Researchers at ETH Zurich have invested in a new fire simulator to test timber’s response to varying fire conditions.
The Swiss university has a dedicated Fire Safety Engineering department with specialization in the following areas:
- Design model for the fire resistance of timber connections
- Design model for the fire resistance of bonded structural timber elements like glulam and CLT
- Design model for the fire resistance of combustible and non-combustible insulation materials
Fire Safety in Cross-Laminated Timber
Amongst recent projects include ‘Fire Safety in Cross-Laminated Timber‘, which looks at the risk of the so-called ‘second flashover’ where fires in buildings cannot be self-extinguished even after the fire has completely consumed all contents.
The project, which Dr. Michael Klippel leads is carried out in collaboration with Henkel AG and supported by Innosuisse, the Swiss Innovation Agency.
The main objective is to demonstrate that CLT bonded with the adhesives does not show significant char layer fall-off and thus, there is no risk for a ‘second flashover’.
Simulating different fire scenarios
Costing CHF 2.5 million ($3.6 million AUD), the new simulator will allow the university to expand its research. It features a combustion chamber and ten gas burners that can heat the oven to over 1,400 degrees Celsius. Various cameras monitor the tests, while additional equipment analyses the combustion gases.
Andrea Frangi, the Professor for Timber Structures, spearheaded the fire simulator’s acquisition. “The furnace allows us to simulate various fire scenarios and study their impact on the timber structures,” she said, adding that the device can adjust temperature and oxygen levels with high precision.
Timber construction is booming in Switzerland
Timber construction is booming across the world and Switzerland is no exception. Timber high-rise buildings ranging from 75 to 108 metres in height are currently planned or already under construction in Regensdorf, Zug, Winterthur, and Zurich.
Before 2004, Swiss regulations limited timber constructions to two stories. This limit was increased to six stories in 2005, and since 2015, there has been no cap on the height of timber structures.
Frangi affirms that timber has proven itself as a reliable material for medium-sized buildings due to its cost-effectiveness, sustainability, and safety. Contrary to common perception, timber can outperform steel in maintaining structural integrity during a fire.
“The planned high-rise buildings are undoubtedly flagship projects,” says Frangi. “However, timber has long established itself as a construction material for buildings of medium height and is attractive due to its good price-performance ratio, sustainability, and safety.”
Timber can outperform steel in fire settings
The latter may come as a surprise, but while steel beams can deform and accordingly become unstable in the event of a fire, timber constructions can retain their structural integrity for longer.
The load-bearing capacity of a timber beam in the event of a fire is fundamentally determined by its size. If the beam burns, around four centimetres per hour, are converted from wood to charcoal on the sides exposed to the fire. Potential weak points are connecting elements and constructional details.
To expand the potential applications of modern timber construction, Andrea Frangi and his team wish to investigate further the combustion behaviour of structural timber elements and connections under realistic conditions.
“The construction sector causes a large share of climate-damaging emissions. With our research, we can help to ensure that even more of the renewable and CO2-saving resource timber is used as a construction material,” according to Frangi.
