Effect of Headed Stud Thickness Embedded in Steel Fiber Concrete on Pull-Out Strength

This paper presents an experimental study on the behavior of the load capacity of handcrafted studs symmetrically embedded in concrete reinforced with steel fiber. A total of eight blocks were subjected to pull-out tests. The main variables were stud head thickness (3.17, 4.76, 6.35, and 7.9 mm) and concrete type. The results showed no significant difference in the mean pull-out strength in both types of concrete mixtures: conventional and fibrous. Therefore, the effect of steel fiber addition tends to reduce the inclination plane of cracks, changing the mode of abrupt failure to more ductile. Moreover, in conventional concrete, the thickness $t_h=7.93\mathrm{mm}$ (0.20 $d_h$) lost about 15% of the pull-out strength compared to the thickness $t_h=3.17\mathrm{mm}$ (0.08 $d_h$); in contrast, it obtained a gain of 5% in concrete with the steel fiber. That is, a thickness of approximately 10% of the head diameter can adequately provide satisfactory results in embedment with or without the addition of the steel fiber for $f_c=35\mathrm{MPa}$. In addition, the literature models were more conservative. Also, a modified concrete capacity design method was proposed, considering the head thickness and the empirical factor for concrete breakout strength adjustment, $k=20$. The results were satisfactory, with an average of 1.00 and a coefficient of variation of only 6% in steel fiber concrete.