Design Criteria For Large Structural Glued Laminated Timber Beams Using Mixed Species Of Visually Graded Lumber PDF Download

A theoretical concept was developed and experimentally evaluated permitting combination of different species of wood within the same glued-laminated beams. Twenty large beams manufactured with visually graded Douglas-fir outer laminations and lodgepole pine inner laminations all attained desired bending strength and stiffness levels. Results indicate that substantial amounts of lower strength and stiffness lodgepole pine can be used in the inner laminations of Douglas-fir glued-laminated beams with little detectable effect on their bending strength and stiffness. Design criteria presented can be used to determine the extent to which such a lower strength species might be used and the effect on beam properties.