INVESTIGATION OF MOISTURE AND PRELOADING EFFECTS ON FLEXURAL BEHAVIOR OF REINFORCED BEAMS WITH FRP

Recent studies have indicated that moisture environmentscan weaken the bond between ber-reinforcedpolymer (FRP) jackets, epoxy adhesive,concrete.Nearly in all of past researches, the specimens have beenexamined under loading,moisture conditions only afterstrengthening the structural elements, while one ofthe important applications of FRP jackets is in restorationand reconstruction of the structures subjected toloading,moisture condition. Additionally, there isa high probability that the structural elements are exposedto surface moisture before strengthening in theseconditions. The aim of this study is to investigate theexural behavior of beams reinforced by FRP jacketssimilar to the real conditions under which the structureis subjected to two essential factors, including moistureand preloading. For this purpose, 20 specimens of concretebeams with dimensions of 150  200  1150 mmwere constructed that falls into two groups with twodierent arrangements of tensile reinforcement. Othervariables were the amount of surface moisture,thelevel of preloading of specimens. Before strengthening,the specimens were subjected to preloading,moistureconditions,then ruptured under exural tests. Theresults obtained from the tests were the load-midspandisplacement curves of the specimen. The results indicatedthat the exural strength of the beam with CFRPjackets without cracks,surface moisture increased upto the 20% of its ultimate strength, while, in the beamswith premier cracks,surface moisture, only 13% and9% increases in exural strength were reported, respectively.Furthermore, in beams with premier cracks andsurface moisture, an increase of 13% in ultimate strengthwas simultaneously seen. The results also suggest thatusing reinforcing bars with a higher diameter,lowernumber in comparison to using a lower diameter andhigher number of bars could decrease the eciency ofFRP jackets,cause brittle failure in the entire mentionedconditions.