Flexural behaviour of steel storage rack beam-to-upright bolted connections

Steel storage pallet racks are usually unbraced in the down-aisle direction in order to make palletised goods always accessible. The down-aisle stability of unbraced rack structures mainly depends on the performance of beam-to-upright connections and column bases. Beam-to-upright boltless connections are commonly employed for their convenience in assembly and adjustment. Since storage racks are being designed to considerable heights for the purpose of improving warehouse efficiency, steel storage rack beam-to-upright bolted connections are gradually being introduced to improve the structural stability. The paper presents an experimental investigation into the flexural behaviour of beam-to-upright bolted connections of steel storage pallet racks. A total of twenty-one specimens were tested under monotonic loading in a single cantilever test setup, including three different size pallet beams, three different upright thicknesses, and beam-end-connectors with two or three tabs. This study examines deformation patterns and failure modes of the connections, their rotational stiffness, moment resistance and corresponding connection rotations. The results show that steel storage rack beam-to-upright bolted connections, classified as “semi-rigid” and “partial-strength” connections, generally experience ductile failure modes. The effects of critical geometric parameters, i.e. upright thickness, beam height and the number of tabs, on the flexural behaviour of bolted connections are also investigated. In addition, comparisons of performance and failure modes between bolted and boltless connections are made. Moreover, in order to promote the design by advanced analysis of rack structures, a preliminary theoretical model based on the Component Method is proposed to predict the initial rotational stiffness of beam-to-upright bolted connections in steel storage pallet racks. A good agreement is obtained between the initial rotational stiffness derived from the theoretical model and the experimental tests.