Hysteretic behaviour of steel storage rack beam-to-upright boltless connections

Abstract The hysteretic behaviour of steel storage rack beam-to-upright connections is of great importance in predicting the seismic behaviour of a rack structure, because the connections not only provide the down-aisle stability of an unbraced rack structure but also serve as a key component contributing to the structural energy dissipation capacity. An experimental study was performed to investigate the hysteretic performance of boltless connections associated with cold-formed steel storage pallet racks. A total of sixteen individual cyclic tests were conducted including the specimens with different upright profiles, upright thicknesses, beam heights and tab numbers. In this paper, the deformation patterns and failure modes, rotational stiffness and moment resistance, ductility and energy dissipation capacity, reloading and unloading behaviour are presented and discussed. The influences of crucial geometric parameters on connections behaviour under cyclic reversal loads are also investigated. The results show that boltless connections, categorised as “semi-rigid” and “partial-strength” connections, exhibit good ductility, moderate energy dissipation capacity and severely pinched hysteresis loops. Moreover, the so-called Pinching4 model is employed to characterise the hysteretic behaviour of a boltless connection, and the associated model parameters are proposed based on the test data. The proposed model of the connection will be further used in the numerical simulation of cold-formed steel storage pallet racks subjected to seismic loads. As such, this study serves as a fundamental step towards developing the Direct Design Method (DDM) for rack structures.