Bending strength and stiffness of three-ply bolt-laminated mixed oak and hardwood industrial mats

Abstract

Crane mats provide safe, stable, and flat work surfaces for heavy equipment and provide environmental protection. In this manuscript, two types of three-ply mats from two geographic regions were evaluated for stiffness and strength. Mats were sourced from the Southern USA and Midwestern USA in both solid configurations where the boards in all plies are touching and waffle configurations where gaps of approximately 1.8 inches were left between boards. Both types were mechanically fastened with regularly scheduled 3/8th inch diameter carriage bolts. The mats consisted of 1.5-inch-thick mixed oak and hardwood lumber oriented in a similar manner to plywood to form 4.5-inch-thick panels, each of which is 8 ft x 14 ft. Mats were prepped for testing by being ripped into strips 24 ± 4 inches wide. In this manner, 28 test specimens were developed from 7 parent mats. Mats were subjected to three-point bending tests. In both types of mats, the Southern-sourced specimens were statistically stronger and stiffer than those from the Midwest. Modulus of rupture (MOR) results showed that solid mats from the South were stiffer compared to waffle configurations produced in either location. The regression analysis indicated that modulus of elasticity could potentially estimate MOR.