Experimental and analytical investigation on seismic behavior of Q690 circular high‐strength concrete‐filled thin‐walled steel tubular columns

Abstract

This paper proposed a new Q690 circular high-strength concrete-filled thin-walled steel tubular (HCFTST) column comprising an ultrahigh-strength steel tube (yield strength f y ≥ 690 MPa). A quasi-static cyclic loading test was conducted to examine the seismic behavior, and the obtained lateral load-displacement hysteresis curves, skeleton curves, and ductility were analyzed in detail. Then, a numerical model based on a nonlinear fiber beam-column element incorporating the modified uniaxial cyclic constitutive laws for concrete and steel was developed mainly to predict the seismic behavior of the tested Q690 circular HCFTST columns. The effects of the concrete cylinder compressive strength ( f c ), steel yield strength ( f y ), axial compression ratio (n), and diameter-to-thickness (D/t) ratio on the seismic behavior were investigated through a parametric study. Finally, a simplified hysteretic model incorporating the moment-resisting capacity and deterioration of the unloading stiffness in addition to a normalized skeleton curve and hysteretic criterion was established. The results indicate the following: the proposed Q690 circular HCFTST columns can display reasonable hysteretic behaviors to some extent; the use of high-strength steel can lead to a significantly larger elasto-plastic deformation capacity and delay the appearance of post-peak behavior, even if a lower ductility capacity is provided; moderately loosening the limitations on the D/t ratio can also result in ideal hysteretic behaviors; and the established numerical model and simplified hysteretic model can satisfactorily predict the experimentally observed load-displacement hysteretic curves, including the deterioration of the strength and stiffness and can, thus, offer design references for the elasto-plastic analysis of circular HCFTST columns. KEYWORDS deteriorating behavior, modified uniaxial cyclic constitutive model, nonlinear fiber element method, Q690 circular high-strength concrete-filled thin-walled steel tubular (HCFTST) columns, seismic behavior, simplified hysteretic model

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