| Composite materials is applied more and more extensively in structural engineering.In addition to reinforcing the structure,Glass Fiber Reinforced Polymer(GFRP)as a kind of commonly used composite materials,often replace the reinforced bar in the structure to form the GFRP reinforced concrete members.This can eliminate the damage of the common reinforcement corrosion to the concrete structure performance,and prolong the service life of concrete structures.The structure is usually in a certain environment and affected by the environment more or less.GFRP is not exceptional.Compared to other types of composite materials,GFRP can be more influenced by the environment.The environmental effect in normal use requires further research and finding out the change regulation in order to provide the reference data in the process of designing and use of GFRP reinforced concrete beam.First of all,certain volume content of alkali glass fiber(36 mm long,ratio of length to diameter is 58),which were0.0%,0.3%,0.5%,0.3%,1.0%,1.3% and 1.5%respectively,were mixed in the concrete.According to the American society for testing and materials(ASTM)and the relevant domestic test standard procedures,it can be concluded that the impervious performance of Glass Fiber Reinforced Concrete(GFRC)is well.The highest compressive strength of the GFRP occurred when fiber mixed content was 0.5%.The best flexural toughness and bending fracture energy appeared when fiber mixed content was 1.5%.When fiber mixed content was 0.5%,the rupture strength is biggest.Absorption shock energy rises significantly when fiber mixed content was in the range of 0.5%~1.3%.The change rule of flexural strength,fracture energy and fiber content was obtained by fitting regression curve equation.The SEM(Scanning Electron Microscope)and EDS(Energy Dispersive Spectrometer)microscopic test was conducted and the conclusion is that within the range of 0.5% to 1.0%,the fiber mortar concrete grout and the fiber package is fine and hydration product uniform fiber has no effect on concrete hydration reaction.Secondly,54 GFRP reinforcement concrete beams were conducted pre-splitting and sustained load processing.After that the beams were placed in the outdoor environment solution,water and strong alkali solution(PH=13).The exposed time is 90 days,180days and 360 days respectively.Four-point bending capacity experiment was carried out.The environmental effect rule of bearing capacity of GFRP reinforced concrete beam were obtained by the method of combining experiment with theoretical calculation.The corrosion damage in alkaline solution is the most significant in three kinds of environment effect.The bearing capacity and deflection decreases gradually,and the crack width decreases and the average crack spacing increases gradually along with the environmental degradation.The coefficient of environmental impact was introduced to amendment the average crack spacing.Meanwhile,the theoretical formula for calculating maximum crack width was corrected.The minimum reinforcement ratio and the balanced reinforcement ratio is raised with the environment effect,the change rule of compressive zone height environmental effect presents the downward trend,bending moment-curvature curve is the same as the deterioration of environment and gradually decline.With the energy method,the ductility coefficient was calculated in the cross section of GFRP reinforced concrete beam.It is concluded that the displacement ductility coefficient of environmental effect,the change rule of decline in short-term flexural rigidity as the environment deteriorates gradually rise.At the same time,Long-term deformation tendency about the environmental effect of GFRP reinforced concrete beam was forecasted.Through the method of fitting the related parameters of GFRP reinforced concrete beam and the impact coefficient of environment,the regression curve of equation about the corresponding change rule was concluded.Finally,the numerical simulation was conducted by finite element software ABAQUS to simulate the fiber content were 0.0%,0.5%,1.0% and 1.5% respectively.The constitutive model of axial tensile stress-strain curves,axial compression stressstrain curves and constitutive parameters is obtained by experiment.The bearing capacity of GFRP steel fiber reinforced concrete beams is best when the fiber content is 1.0%.The glass fiber amount was 0.5% ~ 1.0% of GFRP reinforced concrete beam can bear 60% load.Within the range,the fiber can serve as the role of "bridging",it can inhibit the development of the crack.But the "bridging" effect can disappear with the increased of load.Through the comparison between the simulation and experimental analysis,the results reflected that the GFRP reinforced concrete beam in the mixed with certain volume content of alkali glass fiber can effectively improve the bearing capacity and make up for the effects of environmental degradation. |
