The Effect of Stringer Repair Methods and Repair Frequency on the Performance of Gma-style 48x40-inch Wood Pallets

Over 135 million wood pallets were repaired for reuse in 1995. One of the most commonly damaged components in a wood pallet is the notched stringer. Metal plates, half companion stringers, and full companion stringers are repair methods described in the U.S. industry standard published by the American Society of Mechanical Engineers. This study evaluated the effect of these three stringer repair methods on the bending strength and stiffness of 48x40-inch GMA-style pallets spanning the pallet stringers. Pallets with up to 2 stringers repaired with full-companion stringers were stronger and stiffer than new, undamaged pallets. In general, pallets with one or two repaired stringers using up to 2 metal plate or half-companion stringer repairs were as strong or stronger, but less stiff, than the original pallets without stringer repair. However, on average, pallets with 2 stringers repaired with metal plates or half-companions were less strong and stiff than pallets with only 1 such repair. These results indicate that all three repair practices (metal plates, half-companions, and full companions), when properly applied, will restore pallet strength when used to repair one notch on one or two stringers of a 48x40-inch partial 4-way, 3-stringer pallet. Moreover, there may be an additional species effect on repair performance that warrants further evaluation. Current repaired pallet grades group metal plate repairs in upper grades, while companion member repairs are placed in lower grades. These grades, based on functionality with material handling equipment, do not reflect the racking performance of these repair methods.