Researchers at the University of Melbourne have completed full-scale shake table testing of mass timber building systems, demonstrating that engineered wood structures can meet seismic performance requirements for high-rise construction in Australian cities.

The tests involved subjecting a three-storey mass timber building section to simulated earthquake motions matching historical earthquakes in Newcastle and Adelaide. The structure performed well, with no significant damage and post-quake deformations within acceptable limits.

Mass timber construction uses engineered wood products like cross-laminated timber (CLT) and glue-laminated timber to build multi-storey buildings that traditionally would use concrete or steel. The approach has environmental advantages because wood sequesters carbon and requires less energy to produce than concrete or steel.

But building codes in most Australian cities limit mass timber construction to mid-rise buildings, typically 8-12 storeys, partly because of limited local experience with seismic performance. Testing like Melbourne’s helps build the evidence base for relaxing those restrictions.

Professor Colin Gilbert, who leads Melbourne’s timber engineering research, said mass timber has some inherent seismic advantages. “Wood is lighter than concrete, which means lower seismic forces. And properly designed timber connections have good energy dissipation characteristics that help buildings survive earthquakes.”

Australia isn’t highly seismic by global standards, but several cities have moderate earthquake risk. The 1989 Newcastle earthquake killed 13 people and caused $4 billion in damage, mostly because buildings weren’t designed for seismic loads.

Since then, Australian building codes have incorporated seismic design requirements, though less stringent than California or Japan where earthquake risks are higher. Still, large earthquakes are possible, and vulnerable buildings remain a concern in older parts of cities.

Mass timber construction has grown rapidly in Europe and North America over the past decade, with timber buildings exceeding 20 storeys operating in several cities. Australia has been slower to adopt the technology, partly because of limited local manufacturing capacity for CLT and other engineered timber products.

That’s changing. Several Australian manufacturers now produce CLT, and imports from Europe and New Zealand are readily available. Building designers increasingly specify timber for projects where it offers cost, construction speed, or environmental benefits.

The Melbourne testing used a hybrid system where timber structural elements combine with steel connections. Pure timber connections are possible but typically less stiff than steel, potentially leading to excessive building movement under lateral loads.

The shake table testing simulated earthquakes with peak ground accelerations up to 0.3g, roughly equivalent to a magnitude 6 earthquake at moderate distance. The structure experienced peak floor accelerations of about 0.8g, which would feel severe to occupants but is well within what buildings are designed to withstand.

Inter-storey drift, the relative horizontal movement between floors, peaked at 1.8% of storey height. Building codes typically limit drift to 2-2.5% to prevent damage to non-structural elements like partitions and cladding. The tested structure stayed within those limits.

Some connections showed minor yielding where steel components deformed plastically. That’s actually desirable in seismic design because energy dissipation through controlled damage prevents catastrophic failure. The yielded connections could be inspected and replaced after an earthquake if necessary.

The testing included instrumentation measuring forces, deformations, and vibrations throughout the structure. That data is being used to validate computer models that designers use to predict seismic performance. Better models enable more efficient designs that use less material while maintaining safety.

One challenge with mass timber construction is fire resistance. Wood burns, obviously, which raises concerns about fire safety in multi-storey buildings. Mass timber actually performs well in fires because large timber members char on the surface, and the char layer insulates the interior wood, slowing fire spread.

Still, building codes require fire-resistant coatings or encapsulation of timber structural elements in higher buildings. This adds cost and reduces some aesthetic benefits of exposed timber construction.

The research received $2.8 million in funding from the Forest and Wood Products Australia research program, which promotes use of Australian-grown timber in construction. The program is funded by a levy on forestry products and matching government contributions.

Environmental benefits of timber construction depend heavily on forest management practices. Timber from sustainably managed plantations can have lower carbon footprints than alternative materials, but timber from old-growth forests or poorly managed plantations may not.

Australia has extensive plantation forests, mostly pine and eucalyptus, grown specifically for timber production. Using those forests for construction timber rather than lower-value products like paper could improve economics of plantation forestry while providing low-carbon building materials.

Whether mass timber construction achieves significant market share in Australia depends partly on costs. Timber construction is generally comparable in cost to concrete for mid-rise buildings but becomes less competitive for tall buildings where concrete or steel are more efficient.

Construction speed is another factor. Mass timber elements can be prefabricated offsite and assembled quickly, reducing construction time by 20-30% compared to concrete. That time saving represents significant cost reduction through earlier building occupancy and reduced financing costs.

Several high-profile mass timber buildings have been completed or are under construction in Australian cities, including university buildings, commercial offices, and apartment complexes. These demonstration projects help develop local expertise and supply chains.

The shake table testing at Melbourne is part of broader efforts to build Australian capability in timber engineering. The Australian Timber Design Awards, launched in 2019, promote innovative use of timber in construction. Several universities now offer specialised courses in timber engineering.

Whether timber becomes a major construction material for Australian cities remains to be seen. Cultural preferences matter; some markets embrace timber buildings while others prefer the permanence and prestige associated with concrete and steel.

The Melbourne research provides evidence that seismic performance need not be a barrier to mass timber construction in Australian cities. That removes one technical obstacle, though economic and cultural factors will likely determine actual adoption rates.