The interest in mass timber construction is growing. First used in Europe and Canada, the IBC in the United States most recently developed new code for wooden structures in 2021. Using wood instead of concrete, architects and engineers can design and build with a smaller carbon footprint. Engineered wood is assembled for high strength ratings, using lamination, fasteners, and adhesives. With new technology mass timber is a safe, viable construction alternative to steel and concrete. And better still, the energy involved in the production of materials, known as embodied carbon, is a fraction of traditional construction materials. However, one constraint on mass adoption is the lack of defined timber lateral force resisting systems in building codes.
Several researchers have been working to develop a ductile lateral force resisting system for mass timber buildings by employing a similar concept used in steel buildings in seismic areas, the buckling restrained brace frame. In a new study, “Design and Cyclic Experiments of a Mass Timber Frame with a Timber Buckling Restrained Brace,” researchers Emily Williamson, Chris P. Pantelides, Hans-Erik Blomgren, and Douglas Rammer, explore the use of a timber buckling restrained brace frame. They used four different tests, with and without a TBRB under quasi-static cyclic loads, in this study. Learn more about their experience with the design and testing of a mass timber frame in the Journal of Structural Engineering at https://doi.org/10.1061/JSENDH.STENG-12363. The abstract is below.
Abstract
Mass timber buildings are increasing in popularity as the building industry aims to use more sustainable construction materials. A lateral force resisting system with a mass timber frame and a timber buckling restrained brace (TBRB) is presented as a possible solution to allow the expanded use of mass timber in buildings located in cities with high risk of natural hazards such as earthquakes and hurricanes. A series of nine quasi-static cyclic tests was completed to study the performance of the TBRB frame as well as the elastic performance of the bare mass timber frame. The variables studied included the level of axial force applied to the columns to simulate gravity load and the out-of-plane displacement of the TBRB frame. The mass timber frame was tested four times with a different TBRB. The four subassemblies achieved a drift ratio of at least 2.8% before failure of the TBRB due to weak axis buckling of the steel core. The maximum displacement ductility of the four TBRB frame subassemblies ranged from 3.1 to 3.5. The addition of the TBRB enhanced the energy dissipation capacity of the bare mass timber frame by 4.0 to 8.6 times after 14 cycles of lateral displacement.
Learn more about whether a TBRB might make a mass timber design work for you: https://doi.org/10.1061/JSENDH.STENG-12363.
