Ductility improvement of adjustable pallet rack speed-lock connections: Experimental study

Abstract This paper presents seismic cantilever monotonic and cyclic tests of speed-lock (boltless) beam-to-upright connections of adjustable pallet rack systems; the objective of the monotonic tests is to obtain the bounds that are employed to define the loading protocol of the subsequent cyclic tests. The beam-to-upright connections consist of welding the beam to an intermediate end-plate (L-shaped) that, in its turn, is linked to the upright through a hooked assembly. The performed experiments investigate the connections hysteretic behavior, as it contributes to the rack lateral strength, stiffness, and ductility. More precisely, the main objective of this research is to propose a new strengthened design of the weld beads geometric configuration. This design is oriented for the connection failure not to arise in the weld, but the hooked assembly. This shift is expected to increase the connection ductility; in this sense, specimens with traditional and novel weld geometric designs are tested. In most of the tests performed, the results confirm that the new weld design leads to more ductile failure modes; preliminary evaluations state that the ductility increase might be sufficient to absorb most of the input seismic energy. On the other hand, tests are conducted according to two loading protocols: the traditional one by following European regulations and a new strategy proposed by Prof. Castiglioni accounting for the influence of gravity loads. Comparison between their results shows that the Castiglioni approach is more demanding and seems to reproduce the actual seismic behavior of racks better.