Research & Abstract by Page Clayton, Virginia Tech, CPULD
This study aims to investigate pallet deflection as a result of different sized packages in a column stacking pattern and the presence of headspace in the box.
Pallets are the foundation of unit loads and supply chains. They provide a way to store and transport products in an efficient manner. Currently, however, the use of “component based” designs for unit loads doesn’t consider the interaction between unit load components or how this interaction effects the overall structural integrity of the unit load.
Component based unit load designs also result in the excessive use of raw materials which reduces the sustainability of unit loads, drives costs up, and creates issues for people in the supply chain.
The objective of this study was to investigate the interactions between the unit load components, box size and package head space, especially focusing on the deflection of the pallet as a function of pallet stiffness across multiple common pallet support conditions.
This study aimed to investigate pallet deflection as a result of different sized packages in a column stacking pattern and the presence of headspace in the box. The effect of each of these components on deflection is known as load bridging, in which a redistribution of stress occurs depending on the loads’ characteristics within the unit load.
Results showed that, in a column stacked arrangement, smaller boxes caused greater deflection than larger boxes (up to 53 % higher). Data analysis identified that a change in box size causes a decrease in the deflection of a pallet; smaller boxes, with the same load, transfer less pressure to the supports (31% less) and cause more deflection (53% more) than large boxes, especially on lower stiffness pallets. The presence, or lack, of headspace in a box didn’t have any significant impact on deflection.
This study confirmed that supported pallet components do, in fact, carry more of the weight of the load and that the boxes’ sizes do affect deflection. The experiments from this study confirm that the compressive pressure across the top of the pallet surface redistributes itself towards the supports of pallets when the sizes of the corrugated boxes increase. As more of the compressive forces redistribute across the top of the pallet to the supports, the deflection along the free span decreases.
These quantitative results can help to further understand the load bridging effect and allow us to make adjustments based on the current safety factors. Therefore, to increase the sustainability of pallets and to conserve resources, it is recommended that pallets are always designed with product packaging designs in mind.
Research funded by the Pallet Foundation of the NWPCA and by the U.S. Forest Service. Paper submitted to the IAPRI Peer Review Stream.