Behaviour of bolted end-plate connections to concrete-filled steel columns

This research aims to investigate the cyclic behaviour of composite joints consisting of concrete-filled steel tubular (CFST) columns, steel beams, and through-bolt connections. A total of 10 specimens, including 5 specimens with square CFST columns and 5 specimens with circular CFST columns, were tested under lateral cyclic loading with horizontal displacements imposed at the top of the column. The main experimental parameters were the cross-sectional type of the column, the axial load level in the column and the cross-sectional configuration of the beam. The experimental results are analysed in this paper to evaluate the performance of the through-bolt connections. Based on numerical analysis, the performance of the bolted joint is further compared with that of the counterpart with external diaphragm. In general, the initial stiffness of the bolted end-plate CFST connections investigated is greater than 8EIb/Lb, so a fixed connection can be assumed in modelling non-sway frames. However, the connection rotation in unbraced frames may need to be considered to minimise the modelling error since the initial connection stiffness is usually smaller than 25EIb/Lb.