INTERNATIONAL COOPERATION

Improving Fire Safety in Buildings
In last month’s column introducing initiatives of Japan’s Building
Research Institute, we looked at the Institute’s efforts to unravel themystery of wind damage to buildings. In this month’s issue we look at
the Institute’s work to improve the fire-resistance performance ofbuildings as well as to develop performance regulations for fire control
standards based on clarification of fire phenomena.

Despite starting on the twenty-first floor, a fire in ahigh-rise building in Spainin February 2005 destroyed
almost the whole thirty-two-story towerwith widespread collapse of the exterior
walls and floors of the upper stories(photo 1). Had it been a wooden building, there would have been no wonder
about its total destruction and collapse
in a fire. However, there are hardly any
examples of a high-rise building collapsi n g i n a fire . Sinc e t he Bui l di ng
Research Institute had a very strong interest in the collapse of the building as aresult of this fire, we organized a field
trip to Spain together with Japanese fireengineers. As a result, we found that dueto ongoing refurbishment of fire safetymeasures, no fire compartments wereinstalled in the building where the fire
broke out. Therefore, the fire was able
to spread through the gaps in the exterior
walls and between the floors to theupper and lower floors in a short time,and it became clear that the columns of
the peripheral steel frame lost strengthand broke down in the heat of the firecausing the widespread collapse.

ALL PHOTOS COURTESY OF THE BUILDING RESEARCH INSTITUTE

Constructing Fire-Resistant
Buildings

Photo 1: Total destruction of high-risebuilding in Spain with large-scalecollapse of the upper floors

In the past, many buildings and towns
in Japan were constructed in woodand as a result, we have repeatedly experienced the total destruction of housesor the devastation of whole towns oncea fire breaks out. Therefore, from thelate nineteenth century, buildings havebeen constructed with non-combustible
material such as brick, concrete andsteel to protect buildings and cities fromfire. Certainly, a building constructedwith non-combustible materials will notitself burn, but many of our personal effects including clothes and furniture arecombustible. Even if a building is constructed in concrete and steel, as long as
there are people living in it, they will
use fire and since there are a lot of combustible items inside a house, it is notpossible to completely prevent the outbreak of fires. Buildings constructedwith columns and beams made of steel,for example, also collapse with the impact of the heat from a fire.
What can we do to construct buildings that are fire resistant and do notcollapse in a fire? First, we protect thecolumns, beams and other components
with fire protective covering. Briefly, afire protective covering is a heat insulat-ing material which is made with a noncombustible material, and it prevents theheat of a fire from conducting to thecomponents. As long as the temperatureof the components is kept down, it ispossible to retain the certified strengthof the design.
In addition, it is important to create
fire compartments to contain fires. A
building or a floor is divided into several
fire compartments. If a fire breaks out, itis contained inside the fire compartment
where it started. Using materials that do
not easily conduct heat and securing asufficient thickness for the walls andfloors of the fire compartment make it
difficult for the fire to spread to surrounding areas. It is then possible toprevent the fire from spreading beyond
the fire compartment and to prevent thedestruction of the whole building.
Aiming to improve fire safety inbuildings, the Building ResearchInstitute is promoting research based onincidents such as the collapse of highrise buildings caused by fires in recentyears. This article introduces some recent research on improving fire-resistive
performance in buildings.
Confirming Fire Resistance of FullSize Steel Structural Components

Steel frames and steel are widely usedmaterials in high-rise buildings and inbuildings with large interior spaces.
Steel, of course, does not burn but if theheat of a fire reaches high temperatures,
it loses its strength and as a result, there
is a risk of deformation in steel columns
and beams. Therefore, the steel frame isprotected with so-called fire-protective
covering, which is material with high insulation properties, to prevent the heat ofa fire from driving up the temperature.
The capacity of columns, beams andother components to withstand the heatof a fire and to support the weight of abuilding (load-bearing capacity) and thecapacity of walls, floors and other components to block the heat of a fire andthe flames themselves (insulation, integrity) are collectively referred to as fireresistive performance. Components aretested for fire-resistive performance by9INTERNATIONAL COOPERATION
loading them into a furnace that reproduces the heat of a fire furnace. The duration until fire-resistive performance islost (destruction, heat penetration, holes)under exposure to the heat from the fireis called the fire resistance rating.
Naturally, the longer the time, the higher
the fire-resistive performance.
The Building Standards Law of Japan
determines the required fire-resistive
performance for components, that is, thefire resistance rating, in accordance withthe purpose, number of floors and scaleof buildings. There are notifications ofconcrete specifications. For example,
where the steel frame columns (a minimum breadth end diameter of at least
25 cm) are covered with a fire-resistive
covering of bricks to a thickness of atleast 7 cm, the fire resistance rating is
two hours.
According to the Building Standards
Law of Japan, a fire resistance rating of
three hours is required for columns nearto the ground level in skyscrapers. It isnecessary to conduct fire resistance testsof the columns to confirm they have thenecessary fire resistance ratings with theapplied load, but in the past these tests
have not been possible with full-sizecolumns due to the poor performanceof the testing equipment. Therefore, we
confirmed the fire-resistance performancewith the full-size columns used in thefirst floor of a fifty-story building using
the Building Research Institute’s upgraded fire furnace for columns, which has
the highest load capacity in the country.
Fire protective covering equivalent
to a fire rating of 1 hour was applied tothe steel frame columns that were tested.
We found that the fire-resistive performance of the columns was adequate as
they did not break even after more than
three hours of fire testing. This wasthought to be due to the impact of thelarge dimensions of the steel frame columns in addition to the insulating effectof the fire protective covering. It is thesame reasoning whereby a small amountof heat will warm a cup of water, but alarge amount of heat is necessary towarm a bathtub full of water. Since alarge amount of heat is needed to heat up
a steel frame column of large dimensions,
it is obvious that the column as a wholeis difficult to heat up. As a result, the fire
rating was higher than expected.
10Fire Resistance in Wooden Buildings

Photo 2: Test column
after fire testing where25% of the fire resistive
covering was stripped off

Next, we simulated earthquake
damage to the fire protective coveringand conducted a test with 25% of thecovering removed. As a result of theloss of the insulating effect of the fire
protective covering, the fire rating wasreduced to a mere 27 minutes. Since
the areas without fire protective covering conducted large quantities of heatfrom direct exposure to the fire, thecolumns were heated to a high temperature in a short time despite their large
size (photo 2).
In the past, there has hardly been
any research of fire safety measures following earthquakes. After demonstratingin this manner that damage or loss offire protective
covering has alarge impact onlowering fireresistive performance, we plan
to carry on fullscale research
into measures toprevent damage
or loss of fire
protective covering and othermeasures to secure fire safety
in the wake ofan earthquake.

Since there are definite limits on thestrength, fire resistance and other performance of wooden materials, efforts
are underway to develop wood composites by combination with steel andother materials, or hybrid wooden
structures by combination with reinforced concrete construction and otherstructures. For our research, we implemented the premise of a four-story
building using wood composites andhybrid wooden structures.
The drawback of wood is its combustibility. It is certainly the case that
small components will ignite and burnup within a short time if they are exposed to the heat of a fire but when thecomponents are large and thick, thesurface burns without the combustion
reaching the interior. This is because achar layer forms when wood burns creating an insulating effect that blocks theheat from the flame.
Therefore, we combined wood andsteel to develop a component with glued
laminated timber (called glulam, madeof several layers of dimensioned timberglued together) bonded to the circumference of a steel frame. When this component is exposed to heat, the surface ofthe glulam ignites but as it burns, a charlayer is formed that functions as a fire
protective coating, as it were, and theinsulating effect can prevent the temperature in the steel frame from rising.
After the heat of the fire has been removed, the glulam portion is smoldering. We refer to this material that com-

Photo 3: Full-size fire testing of a wooden hybrid construction

Photo 4: Fire performance after testingwood and requiring fire resistive ratings is already underconstruction in Japan. Woodas a building material has recently attracted worldwide attention as a sustainable material that also reduces CO2. As
a result, much is anticipatedfrom continued research anddevelopment aiming to expand the use of wood while
securing fire safety.
Prevention of Spalling inConcrete Componentsbines a steel frame with wood (glulam)
as a Hybrid Timber Member.
We have developed posts and beams
with a fire rating of one hour using theHybrid Timber Member and we haveconfirmed the performance by conducting fire resistance testing. We also designed a four-story office building using
Hybrid Timber Member posts andbeams, even erecting a part of the building for full-scale fire testing. As a resultof a damage survey after the fire, wewere able to confirm that the performance of the post and beam components
was identical to the fire resistance test,
allowing us to ascertain the fire-resistive
performance (photos 3, 4).
The Building Standards Law ofJapan was established to limit the height,
number of floors and scale of woodenbuildings without any acknowledgementof building fire resistant buildings inwood. However, the revised BuildingStandards Law of Japan (1998–2000) introduced performance-based provisions
for the fire-resistive performance requiredof fireproof buildings without restrictions on the materials used for thestructural components, which effectively constitutes an acknowledgement of
the use of wood in fire resistant buildings. That is to say, it is now possible toconstruct medium-rise buildings of four
to five floors using the Hybrid Timber
Member that we have developed.
A succession of buildings using

Combined with rebars andsteel frames, concrete is a
widely used construction material for buildings, roads andtunnels. Since the concreteitself does not burn, it isthought that buildings made of concrete
can withstand fire. It is certainly the casethat in normal fires, there is only discoloration to the surface of the concrete andthere is hardly any structural damage.
However, in case of exposure to violent
fires burning for a long time, spalling
occurs in the surface of the components
and damage is caused when portions ofthe concrete are stripped off. Also, as thesurface of concrete was lost and the reinforcing steel became exposed, anotherproblem arose whereby the steel became
extremely hot from the heat of the fire.
Since buildings are at risk of collapse ina fire if the components are damaged on
this scale, it is necessary to prevent spalling of concrete (photo 5).
There are various theories for the
spalling mechanism of concrete but themost plausible theory is that spongy
pores in the concrete are destroyed withincreased pressure on the moisture content when exposed to the heat of a fire.
Consequently, one measure to prevent
spalling might be to control the sudden
rise in temperature in the surface of theconcrete, but from an economical viewpoint, it is difficult to apply fire protective covering on a broad scale.
Another method might be to mix theconcrete with organic fiber to create
pathways to allow the moisture content
under pressure to escape to the outside.
Since organic fiber melts at a fairly low
temperature, new pores would be gener-

ated inside the concrete when it conducts
the heat from a fire and it is hoped thatthis would have the effect of allowing
the moisture under pressure to escape.
As a result, tests have confirmed thatspalling would be curbed to a certain
degree even when the concrete is exposed to the heat of a violent fire.
Future Research Topics

To confirm the safety performance ofbuildings, the Building ResearchInstitute is working on topics such as
analysis of the phenomena of fire, evaluations of the performance of fire safetymeasures and performance-based fire
safety standards. Fire safety measures inbuildings have long been required by thespecifications of building regulations.
Naturally, the standards in these laws

Photo 5: Spalling in concrete components

and regulations are the accumulation of
the knowledge of engineers based on
past experiences of fire. However, as aresult of great progress in the fire science and fire safety engineering, there
are now glaring inadequacies in thespecification standards. With regard to
the required fire-resistive performanceof buildings, aside from the specification
standards of the past, it is also necessary
to undertake research in order to clarify
the primary and fundamental performance required by the society. This is
an area that the Building ResearchInstitute plans to tackle in the future.
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