Fire Resistance of Steel Rack Frames: Assessment, Reinforcement and Collapse Mitigation Strategies

Steel rack frames are used to suitably store goods and products and are constructed by means the use of thin-walled cold-formed components. Their competitiveness on the market essentially depends on the total weight of the framed system. In fact, these structures allow for the storage of material that is hundreds or even thousands of times more expensive than the rack itself. Despite great efforts made on seismic and static design, limited attention has been given to the problem of fire design and to the robustness of such structures. No specific design rules or design procedures have been developed until now. Nowadays, the only way to protect these frames against fire is the use of active systems like sprinklers or controlled oxygen chambers. Unfortunately, these solutions cannot be always adopted and a suitable strategy that avoids the global structural collapse following a fire is still necessary. In this paper a parametric analysis is proposed to deeply understand the behavior of steel storage pallet racks against fire. In particular, starting from an existing rack configuration with nine bays and five storage levels, different fire scenarios were modeled by changing the fire position along the frame. Moreover, the progressive collapse of the rack is discussed, and a reinforcing strategy is proposed. Finally, an example of the application of a sprinkler system is discussed, showing the advantages and weaknesses of this solution.