Seismic damage of SRC special shaped column frame joints based on modified Park-Ang model

To research the seismic damage assessment mechanism of SRC special shaped column frame joints, the modified Park-Ang seismic damage model was put forward by introducing the combination coefficient based on the mechanical characteristics of special shaped column structures, due to the poor numerical convergence and limited application scope of Park-Ang damage model. The calculation method of combination coefficient for SRC special shaped column frame joints was built according to the measured hysteresis data under low cyclic reversed loading, and the effects of test parameters on the damage evolution of specimens were analyzed. The results show that the damage index calculated by modified Park-Ang seismic model is close to 1.0 in the upper boundary of this model, it meets the numerical convergence better and it is more reasonable in theory. Under the loading angle of 45°, the damage level of T-shaped column 3D joints is the lowest, while the damage level of cross-shaped column 3D joints is on the contrary. Within certain limits, an increase of axial compressive ratio leads to delay the seismic damage of SRC special shaped column frame joints. There is no noticeable impact of shape steel configuration on the damage of planar joints; while for 3D joints, the damage level of the specimens configured with channel-shaped steel is higher than that of the specimens configured with T-shaped steel, and the damage level of the specimens configured with empty-web steel is higher than that of the specimens configured with solid-web steel. The damage degree of the specimens formed with L-shaped column is larger than that of the specimens formed with cross-shaped column, while the damage development and accumulation of the specimens formed with cross-shaped column is larger than that of the specimens formed with T-shaped column.