Experimental and theoretical analysis of cracking and tension stiffening in UHPFRC under high-cycle fatigue

Abstract

Tension-stiffening controls the serviceability behavior of concrete structures as it is responsible for crack formation and, consequently, the deflection of beams. In fiber reinforced concrete, such as ultra-high performance fiber reinforced concrete (UHPFRC), fibers bridge cracks and thereby transfer tensile stresses across the cracked region, allowing for tensile stresses to be carried by the concrete within the cracked region. Due to structures being designed for longer design lives, the consideration of long-term effects such as fatigue is required. Much research has examined tension-stiffening under fatigue when subjected to low cyclic loading, but very little has considered the effects of high-cycle fatigue, especially for UHPFRC. This paper presents the results of nine UHPFRC tension-stiffening tests under high-cycle fatigue in which the crack formation and development under varying cyclic ranges were studied. Specimens were subjected to as many as 5.7 million cycles, and crack readings were taken during each test. The experimental results demonstrate the random nature of cracking on UHPFRC as well as the increase in the crack width under cyclic loads. Finally, this research described the extension of an existing partial-interaction mechanics model to allow for the stress in the fibers and the increase in crack width due to high cycle fatigue.