The wood that will replace steel and concrete: lighter and more earthquake-resistant buildings

15.02.2024

Progress sometimes means looking back to see how our ancestors solved problems, adding some new technological system or method to improve results. In the case of construction, perhaps the most paradigmatic case is that of wooden structures, which today can be used to erect five-storey buildings in 10 days. According to recent research carried out in an archaeological site found in Africa, the first use of wood in construction dates back more than half a million years, long before we can consider ourselves as human beings.
The latest advances in the production of different types of solid wood and its great acceptance by architects all over the world, including Spain, invite us to expand its uses and to trust in it as opposed to materials such as steel or concrete. In the last century, these have been the absolute protagonists of the sector, favouring the growth in strength and height of buildings. However, beyond new mixes and processes, they are generally more expensive to produce than wood, they are not renewable and their combined carbon footprint accounts for more than 10% of global emissions.

According to a recent report by Mass Madera, a network that brings together experts, companies, institutions and pioneering organisations in the use of solid wood in construction in Spain, it is a growing sector in our country. Moreover, its promising figures (high forestry potential, production capacity and more than 500 projects completed or under construction) could double by 2026.

Intervention with CLT panels in the Mies van der Rohe Pavilion in Barcelona Adrià Goula Omicrono.

Solutions such as CLT (cross-laminated timber) offer numerous advantages, not only because they allow CO2 to be captured instead of generated, but also because they make it possible to build lighter, more durable and resistant constructions very quickly. This is coupled with new research such as that of Chris Pantelides, a professor of engineering at the University of Utah, who has developed a type of building support made of solid wood that protects buildings against seismic damage.

Potential of CLT
Before detailing its properties and advantages over steel and concrete, it is useful to know exactly what CLT is. It is usually manufactured using pine or spruce wood in overlapping layers bonded with industrial glue and pressed together. “The result is a highly industrialised product that gives shape to beams, pillars and panels for floors, roofs or walls, which can reach lengths of up to 18 metres, widths of 3 metres and variable thicknesses starting at approximately 25 mm,” say the authors of the Mass Madera report.

The pages of this update on all things solid wood materials detail their opportunities and potential to address the challenges and barriers they still need to overcome to continue to gain a foothold in construction. They also aim to refute some myths, such as that building with wood is more expensive, something that is disproved by assessing the total life cycle of the building. Or its flammability, which is prevented by encapsulation with non-combustible materials or extra sacrificial layers that protect the structural section in case of fire.
The widely held perception is that wood cannot be used as a high-performance structural material, other than for single-family or low-rise dwellings. On the contrary, products such as CLT and advances in structural engineering with timber offer similar strength and stability to steel and concrete. Skyscrapers made of wood are already a reality, as demonstrated by Mjøstårnet in Norway and the Ascent MKE Building in Wisconsin (USA), both almost 90 metres tall and 18 and 25 stories high, respectively.

As this report reveals and the latest research reinforces, wood represents the past and the future of construction. “It can replace steel or concrete in the structure of many buildings, but it is much lighter,” explains Chris Pantelides in a press release. “A solid timber building weighs a quarter of the weight of a concrete building, so it requires a much smaller foundation.” And that’s just one of the big advantages, as they can also speed up the construction process by up to 25 per cent and, above all, capture carbon dioxide instead of producing it.
Earthquake resistant
Pantelides, after seven years of research into these materials, has just published a research paper in the Journal of Structural Engineering, in which he presents an engineered solid wood solution that protects against earthquakes and seismic damage.
There are many types of mass timber, each with its own properties and specifications. In particular, the University of Utah professor works with mass plywood panel and mass ply lam, which have allowed him to build a buckling bracing brace (BRB) that is stronger and more durable than traditional ones.

Until now, solid wood was considered an unsuitable material for this type of structural element due to its stiffness. The most common braces are made of concrete and steel, or a combination of both materials, and are responsible for absorbing or dissipating the seismic forces of an earthquake so that they do not damage the building structure.

However, research by Pantelides and PhD student Emily Williamson, co-author of the study, shows that it is possible to use Timber Buckling Restrained Brace or T-BRB: bracing that uses a steel strip for the core, but has a timber frame and is adapted to buildings where timber is the main material.
Thus was born this “lateral force resistance system” (LFRS), which was tested in the laboratory to see how it would perform under forces similar to those produced by a major earthquake. An actuator simulates these conditions by shaking the T-BRB horizontally with the equivalent of a 7.0 Richter scale earthquake.

To test the performance of the braces, sensors were installed to record the deformation and displacement of each element during nine demanding tests. Once completed, the frame and steel strips were disassembled for detailed inspection and measurement. The result was unequivocal: T-BRBs are as effective as or more effective than steel and concrete bracing, which will make solid timber buildings stronger and taller than ever before.
“The whole world is waking up. People will look back and say, ‘Why didn’t we build that with solid wood,'” Pantelides says. “I think in the next 20 years there won’t be many buildings under 12 stories, or even 18 stories, built with steel and concrete. It will no longer be feasible. In the near future we will even see skyscrapers of more than 50 storeys built with solid wood.”

By ES Diario.