LVL: Laminated Veneer Lumber, Development and Economics

Laminated lumber standards permit increased working stresses in bending up to 50 percent more than those allowed for dimension lumber. Recent investigations have demonstrated that glued-laminated beams made from rotary-peeled veneer yield high strengths and suffer no reduction in stiffness properties. A study was performed which led to an assessment of lumber recovery from sawlogs. Rotary peeling of 1/4-inch thick veneer from sawlogs resulted in a quarter of the production of sawdust, the same quantity of pulp chips, and 47 percent more dimensional lumber (LVL) from Douglas-fir #2 sawlogs, 16 inches to 21 inches in diameter, than would have been obtained if the logs were sawn into dimension lumber. It was determined that, for LVL to compete with sawn lumber, a special process for manufacture would have to be developed. Two methods are presented which involve continuous-flow processes. An economic analysis indicates that LVL, at current logging costs of $30/C cu. ft. ($50/M fbm), would cost 22 percent more to manufacture than sawn lumber. However, manufacturing economic analysis involving an inherent design advantage of LVL, namely that production of lumber of any length is possible, indicates an 8.5 percent cost benefit a current logging costs, in LVL application as floor joists in a dwelling unit. This savings may be effected due to the greatly increased stiffness which comes from the continuous-beam “two-span” effect obtained by using long lengths of LVL rather than single-span lengths of conventional sawn lumber, thereby allowing joist cross sections at reduced depth. Other products such as millwork, industrial clears, and large glued-laminated beams, are visualized. Specially fabricated curved LVL was assembled into a 32-foot-diameter geodesic spherical space frame. This application demonstrates the possibility for large economics in the use of this structural material to enclose space. The environmental effects of producing LVL consisting principally of possible water and air pollution from glue waste disposal and veneer dryer exhaust emissions are discussed. Due to the greatly increased yield from a saw-log ( percent), the pressure on valuable timber resources.

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