Strength and Stiffness Analysis of Notched, Green Oak Pallet Stringers.
Forest Service research paper,
FOREST PRODUCTS LAB MADISON WI
Pagination or Media Count:
Although 5.4 billion board feet of lumber was converted to 258 million pallets in 1980, design information for notched pallet stringers is limited. In this report, methodology is developed that determines stiffness and strength reductions caused by notches in pallet stringers. A finite element FE structural model is developed to model notched stringers. Displacement and stress predictions agree well with experimental measurements. The author derived closed form equations that approximate FE displacements and maximum stresses as functions of notch depth. The stiffness equations are based on modeling the stringer with beam elements of an equivalent geometry. The stiffnesses and strengths of 600 full-size, green oak, pallet stringers with various notch geometries and loading conditions were measured. Measured deflections agreed well with stiffness equation predictions. Stringer strength was unaffected by varying the fillet radii of the notch from 12 inch to 1 inch. A group of stringers with sharp, rectangular notches no fillet had lower strength values than the filleted groups. I derived equation 15 from the FE results to predict strength as a function of notch depth for any loading condition. By adjusting the equation, both mean and fifth percentile strengths were predicted. Agreement between predicted strengths and experimental results was excellent.
- Wood, Paper and Related Forestry Products
- Numerical Mathematics