Experimental study on concrete filled circular steel tubular column to steel beam composite frames

This paper describes six composite frame tests carried out on steel beam to concrete filled steel tubular (CFST) circular columns using external ring. The frame specimens were tested under a constant axial load and a cyclically increasing lateral load. Each test frame specimen consisted of two CFST columns and a steel beam segments to represent an interior frame in a building. The main test parameters included the axial load level and the beam to column linear stiffness ratio. This paper presents an analysis of the experimental results to evaluate the influences of different testing parameters on various characteristics of the composite frame performance. The test results show that the lateral load versus lateral displacement hysteretic curves of the composite frame were plump shuttle shape. The curves have no obvious strength deterioration and stiffness degradation. It was found that the composite frames exhibited high levels of energy dissipation and ductility. The initial lateral rigidity and the equivalent damping coefficient of the frame was almost unchanged within the current limitation of axial load level. The axial load level of columns have a evident effect for the strength and seismic performance of the frames, and with increase of axial load level of columns, the lateral ultimate strength of the frames become low, and the ductility and the capacity of energy dissipation also become descending.