Experimental study on crack bridging in FRC under uniaxial fatigue tension

This paper presents an experimental study on crack bridging in steel-fiber- reinforced concrete (SFRC) materials under deformation-controlled uniaxial fatigue tension. Two types of commercially available steel fibers, straight steel fiber and hooked end steel fiber, were used separately in this exper imental investigation. A total of six series of fatigue tensile tests with constant amplitude between maximum and minimum crack openings were conducte d. The experimental results show that the bridging stress decreases with th e number of load cycles, and this phenomenon is termed bridging degradation . The general behavior of the bridging degradation with the number of cycle s in SFRCs is represented by a fast dropping stage (reduction in bridging s tress within the first 10-15 cycles) with a decelerated degradation rate, f ollowed by a stable stage with an almost constant degradation rate for stra ight SFRC, or by several periods with a decelerated rate in each period for hooked SFRC. Although fiber deformation, such as in hooked end fiber, can improve the monotonic crack bridging significantly, faster bridging degrada tion is found in hooked SFRC than in straight SFRC with the same maximum cr ack width (>0.1 mm) and minimum load condition.