形劈裂装置，用于自适应加载，以减轻混凝土断裂试验期间的脆性卸载过程。由于增加了弹簧，因此测量并记录了代表混凝土断裂的完整应力-应变曲线，包括微裂纹的演变，损伤累积和最终断裂阶段。此外，一组样本被设计为在准静态载荷下直接分裂以进行比较。给出了测量的载荷-应变曲线和载荷-CMOD曲线，并进行了分析，以确定双K断裂模型的断裂韧性和断裂能。结果表明，往复载荷改变了失效模式，并且在粗骨料周围发生了更多的失效，导致相对比率高达160％以上。当承受有限数量的低周期往复载荷时，混凝土会产生更多的微裂纹或损坏，从而导致较早的裂纹萌生和较低的临界力以及较小的断裂能。同时，由于较弱的粘结区已完全断裂，因此初始力，初始韧性和不稳定韧性的测量值略有增加，而混凝土试件的静置性能主要取决于粗骨料的性能。结果表明，当混凝土承受往复载荷时，混凝土的承载力下降，变形变脆。