Studies On Hysteretic Models For Partially Prestressed Concrete Flexural Members

Moment-curvature hysteretic models are proposed for different types of prestressed concrete members based on hysteresis curves obtained from cyclic loading tests. The research objectives in this paper are flexure dominating concrete members, which are inclusive of concrete members prestressed with steels, concrete members prestressed with CFRP bars and prestressed steel reinforced (SRC) concrete members. This paper focuses on the following details:(1) In review of existing experimental and theoretical researches, this paper summarizes hysteretic behaviors of the three types of prestressed concrete members under cyclic load reversals;(2) A stress-strain relationship under cyclic loading in consideration of damage for concrete is developed, which was incorporated into the ABAQUS FEM model to simulate skeleton curves of the three types of prestressed concrete members. Studies indicate that the analytical results agree well with the test results;(3) All skeleton curves for the three prestressed members can simplified as an unsymmetrical tri-linear model. Formulations for determining the characteristic points for the proposed skeleton curve model are deduced based on section plane assumptions.(4) The shape of hystersis curves of the steel prestressed concrete members and prestressed SRC members are mainly dependent on the hysteretic relationship of the steel under cyclic loading, which results pivot pinching points in hystersis loops of the two types of prestressed concrete members in reloading paths;(4) A pinching point and a negative stiffness turning point would occur in positive unloading and negative reloading paths for steel prestressed concrete members and CFRP prestressed concrete members due to the effect of prestressing tendons. Formulations for determining of the two points are proposed according to statistical evaluations.(5) Pinching is not apparent in hysteresis loops of the prestressed SRC members due to the effect of the encased steel. For this reason, unlading paths for prestressed...