Experimental Study On Uniaxial Elastic-plastic Damage Constitutive Model Of Stirrups Confined Concrete

Although the improvement of concrete strength and ductility under theeffect of stirrup restraint is concentrated on, and unloading and reloadingstress-strain model for confined concrete is proposed by cyclic loading tests, thedamage degradation behavior and quantitative description of stirrup confinedconcrete is less researched. In this article, a series of compressive loading testson reinforced concrete specimens were conducted in order to determine the effectof the volume stirrup ratio, concrete strength, stirrup yield strength on thedamage degradation behavior of confined concrete. Based on existing damagedeterioration equation, a new damage deterioration equation under the effect ofstirrup restraint was established, and elastic-plastic damage constitutive modelwas presented.By the displacement control, monotonic loading and equal strain unloadingand reloading tests were conducted in the MTS electro-hydraulic servo system toanalyze the damage degradation behavior, relationship of plastic deformation andimprovement of concrete strength and ductility under the effect of stirruprestraint.Based on the test results, the relationship of monotonic loading stress-straincurve and envelope of unloading and reloading stress-strain curve is discussed,and the influence on concrete strength and ductility is analyzed. The damagevariable of concrete is defined by the degradation of concrete elastic modulus,and the influence of the volume stirrup ratio, concrete strength, stirrup yieldstrength on the damage degradation behavior of confined concrete is analyzed.The plastic deformation relationship of stirrup confined concrete is fitted bythe experimental data, and based on existing damage deterioration equation, thedamage constraint factor is introduced and its function is determined. In the end,the damage deterioration equation and elastic-plastic damage constitutive modelof stirrup confined concrete are proposed. The proposed damage deteriorationequation and elastic-plastic damage constitutive model are compared to the testresults. The comparison shows that the proposed damage deterioration equationand elastic-plastic damage constitutive model provides good agreement with the test results.