Author Archives: denmark

The world’s tallest and safest timber building

Mjoestaarnet-1

The prestige building, Mjøstårnet in Norway, proves that timber can be used when building to a height. The level of fire safety is high with a number of passive measures and a reinforced sprinkler system, which also covers parts of the facade.

In Norway, the world’s tallest timber building is located. It is called Mjøstårnet and was completed in March 2019. The supporting structure comprises enormous glued timber pellets. The stairway and lift shafts are of CLT (Cross Laminated Timber). The same material was also used for the balconies on the upper storeys. The storeys up to the 11th floor comprise a building system of timber and rock wool. And, of course, the facade is also timber.

– Even though we have extensive experience in building with timber in Norway, Mjøstårnet is an unusual building, says Even Andersen, Senior Fire Engineer in Sweco in Norway and fire consultant for Mjøstårnet.

– It is a prestige project in the field of building with timber. The rules in the area have been the same for many years, but it has only been within the last few years that we have started to build to a height with timber. The environmental and climate aspects are of crucial importance in this development, he says.

Withstands a natural progression of a fire
Another aspect that has to be taken into consideration when building timber tower blocks is fire safety.

– The organisation of fire safety is function-based, and takes as its point of departure the presumption that the building must be able to withstand a natural fire progression, which we have modelled on the basis of Eurocode 1, and which takes account of the timber’s contribution to the fire, says Even Andersen.

The pre-accepted solution stipulates that the supporting structure in taller buildings must be non-combustible and be able to withstand a fire for 90 minutes. In the case of Mjøstårnet,  it was decided that the construction must be able to withstand a natural fire progression which corresponds to a standard fire of less than 90 minutes. Moreover, the building must be able to handle a standard fire for 120 minutes.

– All scenarios and fire progressions have been calculated and are far shorter than 90 minutes. Moreover, the supporting structure has an even greater resistance to fire than we assumed was needed, explains Even Andersen.

The fire safety documentation is controlled by a third party, and even though the emergency services do not have a regulatory authority role in Norway, they have been involved in the dialogue along the way.

A timber frame remains
In connection with the construction, Sweco had fire tests carried out on the glued timber pellets of which the supporting structure was to comprise. The pellets were tested by SP Fire Research and were exposed to the ISO Standard fire curve for 90 minutes. The test showed that the pellets developed a carbonised surface which protected the underlying timber against the fire. And, when the furnaces were turned off, the carbonisation stopped by itself after a while.

– The glued timber pellets are of considerable dimensions, and a relatively small section of them burns away in a fire. Therefore, they are fairly resistant in a fire. Also, they are self-extinguishing if there is nothing around them to feed the fire. Based on the tests, we have calculated that, in a fire that is not tackled but is allowed to develop and burn out, the supporting structure maintains its resistance and leaves behind a timber frame, even if the rest of the building burns away, says Even Andersen.

Its excellent properties mean that the glued timber pellets do not require any further protection or covering, but that they can be visible in the tower’s interior. Any visible timber in escape routes and the stairwell has been fireproofed.

A multitude of fire sections and cells
The weak points in the structure are the steel plates and the dowels placed at the pellet joints. Therefore, spaces and gaps around the joints are endowed with a material that expands at 150 degrees and protects the joints. Each storey constitutes its own fire section, and every single hotel room and apartment is its own fire cell. Every horizontal division structure is dimensioned to be able to remain standing if the overlying horizontal division structure collapses. The horizontal division structures for the top floors are made of concrete, but not because of the fire risk – the concrete adds extra weight to the building, which prevents it swaying too much and making the residents feel ill.

– The facade has been fireproofed and consists of elements which all have cavity barriers in the event of a fire in the cavity. In addition, there are cavity barriers over all the windows, adds Even Andersen.

The swimming pool is a reservoir
On the active side, the building has full sprinkler coverage with a reinforced sprinkler system which also covers the lowermost storeys of the facade in order to prevent incidents due to pyromania or criminality. The communal water supply is good and ensures an abundant supply of water under normal circumstances.

– If extra water is required, the swimming pool – which is part of the building and lies up and down the tower – functions as a reservoir. That is a rarity in Norway, says Even Andersen.

The building also has an automatic fire alarm system with a direct connection to the local emergency services and riser pipes in all stairwells, which have been dimensioned to enable the emergency services to fight the fire from just one of the tower’s stairwells. The stairwells are equipped with overpressure relief valves, and there is also a control room from which the emergency services can easily survey the building and see exactly where the alarm has gone off and where the sprinklers have been triggered.

– Building to a height with timber does not go without its risks, and you have to know what you are doing. Mjøstårnet is located in rural surroundings and it is completely different from building in, for example, the middle of the city where the risk of the fire spreading is different. So, even if it is possible to build to a height in timber, that doesn’t mean that it is always the right thing to do, concludes Even Andersen.

Wild fires in the USA mobilise the fire brigade’s elite troops

Skovbrande-i-USA

Every year, wild fires cause havoc in the USA. They cause people to flee, cost billions and can continue for weeks. When such a fire needs to be brought under control, the authorities enlist the help of the elite firemen – also known as ‘hotshot crews’.

In the USA they have a season we don’t have in Europe: Fire season. This is the time of year when  cause havoc, particularly in the western part of the USA. In 2015, they had the worst season ever, when more than 40,400 km2 went up in smoke. And in 2018 it was even more disastrous, with the fires in California resulting in many fatalities.

More frequent droughts and increasing temperatures as a result of climate change only make the problem much worse. Therefore, combating wild fires in the USA requires a massive effort. And that massive effort in particular is what the so-called ‘hotshots’ provide. They are the fire brigade’s elite troops who specialise in wild fires and are called on to fight the worst and biggest wild fires all over the USA. In the wilderness they create ‘fire lines’ – i.e. Fire belts in the terrain, the purpose of which is to limit the spread of the fires. This is done by hand – using power saws and axes – or by means of controlled burning, when the direction of the wind is favourable.

The most dangerous tasks
There are around 100 hotshot crews in the USA, each of which comprises 20 firemen. They undergo intensive training in all forms of fire fighting tactics, and the physical requirements are rigorous.  Normally, they are sent out into the wilderness without logistical support in order to create fire lines in shifts lasting up to 48-64 hours for several weeks in a row.

The firemen in every hotshot crew each have their own roles to play. Some of them are trained in first aid, while others are highly specialised lumberjacks who are able to cut down dead or burning trees. Others create fire lines by cutting down vegetation bordering the fire and moving the cut down trees into the fire.

They risk their lives
It is dangerous work, so even if you are one of the best, every now and again it costs human lives. Therefore, all hotshots carry a ‘fire shelter’ which they can use if the fire encircles them. It is designed to withstand flames and radiant heat and contains sufficient breathable air so that the fireman, in an emergency situation, can roll out the fire cover, crawl into it and survive.

However, there are no guarantees. In 1994, nine hotshot member perished in the flames in Oregon when a rapidly moving fire engulfed them. And in 2013, a particularly rapidly moving and violent fire cut a hotshot crew off from their escape route in the wilderness in Arizona. The fire spread more quickly than the crew were able to run and the violent wind created 70 metre high flames and temperatures of approximately 1,100 degrees. The crew were encircled and all of them perished.

If hotshots are the elite troops, smokejumpers are the parachute troops. They jump out of an aeroplane instead of driving or trekking to the fires. The rapid mobilisation means that they can often contain the fire before it grows too big and gets out of control.

Lack of focus on toxic smoke from furniture

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The toxicity of smoke is an important parameter when you are caught in a fire. Therefore, there are strict requirements for what the smoke from materials in trains and ships may contain. The same rules, however, do not apply to building materials or the largest source of smoke in our homes – our furniture.

As is well known, in the right quantities, everything is poisonous. And the quantities may be comparatively small when it comes to substances in smoke. If you are in a place where smoke is a crucial factor in case of fire, for example, a ship, plane or train, the toxicity of smoke is an important part of the materials’ fire-safety properties.

– The interest in toxicity in smoke grew after the fire on the Scandinavian Star ferry in 1990, where many of the ship’s passengers died due to toxic smoke, says Lina Ivar Andersen, Bachelor of Engineering and specialist in chemistry at DBI, the Danish Institute of Fire and Security Technology.

The disaster prompted the International Maritime Organization (IMO) to prepare new rules in the area, and today there are also requirements for smoke in materials for planes and trains.

– Especially for trains that are to travel through tunnels, where the risk of being poisoned in a fire is even greater, there are strict requirements regarding the toxicity of smoke. The more difficult it is to escape from a fire, the more important the smoke’s toxicity is, says Lina Ivar Andersen.

When flame retardants are a problem
There is no limit to how many substances there are to test when you investigate the toxicity of smoke, but typically the substances that are most poisonous and have resulted in death are measured – this typically includes carbon monoxide, hydrogen sulphide, nitrogen oxide, hydrochloric acid, hydrogen bromide, hydrofluoric acid and prussic acid. These substances are especially found in smoke from artificial substances, such as fibreglass or plastic materials, and may be fatal even in small doses.

– Therefore, it is a question of using sufficiently small amounts of these materials in a product. The flammable decorations on non-flammable steel walls on ships are, for example, very thin. Nearly all materials can cause problems with regard to the toxicity of smoke if there are too many of them, says Lina Ivar Andersen.

It can be a challenge when a product has to live up to toxicity requirements. Not least because other, good fire-safety properties may increase the toxicity of a product. Low heat development and fire spreading are also good properties, and they can be achieved by using flame retardants in the product.

– Flame retardants often work by making the product smoulder instead of burst into flame. On the other hand, this means that more smoke develops and the toxicity becomes higher than if it did actually burst into flames. Often, the use of more fire retardants results in more smoke and toxicity. These are useful tools, but their use is a difficult balance for manufacturers, says Lina Ivar Andersen.

No requirements for building materials
The toxicity of materials is not just a parameter for transport. And although its application to building materials is not on our doorstep, it is sometimes a topic that is discussed in European forums. Recently, the European Commission investigated the need for regulating the toxicity in smoke from building materials, which resulted in the publication of a report in the autumn of 2017. It showed, among other things, that it is probably not building materials that comprise the greatest risk for emitting poisonous smoke in our buildings and homes. On the contrary, it is the things we fill them with.

– The smoke from materials that we normally build with presumably contain a limited amount of toxicity. On the other hand, we fill our homes with furniture containing many foam materials, which give off much more toxic smoke, says Lina Ivar Andersen.

Focus on sustainability and fire safety in the EU

Construction-site

A new EU directive on the energy performance of buildings is to result in comprehensive energy renovation and strengthen the focus on obligations related to fire safety. This is explained by Bendt Bendtsen, who is a Danish member of the European Parliament and was the main negotiator for the new directive.

What is the purpose of the new energy performance of buildings directive?
– It is intended to stimulate energy renovation of existing buildings. The old directive from 2010 had a lot of requirements for new buildings, but we only build about 1% building stock a year, while 80% of our existing buildings will be in use in 2050. So, in order to have well-functioning and efficient energy consumption and make Europe more sustainable, we have to energy-renovate many more buildings – in fact, three times as many as today. Only by making our buildings more energy efficient can we cost-effectively achieve the climate and energy goals for Europe. This includes fewer fossil fuels, less import from Putin and better indoor climate for European citizens.

What role does fire safety play in the directive?
– A completely new obligation in the building directive is that member states must prepare long-term renovation strategies to achieve highly efficient and de-carbonised building stock in 2050. In the national long-term renovation strategies, the member countries can both tackle fire safety and estimate the strategies’ significance for health and indoor climate – including the safety of residents and users. According to the directive, the EU countries will – by both building new buildings and through major renovations – take healthy indoor climate conditions and fire safety into account. It is important that the industry and stakeholders insist that the governments of the EU countries live up to their obligations. First of all, when the directive is to be implemented in March 2020, but also when the directive is used in practice.

How do we ensure fire safety generally in the hunt for energy efficiency?
– Energy renovations provide a clear opportunity to tackle fire safety in a way that is the least inconvenient and least financial burden for owners, residents and users. When you energy-renovate, it makes sense to take a position on whether all fire-safety measures have been taken, and whether technical or structural changes can be made to buildings that can improve fire safety.

Joint European building regulations have been discussed before. Is this the beginning of developments in this area?
– I do not think that a European building regulation is very likely. My impression is that the governments of the EU countries will continue to insist the geographic location and placement of buildings will be too nationally specific to justify a European building code. I think that it is already a major step forward for Europe and European citizens that our EU countries have obligated themselves to have a highly efficient, de-carbonised building stock in 2050 by looking at energy performance. The toolbox for getting there is in the hands of the governments of the EU member countries, and rightly so.

Facade fires that have occurred in recent years, including, most recently, the Grenfell Tower in London, have had major consequences in Europe. What is the EU doing to confront this problem?
– In the building directive, we have focused on obligations related to fire safety. This is a good first step, but, of course, it requires that the EU countries are conscious of their responsibility when the directive becomes national legislation. In addition, I have just presented a proposal regarding the EU’s 2019 budget to improve fire statistics in Europe. An improved statistical basis is the first step towards being able to optimise fire safety efforts in the EU countries. Today, there are very different national approaches and calculation methods when it comes to fire safety. It would be good to have a joint European data basis so we can identify ‘best practice’ in the EU countries’ fire safety efforts more easily – and, in time, even start European fire safety measures.

USA streets ahead when it comes to the fire safety of mega-batteries

ESS-fire-service-safety

Mega-batteries in the electricity system, industry and in our homes are on the way, and that will throw up challenges when it comes to fire safety. In the USA, development is more advanced, and the work on managing the risks is in full swing.

Our energy system will be transformed in the years to come. Sustainable energy will become more prominent and the storage of surplus energy from wind turbines and solar cells will be an important part of the solution. Therefore, Energy Storage Systems (ESS) will play a pivotal role, both in the general infrastructure, in industry and even in domestic homes. Development is gradually getting underway around the world, but if you look at the USA, it is in full swing, with ESS being constructed on a large scale.

However, it will entail a number of fire safety challenges when you install large-scale batteries with all the chemicals and energy volumes they contain.

– In Denmark, we are sniffing around the area, for example, in connection with solar farms, in large companies and in data centres. However, the technology entails a number of challenges in terms of fire safety. In a fire, the batteries can emit flammable gases, or ‘thermal runaway’ can occur, whereby the battery generates heat uncontrollably with the result that the battery cells can self-combust. When an entire room is filled with batteries, this poses a risk that has to be managed, says Mikael N. Gam, who is a fire safety consultant with DBI – the Danish Institute of Fire & Security Technology.

New standards in the pipeline
Even though the prevalence is greater in the USA, the technology is also fairly new there. There are standards in the field but they are currently being revised thoroughly due to the experiences gleaned in recent years.

– There are new and relatively prescriptive standards on the way which must describe what you need to do to ensure an acceptable level of fire safety according to American standards. This will change, for example, when an ESS is covered by the standard based on the type of battery technology and the volume of energy in the batteries. As far as possible, the standards will also cover future technologies so that unregulated technologies cannot emerge, even though the field is developing rapidly, says Mikael N. Gam.

In addition, there will be limitations to the energy capacity (probably a maximum of 50 kW) in every block in an ESS and minimum distance requirements between the blocks and between a block and the walls, if the system is installed in a building. This way, you are minimising the risk of a fire spreading unhindered in a really large ESS. There are solutions available up to 30,000 kW, and it is expected that this will increase further in the coming years.

– At the same time, in the drafts of the new standards the scene is now set for requirements for sprinkler systems, for which there is a strong tradition in the USA, explains Mikael N. Gam.

What about the emergency response teams?
It is not only in relation to standards that ESS is being looked at in more depth in the USA. Full-scale tests of various ESS systems are being carried out in order to gain more knowledge on how batteries react in a fire when ‘thermal runaway’ occurs, what effect the batteries have in terms of heat in a fire, how fire spreads between the battery blocks, which gases are created and what can be used to extinguish them.

The last point is particularly crucial as some batteries, for example, can flare up again days or weeks after they have been extinguished and because different battery technologies require different extinguishing methods. For example, it is possible to extinguish a lithium-ion battery with water. But, if you pour water on a lithium battery it can create hydrogen, which is extremely flammable.

– Another aspect that is being focused on is the training of emergency response teams so that they can deliver an effective response. This is made more difficult by the fact that different ESS systems require different responses and that the technology is developing at such a rapid pace that standards can’t keep up. This also makes it difficult for emergency response teams to keep up, says Mikael N. Gam.

The work on fire-testing ESS systems and finding a solution to the training of emergency response teams continues apace in the USA. And, there is good reason to keep abreast of the solutions they come up with on the other side of the Atlantic. Because even if the prevalence of ESS is still limited on these shores, it is on its way.

New method of evaluating overall fire safety

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Fire safety is not just one thing. It involves an interplay between a number of different factors. And, if one of them fails, the entire projected safety falls apart.

This is the underlying basis of the NFPA Fire & Life Safety Ecosystem, which is a new approach to fire safety that was presented at the NFPA Conference & Expo in Las Vegas in the summer of 2018.

– The method means that you don’t just look at one factor – for example, the design of the building – but you have to view fire safety from a broader perspective in order to ensure that the overall level of safety is adequate. Many factors determine whether a building is safe, and if just one element does not live up to expectations, then you don’t have the expected level of safety, says Mikael N. Gam, fire safety consultant at the Danish Institute of Fire and Security Technology, DBI.

Prudent principles in tumultuous times
In specific terms, the ecosystem encompasses eight points that must be in place.

– In a time when many of the things we have historically based our fire safety on are changing – for example, the use of many new materials with different fire safety properties, the ecosystem is a highly prudent principle to work to. For everything is interlinked and, to a far greater degree than previously, we have to be aware that numerous factors impact on overall fire safety, explains Mikael N. Gam.

The eight points in the NFPA Fire & Life Safety Ecosystem:

  1. The regulatory authorities must develop and maintain effective guidelines and laws in the field.
  2. Planning and design teams must apply the latest guidelines and regulations in the field.
  3. All standards must be referenced and complied with during all phases of a building project (design, execution, operation etc.).
  4. Safety must be invested in, and it must be prioritised in relation to training, the choice of products and the enforcement of guidelines.
  5. The workforce carrying out the construction of the building must be competent and highly trained so that it can perform the work in compliance with guidelines and regulations.
  6. An effective quality assurance system must be in place in order to enforce rules and guidelines during the construction phase.
  7. Emergency response teams must be prepared, well-trained and have the necessary equipment to be able to respond to any risks that may arise.
  8. The public must be well-informed regarding the risks and dangers posed by fires before fire safety is in order.

Climate change presents new problems for the emergency services

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The dry summer has caused a record number of wildfires. This may well become the new normal, as climate change suggests that there may be many periods of drought in the future. This will present challenges for the emergency services, who will require new equipment, knowledge and training.

Whether summer 2018, with its extreme temperatures, will retain the record for being the hottest for many years, or whether climate change will make summers such as this the new normal, is a good question.

– Our scenarios indicate that in the future, the summer months will bring more precipitation in Northern Europe and less in Southern Europe. Put another way, there won’t be a great difference in the amount of precipitation, it will just be more divided. It will also be heavier and we can expect longer periods without rain, says Mikael Scharling, a climatologist with the Danish Meteorological Institute (DMI).

A higher level of drought requires more weeks dominated by high pressure, which keeps precipitation away. But whether periods of high and low pressure will become longer – such as the period of high pressure we have seen this year, remains to be seen.

New requirements for operational crew and equipment
With more dry periods in the future, operational crew, who have been on overtime this summer, should be prepared for this becoming a regular occurrence.

– If dry periods in summer become the norm, this will place completely new demands on both men and machinery. The summer has presented new challenges to take into account in our risk-based dimensioning, including scenario descriptions and capacity analysis. For example, we have experienced more wildfires and fires in woodland areas, says Emergency Services Manager, Søren Lundhild and goes on to say:

– In woodland, it’s often difficult to gain access with the equipment we have today, and it’s essential that we get in quickly so that a fire does not develop further. I think we have to look into the possibility of acquiring light vehicles such as ATVs with lightweight extinguishing equipment and other materiel.

Forest fires also burn into the roots of trees under the earth, so ground pins with water attached can also become necessary. The use of drones to gain a better overview of the spread of the fire in difficult terrain will also be useful for the fire manager.

– In addition, we will need to look at emergency management statistics to see how we can improve our competences to take the right decisions. We need to capitalise on the experience of outside experts in managing the threats posed by drought. And training must be combined with knowledge of national wind conditions, Lundhild says.

Report prepares the ground for new Building Code in the wake of Grenfell Tower

Grenfell-Tower-14.-Juni-2017

The first report following the Grenfell Tower fire in London has been published. It comes with recommendations for a new building code and fire safety system in England.

The fire at Grenfell Tower in London in the summer of 2017 cost 74 people their lives. The incident sent shockwaves through British society, and numerous studies into the Building Code, the fire and the response have been initiated. How could it all go so wrong? The report, which looked into the fire aspects of the building regulations in the UK following Grenfell Tower and a number of other fires, has now seen the light of day.  And, it concludes that new rules and systems are required.

– The report criticises the ‘race to the bottom’ when it comes to fire safety and fire technical requirements relating to construction in England, where the rules have been liberalised with no thought given to the consequences. For example, it is possible for developers to choose whether their project is to be inspected by local authority or private inspectors and, and at the same time, there are private inspectors who complain that building plans are never rejected, explains fire safety consultant Anders B. Vestergaard, who participated in the 5th International Tall Building and Safety Conference in London, where the Grenfell fire was top of the agenda.

Overall systems rather than individual materials
The situation has to change, the report underlines, while, at the same time, presenting a number of points that ought to be included in the forthcoming revised Building Code. Before the report came out, the public had high hopes that it would recommend a complete ban on the use of flammable materials on the facades of tall buildings. It didn’t. Instead, it argues that the solutions used in complex building projects are evaluated on a case-by-case basis whereby the overall solution is looked at.

– It’s all well and good discussing the individual materials, but the most important thing is that you give some thought to, and are able to document, the safety of the system overall. It’s difficult. In Denmark, there is a tradition of looking at both the cladding and insulation, but, for example, not at how the individual components are fitted, which also play a role in the overall fire safety properties of the solution, says Anders B. Vestergaard.

Clear division of responsibilities
The report also proposes that the future Building Code should include a clear division of responsibilities.  At the moment, it’s unclear who has responsibility for which aspects of fire safety and at what point in the process, and this results in carelessness and mistakes in this area.

– A classic scenario is that an architect designs a building that meets all the requirements. However, during the building process, the materials are replaced due to, among other things, the cost. Who has responsibility for that? The supplier has no insight into the final solution, and the developer perhaps has used the material in another context, or just does what he normally does. Therefore, it is unclear who has the ultimate responsibility for ensuring that the finished building reacts as envisaged in the event of a fire, says Anders B. Vestergaard.

This example is roughly what happened with Grenfell Tower, too. Originally, the building was to be clad inflammable insulation and zinc plates, which do not contribute to the spreading of a fire. However, they were replaced with aluminium plates with plastic cores during the building process, which contributed to the spread of the fire.

– Here, the level of knowledge in the industry is crucial. Consultants, inspectors and others must be aware of these things and know the pitfalls, so that something like this never happens,says Anders B. Vestergaard.

With the clear division of responsibilities recommended in the report, it will be easier to check that everyone is fulfilling their responsibilities. And, at the same time, punish those who aren’t. The report recommends that greater action is taken in the future and that the Building Code is given ‘real teeth’ – i.e. the ability to impose serious penalties. Now, the challenge lies in finding the political will to implement the report’s recommendations and produce the Building Code outlined in the report.

Solid timber elements can self-extinguish in the event of a fire

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There is considerable evidence that timber will become an even more important construction material. In recent years, several researchers have been investigating the strength and fire safety properties of cross-laminated timber, and it is hoped that newer versions of solid timber elements will, by and large, be fire-resistant.

Is it possible to use more timber in building constructions? That is an exciting question which preoccupies researchers in timber around the world. Dr. Richard Emberley from California Polytechnic State University in the USA has, for example, carried out research into the self-extinguishing abilities of burning timber, and Danish architect Kristine Sundahl is investigating the role of materials, particularly timber, in architecture for her Business PhD.

– A major problem in the area is that large swathes of the population perceive timber as a flammable material that isn’t safe to live in. However, the type of timber we are working with today is completely different to the lightweight constructions of light timber used previously, says Dr. Richard Emberley.

Construction material of the future
The two researchers agree that there are exciting opportunities in construction elements made from cross-laminated timber, also known as CLT. Cross-laminated timber is a solid timber element comprising a number of different layers placed perpendicularly on top of one another. The weaknesses are evened out in the cross-lamination so that the bearing capacity is distributed. The layers are glued together with solid timber elements that have substantial rigidity and strength as well as being extremely dimensionally stable.

– There is a lightness in timber, and it has many excellent properties which make it suitable for use as a surface. It is rigid and strong and good for covering long expanses, such as horizontal division structures, floors and ceilings. Moreover, timber is more environmentally-friendly to produce than both concrete and iron and it provides an excellent indoor climate, explains Kristine Sundahl.

On top of that, solid timber elements weigh less than concrete, which means that you can make do with a smaller and less expensive foundation. According to Dr. Richard Emberley, the large transversal sections that can be produced from cross-laminated timber make it possible to utilise the timber’s ability to self-extinguish.

Self-extinguishment
Indeed, the ability to self-extinguish is a subject on which Dr. Richard Emberley has carried out research during his PhD project.

– The term self-extinguishment is used when the energy provided by the flames is not sufficient to break down the material and the fire needs an external source of energy in order to keep going and destroy the timber. Thus, you could say that the fire suffocates itself, says Dr. Richard Emberley, who goes on to explain that the solid timber elements are compressed so tightly together that it provides a high degree of fire resistance in both load-bearing and partitioning structures.

CLT solid timber elements provide such good fire safety that it can be compared to non-flammable construction materials. CLT does not burn, rather it carbonizes slowly and at a predictable speed so that its bearing properties are maintained for a long time.

The construction industry awaits
The strength of solid timber elements, combined with the ability to self-extinguish, make it possible to use timber in construction to a far greater degree than previously. And, research is still being carried out into the properties and limitations of solid timber elements in several places around the world, Dr. Richard Emberley informs us.

He has contributed to the research himself by, for example, carrying out a number of both small and large-scale trials whereby different sizes of rooms constructed from timber were ignited. The purpose of the trials was to determine the extent to which timber can ideally be compressed in order to make it fireproof.

However, Kristine Sundahl believes that re-establishing timber as one of the major construction materials will be a long, drawn-out process. She is following research around the world where the focus is on finding the right quantity and composition of glue while, at the same time, experiments are being carried out on joints, moisture and the spread of fire.

– Architects and engineers are, in a way, biding their time with regard to the testing of CLT and are awaiting the results of, for example, research and experiences gleaned from the buildings of solid timber elements that have already been constructed.  However, it takes time to change a tradition in the construction industry, says Kristine Sundahl.

 

Cause of multistorey carpark fire in Liverpool still unclear

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Never before have 1,400 cars been engulfed by flames in a multistorey carpark. But this is what happened in Liverpool in December 2017. The question now is, what was the reason for the violent fire spread and what effect will the fire have on parking facilities in a number of European countries?

On 31 December, fire broke out in a car in a multistorey carpark in Liverpool. The carpark was a concrete building open on all sides – very much like the ones we know in Denmark. What is totally unfamiliar is the way in which the fire developed. Despite a prompt alarm call, a call-out time of eight minutes and 21 emergency response vehicles during the time of the action, the firefighting forces were unable to prevent the fire from spreading between cars and the storey deck, causing the write-off of all 1,400 cars plus the building. Questions are now being raised as to how this could happen.

– We know of similar fires in multistorey carparks in various locations abroad, but at the worst this has meant five or six destroyed cars and in a few cases more extensive fires, but nothing comparable to the fire in Liverpool. This is an unprecedented case and ought not to be possible, says Ib Bertelsen, Customer & Relations Director at DBI, the Danish Institute of Fire and Security Technology.

Explanations sought
In particular, the rapid fire spread is a matter of surprise.

– Naturally, sprinklers would have retarded fire development, but this was presumably a fully legal building of conventional construction. However, it is possible that difficulties in response tactics played a role, Bertelsen says, with the following explanation:

– When a car fire is reported, a reduced response team is sent out in the first instance, because it is ‘just’ a car fire. And it may be hard for the fire crew to access the scene of the fire.

Another possibility is that petrol and other flammable liquids leaked from the damaged cars and contributed to the rapid and violent fire spread. The local fire force estimates that the temperature was up to 1,000 degrees.

– That’s a lot, and we don’t yet know the specific circumstances, but even so, it is surprising that the situation could go so badly wrong in a properly constructed building. It will be very interesting to hear a likely explanation of why things developed as they did, Bertelsen says.

May change dimensioning
Once the explanation has been determined, the next question is whether this will have consequences in other countries.

– If there is no reasonable explanation, then, to the extent we have similar buildings in Denmark, we ought to be thinking about how we dimension our buildings and what scenarios we are dimensioning them for, Bertelsen says.

And maybe not just multistorey carparks will be subject to change – depending on the explanation from Britain.

– To a certain extent, you can compare them with large open-air carparks. Obviously, conditions are completely different in a building, but the cars are just as tightly spaced in an open carpark.