Monotonic and cyclic tests on beam-column joints of industrial pallet racks

Pallet racks are characterized by boltless beam-column connections and the extensive use of thin-walled cold-formed steel members. Due to the great number of beam-end connector types and member geometries, a reliable evaluation of their structural behavior, especially under seismic loads, requires a thorough modeling of beam-column joints, whose moment-rotation curves can be reliably assessed only through experimental tests. In this paper, the authors present results of monotonic and cyclic tests on four different types of industrial rack joints. Tested joints differ from one another in the type of beam-connector, which is obtained by folding the beam end or is welded to the beam-end section with different welding layouts. Moreover, joints differ in the number of tabs and the relative thickness of the upright and the beam-end connector. Experimental results from cyclic tests allows for moment-rotation curves of joints to be accurately identified, confirming that they are significantly different from traditional steel framed buildings due to pinching in hysteresis loops. Obtained curves can be used for reliable modeling of joints in seismic analyses of steel pallet racks. As producers of steel rack structures are interested in reducing the total welding length of beam-end connectors for time efficiency and cost saving, the influence of the welding layout of beam-end connectors on the structural response and failure mode of joints has also been investigated. Finally, some joints have also been equipped with additional bolts to evaluate their influence on the bearing capacity, initial elastic stiffness and dissipated energy per cycle.