Wood performance

Wood buildings withstand earthquakes

Wood structures can withstand earthquakes, wind and fire. In the aftermath of an unfortunate disaster, wood is a versatile and resilient building material well-suited to repairing and rebuilding structures.

Wood’s proven track record of seismic performance

Wood’s natural elasticity, strength and lighter weight give it an advantage during an earthquake. The natural ability for wood buildings to flex and return to their original shape in the event of an earthquake has made them a popular choice for centuries in regions prone to seismic activity. In some instances, historic centuries-old wooden buildings have remained nearly intact after strong earthquakes, while modern reinforced concrete buildings have endured significant damage, or even collapse. Following earthquakes in Asia, reports indicate that wood structures best maintained their structural integrity and contributed least to injury and loss of life. And recent testing is showing that midrise light-frame wooden buildings up to six stories can endure a 7.5 magnitude seismic test with little damage.

Brock Commons Tallwood House, UBC
Photo credit: KK Law

Wood's lightweight advantage

Damaging forces in an earthquake are proportional to a structure’s weight. Wood is substantially lighter than other building materials, giving it an advantage when paired with good seismic design. The fact that wood buildings tend to have numerous nail- or other metal-connections means they have more pathways to dissipate the load (something known as load paths), so there is less chance the structure will collapse should some fail. This is what is referred to as ductility—a building’s ability to undergo large deformations without failing.

Shaking things up

Testing the seismic resilience of tall timber towers 

On the world’s largest outdoor shake table researchers put the rocking wall design to the test. The results help show that it is possible to design a tall wood building where not only can occupants leave the building unharmed, but they can come back and resume living in the building shortly after an earthquake.

 

Bioenergy Research and Demonstration Facility, UBC
Photo credit: KK Law

What is ductility and how does it boost wood’s resilience? 

Ductility is the ability of a material to be deformed without fracture. A building with more ductility can flex and resist collapse. The numerous nails and other connections commonly used in wood construction gives the building more ductility. Many connections mean more load paths to dissipate the forces of an earthquake or high-wind event. Ductility boosts wood building’s resilience. 

Forest Sciences Centre, UBC
Photo credit: Don Erhardt

Designing for resilience in mass timber and taller wood structures 

Tall wood hybrid structures meet, and in some cases, exceed the seismic performance of comparable steel and concrete buildings. Research shows with the right design, wood-steel composite buildings can achieve sufficient stiffness, strength, and ductility to resist strong winds and earthquakes. In the case of Brock Commons Tallwood House, the hybrid mass timber structure is significantly lighter than a comparably sized concrete structure. This lighter structure reduces resistance to swaying and uplifting forces during an earthquakewhile allowing the building to flex. The building’s concrete core serves as a counterbalancedissipating seismic forces and minimizing damage to the structure. 

When it comes to high-rise wood construction something called a rocking wall—made from cross-laminated timber (CLT) and designed with post-tensioned cables—can deliver resilient seismic performance.

With this design, the building’s core rocks and then recentres itself in the event of an earthquake while inflicting no damage to the primary structure. Such an approach to tall timber seismic design goes beyond basic life safetyavoiding the need to tear the building down after an earthquake and making it more easily repaired.

Wood buildings perform in high winds

Strong winds have an inevitable impact on buildings. Wood buildings can withstand substantial loads for short periods, often characteristic of gusty winds. Light-frame construction combined with numerous fasteners and connectors provides multiple and often redundant load paths that can help reduce the impact of high winds. When structural panels such as plywood or oriented strand board (OSB) are fastened to lumber framing, they form some of the most solid and stable roof, floor and wall systems available.

When it comes to taller timber buildings, research is demonstrating that timber composite system can enhance safety and is a viable option to improve wind resistance.  A number of things can be done to boost their resilience in the face of high winds and uplift forces. Examples include steel anchor rodslateral storey-height trusses, the selective use of precast concrete floors and the use of mass timber panels anchored to the concrete foundation.

RockRidge Canyon Clubhouse, Princeton
Photo credit: Bob Matheson, courtesy HDR Architecture Associates Inc.

Rapid modular wood construction

A place to call home

The BC government created thousands of units of temporary modular housing built with wood to house the homeless in the province. Reports indicate significant benefits to residents’ health and well-being, with 94% of them remaining in their units after six months.  

Light-frame construction

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Civic + institutional

Wood Innovation and Design Centre

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