Study On Flexural Perfomance Of ECC-RC Composite Beams Reinforced With High-strength Reinforcement

Traditional concrete materials have the disadvantages of low tensile properties,poor toughness and difficult control of crack width after cracking.If it is applied to structures or components in abominable environments,such as bridges,seaport wharves and dams,these structures or components will have serious durability problems.The appearance of high performance fiber reinforced cement matrix composites(Engineered Cementitious Composites,referred to as ECC)has changed this situation.This is a new type of building material with the characteristics of false strain hardening and multiple slit cracking,showing very significant nonlinear deformation and excellent toughness.When the volume of fiber is not more than 2%,the ultimate tensile strain can reach more than 2%,and there will be a lot of thin cracks whose widths are less than 100um during the whole drawing process.The tensile strain hardening behavior of the material is caused by the multiple cracks in this case.Nowadays,with the introduction of high-strength reinforcing bar into the field of vision,people have begun to popularize high-strength reinforcing bar vigorously.In practical engineering,the use of this material can solve the problems of the structure durability and deformation ability of modern concrete components and structures.In this paper,by adopting the method of combination of theoretical and experimental research,the high strength reinforced flexural performance of ECC-RC composite beam:In this paper,the domestic PVA fiber reinforced cement matrix composites are used as the research object,and the commonly used flexural members are used as the research carrier,and combined with the existing research results at home and abroad,the following three parts have been completed.(1)On the basis of the original theoretical results of the project group,taking the thickness of ECC layer,the interface treatment mode and the reinforcement ratio of the longitudinal reinforced bar as the variables,the 22 ECC-RC composite beams are poured at the three equal point bending test,and the stress process and deformation characteristics of the normal section under the static load of this type are studied,and the load displacement is analyzed and the load displacement is analyzed.The curve,and the force on the process and influence factors of the specimen were analyzed in detail.The stress and strain curves of longitudinal tensile steel bars are depicted,the cracking moment and ultimate bending moment of 18 ECC-RC composite beams are recorded,the maximum crack width,the average crack spacing and the average crack width under normal use are recorded,and the comparison analysis is made with the ordinary concrete beams.The conclusion is that under the same load,The maximum crack width of the reinforced ECC-RC composite beam is less than that of the ordinary concrete beam,the average crack spacing and the average crack width are less than that of the ordinary concrete beams.(2)Under the assumption of the plain cross-section,the coordination of the steel bar and the ECC deformation and the complete bonding of the concrete layer to the ECC layer,based on the elastoplastic theory,the bearing capacity of the normal section of the ECC-RC composite beams at different stages of the whole loading process is analyzed in detail,and the internal forces of the various stages of the bending are given.The bending failure mode of the component is analyzed,the calculation formula of bearing capacity,the calculation method of balancing the ratio of reinforcement and the minimum reinforcement ratio are obtained according to the effect of the existing theory of PVA fiber.(3)Considering the contribution of fiber to the number and width of cracks,the development law of component cracks is expounded,the distribution characteristics of cracks are obtained,and the fracture morphology of ECC-RC composite beams and ordinary concrete beams is compared,and the principle of fiber resistance is explained.Figure ECC-RC depicts the fracture distribution of composite beams,and the correction formula proposed by Chinese code for calculating crack width.Comparative analysis of experimental and numerical value calculated by the modified formula,the feasibility of modified formula.