On the seismic response of steel storage pallet racks with selective addition of bolted joints

Experimental tests on rack joints have shown that the cyclic response of beam-to-column joints, which in steel storage pallet racks is usually affected by pronounced pinching, could be significantly improved if joints are equipped with bolts. Bolts allow for ultimate moment, ductility, and dissipated energy of joints to be increased. Nevertheless, their installation in all joints of a rack system would be uneconomical and would nullify advantages of traditional boltless dry connections, which allow for beams to be easily disconnected if a new corridor or free space is required. The selective addition of bolted joints and its influence of the seismic response of rack systems is the focus of the manuscript. Different layouts of rack systems, with bolted connections only in some specific positions, are studied and compared. The addition of bolted connections improves the serviceability behavior, as the displacements of the system are reduced. Concerning the seismic capacity, the beneficial effect of bolted connections is appreciable only if seismic actions are sufficiently high and connections undergo plastic deformation. Configurations with bolted connections located only at the lowest levels allow to achieve a similar structural performance of a fully bolted configuration, saving the cost of the structure.