Evaluation of crack-bridging strength degradation in SFRC structural beams under flexural fatigue

Abstract

Steel fiber reinforced concrete (SFRC) at the structural scale exhibits an enhanced fatigue performance compared to conventional reinforced concrete (RC) with lower stress levels and longer fatigue life. The steel fibers contribute to the crack-bridging strength of the concrete, but how this degrades in the tensile stress zone of an SFRC structural beam during flexural cyclic loading remains unknown. This makes the fatigue design and safety verification of SFRC beams an unexplored area. In this work, the degradation in crack-bridging strength of SFRC structural beams with 1.5% by volume of hooked-end steel fibers under different flexural fatigue stress levels is evaluated over the fatigue life using an inverse analysis method. The experimental flexural response is monitored during static and fatigue tests, and compared with the calculated one from the section analysis calculations through the execution of the inverse analysis method. Based on the results, the crack-bridging strength is shown to degrade gradually at different flexural fatigue stress levels over the fatigue life. Further, the residual flexural capacity at the end of fatigue life is shown to be little different from the original capacity obtained in static loading when the flexural fatigue stress level is low.