Effective strengthening schemes for heat damaged reinforced concrete beams

Abstract

Several effective strengthening schemes for enhancing the flexural strength of heat-damaged reinforced concrete (RC), beams are proposed. A series of twenty-eight RC rectangular beams were cast, subject to a temperature of 600 °C for 3 h, strengthened, and then tested in flexure to determine the effect of externally applied carbon and glass fiber reinforced polymeric sheets (CFRP) and (GFRP) respectively, as a method for regaining the beams’ flexural capacity. The load-deflection behavior and the modes of failure of the beams tested are described. The beams strengthened in shear and flexure with CFRP and GFRP sheets applied at the sides and the bottom of the beams in U-shaped jackets or strips showed a significant increase in their flexural strength compared to control and heat damaged ones. They achieved a high percentage of the control beams load carrying capacity, and exhibited a ductile failure characterized by the initiation of typical flexural cracks in the moment zone followed by the occurrence of flexure-shear cracks in the constant shear span. Optimizing the CFRP and GFRP strengthening schemes proposed could provide promising and cost effective repair alternatives for enhancing the flexural capacity of fire damaged RC members.

Keywords

• Concrete
• Fiber reinforced polymers
• Temperature
• Strengthening