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INTERNATIONAL COOPERATION
Improving Fire Safety in Buildings
In last month’s column introducing initiatives of Japan’s Building ing material which is made with a non-
Research Institute, we looked at the Institute’s efforts to unravel the combustible material, and it prevents the
heat of a fire from conducting to the
mystery of wind damage to buildings. In this month’s issue we look at components. As long as the temperature
the Institute’s work to improve the fire-resistance performance of of the components is kept down, it is
buildings as well as to develop performance regulations for fire control possible to retain the certified strength
standards based on clarification of fire phenomena. of the design.
In addition, it is important to create
fire compartments to contain fires. A
espite starting on the twen- engineers. As a result, we found that due building or a floor is divided into several
ty-first floor, a fire in a to ongoing refurbishment of fire safety fire compartments. If a fire breaks out, it
high-rise building in Spain measures, no fire compartments were is contained inside the fire compartment
Din February 2005 destroyed installed in the building where the fire where it started. Using materials that do
almost the whole thirty-two-story tower broke out. Therefore, the fire was able not easily conduct heat and securing a
with widespread collapse of the exterior to spread through the gaps in the exterior sufficient thickness for the walls and
walls and floors of the upper stories walls and between the floors to the floors of the fire compartment make it
(photo 1). Had it been a wooden build- upper and lower floors in a short time, difficult for the fire to spread to sur-
ing, there would have been no wonder and it became clear that the columns of rounding areas. It is then possible to
about its total destruction and collapse the peripheral steel frame lost strength prevent the fire from spreading beyond
in a fire. However, there are hardly any and broke down in the heat of the fire the fire compartment and to prevent the
examples of a high-rise building collaps- causing the widespread collapse. destruction of the whole building.
ing in a fire. Since the Building Aiming to improve fire safety in
Research Institute had a very strong in- Constructing Fire-Resistant buildings, the Building Research
terest in the collapse of the building as a Buildings Institute is promoting research based on
result of this fire, we organized a field incidents such as the collapse of high-
trip to Spain together with Japanese fire In the past, many buildings and towns rise buildings caused by fires in recent
in Japan were constructed in wood years. This article introduces some re-
and as a result, we have repeatedly ex- cent research on improving fire-resistive
perienced the total destruction of houses performance in buildings.
or the devastation of whole towns once
a fire breaks out. Therefore, from the Confirming Fire Resistance of Full-
late nineteenth century, buildings have Size Steel Structural Components
been constructed with non-combustible
material such as brick, concrete and Steel frames and steel are widely used
steel to protect buildings and cities from materials in high-rise buildings and in
fire. Certainly, a building constructed buildings with large interior spaces.
with non-combustible materials will not Steel, of course, does not burn but if the
itself burn, but many of our personal ef- heat of a fire reaches high temperatures,
fects including clothes and furniture are it loses its strength and as a result, there
TITUTEcombustible. Even if a building is con- is a risk of deformation in steel columns
S
N structed in concrete and steel, as long as and beams. Therefore, the steel frame is
there are people living in it, they will protected with so-called fire-protective
ESEARCH Iuse fire and since there are a lot of com-covering, which is material with high in-
NG Rbustible items inside a house, it is not sulation properties, to prevent the heat of
LDI
I possible to completely prevent the out- a fire from driving up the temperature.
U
B
E break of fires. Buildings constructed The capacity of columns, beams and
with columns and beams made of steel, other components to withstand the heat
Y OF THfor example, also collapse with the im- of a fire and to support the weight of a
TES
R pact of the heat from a fire. building (load-bearing capacity) and the
U
O What can we do to construct build- capacity of walls, floors and other com-
OS C
T ings that are fire resistant and do not ponents to block the heat of a fire and
O
H collapse in a fire? First, we protect the the flames themselves (insulation, integ-
ALL Pcolumns, beams and other components rity) are collectively referred to as fire-
Photo 1: Total destruction of high-rise
building in Spain with large-scale with fire protective covering. Briefly, a resistive performance. Components are
collapse of the upper floors fire protective covering is a heat insulat- tested for fire-resistive performance by
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INTERNATIONAL COOPERATION
Fire Resistance in Wooden Buildings
loading them into a furnace that repro-
duces the heat of a fire furnace. The du-
ration until fire-resistive performance is Since there are definite limits on the
lost (destruction, heat penetration, holes) strength, fire resistance and other per-
under exposure to the heat from the fire formance of wooden materials, efforts
is called the fire resistance rating. are underway to develop wood com-
Naturally, the longer the time, the higher posites by combination with steel and
the fire-resistive performance. other materials, or hybrid wooden
The Building Standards Law of Japan structures by combination with rein-
determines the required fire-resistive forced concrete construction and other
performance for components, that is, the structures. For our research, we imple-
fire resistance rating, in accordance with mented the premise of a four-story
the purpose, number of floors and scale building using wood composites and
of buildings. There are notifications of hybrid wooden structures.
concrete specifications. For example, The drawback of wood is its com-
where the steel frame columns (a mini- bustibility. It is certainly the case that
mum breadth end diameter of at least small components will ignite and burn
25 cm) are covered with a fire-resistive Photo 2: Test column up within a short time if they are ex-
covering of bricks to a thickness of at after fire testing where posed to the heat of a fire but when the
least 7 cm, the fire resistance rating is 25% of the fire resistive components are large and thick, the
two hours. covering was stripped off surface burns without the combustion
According to the Building Standards reaching the interior. This is because a
Law of Japan, a fire resistance rating of char layer forms when wood burns cre-
three hours is required for columns near Next, we simulated earthquake ating an insulating effect that blocks the
to the ground level in skyscrapers. It is damage to the fire protective covering heat from the flame.
necessary to conduct fire resistance tests and conducted a test with 25% of the Therefore, we combined wood and
of the columns to confirm they have the covering removed. As a result of the steel to develop a component with glued
necessary fire resistance ratings with the loss of the insulating effect of the fire laminated timber (called glulam, made
applied load, but in the past these tests protective covering, the fire rating was of several layers of dimensioned timber
have not been possible with full-size reduced to a mere 27 minutes. Since glued together) bonded to the circumfer-
columns due to the poor performance the areas without fire protective cover- ence of a steel frame. When this compo-
of the testing equipment. Therefore, we ing conducted large quantities of heat nent is exposed to heat, the surface of
confirmed the fire-resistance performance from direct exposure to the fire, the the glulam ignites but as it burns, a char
with the full-size columns used in the columns were heated to a high tempera- layer is formed that functions as a fire
first floor of a fifty-story building using ture in a short time despite their large protective coating, as it were, and the
the Building Research Institutes upgrad- size (photo 2). insulating effect can prevent the tem-
ed fire furnace for columns, which has In the past, there has hardly been perature in the steel frame from rising.
the highest load capacity in the country. any research of fire safety measures fol- After the heat of the fire has been re-
Fire protective covering equivalent lowing earthquakes. After demonstrating moved, the glulam portion is smolder-
to a fire rating of 1 hour was applied to in this manner that damage or loss of ing. We refer to this material that com-
the steel frame columns that were tested. fire protective
We found that the fire-resistive perfor- covering has a
mance of the columns was adequate as large impact on
they did not break even after more than lowering fire-
three hours of fire testing. This was resistive perfor-
thought to be due to the impact of the mance, we plan
large dimensions of the steel frame col- to carry on full-
umns in addition to the insulating effect scale research
of the fire protective covering. It is the into measures to
same reasoning whereby a small amount prevent damage
of heat will warm a cup of water, but a or loss of fire
large amount of heat is necessary to protective cov-
warm a bathtub full of water. Since a ering and other
large amount of heat is needed to heat up measures to se-
a steel frame column of large dimensions, cure fire safety
it is obvious that the column as a whole in the wake of
is difficult to heat up. As a result, the fire an earthquake.
rating was higher than expected. Photo 3: Full-size fire testing of a wooden hybrid construction
10
Photo 4: Fire performance after testing wood and requiring fire resis- ated inside the concrete when it conducts
tive ratings is already under the heat from a fire and it is hoped that
construction in Japan. Wood this would have the effect of allowing
as a building material has re- the moisture under pressure to escape.
cently attracted worldwide at- As a result, tests have confirmed that
tention as a sustainable mate- spalling would be curbed to a certain
rial that also reduces CO . As degree even when the concrete is ex-
2
a result, much is anticipated posed to the heat of a violent fire.
from continued research and
development aiming to ex- Future Research Topics
pand the use of wood while
securing fire safety. To confirm the safety performance of
buildings, the Building Research
Prevention of Spalling in Institute is working on topics such as
Concrete Components analysis of the phenomena of fire, evalu-
ations of the performance of fire safety
Combined with rebars and measures and performance-based fire
steel frames, concrete is a safety standards. Fire safety measures in
widely used construction ma- buildings have long been required by the
terial for buildings, roads and specifications of building regulations.
tunnels. Since the concrete Naturally, the standards in these laws
itself does not burn, it is
bines a steel frame with wood (glulam) thought that buildings made of concrete
as a Hybrid Timber Member. can withstand fire. It is certainly the case
We have developed posts and beams that in normal fires, there is only discol-
with a fire rating of one hour using the oration to the surface of the concrete and
Hybrid Timber Member and we have there is hardly any structural damage.
confirmed the performance by conduct- However, in case of exposure to violent
ing fire resistance testing. We also de- fires burning for a long time, spalling
signed a four-story office building using occurs in the surface of the components
Hybrid Timber Member posts and and damage is caused when portions of
beams, even erecting a part of the build- the concrete are stripped off. Also, as the
ing for full-scale fire testing. As a result surface of concrete was lost and the rein-
of a damage survey after the fire, we forcing steel became exposed, another
were able to confirm that the perfor- problem arose whereby the steel became
mance of the post and beam components extremely hot from the heat of the fire.
was identical to the fire resistance test, Since buildings are at risk of collapse in
allowing us to ascertain the fire-resistive a fire if the components are damaged on
photos 3, 4).
performance ( this scale, it is necessary to prevent spall-
The Building Standards Law of photo 5).
ing of concrete (
Japan was established to limit the height, There are various theories for the Photo 5: Spalling in concrete com-
number of floors and scale of wooden spalling mechanism of concrete but the ponents
buildings without any acknowledgement most plausible theory is that spongy
of building fire resistant buildings in pores in the concrete are destroyed with and regulations are the accumulation of
wood. However, the revised Building increased pressure on the moisture con- the knowledge of engineers based on
Standards Law of Japan (1998–2000) in- tent when exposed to the heat of a fire. past experiences of fire. However, as a
troduced performance-based provisions Consequently, one measure to prevent result of great progress in the fire sci-
for the fire-resistive performance required spalling might be to control the sudden ence and fire safety engineering, there
of fireproof buildings without restric- rise in temperature in the surface of the are now glaring inadequacies in the
tions on the materials used for the concrete, but from an economical view- specification standards. With regard to
structural components, which effective- point, it is difficult to apply fire protec- the required fire-resistive performance
ly constitutes an acknowledgement of tive covering on a broad scale. of buildings, aside from the specification
the use of wood in fire resistant build- Another method might be to mix the standards of the past, it is also necessary
ings. That is to say, it is now possible to concrete with organic fiber to create to undertake research in order to clarify
construct medium-rise buildings of four pathways to allow the moisture content the primary and fundamental perfor-
to five floors using the Hybrid Timber under pressure to escape to the outside. mance required by the society. This is
Member that we have developed. Since organic fiber melts at a fairly low an area that the Building Research
A succession of buildings using temperature, new pores would be gener- Institute plans to tackle in the future.
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