Constitutive Laws of Consisting Materials and Load-Deformation Mechanism of Pre-stressed Concrete Members

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For predicting load-deformation relations of pre-stressed concrete flexural members, stress-strain relations of pre-stressing (PC) steels under cyclic loading, stress-strain characteristics of confined concrete subjected to shear force and flexural moment, and effects of bond between grout and PC steel on flexural performance of PC flexural members are investigated. Following main conclusions are obtained.1) The cyclic stress-strain models for PC steels using Menegotto-Pinto expression with variable of strain are proposed. The models estimate satisfactorily hysteretic curve of PC strand, stretched and low temperature annealed (blueing) PC bars and induction heating quenched PC bars of different strength and size under various type of cyclic loading, such as gradual increase strain cyclic loadings, random cyclic loadings etc..2) Uni-axial stress-strain characteristics of confined concrete subjected to constant shear force show smaller tangent modulus, smaller compressive strength and smaller strain at the strength, in the case of higher shear force level. Shear strain of confined concrete under constant shear force increase according to axial stress increment in the case of high compression force level.3) The equations to evaluate F value ( strain compatibility factor) for calculating accurately ultimate flexural strength of pre-stressed concrete members are proposed analytically. The F values are investigated with consideration of bond-slip characteristics between pre-stressing steel and grout, on block elements obtained by dividing the members along longitudinal direction. Employed parameters in the analysis are shape and diameter of pre-stressing steel, strength of grout and so on.