Research On Elevated Temperature Property Of Glass Fiber Polymer Rebar

Fiber Reinforced Polymer (FRP) rebar is a new kind of composite material, which is composed of fiber and bonding colloid. Because of its excellent mechanical properties, FRP rebar has been regarded as an alternative to conventional reinforced steel bars in concrete structures, and it has been applied in bridges, civil buildings, offshore structures, underground engineering infrastructures, etc. The fire resistance of FRP bars is weaker than that of steel reinforcement, and now there is little research. In this paper, experimental investigations are carried out on fire resistance behavior of GFRP rebar and steel reinforcement, and some design suggestions on GFRP rebar are proposed. The main contents and achievements of thisthesis are as follows:(1) Through the high temperature test on 7 groups HRB335 steel reinforcement specimens with the length of 400mm, the tensile test on yield strength, tensile strength, elastic modulus, elongation ratio and tensile stress-strain curves of steel reinforcement were investigated at normal temperature, and after 100℃, 200℃, 300℃, 400℃, 500℃, 600℃. The mechanical property of steel reinforcement at different temperature was studied. The test results showed that the mechanical property of steel reinforcement was deteriorated at high temperature. However, the effect was little at experimental temperature.(2) Through the tensile test on 24 groups GFRP rebar specimens with the length of 1200mm, tensile strength, elastic modulus and tensile stress-strain curves of GFRP rebar were investigated at normal temperature, and after 100℃, 150℃, 200℃, 250℃, 300℃, 350℃. The mechanical property of GFRP rebar affected by temperature, heated-time, diameter, matrix resin and ignition loss test was studied. The test results showed that the tensile strength of GFRP rebar decreased with the higher temperature and more ignition loss test. At the same time tensile strength increases with increasing of diameter, however, tensile strength decrease by modifying matrix resin. The stress-strain curve of GFRP rebar at normal temperature and after high temperature were linear, at last their failure mode was brittle.(3) Through the shear test on 21 groups GFRP rebar specimens with the length of 130mm, shear strength of GFRP rebar were investigated at normal temperature and after 100℃, 150℃, 200℃, 250℃, 300℃, 350℃. The shear strength of GFRP rebar affected by temperature, diameter, matrix resin and ignition loss test was studied. The test results showed that the shear strength of GFRP rebar decreased with the higher temperature and more ignition loss test. At the same time shear strength increases with increase of diameter, however, shear strength decrease by modifying matrix resin.(4) Ultimate bearing capacity of rectangular concrete beem reinforced with GFRP bar was investigated after fire at three sides, simplify formula of normal section ultimate bearing capacity of beams with high temperature at tensile area and compressive area were studied respectively.