Hysteresis Performance of Through Bolted Connections in Steel Beam to Circular CFST Column

Abstract

Concrete Filled Steel Tubes (CFSTs) with through bolt connections are demonstrated to be satisfactory for seismic performance. Due to better confinement effect, circular CFST columns possess higher strength to weight ratio compared to square CFST. The only limiting factor in application of circular CFST in construction is the difficulty in joining with the beams. This paper presents an experimental study on hysteretic behavior of interior joint between circular CFST column and steel beam using extended end plates with through bolt. The study focuses on the comparison of connection using flat extended end plate with straight bolts and curved extended end plate with split bolt assembly for circular CFST columns. The experimental results were analysed in terms of strength, stiffness, ductility, failure mode and energy dissipation for the evaluation of cyclic performance. The results indicate that the seismic resistance agrees with seismic recommendations of American Institute of Steel Construction (AISC) and the split bolt assembly increases the performance remarkably. For comprehension of mechanism and prediction of shear capacity of the panel zone for curved endplates, a mathematical model was generated. This includes the influence of axial load, prestressing induced by bolt tightening, anchorage and the concrete strut action. The prediction accuracy was compared with the test result and it showed sound correlation.