Shake Table Study of Dynamic Characteristics of a Typical Pallet Racking System

Industrial pallet racking system was the commonly used structure for storing palletized goods. They were built up from thin-walled cold-formed steel profiles. The upright (column of the rack) has perforations which ensure the typical functionality, adaptability and flexibility needed for accommodating the variability of dimensions of the stored goods. Connections were custom made, where in the beams were generally hooked on to the upright. These connections were significantly semi-rigid in behaviour. The complexity associated with the nonlinear moment-rotation behaviour of the joints in the design of cold-formed steel structure was to be accounted for a realistic capacity estimation. These racks when installed in seismic prone zones must be qualified for different levels of safety such as collapse prevention and immediate occupancy. To assess these performance levels, static and shake table tests were performed on full-scale racking system simulating earthquake conditions. An attempt has been made to quantify the dynamic behaviour of the structure based on the experimental results of both static and dynamic shake table tests. Based on the test results, it was seen that the requirements with respect to performance levels specified by FEMA 460 were met by the structures. With respect to the behaviour of the pallet under severe dynamic excitation, it was observed that the wooden pallets did not have relative body motion and were vibrating integrally with the structure. Therefore, in a full-scale test, the relative performance of pallet/rack system could be quantified for the first time.