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ABSTRACT
The effect of veneer-joint design on the static bending properties of laminated veneer lumber (LVL) commercially fabricated with rotary-peeled full-size yellow-poplar veneers and liquid phenol-formaldehyde resin was investigated. Two types of veneerjoint design(scarfand crashed-lap) commonly used in commercially produced softwood LVL products were considered in this investigation. Three groups (25 in each group) of 96-inch- (243.8-cm) long LVL specimens, randomly selected from a large sample population, were prepared for this study. Group I specimens had scarf veneer-joints, group II had crushed-lap veneer-joints, and group III had no veneer-joints and it served as the control. All specimens were preconditioned and equilibrated in a computercontrolled environmental room at conditions of 65 percent RH and 75F (23.9oC). Edgewise static bending tests were conducted to determine their stiffness and strength. Results showed that yellow-poplar LVLs with crushed-lap veneer-joints are as stiff and strong as those without veneer-joints, but members with scarf veneer-joints had relatively lower mechanical properties. However, significant differences were observed between the specific stiffness and specific strength. Further, statistical analysis showed that yellow-poplar LVL's stiffness and strength probability can be adequately described by a lognormal distribution.
In recent years, the increasing demand for high-quality and more uniform structural lumber, combined with the shrinking supply of harvestable highgrade logs, has led to the development of various types of engineered wood composite products. These products can be reconstructed to perform better for the required structural functions, or to satisfy a specific structural design need by altering or redistributing directional mechanical properties on the manufacturing processes. Laminated veneer lumber (LVL) is one of these well-developed engineering wood composite structural products. In general, LVLs are fabricated with veneers that are rotary-peeled from softwood logs that are commonly used for producing solid lumber for structural uses. It is recognized worldwide that the advantages of using softwood LVL over solid-sawn softwood lumber are the consistency of high strength (modulus of rupture (MOR)), uniform stiffness (modulus of elasticity (MOE)), and the availability in virtually unlimited lengths and sizes (2-4, 6-14,16,17,20,21,24-28,30-34). Because of its unique characteristics of high strength and uniform stiffness, softwood LVL has been used extensively in commercial I-joist products as flange materials and for long-span and heavy-loaded beams and headers (11,28,30). However, most of these LVL products were fabricated with...