Hybrid fiber reinforced polymer (FRP) system of carbon FRP laminate and sprayed glass FRP for strengthening reinforced concrete beams

This work is aimed to combine the potential of CFRP laminates in flexural strengthening of reinforced concrete (RC) beams and that of sprayed glass FRP (GFRP) in shear strengthening to form a better hybrid FRP system. Only the flexural strengthening effects of the hybrid system were investigated in this study.;The sprayed GFRP also contributes to the flexural capacity of the strengthened beams. Tension tests were performed to determine its tensile properties, in terms of tensile strength and stress-strain relationship. These properties were shown to be affected by glass fiber length and content, but not by the orientation and thickness of the specimens.;Eight 2.8 meter reinforced concrete (RC) beams with adequate reinforcing steel were cast. The reinforcing steel and concrete of some beams were then artificially damaged to simulate steel corrosion and related concrete spalling usually occurred to real-world RC beams. These beams were repaired with FRP in various configurations including the hybrid system and tested in lab by a three-point loading setup. The results indicate that the hybrid system improved the load-carrying capacity of the beams but failed mostly in CFRP laminate debonding, a premature failure mode.;A classical RC beam analysis and a 2-D finite element analysis were performed to predict the behavior of the strengthened beams. The results agree well with the experimental results in terms of load-carrying capacity.;With the 'plane section' assumption and the ACI design guide for CFRP flexural strengthening, the effects of the sprayed GFRP were developed for possible incorporation into the existing design guide. The resulting design of the hybrid system was shown to be conservative.;A real-world case study of the hybrid system revealed the issues that have to be addressed before the system could be used effectively. It also showed some technical difficulties related to the spraying operation.