Hysteretic behavior and modelling of ultra-high-strength steel bar including buckling.

The hysteretic capacity of reinforced concrete (RC) structures depends to a large extent on the hysteretic behavior of steel bar to sustain many cycles of high plastic deformations without obvious degradation of strength and stiffness. It is important to develop an accurate and computationally efficient model of steel bar in the nonlinear response analysis of RC structures subjected to cyclic loads. The high strength and ultra-high-strength (UHS, yield strength above 1000 MPa) steel bars are becoming more and more popular in concrete construction, which is beneficial for materials saving and reduction of steel bar congestion. In order to investigate the cyclic behaviors of UHS steel bars and to propose a hysteretic model for this kind of steel bars including buckling, a total of 54 specimens with nine slenderness ratios were carried out under compressive and cyclic loadings. The modified stress–strain curve model of UHS steel bars with different slenderness ratio was developed based on the experimental data, which can take buckling and fatigue-induced reduction of stress into account. This study offers a solid database for researches on the mechanical properties of UHS steel bars. And the proposed empirical model can easily be implemented in the finite element analysis of RC elements with UHS steel bars under cyclic loadings. [ABSTRACT FROM AUTHOR]