FRCM/stirrups interaction in RC beams strengthened in shear using NSE-FRCM

Abstract

The use of a recently introduced "near surface embedded" (NSE) technique for fabric reinforced cementitious matrix (FRCM) system is shown to be a viable alternative to the conventionally used externally bonded FRCM counterpart with the potential to mitigate FRCM/concrete debonding. This paper presents a study on the interaction of FRCM and stirrups for RC beams strengthened in shear using the NSE-FRCM system. The experimental program involved eight (8) rectangular RC beams with and without internal shear reinforcement. Two test variables were considered; namely, fabric type (carbon, glass and polyparaphenylene benzobisoxazole) and internal shear reinforcement within the critical shear span (with and without stirrups). The experimental results revealed that the NSE-FRCM can successfully be used to enhance the shear capacity of the strengthened beams. Carbon FRCM was the most effective of all the fabric types. Moreover, an interaction between the stirrups and the NSE-FRCM system has been observed. The percentage gain in the shear strength was reduced from 69% to 38% due to the presence of stirrups within the critical shear span. Moreover, the NSE-FRCM strengthening has reduced the strain in the stirrups owing to the load sharing between the stirrups and the strengthening system.