Press-Lam Timbers for Exposed Structures

Parallel Laminated Veneer (PLV) products are manufactured by adhesive bonding of rotary-peeled veneer. It has been estimated that a production line PLV process could convert green logs into a finished structural laminate in less than an hour. Press-Lam, a PLV product under investigation at the U.S. Forest Products Laboratory, has exhibited decreases in variability of mechanical properties and increases in chemical preservative penetration and retention when compared to solid-sawn lumber. A prototype highway bridge entirely of Press-Lam has been erected by the Virginia Department of Highways and Transportation. This bridge was field-tested to its AASHTO HS-20 design load. Preliminary allowable stresses were determined by data obtained from destructive laboratory tests on 18 full-scale stringers and 10 sections of decking made from Douglas-fir Press-Lam. In the face of dwindling supplies of large structural timbers, PLV products are attractive alternatives for exposed structural applications.