Is Mass Timber a Good Choice for Seismic Zones?

It may seem frightening to some to imagine that we live in a sphere orbiting our Sun. The Sun’s core is heated to up to 6,000 degrees Celsius. All human activities are located in Earth’s crust (the smallest layer of thickness) in the so-called “tectonic plates”. These plates are found in the asthenosphere and float on the mantle. Sometimes they collide, causing earthquakes. This interactive map shows that earthquakes occur more often than we think. There are dozens of them every day, many of which go unnoticed. They can be deadly and they can cause damage and death to buildings and infrastructure.

Bayview Elementary School Seismic Replacement. Image © Wade Comer Photography. Courtesy of naturallywood.com

Engineering research, experiments, and tests have made it possible for countries and regions that are affected by tectonic activity to reduce the risk of earthquake-related deaths and other damage. Certain materials and solutions work better when there is an earthquake. Wood is one of these materials.

A earthquake produces shock waves in short, rapid intervals. This is similar to a very severe horizontal charge. Vertical loads are supported well by buildings (both dead loads, such as the structural material’s weight, and live loads, such as occupants and furniture, etc.). The lateral forces generated by earthquake waves can make the whole structure vibrate. This can cause everything from superficial damage to total collapse.

Sir Matthew Begbie Elementary School Seismic Replacement. Image © Bright Photography. Courtesy of naturallywood.com
Sir Matthew Begbie Elementary School Seismic Replacement. Image © Bright Photography. Courtesy of naturallywood.com
Fast + Epp Home Office. Image © Mathias Fast Photography

Flexible foundation systems, counterweights, and even pendulums can be used in tall buildings that are located in seismic zones to counter or avoid the structure from moving. The building’s materials can also play an important role, in addition to its structural reinforcements. As wood is a strong structural material, it can withstand earthquakes. It is able to withstand a lot of deformation up until its breaking point. It bends before it breaks. Think about how a tree reacts to windstorms. Wood is made up of thin, long, strong cells. The elongated cell walls give wood its strength parallel to the grain. Wood products can withstand high loads when tension and compression forces are applied parallel to the wood fibers.

Bayview Elementary School Seismic Replacement. Image © Wade Comer Photography. Courtesy of naturallywood.com

Wood is also lightweight, which is another positive attribute in these cases. A building with less mass will produce less seismic waves. Cristiano Loss is an Assistant Professor of Wood Engineering at The University of British Columbia. He specializes in earthquake resistance of wood-based structures and systems. He has been involved in the experimental testing of wood-based assemblies and points out their inherent benefits. Wood’s lighter weight is one of its greatest strengths. He explains that while you might think this is a disadvantage, it’s actually an advantage. “Wood is five-times lighter than concrete, which significantly reduces the seismic forces within a building.”

Bayview Elementary School Seismic Replacement. Image © Wade Comer Photography. Courtesy of naturallywood.com

A building that is both light and stiff will behave well in an earthquake. Buildings that are too rigid will become fragile and break down with the vibrations. A lighter building, however, can be shaken more by occupants and cause large movements that can damage buildings. Numerous tests with real buildings have proven that mass timber houses with metal connectors can withstand these natural phenomena. Cristiano Loss also points out another benefit of wood systems, which is their tendency to have an exposed system for connections. It is easy to detect damage because there is no rebar in the material. It is possible to repair the damage quickly if the connection is well-defined in the system.

Qualicum Beach Fire Hall. Image © Bob Matheson. Courtesy of naturallywood.com

It is crucial to find safe shelters for the population in areas where earthquakes are frequent. This will allow them to provide assistance and rebuild infrastructure. A post-disaster hub or building is an essential facility that provides services in the event a disaster occurs. A facility of this nature will have a much higher seismic load than residential or commercial buildings. These include power centers, support infrastructure, and hydropower operation centers. This type of building can be constructed from wood because of its seismic resistance and durability against wind and fire.

Sir Matthew Begbie Elementary School Seismic Replacement. Image © Bright Photography. Courtesy of naturallywood.com

Fast+Epp Principal Engineer Nick Bevilacqua says schools in British Columbia, Canada are built to a High Issuance category. This means that they can withstand 30% more seismic loads than normal buildings during an earthquake. They are intended to protect students and provide shelter, safety, and access to services in the event of an earthquake or other disasters. He explains that for the seismic design of Bayview Elementary school and Sir Matthew Begbie elementary school, the CLT shear wall system was used. This mass timber structural assembly offers a certain level of ductility that the seismic system must be able meet. Ductility simply refers to the amount of flexibility and give a structure can provide without failure. These structural walls are connected to the foundation via steel support rods at each corner. They allow the whole structure to move and dissipate the energy in the event that an earthquake occurs without it collapsing.

Many researchers from around the globe have been working to find solutions to reduce earthquake damage and the risk of buildings being damaged. Research has shown that timber buildings are light and rigid, and can absorb some of the earthquake’s energy. Earthquakes are a reminder of the fragility of our world and the power of nature. Mass timber is a strong building material that can withstand fire and earthquakes.