A practical design of cold-formed steel bolted moment connection: numerical investigation with an improved bolt slip-bearing model

Abstract

Cold-formed steel (CFS) is in the spotlight as a structural material for buildings and civil infrastructures because it is easy to produce and is cost effective. Recent studies have advanced the popularity and usability of CFS even more by showing its potential as a structural member suitable for special moment-resisting structures. Within the framework of those studies, CFS bolted moment-resisting connections allow the through-plate to protrude beyond the beam depth in both the upper and lower directions, like wings, which could hamper placing decks on the beams. This study proposes a modification to such through-plates, in which one protruded portion is eliminated and the depth of the other is extended instead in order to enhance the practicality in field applications. Finite element analysis is used to investigate and verify the proposed design candidates and finally, suggest an optimum design configuration. Since the bolted connection has a significant impact on the structural response of the CFS beam, an improved bolt modeling approach is suggested based on the bolt modeling approaches proposed by past researchers. The suggested bolt modeling approach is shown to provide better accuracy in simulating plastic deformations in the bolted connection area and the consequent failure behavior when compared to the existing approach. The numerical analysis results show that the through-plate with one wing-side cut should have the depth of the other wing-side such that the diagonal edge could make an angle larger than 35 degrees. To prevent the possibility of buckling in the changed through-plate, attaching the flange plate perpendicular to the diagonal edge is highly recommended. The findings from this study are expected to provide a guidance for the through-plate design in practical structure design. • A practical design for through-plate in CFS bolted connections is suggested. • Modeling approach for bolted connections based on measured torque is proposed. • In modeling of bolted connection, effect of rotational constraint is critical. • Significance of bolt slip-bearing mechanism included in bolt modeling is emphasized.