1. CE 808: Structural Fire Engineering
Ch. 1: INTRODUCTION TO FIRE SAFETY
V. Kodur
Professor
Dept of Civil and Env. Engineering
Michigan State University

2. Ch. 1: Introduction To Fire Safety
Fire Problem
Importance of Fire Safety
Structural Fire Safety within the Context of Overall Fire Safety
Fire Resistance
Codes and Standards
Performance-based Design
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3. Background
Building fires cause thousands of deaths and billions of dollars of damage each year
Fire risk can be mitigated through conscientious design and maintenance
It is impossible to prevent ALL major building fires
Fire safety depends on numerous factors:
Fire prevention, suppression and extinction
Successful evacuation of occupants
Structural integrity (FOCUS of this course)
Engineers must ensure fire safety through proper selection and design of material & structural systems
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4. Fire Problem Fire Costs in US Recent data (2004)
1,550,000 fires
4003 fire deaths (103 FF)
100,000 fire injuries (80,000 FF)
$10 billion direct property losses
Total cost of fire > $50 billion
Residential fires are the most significant
80% of fire deaths, 26% of fires, 60% of the total dollar loss
“Smoker's material and open flame” are the number one source of ignition (~ 25% of the total)
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5. The Great Fire of London
2nd September 1666, London, UK
Within 5 days the city was destroyed by fire
440 acres consumed, 87 churches, homes
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6. Effects of Fire – Structural Fire Safety
45,000 liters in each plane
25% Fire balls
25% Shafts
50% Consumed in few minutes
Fire size – 3-5 GW
Energy – nuclear plant
Fire temperatures – 1100° C
Fires were instrumental
Towers would have been standing
Structural Fire Safety
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7. Effects of Fire – Material Fire Safety
Euro Tunnel Fire - Nov 96
Burned 8 h – 1000°C
Severe damage
Injuries (8), services (£50M)
Thermal spalling
RC tunnel rings (100's m)
Av. depth cm
Strength - 80~100 MPa Permeability - low
Major repairs – damages
Fire-Induced Spalling of HSC Tunnel Lining & Buckling of reinforcement in Channel Tunnel due to Fire on Nov 18, 1996
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8. Significance & Need – Recent Disasters
Oakland Bridge - April 29, 2007
Gasoline tanker crashed into a pylon on the interchange between I-80 and I-880
8600 gallons of gasoline burnt to a temperature 1100˚C.
Continuous fire softened the bolted connections
The result is “clean breaks” at the connections
Severe structural damage
Severe traffic delay
Losses – Millions of dollars
Clean breaks at the connection due to fire exposure
Oakland Bridge Collapse
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9. Significance & Need - Recent Disasters
Tunnel in California - Oct 12, 2007
Two trucks collided
30 trucks & passenger cars
Burned 7 hrs – 1400°C
Severe damage
Deaths (3) & Injuries (10)
Thermal spalling
Spalling depth (concrete cover)
HSC
Permeability - low
Major repairs – damages
Fire-Induced Spalling of Concrete Tunnel in California
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10. Significance & Need – PB Codes
Current approach to fire safety design
Prescriptive based approach
Significant drawbacks
US is moving towards performance-based codes
Rational engineering approaches
Offers cost-effective, innovative & alternate designs
Factors hindering PB Approach
Lack of validated models
Lack of test data for validation
Lack of material properties
Lack of design tools/guidelines
Lack of trained personnel
Lack of monitoring tools
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11. Significance & Need - New Materials
HPM - HSC, FRP, HPS
Benefits
Superior performance
Strength, Durability
Corrosion resistance
Applications
Bridges, Infrastructure projects
Retrofitting & strengthening
HPM – Plastics, Composites
Superior strength, Lt.wt
Auto, Aerospace, Transportation
Major Problem – Fire Performance
High temperature intolerant
Toxicity
Flame spread (combustible)
Faster strength/stiffness degradation
Ex: Euro-tunnel fire
Ex: Challenger, Colombia crash
Column Strengthened
with FRP
FRP Rebar
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12. Structures Building - commercial, industrial, residential
Outdoor stadium
Oil platform
Tent
Stage
Tower
Liquid storage tanks etc.
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13. Role of Structures Provide comfortable, safe, functional space
Shelter and Support
Resist forces - human and natural:
Dead
Live
Wind (hurricane & tornado)
Flood
Snow
Earthquake
Thermal
Fire
Primary or Secondary Event
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14. Fire Safety Not possible to prevent ALL fires
So, designers need to put in-place strategies to minimize the occurrence of fires & consequently reducing their impact on life, property and environment
Main strategies include providing for:
Automatic fire sprinklers - statistics show that sprinklers have a very high probability of controlling or extinguishing any fire
Systems for fire detection and notification of fire service
Safe travel paths for the movement of occupants & firefighters
Barriers to control the spread of fire & smoke
Fire resistant structures - not collapse prematurely in fire
To strategize, the designer has the important responsibility to properly select, design and use building materials
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15. Structural Fire Safety
Fire - severe conditions
Buildings, transit systems
Fire safety - design requirements
loss of life and property
Fire resistance - structural elements
Safe evacuation of occupants & fire personnel
Minimize property damage
Control spread of fire
Recent events
WTC, Tunnels
Structural Fire Safety - Fire resistance
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16. What is Fire Resistance?
Fire resistance: “the property of a material or assemblage to withstand fire or give protection from it.
Discussion: As applied to elements of buildings, it is characterized by the ability to confine a fire or to continue to perform a given structural function, or both.” [ASTM E176, 1997]
Note the absence of specification of exposure or time
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17. Fire Resistant Assemblies
Provide physical barrier to restrict fire spread
prevent fire and smoke spread
Maintain structural integrity/ load carrying ability despite exposure
prevent structural collapse
Compartmentation & Structural integrity are principal aspects of fire safety in buildings
Fire Resistance Rating - Codes
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18. Fire Resistance
Fire resistance is usually described as passive fire protection, always ready and waiting for a fire
does not play a significant role in the early stages of a fire
becomes very important as a fire grows beyond flashover
The importance of fire resistance depends on the size of the building & the fire safety objectives that need to be satisfied
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19. Fire Resistance & Fire Safety Goals
Life safety
Occurrence of civilian fatalities in fire resistive buildings: MGM, Winecoff and DuPont Plaza Hotels
Occurrence of fire fighter fatalities in collapses
Mission continuity
Appreciable down time if collapse occurs: GM Livonia Plant, McCormick Place
Outcome of 1st Interstate, Broadgate, Meridian Plaza, WTC
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20. Codes and Standards
Building codes set fire-resistance requirements for building assemblies to resist
Spread of fire within buildings &
Collapse of structural elements exposed to fire
Fire Resistance Rating
“The Subcommittee believes that the idea of designing some buildings for the full fire severity corresponding to the occupancy … is a logical advance in fire protection engineering”. (BMS 92, 1942)
Formulated based on Ingberg’s hypothesized relationship betn
occupancy (fuel load)
building area (compartmentation level)
Determine maximum allowable height & area of a building based on:
Construction type
Occupancy
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21. Codes - Fire Resistance Rating
Fire resistance rating (or fire endurance): “a measure of the elapsed time during which an assembly continues to exhibit fire resistance under specified conditions of test and performance” [Boring, Spence and Wells, 1981].
Fire Resistance Rating – 30 min, 45 min, 1, 11/2, 2, 3, 4h
which test?
ASTM E119, NFPA 251, UL 263, ISO 834
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22. Codes - Occupancy Types
Institutional
Mercantile
Residential
Storage
Utility/Miscellaneous
Assembly
Business
Educational
Factory & Industrial
High Hazard
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23. Codes - Types of Construction
Type I - Non-combustible, fire resistant
Concrete, Masonry, Structural Steel
Type II - Non-combustible, minimally or non-fire resistant
Lt gauge steel framing
Type III - Non-combustible exterior walls, combustible interior elements
Wood stud walls
Type IV - Heavy timber
Structural members
Type V - Wood frame
Wood stud walls/wood joist floors
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24. Codes - Types of Construction
3 Digit Code, e.g. 332.
1st digit: fire resistance of exterior bearing wall
2nd digit: fire resistance of columns, beams, girders, trusses and arches supporting bearing walls, columns or loads from more than one floor
3rd digit: fire resistance of floor construction
H Heavy timber
UL Unlimited height/area
NFPA 220, Standard on Types of Building Construction
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25. Codes - Height and Area Table (NFPA 5000)
Type 1
Type 2
Type 3
Type 4
Type 5
Group
442
332
222
111
000
211
200
2HH
Business UL 11 5
37.5 4
23.0
28.5
19.0
36.0 3
18.0 2
9.0
Education
26.5
14.5
23.5
25.5 1
18.5
9.5
Mercantile
21.5
12.5
20.5
14.0
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26. Codes - Construction Type Requirements
Group
442
332
222
111
000
211
200
2HH
Structural Frame
4/3
3/2
2/1 1 H
Bldg Walls
Exterior
Interior 4 3 2
Floor
Roof 1½
NFPA 5000
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27. Fire Resistance Analysis
Typical:
Prescriptive Approach
Refer to results from standard test; no “engineering analysis” required (structural design given)
ASTM E119, NFPA 251, UL 263, ISO 834
Conduct new test
Special cases:
special buildings, problems with architectural features, cost
Future:
performance-based design, integrated into the structural and fire protection engineering design
Primary responsibility: FPE, CE, or ?
Preserves structural design
Meets architectural requirements
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28. Prescriptive Approach
Till recently codes have been prescriptive in nature for fire resistance evaluation
Prescriptive codes
state how a building is to be constructed
restrict designers to take a rational engineering approach to the provisions of fire safety
Traditional method for assessing the fire resistance of building assemblies is by means of standard fire tests
Recently, there has been an increase in the use of calculation/engineering methods
Performance-based design
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29. Performance-based Building Codes
Many countries are moving towards performance-based codes which
Sate how a building is to perform under a wide range of conditions
Allow designers to use alternate fire safety strategies, provided adequate safety can be demonstrated
Use of calculation/engineering methods
Within a prescriptive code, there may be possibility to allow for performance-based selection of structural assemblies
if a code specifies a floor with a fire resistance rating, designers have the flexibility to select from a range of listed systems which have sufficient fire resistance
This course, will examine provisions for assessing fire performance of systems where no tests or listings are available
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30. Performance-based Building Codes
In developing new codes, many countries have adopted a multi-level code format in the form of:
overall goals, functional objectives and required performance which must be achieved
selection of alternative means of achieving those goals. The three most common options are:
to comply with a prescriptive 'Acceptable Solution',
to comply with an approved standard calculation method, or
to perform a performance-based fire engineering design from first principles
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31. Performance-based Building Codes
Standard calculation methods have not yet been developed for widespread use
So, compliance with performance-based codes is usually achieved by:
Mainly satisfying the requirements of acceptable solutions, or
Carrying out a performance-based alternative design based on fire engineering principles
Alternative designs can be used to justify cost-effective solutions
Under a performance-based design, it is essential to have comprehensive documentation & quality control
The calculations should be included in a report which describes the building & the complete fire design process
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