Performance Standards for COM-PLY Floor Joists. COM-PLY Report 14

摘要

This report presents standards for evaluating the strength, stiffness, durability, and dimensional stability of COM - PLY (a structural sandwich construction with a particleboard core placed between layers of solid wood veneer) floor joists used in frame floors of single - family homes, apartments, and light - frame construction. Test methods for evaluating performance and determining acceptability are detailed. After selecting the thickness and number of veneers, species of wood, laminating adhesive, and particleboard resin binder that appear economically feasible to use, the manufacturer can determine from these standards whether the proposed design is acceptable. The initial sample submitted to a testing laboratory must contain 10 specimens. According to the structural strength and stiffness standards, a COM - PLY floor joist for all rooms except sleeping areas and floored attics must safely withstand a transverse bending load equivalent to 50 pounds per square foot (PSF) of uniformly distributed floor load (40 PSF of live load plus 10 PSF of dead load). The bending load can then be applied with a universal testing machine, hydraulic cylinders, or any equivalent device. Proposed COM - PLY joists will be qualified for strength and stiffness performance on the basis of tests that assume a 16 - inch joist spacing, a total design load of 50 pounds per square foot, and the maximum clear span specified by the manufacturer. The standard for durability requires that a group of control specimens be tested for structural strength and stiffness; second group of specimens is then exposed to accelerated aging. The adjusted value of bending strength after accelerated aging must be at least 50 percent of the adjusted value for unexposed joists. The standard levels for dimensional stability require that, after water soaking, average dimension increases of all COM - PLY specimens not exceed 8.0 percent for width and thickness and 0.1 percent for length and that the average warpage not exceed that described as ''light'' in lumber grading rules for the length and width nearest that of the specimen size. Photographs, diagrams, and 13 references are provided. (Author abstract modified).