Mechanical performance of column-column joints in ultra-low energy modular wall prefabricated building system

Abstract

This paper proposes a column-to-column connection for cold-formed, thin-walled steel-concrete composite columns in ultra-low energy modular wall prefabricated building system. The study investigates the effects of two parameters—section type and concrete confinement—through low-cycle reversed loading tests conducted on four sets of full-scale column-to-column connection specimens. The experimental results revealed the following findings: For cases without unconfined concrete, the failure modes in I-shaped column (I-S) and L-shaped column (L-S) structures were caused by excessive deformation of the steel section at the column base. In contrast, for cases with concrete, the failure modes of the I-shaped column (I-C) and L-shaped column (L-C) specimens involved concrete spalling at the column base and internal buckling of the steel section. Notably, the I-C specimen showed no significant damage at the column-to-column joint when the column failed, while the L-C joint failure occurred after the column base failure. With the same concrete parameters, the I-shaped column exhibited better load-bearing capacity and ductility when compared to the L-shaped column. Based on the experiments, a refined finite element model was developed, and a parametric analysis was performed. The influence of axial compression ratio, concrete strength, steel thickness, and connection plate thickness on structural load-bearing capacity and ductility was examined. The recommended ranges for these parameters are as follows: the axial compression ratio should not exceed 0.3; the concrete strength should be at least C30; the cold-formed thin-walled steel thickness should not be less than 1.8 mm; and connection plate thickness should not be less than 10 mm.