Monotonic and Cyclic Response of Strengthened Dry Joints in Steel Pallet Racks

This contribution reports an experimental study on strengthening measures for dry-joint connections in cold-formed steel storage racks, focusing on their down-aisle seismic response. Conventional rack joints often represent a critical vulnerability under earthquake loading; this work therefore investigates practical, industry-feasible retrofit options intended to improve robustness and structural reliability. A test programme on full-scale specimens was carried out under both monotonic and cyclic loading, comparing the unreinforced joint with four bracket-based strengthening configurations (R1–R4), differing in bracket thickness (3 or 5 mm) and fastening system (M12 bolts or M6 self-drilling screws). Relative to the unreinforced joint, all four solutions increased the secant rotational stiffness (by 37–56%) and the peak moment (by 32–41%). Under cyclic loading, the bolted configurations (R2, R4) proved markedly more effective at dissipating energy, with increases of 212% and 205% respectively, against 82% and 148% for the screw-fastened ones (R1, R3). The discussion addresses the governing deformation mechanisms and failure modes, showing that the brackets provide a redundant load path that activates once the beam-to-connector weld fails. Overall, the findings provide actionable, quantitative insight for the seismic design and retrofit of cold-formed steel rack systems, supporting safer and more reliable storage installations in seismic regions.