STUDY ON DAMAGE-BASED RESTORING FORCE MODEL OF STEEL REINFORCED CONCRETE SPECIAL-SHAPED COLUMNS

Based on the experimental results of 16 solid-web steel reinforced concrete (SRC) special-shaped columns under low cyclic reversed loading, the hysteretic performance and damage-based restoring force model of the column were investigated. A composite skeleton model, including the ascent stage consisting of two straight lines and the decent stage in the form of exponential function, was put forward. The calculating method for the characteristic value of skeleton curve with different section forms, axial compression ratios and steel ratios was proposed by using theoretical derivation and regression fitting. Considering the influence of second-order moment effect, lateral stiffness due to axial compression, strength degradation, Bauschinger effect and loading history, the unloading stiffness degradation law of the hysteresis hoops of special-shaped column was proposed quantitatively by means of introducing the damage model based on experimental results fitting; and then the corresponding restoring force model was established. The results show good seismic performance of specimens with shuttle-shaped hysteresis curves. All hysteretic hoops under different loading cycles roughly pass two common points. According to the theoretical derivation and considering the influences of various parameters, the damage-based restoring force model of SRC special-shaped column was established, of which the calculated results agree well with the experimental results. It can provide basis for the nonlinear seismic response analysis of SRC special-shaped column structures.