Flexural Behavior of Reinforced Concrete Beams Strengthened with Externally Bonded Hybrid Systems

Abstract

The demand for strengthening of aging reinforced concrete (RC) structures are continuously rising. Carbon fiber reinforced polymers (CFRP) are the most widely used externally bonded-reinforcing (EBR) materials for strengthening and retrofitting of RC structural members. The use of high strength galvanized steel mesh (GSM) strengthening material has recently gained some acceptance. However, Both CFRP and GSM have high strength but have low ductility. Recently developed aluminum alloys (AA) have high ductility and some desirable characteristics that may overcome some of the shortcomings of CFRP and GSM. Combining AA with CFRP and GSM will result in a hybrid material with balanced strength and ductility. Therefore, the major aim of this research is to develop a hybrid ductile and strong retrofitting system by combining AA plates with GSM and CFRP laminates to strengthen RC beams in flexure. A comprehensive experimental program was carried out to determine the tensile strength and the bond strength of the hybrid system. Fifteen-coupon specimens were tested for tensile strength, six specimens of concrete prisms for bond strength and 25 T-beam specimens for flexural strength under a four-point loading. Results showed an increase in the flexural capacity of the strengthened specimen ranging from 10% to 77% compared to the control beam and a decline in ductility of 13% to 59% compared to the un-strengthened specimen. Furthermore, analytical models based on ACI 440.2R-08 guidelines were employed to capture the flexural behavior of the tested specimens. Experimental results correlated well with the analytical predictions in a range of 30% of the experimental values. The study concluded that the newly proposed hybrid systems are promising systems for the improvement of the flexural behavior (strength and ductility) of RC beams.