Design of Fire Protection Systems for Tall Buildings

8/17/2019 Design of Fire Protection Systems for Tall Buildings

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Design of Fire Protection Systems for Tall Buildings

And

Problems in the light of Case study


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Index

1.

Background of fires in Tall Buildings

2. Characteristic of Tall Buildings

3. Comparison between Low Rise and High Rise Buildings

4. Design Of Fire Protection Systems in the light of Standards and

Codes

5. Fire-Resistance-Rated Construction

6. Fire Protection System

7. Problems of Fire protection systems with WTC Case Study

8. Conclusion

9.

References

10. Appendices


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Background of Fires in Tall Buildings

Recent collapse of tall building had a havoc effects and have made an all designers and building

engineers reconsider the potential dangers to the structures and the safety of the inhabitants. Now

fires in Tall buildings have become a prominent possible reason for collateral damage of both

life and finances. These structures pose an equal threat to the neighboring structures as well.

The only reason that designer didn’t previously considered it as a potential threat was that

occurrence of these events are very less. But detailed studies after the WTC event have shown

immense levels of flaws in the fire protection systems of tall buildings. The recent examples of

fires resulting into complete collapse are the WTC 1, 2 and 7. Then the complete collapse of

Apartment Block in St. Petersburg, Russia in June 3.2002, then Jackson Street apartments in

Hamilton, Ontario, Canada in Feb 8,2002. A list of collapses has been provided in the Appendix

2 of all the collapse that was seen in the past. The concept of fire proof construction is that the

despite the complete burnout of the structure, the structure must not collapse at any cost. For this

there are two steps that are taken by the standards and other implementation bodies. Firstly the

building should be resistant to fire for a certain level which about 3 hrs, this is done to safeguard

from the collapse of structure and secondly an effective fire protection system should be in place,

which is present for the purpose of detection, fire fighting and for effective evacuation of

inhabitants. At present the only International Building Code IBC 2006 solely has prescriptive fire

resistance construction regulations and bounds the designer to follow it for protection of

structure against fire. IBC is also supported by National Fire Protection Association and other

similar organization, which I have discussed in detail in later sections. The Approach of this


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report would be very similar to the process involved in designing a fire resistant Tall building

with effective fire protection system.

Characteristic of Tall Buildings

As we are well aware of the processes through which the fire protection facility is brought into

commission, where the first phase is the analysis and requirement determination of the fire

protection, then the second is the design of these required systems, the third is the construction

and finally the maintenance and operations of these systems.

Before the commencement of the design phase of a fire protection system the first and foremost

step is to evaluate and analyze the building features and when does it become of detrimental to

design a prefect system. What are the different category of buildings and the types of

construction. The first and basic categorization is on the basis of number of stories, under which

the building which has more than 7 stories is declared as tall building. Then these tall building or

high rise building are subdivided into four property classes, where first is Apartment Buildings,

second being Hotels, Hospitals and other facilities that care for the sick and Office Buildings

being the third and fourth type.

On the other hand the discrimination is made on the basis of construction material. According to

National Fire Protection Association, (NFPA 220, 2006) there are two basic types of

construction: it either burns (combustible) or it does not (noncombustible). These types of

construction can be further broken down into five categories. Type I is fire-resistive construction

which majorly consists of materials such as precast concrete slabs, concrete columns and beams

in this type the structural members are designed to resist fire for about 3 -4 hours and have

sufficient fire resisting rating. Type II is Noncombustible, this type represents those building


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having steel beams and girders, they are susceptible to steel deformation and resulting collapse

with less or no warning. Where as Type III is the ordinary construction, Type IV is the Heavy

Timber, Type V is Wood Frames but these structures are not used to make tall buildings and IBC

permits only Type I and Type II to be used.

Now the first problem that arises is that, at present all over the world fire regulations and

building codes through out the world using performance-based systems. These systems include

aspects like (David Scott, 2006) Calculation of fire size, means of detection and suppression,

smoke management fire initiation and development, means of escape, fire fighting facilities and

response, materials and their response to fire – internal linings and finishes and etc. But the real

issue is that all these provide us the post fire situation and does not consider the collapse analysis

of the structure as a whole and elements as individuals. Where as the latest concept of induced

progressive collapse solves the major issues and now through these analysis techniques and

procedures we can simulate and calculate the failure pattern and forces due to fire loadings

which were not possible before. The progressive collapse analysis is now becoming the basis of

almost all codes that consider fire protections. The structural response is evaluated on the basis

of two aspects, firstly it is the dimensions of the facility, secondly and more importantly it is the

burning behavior of material. As mentioned before mainly there are two materials used in the

structures esp the high rise. These are concrete and steel.

The interaction between fires and structural element and then the consequent response of the

structure as whole is largely analyzed and affected by few aspects which includes burning

behavior of materials including the mass loss and energy release, then stages of fire development

and lastly interaction of fully developed fire. Covering these aspects briefly the burning behavior

of materials can be shown in the following equation. (James, FEMA)


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′′ =′′

∆

Where

Q’’= energy released per unit surface area of fuel

q’’= incident heat released per unit surface area of fuel

Lv= latent heat of vaporization ∆ = Heat of combustion

Where as other aspects included stages of the fire development, these include initiation of fire

from single fuel object. The next stage is the transfer of smoke plume’s heat energy into smoke

layer. Therefore the temperature and depth of these layers are increased. The layer produced till

now then starts to ignite the unburned material or fuel giving further rise to temperature.

Therefore it can be deduced that the fire is transfer through mainly two means the first is from

radiation of heat and the other is through the smoke layer that is created. This cycle is repeated

resulting into exponential increase in the temperature of fire. Then comes the stage of subsequent

pattern of burning of fuel, which subdivided by compartment size. The small compartment’s

unburned object normally catches fire simultaneously and this process is called Flashover.

Where as large compartment’s objects can fire in an order and sequence.

A fire is declared as fully developed when it acquires a steady state burning stage and the mass

loss is a constant with respect to time. The main reason for this state is the lack of ventilation or

the fuel type. According to the equation given above if the rate of burning with constant influx

heat exceeds the quantity that can be supported by available air, then under these conditions the

burning becomes ventilation controlled otherwise it is fuel controlled.


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The case study of WTC 1 and WTC 2 shows that 3 GW fire could be supported by a flow of

1500000 cfm and which could have been supplied through openings in exterior wall and shaft

walls. Given that heat released per unit of oxygen is a relatively constant value of 13.1 kj/g for

common fuels, the air supply required to support fires. It is to be noted that every 1 MW of heat

resale rate consumes 76 g/s and there is 21% of oxygen which requires 0.24m3/s (500 cfm) of

ambient air.

As we are well aware of the fact that the fire resistance of the structure is deduced on the basis of

several aspects which include the loading on the structure, member types and dimensions and

finally and most importantly construction materials used. Fires in buildings induce geometric

(thermal expansion) and material effects (reduction in strength and stiffness) in structural

elements. There are two types of materials that need to be assessed for fire resistance, firstly steel

and secondly concrete. The mechanical and thermal properties of these materials are of

importance to assess the structural response. To assess these attributes test such as ASTM E119,

ASTM E1529, UL 1709 are performed and then later the results are translated into codes. The

response of steel structures is based on the deflection and deformation. The reason for this is that

when fire increases the temperature of the steel frame as a result the strength also decreases, this

gives rise to dangerous deformations, consequently the very basic structural properties of the

material such as modulus of elasticity changes which was considered constant in the design

phase and eventually the failure of facility is inevitable. So to analyze the structural response of

the structure we resort to structural mechanics analysis methods such as progressive collapse

analysis.


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Comparison between Low Rise and High Rise Buildings

The level of danger in small buildings and high rise building, although much research has not be

done on this comparison, the reason for which is lack of data available and basic difference of

conception & design may make it incomparable. Where as a comprehensive research has been

made by Fire Analysis and Research Division at National Fire Protection Association. According

to which they have gather all the data available both high rise and non high rise buildings and

after the analysis of the data sample. They have come to a conclusion that during 1999-2002, an

average of 7.7%-11.6% apartment fire broke out in non high rise building, in the analysis one

assumption is considered which is that these apartments were occupied throughout the year and

the building consisted of 3 or more housing units. Whereas on the other hand in the very same

time period of In 1999-2002, the high-rise percentage of apartment fires was in the range of 8-

10%.

The two percentages 7.7-11.6%(non high rise ) and 8-10% (high rise) are almost the same.

Therefore it cannot be declared that the fire risk in high rise building is lesser or higher when in

comparison to non high rise or apartment buildings.

Another estimate and analysis is made by U.S. Energy Information Administration which

calculate the fire risk on the basis of floor space which is represented by the percentage exposure

that is directly proportional to floor spaces in high rise buildings. Accroding to the the empirical

relationship developed by EIA the high rise share of exposure (floor space) for lodging, hotels is

7%-24.8% (considering 17.2%),for office buildings the figure ranges from 9.4-26.9% (middle

estimate 19.4%) and for health care facilities it is 15.7-37.4% with an average value of 28.1%.


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After similar calculation, analysis and estimate it was suggested by John R. Hall, Jr. of National

Fire Protection Association that “high-rise buildings are less risky than low-rise buildings

for office buildings. For hotels and motels and for hospitals and other facilities that care for the

sick, the risks appear comparable in high-rise and low-rise buildings”.

Hence from all this discussion and research it can be concluded that evidence and ground cases

and their studies shows that the risk of fires does not directly links to the height or its being high

rise or non high rise. The risk of fire is mainly dependent on the purpose, usage and

serviceability of the structure and does independent to the no of floors.

Design Of Fire Protection Systems

in the light of

Standards and Codes

There are many standards and codes that dictate the design and planning of fire protection

systems. Through researching I have come to a conclusion that there are very few regulations

and standards that legally bound the designer to design keeping fire protection as the primary

basis of failure. In British standards unlike others the difference for fire protection is made on the

basis of the material of construction which is steel, for which British Standard EuroCode 3. Part

1-2: General rules — Structural fire design is employed, then for composite or concrete

structures are based on BS EN 1994-1-2 Design of Composite Steel and Concrete Structures.

General Rules Structural Fire Design. Then other standards include BS 5950-8: Part 8: Code of


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practice for fire resistant design. Where as on the other side the most prominent among these are

National Fire Protection Association (NFPA) and then comes the International Code Council and

its International Building Codes IBC. Where as the there are many organizations that also

provide these guidelines and assistance to the design and regulation system. The organizations

with good implementation and impact include Health, Safety, and the Environment (HSE),

Health and Safety Executives, Royal Institute of British Architects and Society of Fire Protection

Engineers (SFPE) a professional association for fire protection engineering, E-5 committee,

ASTM International, National Institute of Standards and Technology (NIST)—The Building and

Fire Research Laboratory at NIST, Underwriters Laboratories (UL) which is a product-safety

testing and certification organization. The list of bodies and local regulatory organization is quite

extended. So for the time moment we have to restrict ourselves to only those which have the

highest impact value in the world and have a status of a regulatory body, which the builder of

facility is legally bound to follow.

The most widely used code around the world is the International Building Code IBC 2006. This

code is followed and used throughout the globe , in addition all the local or national codes that

are developed in the other country are derivative of the IBC 2006. Where as on the other hand in

the UK the BS 5950-8 Code of practice for fire resistant design is the most widely used. The

another reason apart from the extensive usage of the IBC 06 and BS 5950-8 that these are the

only codes available which has incorporated both aspects of fire protection system. It has

extensive restriction and bounding of design of structural member that is covered in the chapter 7

of the IBC 06 and Part 8 of the BS 5950 under the title of Fire-Resistance-Rated Construction.

This makes it the only code that bounds the designer to design every aspect according to fire

protection, without going to any other standard separately. Therefore the upcoming discussion

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would be on the basis of two aspects of fire protection, firstly it would be using the codes for

protection of the building and structure which would employ the fire resisting construction of the

facility. Secondly the discussion would be on the fire protection system themselves. Then the

British standard has provided us with a design flow chart to follow as well which I have included

in the appendix 1. Where as there are many British Standards and Euro codes on fire protection

some of which are listed below which are acquired from the web portal of British Standards

Institution. These are

Fire detection and alarm systems:

BS 10999:2010Specification for distress signal units for the fire and rescue service

BS 5839-1:2002+A2:2008

Fire detection and fire alarm systems for buildings. Code of practice for system design,

installation, commissioning and maintenance

BS 5839-8:2008

Fire detection and fire alarm systems for buildings. Code of practice for the design, installation,commissioning and maintenance of voice alarm systems

PAS 79:2007

Fire risk assessment. Guidance and a recommended methodology

The bestselling guide gives a nine-step approach to fire risk assessment in buildings

Fire extinguishing/fighting equipment:

BS 336:2010

Specification for fire hose couplings and ancillary equipment

BS 5306:2009

Fire extinguishing installations and equipment on premises. Commissioning and maintenance of portable fire extinguishers. Code of practice

BS 750:2006Specification for underground fire hydrants and surface box frames and covers

BS EN 14339:2005Underground fire hydrants

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Design & fire safety:

BS 9999:2008

Code of practice for fire safety in the design, management and use of buildings

Fire sprinkler systems:

BS EN 12845+Amendment 1:2009

Fixed firefighting systems. Automatic sprinkler systems. Design, installation and maintenance

Fire testing:

BS 476-10:2009

Fire tests on building materials and structures. Guide to the principles, selection, role andapplication of fire testing and their outputs

Fire-Resistance-Rated Construction

The first thing that is determined is the fire resistance rating of the key building elements for

which the test such as BS 476-10:2009 and ASTM E 119 is employed as the basic and

preliminary yard stick. On the other hand BS 10999:2010 , ASTM E1529 and UL 1709 are also

used for the reference and quality assurance. Whereas alternative methods to determine the fire

protection rating includes NFPA 252 or BS476 Part 21. Then materials required to be

noncombustible shall be tested in accordance with ASTM E 136, in addition with a surfacing not

more than 0.125 inch (3.18 mm) thick that has a flame spread index not greater than 50 when

tested in accordance with ASTM E 84 shall be acceptable as noncombustible materials. Then

under the section 705 of the IBC 06 we have to make a firewall, this is a wall which is fire-

resistance rated wall used to protect opening and contain fires to a certain area. These are

extended from the foundation to or through roofs. The material should be noncombustible and

they should be structurally stable so that under fire conditions the possible collapse of

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construction but not the wall providing a safe exist duration to the inhabitants. The fire resistance

rating of fire wall is in the table below which is taken from IBC 2006 section 705.4

The codes bounds to have continuous from exterior wall to exterior wall and shall extend at least

18 inches (457 mm) beyond the exterior surface of exterior walls for Horizontal continuity and

for Vertical continuity. Fire walls shall extend from the foundation to a termination point at least

30 inches (762 mm) above both adjacent roofs.

Among the walls for fire protection then it’s the fire partitions, these are the wall which include

separation in housing units in the same building, sleeping units in hotels, corridor walls and

elevator lobby separation. The material must be used must be resistant for at least 1 hour. Next it

is the smoke barrier that needs to be build, a smoke barrier is a continuous membrane, either

vertical or horizontal, such as a wall, floor, or ceiling assembly, which is designed and

constructed to restrict the movement of smoke. A1-hour fire-resistance rating is required for

smoke barriers at minimum.

Then it’s the design of Fire-Resistant Joint Systems that is of major concern to the fire protection

of the structure. This includes joints between walls, floors, roofs and their assemblies. These

joints must comply with the requirements of either ASTM E 1966 or UL 2079.The fire resistant


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joints in smoke barriers are of prime importance and it shall be tested in accordance with the

requirements of UL 2079 for air leakage.

The air leakage rate of the joint shall not exceed 5 cfm per lineal foot (0.00775 m3/slm ) of joint

at 0.30 inch (7.47 Pa ) of water for both the ambient temperature and elevated temperature tests.

One of the most important part of structural fire safety involves the description of fire resistance

of structural members, these members include columns, griders, trusses, beams and other force

bearing members and they all must comply to a the required fire resistance. For these members

in high rise building the codes bounds that the all members must have individually protected on

all sides for the full length with materials having the required fire-resistance rating. Then the

connection points and edges of lugs, brackets, rivets and bolt heads attached to structural

members shall be permitted to extend to within 1 inch (25 mm) of the surface of the fire

protection. The reinforcement of the concrete must also be protected but the stirrups and spiral

reinforcement ties are permitted to project not more than 0.5-inch (12.7 mm) into the protection.

Then it is to be noted that the fire protection is not required in bottom flange of lintels, shelf

angles and plates. Whereas the isolation systems used for the protection of earthquake must also

be fire protected and should have a sufficient fire resistance rating which comply with ASTM E-

119.

The section 715 of the IBC 2006 has a detailed standards on opening protections which the types

of assembly. The table below is the descriptive of all the contents in the standards regarding the

opening protections.


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These were a few most important aspects of the fire protection of the structure itself, there are

several more aspects that are to be considered in the design of the fire resistant construction in

the code which include Ducts And Air Transfer Openings, Thermal- And Sound-Insulating

Materials, Fire-Resistance Requirements For Plaster. Lastly the code describes the procedure for

calculating the fire protection rating of certain material and in different combinations. Now we

will move towards the fire protection systems and how are they designed according to the codes

and standards.

IBC is one of the very few codes which dictate the dimensions and restrictions on the dimensions

of the key structural members with respect to the fire protection ratings. So we will discuss a few

most important members and the restrictions that are imposed under the IBC. All the tables

below are extracts from the International Building Codes. The minimum slab thickness is shown

in the table below. Which is self explanatory.


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Then the next structural component is cover which is to be provided to the concrete.

Then we have to look into the dimensional restriction of the columns, where the IBC say to have

a restricted the dimensions to values indicated in the table below.


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Fire Protection System

The IBC 2006 is in direct coherence with the International Fire Code, and all the sections and

clause related to fire protection in IBC 2006 are derivatives of International fire Codes. The first

aspect of the fire protection system would be the Automatic Sprinkler System. The positions of

the system are extensively prescribed in the code and these locations are categorized in groups of

occupancies and other aspects. The first group is Group-A and its sub-group is Group A-1 which

is defined as that occupancy where fire area exceeds 12000 square feet and there are more than

300 occupants and area contains a multiheater complex. There are many other groups which

include various and diverse conditions and specified buildings. The conclusion from this section

is that, we have to provide an automatic Sprinkler system in a high rise building. Now the issue

is what standards to follow in regards to the specification of sprinkler system. The system shall

be designed and installed in accordance to NFPA 13 sprinkler systems. Then the water supply

system must comply with the international plumbing codes as well, where the protection from

backflow must be provided. A very important aspect that can not be overseen in the high rise fir

protection system is the Secondary Water supply. A back up or secondary water supply is to be

designed hydraulically and the sprinkler demand and hose stream is calculated and is provided in

high-rise buildings in Seismic Design Category C, D, E or F. The secondary system sustenance

time should be greater than 30 min and the rest must be in coherence with NFPA 13.

Alarms should be connected to the automatic sprinkler system and these alarms must be audile

and should be activated on abnormal flow in the sprinkler system. They should be provided on

the exterior size of the buildings and the activation of sprinkler system should activate the

facility’s fire alarm system. It is detrimental that floor control values should be provided in Tall


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Buildings. These values should be located at the point of connection to the riser on every floor in

tall building.

The Standpipe Systems is an integral part of the fire protection system and it becomes of

immense importance when it comes to high rise buildings as the fires are of massive and

normally sprinkler systems alone cannot handle the fire. The stand pipe must be selected and

installed in accordance to NFPA 14. According to which Class I system is used in high rise

buildings. Class I system is a system providing 21/2-inch (64 mm) hose connections to supply

water for use by fire departments and those trained in handling heavy fire streams. In the design

of standpipe system and its connection’s location is of key importance, the stand pipe hose is to

be provided in every floor’s stairway and should be provided at an intermediate floor level

landing. It should be on each side of the exit opening, at every exit passageway at entrance from

the exit passageway. It is also important to provide hose where the sprinklers are absent. Then

the cabinets having fire fighting equipment that are standpipes, fire extinguishers, hoses must be

visible at all times and should not be locked. In addition portable fire extinguisher should be

placed throughout the building at various locations so that any localized fire can be suppressed as

soon as possible.

Another aspect is fire alarm and detection system that needs to be catered as well. The alarm and

detection system must be in accordance to NFPA 72 and for tall buildings it must be connected

to the automatic sprinkler system along with automatic heat detection and automatic fire detector

which is basically smoke detector. The location of smoke detector is important, it should be

located in the main return air and in the main return air and exhaust air plenum of each air-

conditioning system having a capacity


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Greater than 2,000 cubic feet per minute (cfm) (0.94 m3/s). Such detectors shall be located in a

serviceable area downstream of the last duct inlet and each connection to a vertical duct or riser

serving two or more stories from a return air duct or plenum of an air-conditioning system. In

Group R-1 and R-2 occupancies a listed smoke detector is allowed to be used in each return air

riser carrying not more than 5,000 cfm (2.4m3/s) and serving not

more than 10 air inlet openings.{IBC, 06}.

Then the operation of automatic fire detection and sprinkler’s water flow device is connected to

emergency voice and alarm communication system and the paging zones must be elevator

groups, exit stairways, each floor and areas of refuge. In addition a two-way communication

system must be established between the facility and fire department is of vital importance.

After the detection of smoke the next step is the controlling of smoke for which an effective

smoke control system is to be designed. This will assist the suppression of the fire. The smoke

control systems must be designed on the basis of stack effect, projected temperature effect of

fire, wind effect, HVAC systems efficiency, climate in the surrounding of the facility and lastly

duration of operation. While on the other hand the smoke control system includes firstly the

smoke barrier construction, where the openings and leakage areas must be monitored the

maximum allowable leakage areas ratios are given by IBC 06 in coherence with International

Fire Codes which is


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The opening and the leakage areas must be safeguarded and well-protected by automatic-

closing devices and other electro-mechanical systems. Where as the fire doors can be used to

protect the door openings.

Next measure for the smoke control protection are the systems that work on pressure

measurement, the codes say that the minimum pressure should be 0.00124 kPa in a fully

sprinkled facility. Where as the maximum pressure difference across the smoke is to be

calculated by the force applied by the smoke on the smoke barrier, the formula of which is as

under provided by the international fire code,

Lastly and most important is the fire command center and its working. This is the place where

the decisions in crisis situations are to be made and is very detrimental in the level of damage

that might be caused by the fires. For this we must comply to the National Fire Protection

Association NPFA 72. According to which commands to have a emergency voice/alarm

communication system unit, a communication link with the fire department, operational

command over the elevators and auto locking doors. The command center must be in control of

all air handling systems, sprinkler values and water flows. The center must be in full possession


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of the building plans, every aspect and details of the each floors, details and specifications of all

fire protection systems, status and locations of fire fighting equipments on each floor. Controls of

backup power supply and backup communication systems can be decisive nature for the

command center.

Problems of Fire protection systems

With

WTC Case Study

There are many issues and problems that are not foreseen while designing the facilities and need

to be focused on by the information from the case studies and analysis of the fire that have

actually occurred. Although there are very few fires observed in the tall building there are several

reasons which include the over protective designs and then secondly very few are taken up by

forensic engineers. But there are some case studies that offer extensive research to fire systems,

their failure and the performance of structures under fires. Extensive research has been done and

case studies have been compiled on the incidents that have occurred. The most prominent and

researched among these are NIST National Institute of Standards and Technology and its

committee on World Trade Center Investigation. The outcomes have been really helpful in

understanding the problems and rectifying them for other tall buildings. There are several issues

that are highlighted, the first and the foremost issue is that all standards and codes rely on the

results of tests that are preformed in the labs. The problem here is that these tests can not

simulate the same temperatures or conditions that are present in a real time fires. Neither do we

have enough data or even knowledge about the response of different materials which acts as

http://www.google.com.pk/url?sa=t&source=web&cd=1&ved=0CCQQFjAA&url=http%3A%2F%2Fwww.nist.gov%2F&rct=j&q=NISt%20&ei=eRuxTZuLK-vXiAL5r_SvBg&usg=AFQjCNHDr2hK4iSbBWNRBUpEAC29fOPNwA&cad=rjahttp://www.google.com.pk/url?sa=t&source=web&cd=1&ved=0CCQQFjAA&url=http%3A%2F%2Fwww.nist.gov%2F&rct=j&q=NISt%20&ei=eRuxTZuLK-vXiAL5r_SvBg&usg=AFQjCNHDr2hK4iSbBWNRBUpEAC29fOPNwA&cad=rja


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fuels under fire at different temperature. So the problem can be solved through establishment of

better testing procedure and better lab equipments.

On the other side the case studies made by the investigation team of Project 4 made under the

NIST World Trade Center Investigation have also highlighted some major issues that were faced

in case of fires in WTC 1, 2, 7. These issues related the minimum level of performance for active

fire protection systems, then they emphasized on the quantity and reliability of information to

first responder at fire and significance of command center in crisis situations. Then the study

focused on the data and information given by Fire Alarm Systems for the declaration of crisis

and response and other preventive measures which includes the evacuation and fire fighting.

Lastly the study accentuated on the survival of fire alarm system and other recording systems

So that later these data collecting systems can be recovered and the data analysis can help in a

more accurate case study. Therefore probability of future fires can be reduced.

Lets analyze what was the first major issue highlighted in the case study and its findings, It stated

that all Fire Sprinkler Systems design method for WTC 1, 2, and 7 was based on the occupancy

hazard fire control approach from NFPA 13. Light hazard was the occupancy classification for

water spray density which had a density of 0.1 gpm/ft2. Where as the area is 1500 ft2. It was also

found that almost all tall buildings have the same classification, which is danger and has proved

to be insufficient in strong fires. Then there was another assumption that proved to be wrong was

that the fire’s fuel was only ordinary office material so the system was designed accordingly.

As a result the recommendation said that the NFPA 13 should now reconsider the minimum

requirements and should also consider the threat profile, terrorism, prohibited activities and fuel

loads in the building, compartmentation, population in the building while designing thee


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sprinkler systems and water spray density. The designer must consider these factors and should

design accordingly if not considering all may be a part in to his design.

Then another fault that was seen in the system was that the fire sprinkler system was automatic

for water from tank but for continuous operation they solely relied on manually operated pumps

as a result the whole system became manually operated and consequently making efficiency

lesser. Then again the fire alarms systems in WTC 1 and 2 were automatic but the activation of

notification devices was manual. Where as the smoke purge systems were manually activated.

All this shows that the coherence in the automation of the systems is very vital for maximum

efficiency. The case study also unveiled the danger of system’s complete failure due to damage

at a single point. The report stated WTC 1, 2, and 7 fire sprinklers and standpipe systems were

vulnerable to single point failures as shown in the APPENDIX 3. Almost the same problem was

observed with the fire alarm system voice notification, fire warden telephones, and fire fighter

telephones that they all halted due to one place disconnection, as shown in Appendix 4.

The next issue that was observed was pertaining availability and reliability of information that

was reaching the Fire command Center and how did it respond to the emergency. At the WTC 1

there were numerous alarms that were registering fires in their zones but none of them was used

to show the status of the water supply’s conditions. Then at WTC 1 the alarm systems showed

only those area that were on fires and had no other information what so ever. Then there was

system that could announce any information at a specific floor in the building. This show that

how even the most well designed building small mistakes can lead to chaos in both management

and life toll. Then another issue that was seen in the building as a whole and system as specific,

this was that no information or data about events and happenings inside the building was

available outside, eventually any one outside had any idea what was going on inside the build


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and no accurate actions were possible to safeguard the loss. These systems which can transport

and communicate the information outside the building can be really helpful, so that the future

events in the fire can be projected more accurately and fire fighting and damage control can be

done effectively and strategically. Lastly the recommendation of the case study pointed out that

there alarm system and other backup systems provide valuable information about all events and

the response of the facility under fire. There were many hardware and systems installed for the

data collection under a fire situation but almost every system was damaged in the fire and no

information was available or recovered from the fire alarm system. Hence the Survivability of

alarm systems and data collection devices and the communication/ transmission of information

from within the building is very detrimental for fire fighting and forensic studies of the fires and

hence a lot of work is to be done in this field.


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Conclusion

The reiterative process of learning from the mistakes and then using them to understand more

closely the principles that govern will carry on. The first priority for every designer must be the

safety of the life and should be protected at any cost. There are very few regulatory bodies and

standard that directs the designer to have a fire resistance construction. Many standards and

codes throughout the world are yet to have clauses for fire protection and this aspect has been

previously neglected but things have changed now, the trend is now heading towards

improvement and they should because our structures are getting higher and higher every day, so

shall the protection standards should. On the other hand there is immense work and research to

be done to make our fire protection systems effective and fire testing procedures more accurate.

Till we have the full confidence and grasp of the knowledge of fires and its interactions with the

facilities we must have an over protective system, the cost might be more but not more than

human life.


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References

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UK: British Standards Institution.

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NFPA 5000. (2009). Building Construction and Safety Code. U.S: National Fire Protection

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Management Agency WTC Performance Study . Appendix A.

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Available: http://wtc.nist.gov/. Last accessed 21-04-2011.

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National Fire Protection Association (2009). NFPA 13: Standard for the Installation of Sprinkler

Systems. US: National Fire Protection Association

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Appendix 1

British Standards Institution (2008). BS 5950-8 Part 8: Code of practice for fire resistant design. UK:

British Standards Institution. ..


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Appendix 2

Beitel, J. J. (2005). Historical Survey of Multi-Story Building Collapses Due to Fire. Hughes Associates, Inc


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Appendix 3

Project 4: Investigation Team (2003). Active Fire Protection Systems Issues. New York, US: NIST World

Trade Center Investigation. 2-20.


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Appendix 4

Project 4: Investigation Team (2003). Active Fire Protection Systems Issues. New York, US: NIST World

Trade Center Investigation. Pg 8.

Design of Fire Protection Systems for Tall Buildings

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