Interaction Between Pallets and Pallet Beams of Steel Storage Racks in Seismic Areas

Steel storage racking systems are heavily loaded light structures that need special attention in design. The problems increase for racks in seismic regions, where the structure is subjected additionally to high lateral forces. This paper focuses on the seismic design of pallet beams in pallet racking systems and concentrates on three issues in order to verify or improve rules of European Codes on racks: (1) the horizontal seismic forces on the pallet beams, (2) the developing horizontal bending moments and (3) whether the buckling length of the beams on the horizontal plane may be reduced due to a potential diaphragmatic action, offered by the pallets. Investigations are based on theoretical and numerical analyses. It was found that opposite to the Code provisions the lateral seismic forces are not equal distributed between the pallet beams and, confirming field observations, that the forces directed towards the outside of the rack are higher compared to those directed towards the inner side. Concerning the horizontal bending moments appropriate correction coefficients were proposed that deviate from the codified values. Finally, it was found that pallet friction does not affect so much the buckling length to safely reduce its buckling length.