Four key classifications

There are four basic fire safety classifications for structures and one classification specifically developed for timber structures. The first deals with ignition and fire spread on the surface of the structure, sometimes referred to as 'reaction to fire'. This classification can be used to select appropriate finishes in escape routes, for example, to minimise the risk of rapid fire spread that could impede evacuation. The extent to which a finish or building product contributes to the development of a fire when installed on both the walls and ceiling of a standardised room is the starting point for the classification. Exposed wood in escape routes must be treated to ensure a sufficiently low risk of ignition and fire spread.

The second classification concerns the fire resistance of the structure. It classifies the ability of a structure or building component to maintain its function when subjected to a standardised fire exposure. The standardised fire exposure is called the standard fire curve which can be seen as a kind of simplified representation of a fully developed fire in a room. The standard fire curve is simulated using fire test furnaces. After testing, the structure receives a classification where the most common classes are R the load-bearing capacity, E the integrity and I the insulating capacity. The different classes are always followed by a time indication, for example, when a wall that does not carry any load has the class EI90, it means that it encloses and isolates the standard fire for 90 minutes.

The third classification, the so-called K-class originally developed for timber structures, relates to fire resistance. The classification indicates how long a protective layer protects the structure from ignition at the standardised fire exposure.

The fourth classification refers to the resistance of the façade structure, including any air gaps, to vertical fire spread. This property is tested in a facade rig where a 6 metre high and 4 metre wide facade is exposed to flames emanating from a window during a fully developed fire in a room. The classifications of finishes, structures and fire resistance can be determined using standardised fire tests. The fire resistance class can also be determined by theoretical calculations according to the instructions in the common European construction rules, the Eurocodes. We therefore have a common European system for both classifications and theoretical calculations, but each country decides which requirement level should apply nationally. Only the fire classification of facade structures is done according to national standards.

Achieving robust fire protection - more than just classifications

A common approach to meeting fire resistance requirements is to use different types of protective layers such as plasterboard to form a protective membrane that delays the spread of fire, protects the supporting structure and prevents fire from entering hidden spaces in the structure. All installations, penetrations through the membrane and all connection details between elements must be fire rated, designed and installed correctly as they could otherwise jeopardise the performance of the protective layer. A German study (from 2006 for different types of houses) showed that 50 % of the installations inspected in the study compromised the fire protection membrane. During the lifetime of a building, there is a risk of damage to the fire protection membrane, for example through holes from removed or new installations. If there are combustible materials behind the protective membrane, the risk of a possible fire continuing and spreading in the timber structure increases.Post-extinguishing in structures where the fire has spread through the protective membrane to the timber frame requires more effort than in completely non-combustible frames.

Experience from previous high damage fire incidents shows that improvements to a few strategic details would have significantly reduced the spread of fire A robust and well thought-out fire protection strategy that stands the test of time is an important step in the sustainability and insurability of timber multi-storey buildings. A strategy to keep track of all important details should be the first step for the whole industry.

This is an article from our magazine Trävärden, view it here! (Link)

Taller buildings with timber frames are still uncommon, although examples as high as 20 storeys can be found in Sweden, but buildings up to eight storeys are very widely built. Building high, regardless of the materials used, poses some new challenges compared to building lower buildings. Challenges drive the development of construction in timber, which benefits construction in general for the industry.

For high-rise timber buildings, the challenges are mainly related to stabilisation, fire safety and production aspects. The "High-rise timber buildings" project has established that it is entirely possible to design and build 22-storey buildings with a timber frame that meet the requirements for stability, vibration and fire safety. Two critical aspects were fire safety and the risk of movement caused by wind loads at the top of the building. RISE and the consulting companies BRIAB and Brandskyddslaget have developed guidelines for fire safety challenges that have been developed to support similar design processes. Wind-induced movements proved to be a challenge already at 10-12 storeys, but became manageable even for 22-storey buildings with the help of related projects. The magnitude of wind-induced movements depends on the weight, stiffness and damping of the building, but due to the few other examples of tall timber buildings, there is great uncertainty as to how large the damping can be. To increase the understanding, it was studied in a European co-operation project, with RISE as coordinator, by evaluating the damping in eight large timber buildings in Europe.

In Sweden, Linnaeus University and RISE carried out measurements in a building in Mariestad to evaluate the properties of the building with respect to wind load. Results from the project will be summarised in recommendations for how calculation models for wind load of tall buildings should be designed to best describe the actual load. Funding Formas, Vinnova, Energimydnigheten and ForestValue.

Further reading
Tall timber buildings - concept study (Link)

This is an article from our magazine Trävärden, view it here! (Link)

“It's been a crazy time to make a billion dollar investment like this. But we are extremely proud and happy to now be able to open the doors to three new test environments for electromobility. And the interest, well, that’s grown more than the construction index and timber prices,” says Henrik Svenningstorp. 

Full-scale vehicle testing 

Henrik Svenningstorp is CEO of SEEL,owned by RISE and Chalmers University of Technology and which in 2023 will begin testing vehicles and components for electromobility on a full scale in Gothenburg, Borås and Nykvarn. 

“We’re not trying to be the best at making batteries or electric motors, we’re simply trying to be the best at measuring them. In Säve, we have facilities covering some 15,000 square metres with essentially everything you need to test whatever needs to be tested within electromobility: batteries, shafts, vehicles, electrical components, noise and vibration, charging systems… The facility in Nykvarn is a little smaller, with a focus on heavy vehicles. This is where, for example, we have the most powerful equipment for testing electric motor shafts. The only thing we can’t do in Gothenburg or Nykvarn is safety-critical and destructive testing. That we do in Borås.” 

"The lab for safety-critical testing in Borås is a world-leading test environment with the greatest possible concern for the environment. All tests take place in a controllable and fully repeatable indoor environment, and thanks to a state-of-the-art treatment plant, both flue gases and extinguishing water are taken care of, which means the highest possible environmental friendliness when testing batteries", says Michael Rahm, department manager for Fire and Safety at RISE.

The fume treatment plant can handle 170,000 cubic metres of smoke an hour. This makes it possible to incinerate an entire passenger car in an orderly fashion, taking care of all the fumes and measuring their composition. Since the facility is run by RISE, certification will be possible from the outset. The long-term ambition is to accumulate extensive technical expertise that will enable the testbed to offer virtual testing as well. 

The goal: A neutral meeting place for small, innovative companies to meet major players 

“Our goal is clear: We want to be a neutral meeting place conducive to new collaborations, whether between large and small companies or industry, academia and institutes. Europe has relatively few open and accessible testing facilities of this size. And we’re well aware that large companies appreciate the innovation boost they can gain from collaborating with smaller, innovative companies. Similarly, smaller companies may need to test their ideas in the environments in which major players are found while protecting their future patents,” Svenningstorp explains. 

In collaboration with RISE, it will be possible to support small companies seeking funding for their first major investments. SEEL will be judged by its owners on how well it succeeds in encouraging collaboration. Four major industrial companies are involved in the project as guaranteed customers, and their testing needs are extensive. Parallel to this, there is room for other companies of different sizes, and should space prove to be limited as time goes by, there are ambitions to expand.  

Sharply increased interest in recent years 

“There’s a great deal going on right now. Since receiving our EU approval in 2019, interest has only increased. We’re also busy on several fronts. In Säve, parts of the laboratory are even prepared for hydrogen and fuel cells, a possible replacement power source for all large vehicles with internal combustion engines currently trafficking the roads that need to transition. We’ve entered into a partnership with the shipping industry and signed an MoU (memorandum of understanding) with several stakeholders.”  

Initial contact has been made with the aviation industry. Svenningstorp underlines that while there are major differences between truck and jet engines, the differences between electric motors for different types of transport are smaller. 

“In principle, if we can measure rotational speed, torque, current and voltage, then we can test a powertrain regardless of whether it’s for a vehicle, a ship or an aircraft.” 

“We’ll also be able to test infrastructure, such as charging stations. For some areas of the recycling industry, our labs may prove necessary when making new products from what is currently treated as waste. The same applies to the energy industry, which is developing vehicle-to-load and vehicle-to-grid – different systems for using electric vehicle batteries for energy storage.” 

Facilities designed for education and training 

On top of all this, there is a need to train the workforce for all the battery factories and other operations in the growing electromobility industry. The testbed facilities are designed to enable education and training. 

“We are now ready to open our three sites with grand openings in September. These are exciting times,” Svenningstorp ends.