This week's magnitude 7.8 earthquake in the Philippines caused scenes of collapsed buildings and shattered facades, reminiscent of the 2011 Christchurch earthquake. Such extreme events test buildings to their limits, and while preventing collapse is crucial, structural engineers increasingly focus on what happens to buildings that survive. Modern buildings often protect lives but sustain costly damage, leading to years of repairs or even demolition. Additionally, the construction sector faces pressure to cut greenhouse emissions, driving demand for sustainable and resilient building systems.
The Need for Resilient and Sustainable Buildings
Many modern buildings are designed to prevent collapse during earthquakes, but they often suffer significant damage that requires extensive repairs. Some buildings are ultimately demolished despite never being near collapse. The construction sector's substantial share of global greenhouse emissions adds urgency to finding low-carbon alternatives. Timber, particularly cross-laminated timber (CLT), has emerged as a promising solution. CLT is made by bonding timber boards at right angles to create large structural panels for multi-storey buildings. It stores carbon, reduces embodied emissions, and suits prefabrication, cutting construction time and waste.
Testing a New Timber-Based System
Last month, researchers at the University of Auckland conducted one of the most demanding full-scale earthquake tests on an emerging timber-based technology. The system allows storeys to move relative to one another during an earthquake, reducing strain and helping the structure return to its original position after shaking stops. This controlled movement prevents permanent displacement and minimizes damage, improving the chances of quick reuse.
Full-Scale Shake Table Experiment
The team built a full-scale, modular CLT building and tested it on a shake table simulator. Although physically two storeys high, additional weight at roof level replicated forces of a typical three-storey building, common in New Zealand's medium-density housing. The simulation subjected the building to increasingly demanding earthquake motions, from distant to near-source events. The building performed as hoped: the connection system allowed controlled movement, absorbing and dissipating energy while protecting the main timber structure. Crucially, the building self-centered after shaking, returning to its original position without permanent tilt or displacement.
Key Findings and Implications
The main timber structure remained undamaged, suggesting lower repair costs, less disruption, and faster return to normal use in a real earthquake. However, the test did not assess non-structural elements like wall linings and interior finishes, which often suffer damage. Despite this, results provide encouraging evidence that modular timber buildings can withstand major earthquakes and recover with minimal damage.
Next Steps and Future Potential
The next step is to incorporate the technology into complete building systems and evaluate long-term performance, practicality, and commercial viability. If successful, this innovation could support a new generation of low-carbon buildings that are safer, more resilient, and quicker to restore after major earthquakes. As countries like New Zealand grapple with seismic risk and construction emissions, such innovations show that resilience and sustainability can go hand in hand.
