Constitutive Model for HSC Confined by UHS and NS Transverse Reinforcements under Cyclic and Earthquake Loadings Stress
In this paper, a cyclic constitutive model is developed for high-strength concrete (HSC) confined by ultra-high-strength and normal-strength transverse reinforcements (UHSTR and NSTR), with the intention of providing efficient modeling for the member and structural behavior of HSC in seismic regions. The model for HSC subjected to monotonic and cyclic loading, comprises four components; an envelope curve (for monotonic, cyclic and earthquake loadings), an unloading curve, a reloading curve, and a tensile unloading curve. It explicitly accounts for the effects of concrete compressive strength, the volumetric ratio of transverse reinforcement, yield strength of ties, tie spacing, and tie pattern. The proposed envelope curve models for confined HSC cover four options; namely, (1) rectangular (square) cross section with NSTR, (2) circular cross section with NSTR, (3) rectangular (square) cross section with UHSTR, and (4) circular cross section with UHSTR. Comparisons with test results showed that the proposed model provides a good fitting to a wide range of experimental results. The configuration of transverse reinforcement had a particularly large effect.