STUDY ON RESILIENCE MODELS OF HIGH-STRENGTH CONCRETE FRAME COLUMNS

Based on the experimental results of 108 high-strength concrete frame columns under constant axial loading and horizontal cyclic loading, the relationships among the horizontal projective length of strengthened portions, the ratios of maximum loads to yielding loads, the various rigidities of testing columns and shear span-to-depth ratios, the axial compression ratios, the transverse reinforcement characteristic values, and the ratios of gross cross-section areas to confined core concrete areas are analyzed and regressed. The horizontal displacements and loads at column tops are deduced according to the equilibrium conditions on the cross-section at yield. The lateral maximum loads at column tops are calculated according to the current Chinese concrete code. Regressive formulas are then used to establish the resilience models of high-strength concrete frame columns. The main results show that the ratios of the horizontal projective length of strengthened portions to the yielding displacements are directly proportional to the transverse reinforcement characteristic values and inversely proportional to the axial compression ratios, shear span-depth ratios and the ratios of gross cross-section areas to confined core concrete areas; the elastic rigidities, stiffened rigidities and degraded rigidities of specimens change proportionally with axial compression ratios and the ratios of gross cross-section areas to confined core concrete areas and change inversely with the transverse reinforcement characteristic values and shear span-depth ratios; the resilience models of high-strength concrete frame columns proposed consider various influential factors and are close to the experimental results and can be conveniently applied for practical purpose.