Fatigue Behavior of FRCM-Strengthened RC Beams

Abstract

Fabric-reinforced cementitious matrix (FRCM) composites are thin laminates of mortar that embody synthetic and mineral-based continuous fabrics. FRCM materials are proven to be an effective strengthening and rehabilitation technique for concrete structures under flexural, shear, and axial stresses. This paper reports analytical and experimental studies of the mechanical performance of glass FRCM (GFRCM) strengthened RC beams subject to monotonic and cyclic loads. First, material properties of the GFRCM system were determined according to “Acceptance Criteria AC434.” The material properties were then used to analytically determine the capacity of strengthened reinforced concrete (RC) beams, using ACI 549.4R design guidelines. RC beams were strengthened with the GFRCM system and tested under monotonic and cyclic loads to determine ultimate flexural capacity, concrete cracking pattern, failure mode, bond performance, and fatigue threshold. Under monotonic loading, GFRCM increased the steel yielding and ultimate flexural capacity of the strengthened RC beams, but did not change their stiffness. Thus, GFRCM had a minimal effect on serviceability. Fatigue failure of the GFRCM-strengthened beams resulted from progressive cracking and rupture of the steel rebars, followed by fabric slippage within the GFRCM system and rupture of fibers. The GFRCM restrained crack width in concrete, and cracks were more distributed over the length of strengthened beams.