Experimental Study On RC Beam Strengthened With Externally Bonded Fiber Reinforced Polymer Sheets

As a new type of strengthening materials, the advanced composite FRP (Fiber Reinforced Polymer/Plastics) has been applied more and more widely at home and abroad due to their good characteristics of lightweight, high tensile strength, easy installation and nocorrosion. This paper is engaged to investigate the flexural behavior of reinforced concrete beams strengthened with externally bonded FRP sheets based on the experiment and analysis, and the main contents of present thesis are briefly summarized as following:(1) Eight RC beams strengthened with externally bonded FRP sheets have been tested, in which two parameters of load level at strengthening and different combination in bonded FRP sheets are involved. There three different initial stress levels, such as zero applied load, 50% ultimate load and 25% ultimate load unloaded from 50% ultimate load, exist in beams at FRP sheet bonding. And there different FRP sheet combinations of only CFRP, GFRP and hybrid CFRP/GFRP are used in those strengthened RC beams. The experiment results show that ultimate load-carrying capacity of RC beams can be improved significantly but their cracking load improved little, and cracks become narrower and denser by epoxy bonding FRP sheets on the bottom surface of the beams. The beam stiffness can be improved significantly only after the tensile steel bars yield. The beam ductility decreased compared with those RC beams without bonded FRP sheets.(2) Based on the some appropriate basic assumptions, the calculating formula for the flexural ultimate load-carrying capacity, cracks width, cracks spacing, and stiffness of RC beams strengthened with externally bonded FRP sheets have been developed and the feasibility of these formula have been verified well by the relating test ones.(3) A FORTRAN program for the full-range analysis of RC beams with externally bonded FRP sheets has been developed. A good agreement between the results from the program and test can be found. The parametric study about those beams has been conducted using the program.(4) Finally, The conclusions are drawn and further research requirement at the field as present thesis are pointed out.