Study On ECC Mechanical Properties And Bending Performance Of Concrete Composite Beams Reinforced With Steel Bars Or FRP Bars

Reinforced concrete structure crack phenomenon is common, and susceptible to corrosion with the increase of the crack’s width, that will damage under normal load. Destruction of FRP reinforced concrete structure is brittle failure, its energy performance less than reinforced concrete structure, and has large crack width and deflection deformation. In order to solve those problems of the reinforced concrete and FRP reinforced concrete, using ECC to improve them. Specifically, to replace the tension zone concrete with ECC, using the good crack control ability of ECC to solve problems of reinforced concrete structures corroded easily and FRP reinforced concrete structure has large crack and deflection deformation.In order to produce engineered cementitious composites, solve the problem of fiber balling and ensure the phenomenon of strain hardening and multiple fractures occur in the tensile test, the method of adding silica fume and using integral casting to protect fiber dispersion are proposed. Tests of tensile specimens with three different kinds and compressive strengths of some mix proportion were analyzed. The results show that silica fume can solve the problem of fiber balling better; Integral cast has advantageous to the occur of strain-hardening and multiple-cracks; Compressive strength decreases with the increasing of water-cement ratio or cement content (fly ash content increases); Strain hardening phenomenon all occurs in the tensile tests of three kinds specimens.To solve the failure or damage caused by steel bar concrete structure durability of the concrete structure corrosion, using ECC replace concrete and FRP tendons concrete replace steel bar to prevent corrosive substances into the concrete, control the crack width, prevents the steel corrosion. By comparing the Stee1/FRP bars concrete beams, Steel/FRP bars composite beams, Steel/FRP bars ECC beams, verified plane section assumption, strain compatibility, and the experimental study was carried out on cracking load, yield load, ultimate load, crack development and ductility. Verified the advantages of ECC replace concrete. Analyzed replace high rate with ECC for the improvement of reinforced/FRP reinforcement beam.With reference to theory of reinforced concrete, on the basis of simplifying the ECC tensile constitutive, compression constitutive and flat section assumption and strain coordination, established ECC bending specimen calculation model. On the whole loading process centre sill change of stress and strain are discussed in this paper, the bending normal section crack load and yield load, limit load analysis method and the derivation of optimum reinforced specimen is given. And curvature, deflection, ductility and ECC best replace height, etc.Provides a new type of structural form for the structure durability of high structure, and provides the design theory for its popularization and application, laid a theoretical foundation for new material design and application of the composite structure. Finally through comparing with the test results, verify the rationality of theoretical analysis.