Design Method Research On Head-On Cross-Section Capacities Of Concrete Members Reinforced With GFRP Bars

Glass fiber reinforced polymer (GFRP) materials have emerged as a practical alternative material for producing reinforcing bars for concrete structures, which can solve the problems such as difficultly incising traditional steel reinforced concrete supporting piles, complicated techniques and bad security when shield passed by the portal in shield shafts. GFRP reinforcing bars offer advantages over steel reinforcement in that GFRP bars are high tensile strength, nonmagnetic, non-corrosive, lightweight, low thermal and electric and easy incision. Due to other differences in the physical and mechanical behavior of GFRP materials versus steel, unique guidance on the engineering and construction of concrete structures reinforced with GFRP bars is needed, because GFRP bars are crisp materials with low elastic modulus, characterized by a linearly elastic stress-strain relationship until failure. Now there are only some experimental researches on concrete members reinforced with GFRP bars, but no GFRP reinforcement applications in our country.The paper is important components of design method of concrete supporting pile in shield shafts reinforced with GFRP bars in Chengdu Metro, and study the head-on cross-section capacity theory of GFRP bars concrete members based on tensile tests of GFRP bars, pullout tests between GFRP reinforcement and concrete, and members of GFRP bars concrete tests:1. The test is used to determine the tensile properties of GFRP bars, and tensile strength and modulus of GFRP bars are calculated on the basis probability statistics. Finally, standardization examination and how to sample GFRP bars are discussed.2. Pullout tests are conducted to test bond stress between GFRP reinforcement and concrete, and the factors that affect bond strength are studied. A safe, economical and logical calculating method of development length is applied based on statistic and regression results of the factors.3. GFRP concrete remembers and Reinforced Concrete remembers are tested, respectively, and their failture mechanics are different, but GFRP bars concrete beams and eccentric columns have the same failture models, which divided into two types, namely when reinforcement ratio less than balance reinforce ratio, the failure of the member is initiated by rupture of GFRP bar, for short tensile failure; when reinforcement ratio greater than balance reinforce ratio, the failure of the member is initiated by crushing of the concrete, for short compressive failure. The two types are crisp, but compressive failure is similar to the one of Reinforced Concrete remembers, with high capacity and greater deflection. So the failture of GFRP concrete remembers should be crushed. At the same time, the contribution of the reinforement ratio of GFRP is studied, and the capacity is higher by increasing the number.4. Head-on cross-section capacity of GFRP concrete remembers are analyzed in the course of loading, according to the assumptions of a plane section before loading remains plane after loading and internal force equilibrium. The simplified and applied methods for estimating the head-on cross-section ultimate capacities of remembers tested are presented based on compressive stress figure simplified equivalent rectangle stress figure. Comparisons between the ultimate capacity obtained from the theoretical analysis and that experimentally measured in the current investigation and elsewhere show good agreement. At the same time, the data of experiments and the mehods are validated by nonlinear finite element method.