Urbanization and the evolution of modern cities have led to the development of high-rise building constructions, but what is the real environmental impact of these buildings? Traditionally designed with concrete as the main structural material, their construction implies an increase of CO2 emissions released into the atmosphere, air pollution and a rise in energy and water consumption. The structure was tested on a shake table that simulated the 1994 Northridge earthquake in Los Angeles, magnitude 6.7, and the 1999 Chi-Chi earthquake in Taiwan, magnitude 7.7. To dispel doubts, the Tallwood Project recently erected a 10-story building made of cross-laminated timber (CLT) at the University of California, San Diego (UCSD). This has been extensively verified in smaller-scale structures around the world, but how does a high-rise mass timber building behave in the face of an earthquake? Furthermore, unlike steel or concrete, wood is a lightweight material with a good strength-to-weight ratio, enabling it to withstand seismic forces without adding excessive load to the construction. However, its ductility allows it to deform plastically without breaking, absorbing and dissipating the energy generated by movement and vibration. When it comes to seismic resistance, there are a number of myths that question the ability of wood to adequately perform in the event of an earthquake. Image © David Baillot / Jacobs School of Engineering / University of California San Diego Surely this isn’t the first time someone’s realized it gets stronger the more you use it? Well… as you’d expect, the changing popularity of cross-laminated timber in construction does coincide with a greater understanding and focus on environmental causes, but the relationship hasn’t always been positive.Ĭonstruction of the 10-story Tallwood structure on the UC San Diego shake table. So what’s new? Wood’s been around for long enough now, and we’ve been using it as a building material for centuries. Simply put, due to the complex physics involved in the perpendicular lamination, the strength of CLT board is similar to that of reinforced concrete, and has proven performance under seismic forces. CLT boards start with a minimum of three layers but can be strengthened further with the addition of more. By crossing the direction of the grains, CLT achieves a far higher level of structural rigidity along both axes. In comparison, the manufacture of cross-laminated timber (CLT) involves simply gluing multiple layers of timber together at right angles.
As a construction material, however, when put under enough directional force along its grain, sawn timber is structurally unstable, so deemed unsuitable under higher loads. Timber is a natural, renewable material, easy to fabricate, and with low-carbon emissions.
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