Validating Wood Application in Brace Frames
Timber Braced Frames | Salt Lake City, Utah
As the market for mass timber buildings rapidly expands across the United States, it spurs the development of technologies to economize the new construction type further. The use of glulam and cross-laminated timber panels are readily applied as the beams, columns, and floor panels for multi-story buildings. These members support the dead and live (i.e. gravity) loads of the building; however, all buildings also require a defined lateral load system, such as shear walls or braced frames to provide stability against wind and earthquake loading. When designing a building, structural engineers must utilize lateral systems defined in the governing building code. Unfortunately, there are currently no mass timber lateral systems defined in the building code. This results in mass timber buildings becoming hybrid in nature with a timber gravity system and a steel or concrete lateral system.
There is a desire from contractors to build completely out of mass timber above the foundation because of the efficiency of using one material type with one trade on site and reducing the tolerances issues that inevitably arise at the connection points between mass timber and steel or concrete. To help work towards this goal, Timberlab has been a sponsor and technical advisor to the recently completed testing of a Timber Braced Frame system at the University of Utah funded through a US Forest Service Wood Innovation Grant. The braced frame comprises timber columns, beams, and a specially engineered diagonal brace with a steel core and timber casing. In 2018, the first phase of the University of Utah testing focused on the design of just the diagonal brace. The performance of this component was successfully validated through full-scale testing using criteria for conventional (steel and concrete casing) buckling restrained braces already defined in the building code.
Dr. Chris Pantelides | University of Utah
Emily Diedrich | University of Utah
Doug Rammer | Forest Product Laboratory
Hans-Erik Blomgren | Timberlab