###### Abstract
However, all the above-mentioned research only investigated the fatigue behaviors of headed shear studs in normal concrete. Recently, several new types of concrete materials with unique properties, such as lightweight concrete (LWC), ultra-high performance concrete (UHPC) and engineered cementitious composites (ECC), have been used to improve the mechanical performance of steel-concrete composite beams. Thus, increasing experimental research has been conducted to study the fatigue behaviors of headed shear studs embedded in the LWC [20; 21; 22], the UHPC [23; 24; 25] and the ECC [26; 27]. The research results indicated that the fatigue  
Figure 1: Failure modes of headed shear studs: (**a**) in the root of the stud [3]; (**b**) in the root of the weld collar [18]; (**c**) from the root of weld collar and propagated to the flange [19]. strength of studs in the LWC and ECC was lower than that of studs in normal concrete. However, the studs in the UHPC improved the fatigue performance compared to normal concrete. Compared with push-out tests, large-scale beam tests are more accurate to capture the actual fatigue behaviors of headed shear studs [28]. Hence, some studies investigated the fatigue performance of headed shear studs through the testing of beam specimens [3; 19; 29]. Comparing the beam test results with a larger dataset for headed shear studs in the above studies, the potential of studs in the beam tests in terms of the relative fatigue performance is apparent. With the deepening of research, some studies then adopted numerical methods to better analyze the behaviors of headed shear studs in steel-concrete composite beams. For example, [PERSON] and [PERSON] [30] proposed an effective numerical model to simulate the load-slip behavior and the shear capacity of shear studs in the push-out tests. [PERSON] et al. [14] studied the failure mode and shear strength of grouped shear studs based on a push-out test of shear studs and numerically simulated the test results using the finite element analysis. Their numerical models provided a better understanding of the different failure modes observed during experimental testing and, hence, the shear capacity of headed shear studs. [PERSON] and [PERSON] [31] then presented a finite element-based approach using a push-out specimen to the fatigue life estimation of headed shear studs. Both the crack initiation and crack propagation life were estimated. However, it is noteworthy to point out that all the finite element analyses in the above studies were conducted aiming at the parametric comparison, not the simulation of the fatigue push-out test process. The precise simulation of the fatigue push-out test process (i.e., fatigue crack propagation process) by the finite element analysis is too complicated [16]. To the authors' knowledge, there is only one published research concerning the numerical simulation of the fatigue crack propagation process of shear studs in push-out test. In our previous research work [32], a numerical method was presented to calculate the stress intensity factor using the crack box technique and M integral method, and it applied to study the fatigue behavior of headed shear studs. It was found that the crack propagation in the stud shank was a composite state of the opening mode crack and the sliding mode crack. However, the numerical method in the preliminary study did not reach the step to be valid for simulating the fatigue crack propagation process of shear studs. It lacks detailed fatigue crack data of shear studs in the push-out tests to support the progress of the numerical method. To develop an accurate numerical simulation of fatigue crack propagation, it is indispensable to dynamically inspect the fatigue crack of headed shear studs in push-out tests. However, there are too few studies on fatigue damage inspection of headed shear studs. [PERSON] and [PERSON] [33] chiseled away the concrete surrounding shear studs and carried out a stud crack inspection on two in situ bridges, using magnetic particle inspection and dye penetrant testing.