Often times walking through the rack warehouse damage to frame bracing can be seen. Many believe that damage to bracing is not a problem if the columns are not damaged. This is not true. Damage to frame bracing can cause a rack frame to collapse even if the column seems to be undamaged. The column analysis relies on presence and structural contribution of the bracing.
In general a frame-beam rack structure has two very different structural systems that enable the rack to stand up and support the loads. In the down-aisle direction strength and stability are provided by the strength and stiffness of the column, the beams, the beam-to-column connections and the fixity of the base. This structural system is known as “semi-rigid” framing.
In the cross-aisle direction, strength and stability are provided by tension-compression strength of the frame bracing, the columns and also the anchorage. This structural system is known as “braced” framing. If a brace is damaged or lost for any reason the frame weldment can lose its integrity and ability to withstand cross-aisle force. This would be similar to a bridge truss with vertical or diagonal members removed. The bridge span strength would be compromised.
Part of any rack inspection should be to observe and report any damage to the bracing or their connections as well as column or beam damage. This damage should be repaired or the frames replaced. The safest warehouses utilize a regimented inspection program where all warehouse employees are trained to spot and report damage immediately. It is better to question whether a damaged brace has an impact on the racking system than to have damage go unreported and find out through a failure how important the structural integrity of the bracing is to the pallet rack as a whole.