Travelling fires pose an underestimated risk to open building spaces


Date:
October 4, 2021
Source:
Imperial College London
Summary:
New research has shown that traveling fires pose a risk to the
structures of large open building spaces over 100m2.



FULL STORY ==========================================================================
With more and more large office spaces designed as open-plan,
the researchers say their findings should be taken into particular consideration when designing spaces like offices and warehouses larger
than 100m2.


==========================================================================
The lesser-known 'travelling fires', which travel within large building compartments rather than engulfing whole rooms at once, can cause at least
as much structural damage and potential building collapse as typical
fires. They are likely to be especially prevalent in large spaces with
ample fuel and fewer doors and interior walls, like open-plan offices
and warehouses.

Structural engineers design buildings to survive fires use guidelines like standard fire and Eurocode parametric fires. Using these guidelines,
they typically focus on the fires that engulf whole rooms at once,
known as flashover fires.

This new research, published today in the journal Fire Technology, shows
that open spaces are also vulnerable to travelling fires -- a lesser-known
fire type that burns locally and moves across an entire floor over time.

Senior author of the paper Professor Guillermo Rein of Imperial's
Department of Mechanical Engineering said: "Previous fire experiments
have found that designing against flashover fires is key for buildings
with smaller spaces separated by walls and doors. However, now that
structural engineers are designing large open-plan spaces more frequently,
it's important to better understand how fires behave in these spaces.

"We found that buildings with open plans are in fact vulnerable to
travelling fires, but this fire type is not yet weighted as heavily as flashover fires when designing buildings. We want engineers to understand
that protecting against travelling fires could be just as important as protecting against more typical ones. By considering both fire types,
engineers can be confident that they are considering the worst-case
scenario." Travelling fires


========================================================================== Traditional engineering guidelines for assessing fire safety in new
buildings are based on observational experiments of fire dynamics in compartments much smaller than 100m2. These experiments have led to
the assumption that flashover fires should be the main objective in
structural design against fire. However, due to the lack of experiments
in larger compartments, the potential significance of travelling fires
in larger compartments is poorly understood.

To put travelling fires to the test, Imperial researchers designed the
largest compartment fire experiment ever conducted, known as x-ONE. Using
a disused 380m2 open-space concrete farm building in Poland, they started
a fire at one end and measured its behaviour as it spread across the 35.5-metre-long compartment. Before doing so, they applied fire protection
to columns to prevent structural damage and laid down a bed of fuel to
feed the fires.

Within 12 minutes, the fire had spread the length of the compartment
and had increased in speed from 0.33 to 16.7 centimetres per second as
the size of the fire increased. It burned out after 25 minutes. Despite
the size increase, the fire did not reach flashover.

The researchers reported that the fire dynamics observed during
x-ONE differed greatly from the fire dynamics reported in small-scale compartment fires in previous studies. The findings also challenge
flashover fires as the sole worst-case scenario in designing buildings.

They say this highlights the need for further experiments in large
compartments to understand open-space fire dynamics and continue improving
the safe design of modern buildings.

Dr Egle Rackauskaite, who led the work while at Imperial's Department
of Mechanical Engineering and is now at Arup, said: "Despite the lack of advanced studies, travelling fires have been observed in real incidents --
for example, in the World Trade Centre towers after the 11 September 2001 attacks. However, these fires have rarely been studied on an experimental basis. At the same time, some modern structures have open-plan spaces
between four and 50 times larger than the largest compartment fire
experiments conducted to date. This highlights a key knowledge gap in
fire engineering design which must be addressed with further research." ========================================================================== Story Source: Materials provided by Imperial_College_London. Original
written by Caroline Brogan. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. Egle Rackauskaite, Matthew Bonner, Francesco Restuccia, Nieves
Fernandez
Anez, Eirik G. Christensen, Nils Roenner, Wojciech Wegrzynski, Piotr
Turkowski, Piotr Tofilo, Mohammad Heidari, Panagiotis Kotsovinos,
Izabella Vermesi, Franz Richter, Yuqi Hu, Chloe Jeanneret, Rahul
Wadhwani, Guillermo Rein. Fire Experiment Inside a Very Large
and Open- Plan Compartment: x-ONE. Fire Technology, 2021; DOI:
10.1007/s10694-021- 01162-6 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/10/211004104126.htm

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