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Massive timber systems for buildings in high-seismicity areas

The wood-building design community strives to build taller and more complex structures and it seeks innovative timber techniques to achieve this.  In parallel, the global drive towards more sustainable buildings means that wood is an attractive material as it is a renewable resource with a relatively low environmental impact. Massive timber, comprising solid panels of wood engineered for strength through different layers of lamination, has been the focus of much research and testing in recent years. Several mid-rise buildings have recently been completed in massive timber, but very few are in highly seismic regions. The seismic performance of tall wooden buildings is a new field of study.

This project reviewed recent research and technical literature on the use of massive timber for lateral systems in highly seismic areas. The research identified the systems with the greatest potential for application in the design and construction of mid-rise buildings in the Americas region. The team reviewed seven existing massive timber lateral systems, determining the advantages and disadvantages of each for use in highly seismic areas.  This involved considering the seismic performance, market applicability and construction advantages of each system, as well as studying buildings already constructed using that system.

Based on the review, two new hybrid systems were proposed that may forge a path for increasingly taller wood buildings in highly seismic regions.

Four of the reviewed massive timber systems were found to be applicable to mid-rise structures in highly seismic areas:
- coupled shear walls with energy dissipating devices and vertical post-tensioning;
- cross-laminated timber shear walls with conventional connections;
- post-tensioned motion frames;
- rigid frames with self-tapping screws.

Two new, hybrid systems were proposed:
- moment frames with adhesive ductile plates: this uses a perforated steel plate glued within a beam span to dissipate energy during a seismic event;
- coupled shear walls with adhesive ductile plates: this uses a steel plate glued to adjacent shear walls to act as an energy dissipating device during a seismic event.

There is a growing global market for buildings made from massive timber. This is particularly true in the Americas where the timber industry is well developed and wood is low-cost and readily accessible. In several Canadian provinces the Wood First Act encourages all new provincially-funded buildings to use wood as a primary building material. In Seattle, Washington, the city’s building department has been considering expanding the use of massive timber in commercial construction to meet its sustainability objectives.

The research takes us closer to a viable design for a timber, mid-rise building in a highly seismic area in the Americas. The adoption of existing timber systems or the introduction proposed new hybrid systems into high seismicity regions would require implementation of various testing, some of it extensive, that is required by local code authorities.

Research and innovation in this area is moving rapidly. The work has helped ensure that Arup is in position to spearhead full-scale seismic testing, moving towards a viable method for use in our designs for high seismicity regions.

In a rapidly urbanising world, mid- and high-rise buildings will be needed to house denser populations, while environmental sustainability remains crucial to protecting resources. Timber construction has the potential to meet these interrelated challenges. Although this research focused on the American market, its impact is more widespread as seismic regions across the globe seek to benefit from these emerging new building technologies. Arup’s knowledge will enable professionals in the field to find and evaluate systems that will work with their local building codes.