Unit
Load - "A single item, a number of items, or bulk material
which is arranged and restrained so that the load can be stored,
picked up, and moved between two locations as a single mass."
(Tanchoco)
Development of a Reliability-Based
Design Procedure for Wood Pallets
Joseph R. Lofereski and Thomas E. McLain
Pallets are widely used to store
and handle goods and are often subjected to bending and impact loads. Their
Productions annually consumes 20 percent of the lumber manufactured in the
United States. The consequences of structural failure of a loaded pallet can
include loss of goods, increased labor and equipment costs, and possibly severe
or fatal injury to workers. This paper discusses a methodology to design pallets
for strength, stiffness, and durability that was developed by a joint university-industry-government
task group. Simplified structural analysis models were empirically and theoretically
verified. The procedure uses a classical beam theory and matrix structural
analysis techniques to analyze pallets in four general support modes and loaded
with five types of loads. Material properties are estimated by modifying cleat
wood properties, similar to ASTM D-245, and from in-grade testing of pallet
lumber. A reliability-based procedure was used to account for load and resistance
variability and to provide safety in the resulting designs. The design methodology
was computerized for common microcomputers and can be used by manufacturers
and pallet users.
