Effects of loading patterns on seismic behavior of CHS KK-connections under out-of-plane bending

This paper deals with experimental investigations to study the seismic behavior of circular hollow section (CHS) KK-connections used in steel tubular structures. Cyclic out-of-plane bending (OPB) loading patterns were varied in testing two full-scale specimens in order to evaluate their effect on connection behavior. Test results indicated that the strength efficiency of these connections significantly depended on the loading patterns. CHS KK-connections under alternate opening and closing out-of-plane bending (AOCO) developed more satisfactory levels of ductility and energy dissipation than that under alternate clockwise aligned and counter-clockwise aligned out-of-plane bending (ACCO), although the final failure modes for both showed similar fracture initiated from the chord wall. This observation was further verified by the proposed simplified analytical model results. Finite element (FE) analyses were performed to simulate the experimental behavior and facilitate the interpretation of the important test observations. Additionally, it was found that the energy dissipation due to the ductile chord crack propagation could be utilized effectively to some extent for earthquake resistance.

► Seismic behavior of CHS KK-connections was experimentally investigated. ► Strength efficiency of KK-connections significantly depended on loading patterns. ► AOCO loading led to better ductility and energy dissipation than ACCO loading. ► Final failure modes showed similar fracture initiated from the chord wall. ► Energy dissipation due to ductile crack propagation can be favorably utilized.