Stiffness and resistance of brace-to-upright joints with lipped channel braces assembled flange-to-flange

Industrial cold-formed steel pallet racks are constructed of upright frames bolted to braces in the cross-aisle direction. The flexibility and resistance of these brace-to-upright joints play a key role in the structural behavior of pallet racks in the cross-aisle direction. In this paper, the behavior of these joints has been evaluated through monotonic and cyclic experimental tests to determine the dominant failure modes and the stiffness. The resultant cyclic structural response is pinched, which suggests that upright frame connections are non-dissipative. An analytical model based on the Component Method has been developed to evaluate the ultimate resistance and the flexibility of these bolted connections, with braces oriented flange-to-flange. The model is capable of identifying the influence of each component on the connection structural response. A comparison with results obtained by a Finite Element numerical model, typically used in common practice, in which members are modelled by elastic frame elements and connections are assumed rigid is conducted. The numerical model overestimates the effective stiffness by nearly 14 times. The same model, when modified with a linear link with a force-displacement response determined from the analytical model, provides reliable results in agreement with the experiments. The developed modelling approach is recommended for adoption by practitioners for the design of steel storage pallet racks.