Published: 19.08.26
Postdoc Guoxiang Zhao is working to improve computer simulations of fire in a facade. A new scientific article brings simulations one step closer to the ultimate goal: reducing the number of failed fire tests and shorten products’ time-to-market.
Facade constructions, like all other building products, must have documented fire safety properties in order to be legally used in construction. With the growing focus on bio-based materials in facade constructions, the need for facade tests is increasing. Building with bio-based materials and ensuring fire safety at the same time is not straightforward, which can place significant demands on product development and result in more fire tests during the development phase.
At present, each fire test only provides data and documentation for one specific way of constructing a facade (although the upcoming European facade standard is expected to make it possible to cover several variants per test). Therefore, DBI is working on developing tools that can assist building product manufacturers during the product development phase, and one of the methods for predicting fire impacts is computer simulation. Progress in this field is being made – even though there is still a long way to go before simulations can fully replace fire tests.
In a new study, Guoxiang Zhao, postdoc at DBI – Danish Institute of Fire and Security Technology – has now tested a CFD-based model (Computational Fluid Dynamics, see fact box), where he simulated how a fire in a multi-storey building affects a non-combustible facade, and then compared the results with data from a corresponding real fire test carried out at DBI’s Swedish sister institute RISE.
The simulations turned out to align reasonably well with the data from the physical fire test, and the results have just been published in the article Numerical investigation of thermal exposure on external walls in the harmonized European approach to assess the fire perfomance of facades, which appeared in the June edition of the scientific journal ‘Fire and Materials’.
“We have taken the first steps in simulating a non-combustible facade. Our aim was to see if we could predict the overall trend of temperature distribution and flame height over time as observed in the fire tests. So far, the results are very promising,” says Guoxiang Zhao.
The model has proven good at capturing the general development of a facade fire, but it also produced both over- and underestimations. For example, measurements in RISE’s fire test showed that the temperature inside the ‘apartment’ was 9 % higher than predicted, and the temperature at facade window was 17.6 % higher in reality. Although the methods for determining flame tip differ between tests and simulations, the predicted flame height (based on a reference temperature of 550 °C) was 7.4 m – compared with just over 5 m in the test.
The fact that simulations can deviate 10-20 % from the measured results may sound like a lot, but Guoxiang Zhao emphasizes that this is entirely in line with expectations.
“When we repeat a physical large-scale fire test, the results also vary considerably, even when all parameters are the same. So when the simulation generally lands within 20 %, that is actually very promising,” Guoxiang Zhao explains.
The results mean that Guoxiang Zhao and the rest of the research team are well on their way to being able to replace some of the fire tests with computer simulations – or, at first, to help make qualified choices of solutions when a facade has to be documented through a fire test. This will increase the chances of passing a test and shorten products’ time-to-market. So, if you are a developer, consultant, or manufacturer looking to document the fire safety properties of a facade, a combination of simulation and fire testing may be the right approach.
“For example, we hope to use simulations to help determine the optimal width of the flame deflectors that are often installed between storeys in bio-based and combustible facades,” says the China-born researcher.
In the simulations, the wood crib fire in the test setup was modeled in different ways to see what produced the most realistic data. Interestingly, the simplest model – where the ‘block’ was assumed to emit heat only from the top – gave better results than more realistic alternatives where flames and heat could also spread from the sides of the block.
CFD (Computational Fluid Dynamics) is a method that can predict the behavior and spread of smoke and fire over time. Using intensive computer calculations, CFD can, among other things, be used to predict fire development, flame spread, and smoke movement.
Contact
Guoxiang Zhao
Postdoc
