Mass timber is in the news all over the Willamette Valley (and fairly old news in Europe) so we OSWA members scheduled a tour on March 8, 2018. Mass timber structures, such as cross-laminated timber (CLT) push beyond wood’s perceived boundaries, achieving building heights and spans that would have once required a concrete or steel structural frame. Originally conceived in Europe using spruce, OSU researchers showed that the use of douglas fir and other refinements can significantly enhance CLT, and the new Peavy Hall is a demonstration of this revolutionary building technology. The CLT panels were manufactured at D.R. Johnson in Riddle and the mass plywood panels were made at Freres Lumber in Lyons.
CLT consists of layers of dimension lumber (typically three, five, or seven) oriented at right angles to one another and then glued to form structural panels with exceptional trength, dimensional stability, and rigidity. Panels are particularly cost effective for multistory and large building applications up to 12 floors. Some designers view CLT as both a stand- alone system and a product that can be used together with other wood products, such as mass plywood panels. CLT and mass plywood offer two-way span capabilities, making them well-suited to floors, walls, and roofs, and may be left exposed on the interior for aesthetics. The composite action between CLT and concrete provides extreme stiffness and minimal deflection which, along with an insulation layer between the materials, provided good acoustic separation between floors. (Update: one panel delaminated at the joint but has since been replaced. All panels made at the same time are being tested in place using radar.)
Recent advances in CLT panel connectors allow controlled structural flexing during extreme seismic and wind loads, and were recently shake-table tested over 9.2 Richter scale.