Flexural response of reinforced concrete continuous beams strengthened with fiber-reinforced cementitious matrix (FRCM)

Abstract

This paper reports on the efficiency of fabric reinforced cementitious matrix (FRCM) composites in enhancing the flexural and deformation capacity of continuous reinforced concrete (RC) beams. The experimental program consisted of eight two-span RC beams having flexural deficiency in either their hogging or their sagging sections. The amount of internal steel reinforcement in the strengthened sections was 50% of that of the unstrengthened sections. The deficient sections were strengthened with one, two, or four plies of Polyparaphenylene Benzobisoxazole (PBO) FRCM system. The obtained results indicated that strengthening with FRCM systems improved the stiffness and the load-carrying capacity of the tested beams with an insignificant loss in their ductility. Increasing the number of FRCM layers increased the yielding and ultimate capacity up to 52 and 11% for beams strengthened in their hogging regions and up to 26 and 30% for those strengthened in their sagging sections, respectively. The obtained results confirmed the ability of the FRCM-strengthened sections to efficiently redistribute the flexural moments after the formation of the plastic hinges. The moment redistribution ratio decreased with the increase in the number of FRCM layers used. This ratio varied between 65 and 84% for beams strengthened with one and two FRCM layers and between 42 and 51% for those strengthened with four layers. These results suggested the revision of the provisions of both CSA and ACI codes and design guidelines, which prohibited the moment redistribution between the critical sections in RC strengthened elements.