Recent development on the seismic devices for steel storage structures

Goods and products are stored in framed systems, such as pallet racks, used for industrial and commercial activities. In the last years, pallet rack code provisions for seismic loads have been significantly improved, but there are still relevant aspects that need attention for guaranteeing a safer structural design. For example, in the current European and American standards, no indications are given about the seismic isolation systems applied to these structures. Only two ways to enhance the performance of racks in seismic zones are reported: rack netting and structural strengthening. Both methodologies present logistic and technical problems. For this reason, researchers are investigating more efficient solutions, like the base isolation systems. An accurate isolation system can bring benefits in terms of reduction of the structural damage and improving the safety of the stored items. Since the cost of the structural frame is often negligible, with respect to the cost of the stored products, avoiding the overturning of merchandise is an important challenge. Moreover, falling pallets can bring to the overall global collapse due to an impact given on beams or columns. In the paper, a critical overview of base isolation systems developed for different steel storage rack typologies is presented and discussed, highlighting the main characteristics and the advantages associated with their use in practical cases. Furthermore, four different applications of energy dissipation devices are briefly discussed, comparing these systems with the previously introduced devices.