## 1 Introduction  
Concrete is a porous, brittle material widely used in civil engineering. It has a high compressive strength but poor tensile strength, impact resistance, and toughness, which results in a weak resistance to cyclic, impact, seismic, and explosive loads. Therefore, many scholars have been exploring ways to improve the tensile performance of concrete. One of the most promising methods of modification is to add an appropriate amount of chaotic fibers to plain concrete, which can improve the tensile strength, stiffness, fatigue life, and ductility of the concrete, based on the influence of the fiber on the initial crack initiation and propagation [1; 2; 3]. There are a wide variety of fibers that can be used for the reinforcement of concrete--i.e., metallic fibers, organic fibers, and inorganic fibers--according to material composition. These fibers mainly include steel fiber, glass fiber, polypropylene fiber, polyvinyl alcohol (PVA) fiber, basalt fiber, and coir fiber [4; 5]. Presently, there are many studies on the enhancing and toughening effect of fiber-reinforced concrete (FRC) under static loads. [PERSON] and [PERSON] [6] studied the characteristics of the compressive strength, split tensile strength, and fracture modulus of concrete with different steel fiber contents. It was found that compressive strength was the highest with a fiber content of 1.5%, and the split strength, toughness index, and fracture modulus increased with increasing fiber content. [PERSON] et al. [7] studied the characteristics of compressive strength, split tensile strength, flexural strength, and ultrasonic velocity of steel FRC with different aspect ratios and volume contents. Some conclusions have also been drawn, that the addition of steel fiber could significantly improve the split and bending strength, while the improvement in compressive strength was not obvious and ultrasonic velocity showed a downward trend. [PERSON] and [PERSON] [8] focused on the characteristics of natural fiber concrete with different types of fibers, including basalt fiber, jute, sisal, hemp, banana, and pineapple. The results showed that the properties of FRC were related to the material properties of the fiber itself. There are also many studies on natural fiber concrete, which show that the addition of natural fibers results in a certain degree of improvement in the split tensile strength, bending strength, and absorbing energy of the concrete, with the fiber content in concrete relating to the fiber type [9; 10; 11]. [PERSON] et al. [12] carried out a three-point bending experiment on PVA and basalt FRC beams with different contents (1-3%). The results showed that PVA fibers could significantly improve the post-peak bending behavior of concrete beams compared with basalt fiber. The PVA concrete beams showed deflection hardening characteristics with 3% content, while the basalt fiber concrete beams showed deflection softening characteristics with high content. However, the diameter of the PVA fiber (0.66 mm) was larger than that of the basalt fiber (0.018 mm). The different bending properties of FRC beams should have a certain relationship with fiber diameter. From the above studies, it is evident there have been many achievements in testing fiber concrete with different kinds of fiber under static loads. However, concrete is a brittle material with a high sensitivity to strain rate [13; 14]. Concrete structures will inevitably encounter a variety of dynamic loads during their service period, such as the wind load suffered by ground constructions and bridges, the hydrodynamic pressure encountered by dams and maritime terminals, and the seismic loads encountered by engineering structures in strong earthquake areas. Many studies have shown that the properties of concrete under a dynamic load are quite different from those under a static load. Therefore, it must be irrational to use the concrete strength parameters under static loads to design concrete structures that may be subjected to dynamic loads during service.