HYSTERETIC RESISTANCE MECHANISM OF EXPOSED STEEL COLUMN BASES

Based on quasi-static test results of exposed columns, the lateral resistance mechanisms of the exposed columns under compressive or tensile axial loads are summarized. The method for predicting the yield moment, ultimate moment, and initial stiffness of exposed column bases under compressive or tensile axial loads is proposed; and the errors of the resulting predictions are within 10% of the experimental tests. A hysteretic model of exposed columns under compressive or tensile axial loads is proposed. Under compressive axial loads, the hysteresis curves of exposed column bases are "flag-shaped", and the backbone curve is simulated using a bilinear model without strain hardening. Under tensile axial loads, the resistance of exposed columns is reduced significantly, and the hysteresis is full. The backbone curve is simulated by an idealized elastic-plastic model which does not consider the strain hardening of the anchor rod. The hysteresis curves from the model agree well with the experimental results. The hysteretic model can represent the bending behavior of exposed column bases with different anchor rod arrangements well, and thus can be used to analyze the seismic performance of whole frames in future research.