1. INTRODUCTION
Although several studies on the structural performance of concrete filled steel tubular (CFT) columns and steel beam-to-concrete filled tube (CFT) connections have been reported, the structural performance of rectangular CFT columns has not been clarified yet.
Herein, seismic behaviors of the rectangular CFT connections were investigated to evaluate their stiffness, shear strength, and hysteresis characteristics. This paper summarizes the test results and discusses the approach to evaluate the structural characteristics, such as yield and ultimate strength, required in the structural design practice, as well as the hysteresis characteristics of the CFT connections. In addition, the paper presents analytical models for representing the hysteretic behaviors of the CFT connections.
2. TEST PROGRAM
Eight specimens were tested to investigate the effects of the sectional shape on the seismic behaviors of the CFT connections.
3. TEST RESULTS AND DISCUSSION
All specimens showed very ductile and stable spindle-shaped hysteresis loops. The brittle failure was not significant during testing.
4. STRUCTURAL PERFORMANCE OF RECTANGULAR CFT PANELS
The shear strength was calculated according to the design formula of the Architectural Institute of Japan (AIJ). The maximum strengths of all specimens were larger than the calculated shear strengths. It is understood that the experimental shear strength values fairly agreed with the calculated strengths. The skeleton curve of the shear-rotation angle relation of the CFT connections can be expressed using the tri-linear skeleton model.
5. CONCLUSIONS
The following findings were obtained from the structural experiments simulating a rectangular CFT column-steel beam connection.
1) The rectangular CFT connection had an excellent deformation capacity and showed stable behavior up to large deformation.
2) A simple numerical simulation demonstrated the impact of the difference in the cross-sectional shape on the shear behavior.
3) The shear resistance of the rectangular CFT connection could be appropriately evaluated using design formulas (1) to (5) and formula (6)’.
4) The restoring force characteristics of the rectangular CFT connection could be appropriately evaluated by estimating sk in design equations (7) to (8) using equations (10) and (11).
