Study on Seismic Behavior of High-Strength Concrete Columns with Different Strength Stirrups

To investigate the influence of stirrup strength on the seismic performance of high-strength concrete (HSC) columns reinforced with high-strength longitudinal bars, this paper selects 2 existing experimental specimens as the basis for numerical model validation and establishes 16 numerical specimens with concrete strength ranging from C50 to C80 and stirrup strength ranging from 300 MPa to 800 MPa (longitudinal bar strength fixed at 600 MPa). Low-cycle cyclic loading simulations are conducted using the finite element software OpenSees 3.8.0 to verify the reliability of the fiber beam-column model. On this basis, parametric analysis is carried out to reveal the effects of concrete strength and stirrup strength on the hysteretic curve, skeleton curve, ductility, and energy dissipation capacity of the columns. Different from previous studies that mainly focused on single strength matching cases, this study quantitatively explores the compatibility matching relationship between stirrup strength and HSC and proposes a quantitative selection method for stirrup strength. The results show that the hysteresis curves of all specimens are generally spindle-shaped and relatively full, with good energy dissipation capacity. The skeleton curves show little difference before the peak load; after the peak load, the bearing capacity improvement is more significant with the increase of stirrup strength, especially for C70 and higher-a strength concrete. Stirrups with strength of 600 MPa and above can significantly improve the ultimate energy dissipation capacity of HSC columns with strength grades from C50 to C70. When the strength matching coefficient ξ (defined as ten times the ratio of the stirrup yield strength to the standard compressive strength of concrete) is 12 ± 2, the specimens can satisfy the bearing capacity requirement and maintain very good ductility.