Strength and stiffness of 8-inch deep mixed hardwood composite timber mats

Abstract

There is a current and pressing need to develop engineering standards for timber- and other wood-based mats. In 2018 a group of mat producers and users began discussing a potential grading specification standard specific to mats. There are large gaps in the literature regarding the performance of the available raw materials as well as bolt-laminated mat systems. This work represents a novel attempt to begin to assess the mechanical properties of timber mats. Eight-inch deep mixed hardwood timbers were graded according to an experimental specification standard. Then, they were drilled and bolt laminated into 28 three-timber composite mats that were 24 inches (60.96 cm) in width. The bending stiffness (modulus of elasticity [MOE]) and strength (modulus of rupture [MOR]) performance were evaluated with a static bending test. The 5th percentile nonparametric tolerance limit (5% NTL) and design value for fiber stress in bending (Fb) were calculated. The nonparametric design value compared favorably with that of graded timbers, as described in the 2018 National Design Specification (NDS) for wood.

Strength and stiffness of 3-ply industrial bamboo matting

“…For comparison, the allowable design strength (Fb) of these 3-ply bamboo mats (8,090 kPa) is approximately half of that for mixed hardwood timber mats (15,990 kPa) as reported by Owens et al (2020). By similar comparison, the stiffness (MOE) of these 3-ply bamboo mats (1,920 MPa) is approximately one quarter of that for mixed hardwood timber mats (7,650 MPa) as reported (Owens et al 2020). The stiffness would increase with minimal additional cost if the discrete bamboo lamina could be more securely fastened to each other and thereby develop better composite action.…”

“…Wood and timbers are likely the most recognizable materials that are used in mat construction. Past research has examined the mechanical performance of sawn hardwood timber mats (Owens et al 2020). Yang et al (2015) studied face-laminated pine lumber beams as a raw material that was intended for use in bolt-laminated mats.…”

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

“…As part of graduate research, Herberg (2018) reported on the bending performance of nail-laminated crane mats. Others have reported on the mechanical properties of mixed hardwood bolt-laminated 8-inch deep mats (Owens et al 2020) and mixed oak bolt laminated 8-and 12-inch deep mats (Shmulsky et al 2021). While these research findings detail varying aspects of the flexural behavior of mats or mat components, none speaks to the behavior or design properties of three-ply, mechanically fastened, hardwood mats.…”