A MODEL FOR PREDICTING MOMENT-CURVATURE BEHAVIOR OF SELF-STRESSING SSACFST COLUMNS UNDER LOW CYCLIC LOADING

This paper reports the experimental investigation and theoretical model of self-stressing steel slag aggregate concrete-filled steel tubular (SSACFST) columns under low cyclic loading. Fourteen specimens including ten self-stressing SSACFST columns and four ordinary SSACFST columns (reference columns) are tested, and the effects of four experimental variables, such as axial compression ratio (n), diameter-thickness ratio (D/ts), shear-span ratio ( ), and expansion rate (Pct ) of steel slag aggregate concrete (SSAC) on failure mode, moment-curvature hysteretic curves and skeleton curves are examined. Experimental results demonstrate that the failure mode of columns with high shear-span ratio is bending failure while the bending-shear failure dominates the damage of columns with low shear-span ratio. With the enhancement of axial compression ratio or expansion rate of SSAC, the peak moment of specimens increases. The increase of shear-span ratio or diameter-thickness ratio decreases the peak moment of specimens. The peak curvature of specimens decreases as axial compression ratio increases, while it increases as shear-span ratio increases. The impacts of diameter-thickness ratio and expansion rate of SSAC on peak curvature of specimens are marginal. A simplified calculation method of moment-curvature skeleton curves is suggested and the hysteresis rules of self-stressing SSACFST columns are also proposed by analyzing the features of hysteretic curves. Ultimately, a model for evaluating moment-curvature behavior of self-stressing SSACFST columns under low cyclic loading is established and validated the experimental results with good agreement.