THE OFFICIAL MAGAZINE OF THE SOCIETY OF FIRE PROTECTION ENGINEERS

FIRE PROTECTION

SPRING 2003 Issue No.18

BUILDING PERFORMANCE

UNDER FIRE
EXPOSURE page 6

ALSO:

19 RESTRUCTURING CONFIDENCE
IN THE FIRE SAFETY OF
BUILDINGS

24 CONSEQUENCES OF
IMPERFECT INSULATION –
NUMERICAL MODELING

37 CALCULATING STRUCTURAL
RESPONSE TO FIRE

46 INTEGRATING STRUCTURAL
FIRE PROTECTION INTO THE
DESIGN PROCESS
 FIRE PROTECTION

Fire Protection Engineering (ISSN 1524-900X) is

published quarterly by the Society of Fire Protection
Engineers (SFPE). The mission of Fire Protection
Engineering is to advance the practice of fire protection
engineering and to raise its visibility by providing
contents SPRING 2003

information to fire protection engineers and allied 6

professionals. The opinions and positions stated are COVER STORY
the authors’ and do not necessarily reflect those of SFPE. Building Performance Under Fire Exposure
Editorial Advisory Board Highlights of the principle observations gathered from a seven-month FEMA-spon-
Carl F. Baldassarra, P.E., Schirmer Engineering Corporation sored investigation that studied how the buildings attacked on September 11 per-
Don Bathurst, P.E. formed under fire exposure. Emphasizes the need for interaction between the fire
Russell P. Fleming, P.E., National Fire Sprinkler Association protection and structural engineering professions during the design process.
Morgan J. Hurley, P.E., Society of Fire Protection Engineers James Milke, Ph.D., P.E.
William E. Koffel, P.E., Koffel Associates
Jane I. Lataille, P.E., Los Alamos National Laboratory 3 Viewpoint
Margaret Law, M.B.E., Arup Fire
Ronald K. Mengel, Honeywell, Inc.
4 Flashpoints
Edward Prendergast, P.E., Chicago Fire Dept. (Ret.) 19 Restructuring Confidence in the Fire Safety of Buildings
Warren G. Stocker, Jr., Safeway, Inc. The author takes an in-depth look at the fire safety concerns of high-rise
Beth Tubbs, P.E., International Conference of Building buildings, are they safe today and can they be safer in the future.
Officials Robert Berhinig, P.E.
Regional Editors
24 Consequences of An Imperfect Insulation – Numerical Modeling
U.S. H EARTLAND
John W. McCormick, P.E., Code Consultants, Inc.
How engineers studied the detailing of structural columns in a 13-story
building in Germany to analyze what would happen during a fire – and to
U.S. M ID -ATLANTIC
Robert F. Gagnon, P.E., Gagnon Engineering, Inc.
recommend corrections if and where necessary.
Jean-Marc Franssen, Ph.D.
U.S. N EW E NGLAND
Thomas L. Caisse, P.E., C.S.P., Robert M. Currey & 34 Accuracy, Precision, Resolution and Uncertainty in
Associates, Inc.
Fire Protection Engineering
U.S. S OUTHEAST This article provides a brief refresher on accuracy, precision, resolution, and
Jeffrey Harrington, P.E., The Harrington Group, Inc.
uncertainty, and challenges the fire protection community to take the next
U.S. W EST C OAST step for an evolving discipline: recognition and public reporting of measure-
Michael J. Madden, P.E., Gage-Babcock & Associates, Inc.
ment uncertainty.
A SIA National Electrical Manufacturer’s Association
Peter Bressington, P.Eng., Arup Fire
A USTRALIA 37 Calculating Structural Response to Fire
Brian Ashe, Australian Building Codes Board The author details a three-step, performance-based process for calculating a
C ANADA structure’s response to fire: fire hazards analysis, thermal analysis, and struc-
J. Kenneth Richardson, P.Eng., Ken Richardson Fire tural analysis.
Technologies, Inc. Robert H. Iding, Ph.D.
N EW Z EALAND
Carol Caldwell, P.E., Caldwell Consulting 46 Integrating Structural Fire Protection Into The Design Process
U NITED K INGDOM The author presents considerations for integrating structural fire protection into
Dr. Louise Jackman, Loss Prevention Council the design process at an early stage using a performance-based solution that
allows for greater flexibility in achieving an optimal design solution.
Personnel
Harold A. Locke, P.E.
EXECUTIVE DIRECTOR, SFPE
Kathleen H. Almand, P.E. 52 SFPE Resources
T ECHNICAL E DITOR
Morgan J. Hurley, P.E., Technical Director, SFPE 56 Products/Literature
P UBLISHER 58 Brainteaser/Ad Index
Terry Tanker, Penton Media, Inc.
A SSOCIATE P UBLISHER 60 From the Technical Director
Joe Pulizzi, Custom Media Group, Penton Media, Inc. Morgan J. Hurley, P.E.
M ANAGING E DITOR
Joe Ulrich, Custom Media Group, Penton Media, Inc. Cover illustration by ©Will Crocker/The Image Bank
A RT D IRECTOR Online versions of all articles can be accessed at www.sfpe.org.
Pat Lang, Custom Media Group, Penton Media, Inc.
M EDIA S ERVICES M ANAGER Invitation to Submit Articles: For information on article submission to Fire
Lynn Cole, Custom Media Group, Penton Media, Inc. Protection Engineering, go to http://www.sfpe.org/publications/invitation.html.
C OVER D ESIGN
Dave Bosak, Custom Media Group, Subscription and address change correspondence should be sent to: Fire Protection Engineering,
Penton Media, Inc. Penton Media, Inc., 1300 East 9th Street, Cleveland, OH 44114 USA. Tel: 216.931.9180. Fax: 216.931.9969.
E-mail: asanchez@penton.com.
Copyright © 2003, Society of Fire Protection Engineers. All rights reserved.

www.sfpe.org
viewpoint

LIFE SAFETY IN HIGH-RISE BUILDINGS AFTER 9/11

By W. Gene Corley, P.E. fires when they work properly, sprinklers not sufficient water available to prevent
cannot always be expected to function. the collapse of the building.

G reat catastrophies often cause

major changes in the construc-
tion industry. The Chicago fire
in the 19th century demonstrated the
risks of combustible construction in
Sprinklers can malfunction due to inade-
quate inspection, willful shutoff of valves,
or catastrophic events interrupting the
water supply. Since inspection and main-
Building 5 sustained collapse of sev-
eral floors that were not directly hit by
debris. This structure had no extraordi-
nary fuel load in it but still collapsed
tenance of sprinklers are seldom manda- when the sprinkler systems were unable
large cities. During the rebuilding after tory in commercial buildings, the poten- to control the fire and a burnout of the
the Chicago fire, many of the bright tial failure rate is of concern. office contents occurred. Buildings 5 and
engineering and architectural minds of Despite the recognition that sprinkler 7 became the first documented collapses
the world were attracted to the city to systems do not always function properly, of fire-protected and sprinkled buildings
assist in the rebuilding. Among the model building codes have continued to in the more than 100-year history of
many innovations that came out of this reduce the fire-resistance requirements of high-rise structures.
decades-long rebuilding effort was the structural elements where sprinklers are Sprinklers should continue to be man-
invention of the “skyscraper.” Use of the used. In the International Building Code3 datory in high-rise buildings. However, it
structural skeleton to permit buildings to and NFPA 5000 Building Code,4 required is clear some fires in buildings, both low-
be built higher, and thereby get more fire resistance for sprinkled buildings is rise and high-rise, cannot be controlled.
use out of expensive land, revolution- two hours for beams, columns, and floors. When control is lost, a burnout will oc-
ized the building industry. NFPA 5000 requires that buildings over cur. For the life safety of those who may
Fires that followed the 1906 San Fran- 420 feet (126) tall add an additional hour be trapped in the building and of those
cisco earthquake demonstrated the need to columns, for a total of three hours. who must fight these fires, the design ob-
for fire protection in high-rise buildings. These reductions in structural safety are jective should be that no collapse occurs
Lack of water to fight fires in San Fran- based on a growing belief that fire-pro- with a burnout. Also, the burnout consid-
cisco caused many buildings to com- tected buildings will not collapse, even in ered should be related to the amount of
pletely burn after the earthquake. By a burnout. fuel in the building if fuel exceeds the
1927, the Uniform Building Code,1 writ- The experience after the 9/11 attack on amount that would produce a standard
ten by western United States building of- the World Trade Center proved a building ASTM E119 fire.
ficials, required buildings that were taller can collapse as a result of fire. The Build- Fire-related collapses that occurred af-
than 8 stories or 85 feet (26 m) have fire ing Performance Study2 carried out for ter the 9/11 attack on the World Trade
resistance of structural elements of three the American Society of Civil Center provided information that should
hours for floors, four hours for columns Engineers/Structural Engineering Institute be used to guide our future fire protec-
and beams. and the Federal Emergency Management tion of high-rise buildings. The lessons
Following the adoption of fire-resis- Agency concluded that fire played a ma- from the horrible tragedy of 9/11 should
tance requirements for high-rise build- jor role in the collapse of four buildings. be used to improve the safety of later
ings, the experience has been very good. It is believed, even though badly dam- generations who live and work in high-
No modern fire-protected building had aged by the impact of very large aircraft, rise buildings.
collapsed as a result of a burnout prior to the twin towers would have been able to
9/11.2 Similarly, the fire-related casualty stand had there not been a second major W. Gene Corley, SE, PE, is with Con-
rate for occupants of high-rise buildings event, the fire that followed the impact. struction Technology Laboratories, Inc.
has been extremely low. Of more importance to the fire protec-
In the 1970s it became clear to model tion community, however, were the col- REFERENCES
code groups that sprinkler systems in high- lapses of buildings WTC 5 and WTC 7. 1. Uniform Building Code, 1927 Edition,
rise buildings would further reduce the These two buildings collapsed during International Conference of Building
property losses during a fire. Properly op- burnout fires even though there was no Officials, Long Beach, California, 1928.
erating sprinkler systems have had a good evidence found that the collapsed areas 2. Corley, W.G. et al, “World Trade Center
record of reducing the effects of fires. had been seriously damaged by impact Building Performance Study: Data
As modern building codes evolved, of debris. Collection, Preliminary Observations, and
two that have recently been developed Building 7, a 47-story fire-protected Recommendations,” Federal Emergency
are the International Building Code3 and and sprinkled structure, burned from the Management Agency Mitigation Directorate,
FEMA 403, Washington, D.C., May 2002.
NFPA 5000 Building Construction and time of the attack until it collapsed at 4:20
Safety Code.4 Sprinkler systems are man- in the afternoon. It is apparent that this 3. International Building Code, International
datory by these codes in all buildings building had a fuel load that fed the fire Code Council, Falls Church, Virginia, 2000.
that exceed 12 stories or 180 feet (54 m). throughout this long period of time. 4. NFPA 5000 Building Construction and
While sprinklers can be expected to re- Although the sprinklers are believed to Safety Code, National Fire Protection
duce property loss and contain many have fused, there was either no water or Association, Quincy, Massachusetts, 2003.

S PRING 2003 www.sfpe.org

flashpoints
fire protection industry news

NFPA Addresses On February 26, 2003, the National Fire Protection Association (NFPA) called upon its
Technical Committee on Assembly Occupancies to convene in Quincy, MA, for an im-
Safety Issues in mediate review of the safety issues relevant in public assembly buildings.
At issue are several core components of a total system of building safety that have
Public Assembly come to light following the two recent deadly nightclub incidents in Chicago and Rhode
Buildings Island.
“We must not waste any time in examining all the available information about public
assembly occupancies in the wake of these building emergencies,” said NFPA Executive
Vice President Arthur E. Cote, P.E. “Although we still don’t have all the facts about these
terrible incidents, we know enough right now to warrant a serious review and scrutiny
of the future direction of codes and standards, and their enforcement locally. We must
learn from these tragedies, and the time to act is now.”
NFPA is calling for a review of the following issues addressed or affected by NFPA
codes:
• The minimum thresholds for requiring automatic fire sprinkler protection.
• Allowable interior finish and decorations.
• Adequate egress.
• Exiting arrangements.

The Society of Fire Protection Engineers (SFPE) recently released a new engineering
SFPE Releases New guide entitled, The Evaluation of the Computer Model DETACT-QS. DETACT-QS is a
Engineering Guide model for predicting thermal detector response. The guide is the first in a series of
evaluations undertaken by SFPE’s Computer Model Evaluation Task Group.
Evaluating Computer The evaluation addresses the model definition and evaluation scenarios, verification
Model of theoretical basis and assumptions used in the model, verification of the mathematical
and numerical robustness of the model, and quantification of the uncertainty and
accuracy of the model predictions. This evaluation is based on comparing predictions
from DETACT-QS with results from full-scale compartment fire experiments.
An extensive set of references and background on the technical basis of the model
is provided.
For more information, go to www.sfpe.org.

MEMBERS SMALL BUSINESS MEMBERS

Altronix Corporation Bourgeois & Associates, Inc.
Arup Fire Demers Associates, Inc.
The SFPE Corporate 100 Program was founded in 1976 to Automatic Fire Alarm Association Fire Consulting Associates, Inc.
strengthen the relationship between industry and the fire BFPE International Fire Suppression Systems Association
protection engineering community. Membership in the pro- Cybor Fire Protection Company Gagnon Engineering, Inc.
gram recognizes those who support the objectives of SFPE FM Global Corporation Grainger Consulting, Inc.
and have a genuine concern for the safety of life and prop- GE Global Asset Protection Services J.M. Cholin Consultants, Inc.
Harrington Group, Inc. MountainStar Enterprises
erty from fire.
HSB Professional Loss Control Poole Fire Protection Engineering, Inc.
BENEFACTORS James W. Nolan Company (Emeritus) Risk Logic, Inc.
Koffel Associates, Inc. S.S. Dannaway & Associates, Inc.
Rolf Jensen & Associates, Inc.
Marsh Risk Consulting The Code Consortium, Inc.
National Electrical Manufacturers Association Van Rickley & Associates
PATRONS National Fire Sprinkler Association
Code Consultants, Inc. Nuclear Energy Institute
Edwards Systems Technology The Protectowire Co., Inc.
Gage-Babcock & Associates, Inc. Reliable Fire Equipment Company
Hughes Associates, Inc. Risk Technologies LLC
National Fire Protection Association TVA Fire and Lifesafety, Inc.
The Reliable Automatic Sprinkler Company Tyco Services, Pty
Schirmer Engineering Corporation Underwriters Laboratories, Inc.
SimplexGrinnell Wheelock, Inc.
W.R. Grace Company

Fire Protection Engineering N UMBER 18

 Study of Building Performance

in the WTC Disaster

By James Milke, Ph.D., P.E.
In late September, the Building Per-
formance Study (BPS) team was formed
INTRODUCTION
to study the response of the affected
buildings to impacts and fires. The prin-

T
he impacts of aircraft into the twin towers of the World cipal support for the study was provided
Trade Center set off a chain of events seen via televi- by the Federal Emergency Management
Agency (FEMA) and the Structural Engi-
sion coverage by many of the world’s population on neering Institute of the American Society
September 11, 2001. These aircraft damaged portions of the of Civil Engineers. Also supporting the
effort was a coalition of organizations
structure of the twin towers and also initiated fires on several including the Society of Fire Protection
floors. By the end of the day, four buildings collapsed, three Engineers and National Fire Protection
Association (NFPA).
buildings were severely damaged by fire, and seven buildings Team members included structural
sustained significant engineers and fire protection engineers.
Some of the structural engineers special-
damage, while numer- ized in the response of buildings to sta-
ous others suffered tic loads, the effects of dynamic loadings
on buildings, or metallurgy. Fire protec-
minor damage.
tion engineers included on the team had
backgrounds in fire behavior and re-
sponse of structures to fires. Individuals
selected for the team with fire protection
expertise included:

Fire Protection Engineering N UMBER 18

 Figure 1.
Map of Buildings
included in BPS1

Jonathan Barnett, Ph.D., P.E., seven-month period of the study, the tary analyses conducted by others. In
Worcester Polytechnic Institute team met with members of the design addition, a limited number of metallurgi-
Robert Duval, NFPA teams for the World Trade Center build- cal laboratory analyses were conducted
Richard Gewain, P.E., ings and spoke with eyewitnesses and on steel samples recovered from the re-
Hughes Associates emergency responders. Information re- cycling centers.
Venkatesh Kodur, Ph.D., viewed by the team included videotapes
National Research Council of Canada from television networks and private in- SCOPE OF STUDY
Chris Marrion, P.E., ArupFire dividuals, photographs of the incident,
James Milke, Ph.D., P.E., audio tapes from New York’s Emergency The principal purpose of the BPS was
University of Maryland Operations Center, plans, engineering to establish the basic facts involving the
Harold “Bud” Nelson, P.E., documents, and aircraft data.1 In addi- performance of the affected buildings.
Hughes Associates tion, the team returned to the recycling In addition, the study team sought to
The team met in New York in early yards many times. The team conducted provide preliminary thoughts about the
October 2001, visiting Ground Zero and some elementary numerical analyses probable collapse mechanisms and
also the recycling yards. During the and also reviewed the results of elemen- identify areas for future study.

S PRING 2003 www.sfpe.org

■ Study of Building Performance

While much of the attention of the (990 mm o.c. spacing) car-

BPS was directed to the twin towers, the ried the remainder of the
performance of a total of 16 affected gravity load and were also
buildings was addressed in the study. specifically designed to
The buildings included in the study and withstand the design wind
indicated in Figure 1 are: load posed by a storm. In
• WTC 1, 2, 3, 4, 5, 6, and 7 general, the columns were
• Banker’s Trust lightly loaded relative to
• The Winter Garden and WFC 3 their allowable load capac-
(The American Express Building) of ity.
the World Financial Center The interior core was ap-
• Verizon Building proximately 26.5 m x 41.7
• 30 West Broadway m. The bar joists spanned
• 130 Cedar Street the distance between the in-
• 90 West Street terior and exterior columns.
• 45 Park Place One-way spans of 18.3 m or
• One Liberty Plaza 10.7 m were oriented be-
The emphasis of the Building Perfor- tween the core and exterior
mance Assessment Team (BPAT) report as indicated in Figure 2.
was to describe the structural perfor- Two-way framing was pro-
mance of the affected buildings. A brief vided in the corners.
Figure 2. Floor System in WTC 1, 2
description of the evacuation of WTC 1 A Vierendeel truss was located be-
and 2 was also included in the report tween the 106th and 110th floors of
based principally on media accounts. WTC 1 and 2. Conceptually, the truss that time) to increase the protection
The focus of this paper will be on the served to connect the interior and exte- thickness to 38 mm as spaces were be-
structural performance of WTC 1, 2, 5, rior columns together. Consequently, the ing renovated. As of September 11,
and 7. A description of the performance truss provided stiffening of the frame for 2001, the impact floors of WTC 1 were
of the other 12 buildings is included in wind resistance, increased the resistance all provided with 38 mm of protection,
the BPAT report.1 An analysis of the of the structure to wind-induced over- while the protection thickness was in-
evacuation behavior of the occupants of turning, and supported the antenna on creased to 38 mm on only one of the
WTC 1 and 2 is ongoing. the roof (WTC 1 only). impact floors of WTC 2.
The fire resistance ratings provided in- The top and bottom chord of the bar
WTC 1, 2 cluded three-hour designs for the joists were connected to the exterior
columns and a two-hour floor assembly. columns, though only the top chord was
Each building was 110 stories tall, The core columns were protected by a attached to the core columns. Connec-
with seven subgrade levels. The floor combination of spray-applied fire-resis- tion to an exterior column was via a
plate for each building was 63.1 m tive material (SFRM) and gypsum wall- steel angle. The bar joist was bolted to
square, with chamfered 2 m corners. board shaft walls. Exterior columns were the angle and also welded to the angle.
The area per floor was approximately protected with a plaster material on the A damper connected the bottom chord
3,980 m2. The buildings were steel frame surface facing the inside of the building to the exterior column. The damper was
buildings. Because of their tall height, and also had a spray applied insulating provided to limit movement of the
weight was a design constraint, with material applied to the surfaces facing building under wind conditions. The an-
lightweight alternatives used where pos- the exterior to limit the solar heating of gle was protected in the same manner
sible. the columns. as the column, though the damper was
Most of the interior columns were The bar joists were also protected left unprotected to preserve its function-
hollow sections up to about the 80th with an SFRM. The original installation ality. The connection of the bar joist to
floor, above which the columns were provided 19 mm of thickness of the the core column consisted of two bolts
wide flange sections. The exterior SFRM as a result of an analysis con- to a plate connected to a channel that
columns were nominally 356 mm ducted comparing the insulating abilities was welded to the column.
square, hollow sections (wall thickness of the mineral fiber SFRM selected for The stairwell and elevator shaft walls
approximately 12 mm at the impact the project as compared to a cementi- consisted of two layers of Type X gyp-
floors). Sets of three exterior columns tious material. (The analysis indicated a sum wallboard on each side of steel
were welded to plates forming span- thickness of 13 mm was needed, though studs. This shaft wall design was
drels. The floor assembly consisted of inspections following the initial applica- selected based on its lightweight char-
lightweight concrete poured on a metal tion indicated that the average protec- acteristic.
deck supported by steel bar joists. tion thickness on the bar joists was 19 At 8:46 a.m. on September 11, 2001,
The exterior columns were designed mm.) In the early 1990s, a decision was American Airlines Flight 11 impacted
to carry 60 percent of the gravity load. made by the Port Authority of New York WTC 1, also referred to as the North
The closely spaced exterior columns and New Jersey (the building owner at Tower, on its north face between the

Fire Protection Engineering N UMBER 18

■ Study of Building Performance

the jet fuel in WTC 1 and 2.

1.20 At impact, each aircraft was estimated
Ratio of Demand to Computed

to be carrying 38,000 liters of jet fuel.1 In

Room Temperature Capacity

1.00 addition to being released on the impact

floors, the jet fuel was consumed in the
0.80 fireballs, flowed down shafts (in some
cases igniting in shafts or the concourse
0.60 of WTC 1, and some may have flowed
down the outside of the building. The
0.40 amount of jet fuel needed to support a
fireball of a particular size can be esti-
0.20 mated from correlations in the
literature.3
0.00
6 5 3 2 n n n n 6 5 4 3 2 1
44 44 44 44 lum lum lum lum 40 40 40 40 40 40 D = 5.25m 0.314
co co co co
n g ng ng ng where D is the diameter of the fireball
i i i i
iss iss iss iss (m) and m is the mass of fuel vapor (kg).
M M M M The fuel consumed for different fireball
South Face Column Mark
diameters is presented in Figure 4. A
Figure 3. Load Redistribution for Exterior Columns photograph of the fireballs following the
impact of WTC 2 is presented in Figure
94th and 98th floors. The aircraft was a
5. In Figure 5, the diameter of the fireball
Boeing 767-200ER, traveling at an esti-
mated speed of 750 km/hr. The impact
Figure 4. Fuel
fractured approximately two-thirds of the
exterior columns on the north face of the 150 Consumption
Fireball Diameter (m)

versus Fireball
building, damaged floors in the vicinity 125 Diameter
of the impact location, inflicted some
damage to interior core columns and 100
shaft walls, dislodged fireproofing mater-
75
ial, and initiated fires on multiple floor
levels. 50
An elementary analysis was conducted
to determine the load redistribution along 25
the exterior columns to assess the level of
0
damage caused by the aircraft impact. 0 10000 20000 30000 Figure 5. Fireballs
The analysis assumed that none of the
Fuel Quantity (liters) Following Impact of
core columns were affected. The results
WTC 2.
of the analysis indicated that columns in
the immediate vicinity around the sev- fires were initiated in 90 West St. and
ered exterior columns were highly 130 Cedar St. In addition, fires were also
stressed, as indicated in Figure 3. How- observed in WTC 7 following the col-
ever, the stress level decreased to approx- lapse of WTC 2.2 Later at 10:28 a.m., 102
imately 20 percent of load capacity, near minutes after its impact, WTC 1 col-
preimpact levels, within a few column lapsed. WTC 3, 5, 6, and 7, The Winter
lines of the impact area. Garden, and WFC 3 were all impacted
Sixteen minutes later, at 9:02 a.m., an- by debris from the collapse of WTC 1.
other Boeing 767-200ER, United Airlines
Flight 175, impacted WTC 2, also re- FIRE BEHAVIOR
ferred to as the South Tower, on its south
face between the 78th and 84th floors. Much of the initial media accounts of
The speed of this aircraft was estimated the performance of WTC 1 and 2 sug-
to be 950 km/hr at impact. The impact gested that the collapse of the buildings
resulted in the same type of effects as in was attributable to the jet fuel being the
WTC 1. principal fuel source for the fires in
At 9:59 a.m., 57 minutes after impact, these buildings. With so much of the ini-
WTC 2 collapsed. During the collapse of tial attention being paid to the jet fuel,
WTC 2, sections of the building impacted the team conducted an analysis to assess
WTC 3 and 4, and Banker’s Trust, and the early fire behavior and the role of

S PRING 2003 www.sfpe.org

■ Study of Building Performance

from the north side of WTC 2 appears to also predicted to vary greatly, being as 2. The susceptibility of the columns to
be approximately the same as the length high as 900°C to 1,000°C in some areas, buckling failure increases as the modu-
of a side of the building, i.e. 60 to 70 m. while being 400°C to 800°C in others. lus of elasticity decreased with an in-
Based on the correlation from the litera- This range of temperatures is attributed crease in temperature of the fire-ex-
ture, approximately 3,700 liters of jet fuel to the changed geometry and fuel load- posed steel columns. Further, as
were consumed in each fireball. Given ing in the space as a result of the aircraft portions of floors collapsed, some sup-
the presence of three fireballs, this repre- entry into the building. The range in fire port for the columns may have been re-
sents approximately 11,000 liters. behavior is evident in the photographic moved, resulting in an increase in the
An estimate of the time required for evidence where flame projections from unsupported length of the columns.
the remaining jet fuel to be consumed openings are visible in some areas and 3. Following the aircraft impact, the
was generated by neglecting any fuel not others. In addition, in some areas Vierendeel truss at the roof was a princi-
that may have flowed down shafts or where the exterior columns and glass re- pal component in transferring load be-
otherwise left the impact floors. An up- mained intact, flames are visible, while tween the interior and exterior columns.
per limit of the duration of the jet fuel in other areas they are not. As such, the As the strength of the columns further
was provided by assuming that the fuel well-stirred reactor view of fully-devel- decreased as a result of increasing tem-
formed a pool. The mass burning rate oped fires does not appear to apply to perature, the stresses in the truss ele-
for liquid fuels is on the order of 50 this situation. ments increased. When these elements
g/m2-s.4 Assuming that the fuel spread reached their load capacity, the truss
throughout one floor with an area of PROBABLE COLLAPSE failed and load transfer could no longer
3,980 m2, the duration of burning for the MECHANISMS be accomplished, leading to interior
remaining 11,000 liters of jet fuel would columns being overwhelmed.6
be less than one minute. Actually, the In both WTC 1 and 2, the collapse of
fuel was probably dispersed over the of- the buildings is attributed to the com- WTC 5
fice furnishings present on the floor bined effects of the damage caused by
(thereby increasing the fuel surface the aircraft and the weakening of the WTC 5 was a nine-story, steel frame
area) and served as an igniter for the steel as a result of the fire. The damage building. The overall dimensions of the
mix of office furnishings present on the caused by the aircraft included: L-shaped building were approximately
impact floors. Some of the jet fuel may • Destruction of some exterior and in- 100 m x 128 m, with an approximate
also have formed small pools in sections terior columns, resulting in some of the floor area of 11,150 m2 per floor. The
of wing tanks that survived the effects of remaining columns becoming highly moment-frame design consisted of a
the impact. The jet fuel may have stressed. composite floor system with wide flange
burned in these small sections of the • Destruction of some portions of the steel beams connected to a lightweight
building for several additional minutes. floor framing and slab, at least in the concrete fill on metal deck floor. The
Consequently, for the majority of the vicinity of the impact areas. Floor slabs columns in the building were wide
duration that the fires burned in WTC 1 under the collapsed areas were required flange steel sections. A pair of wide
and 2, the fires involved the office fur- to support additional loads associated flange beams was provided from each
nishings present in the buildings. Rehm, with the damaged aircraft and thus were column line to provide support for the
et al., at NIST conducted an analysis of more heavily stressed. cantilevered floor slabs (4.6 m).
the fire behavior in the towers using • The force of the impact and the tra- The fire resistance designs of the
FDS.5 Their analysis was based on jectory of the components of the aircraft structure were believed to have in-
matching the rise of the smoke plume through the space resulted in some dis- cluded three-hour columns and two-
from videotapes and photographs with lodgement of fireproofing material from hour floor-ceiling assemblies. Fire resis-
that provided by the computer simula- the bar joists and core columns. tance was provided by a mineral fiber
tion. Input for the model involved esti- Unfortunately, eyewitness accounts of SFRM. As with WTC 1 and 2, the stair-
mating the size of the hole(s) created by the damage caused by the aircraft on the well and elevator shaft walls consisted
the aircraft impact and ambient weather impact floors are unavailable. of two layers of Type X gypsum wall-
data. The size of the holes was esti- Three probable failure mechanisms board on each side of steel studs.
mated based on photographic evidence. include: There was some localized collapse as
Weather data were reported from three 1. As the temperature of the bar joists a result of the impact of debris from one
departing aircraft from nearby LaGuar- increased, they lost rigidity and sagged or both of the towers, including a pene-
dia and Newark airports between 7:15 into catenary action. As catenary action tration of the roof in one area and seg-
a.m. and 9:00 a.m. at heights compara- continued, stresses on connections to ments of the southern edge of the build-
ble to the floor levels of the impact. The framing elements and exterior columns ing from floors 3 to 9. Fires were
wind speeds were 16 to 32 km/hr. and increased until the connections failed. initiated as a result of impacts by debris
the ambient temperature was 20°C to As a portion of the floor assembly failed from the collapse of WTC 1 or 2. The
21°C and fell to the floor below, the lower fires burned without any significant sup-
The peak heat release rate estimated floor became overloaded, causing its pression effort, either by the automatic
by Rehm, et al., in the towers was likely connections to fail. This sequence con- sprinkler system or the fire department.
to be approximately 1.0 to 1.5 GW. Tem- tinued with the progressive collapse of The inaction by the sprinkler system
peratures within the floor areas were all of the lower floors. was probably due to a loss of pressure

Fire Protection Engineering N UMBER 18

■ Study of Building Performance

in the water mains following the col-

lapse of WTC 1. As a result, significant
fire damage was evident on floors 4 to
9, with the greatest destruction evident
nearest the windows.
Most of the structure responded to the
fire in a manner typical of other fire inci-
dents and fire tests.7, 8 As such, significant
deflections of beams were observed
where tensile membrane action evi-
dently occurred to prevent collapse of
the structure. However, the collapse of
one area of 3 x 3 bays appeared to be
due to fire effects. This collapse was ini-
tiated at the 8th floor slab and was ar-
rested at the 5th floor. The collapse is at-
tributed to a failure at the shear tab
indicated in Figures 6 and 7. The shear Figure 6. Schematic Diagram of Framing for WTC 5
tab was evidently unable to resist an in-
crease in tensile stresses induced follow-
ing the deflection of the beam. ers report that while the fire
appeared on several floors
WTC 7 throughout the day, it ap-
peared to be located on the
WTC 7 was a 47-story, steel frame 6th floor for the entire du-
building located across Vesey St. from ration. A camera from the
the remainder of the World Trade Center north of the building re-
Complex. The building was an air-rights corded light gray, modestly
building, being constructed over a Con buoyant smoke emanating
Ed substation located on the lower four from the building through-
floors. The next three levels contained out much of the day. Ap-
switchgear and emergency generators. A proximately one hour be-
total of 91,000 liters of diesel fuel was fore the collapse, the
stored below grade to supply the gener- smoke became dark gray
ators. The top 40 stories contained office and appeared to be much
space, including space for New York more buoyant.
City’s Office of Emergency Management At 5:20 p.m., the collapse
on the 23rd floor. sequence initiated. First, the
Figure 7. Location of Failed Shear Tab
On the 8th floor and above, a mo- penthouse on the east side of the roof
ment-frame design was utilized with disappears from view, then about 10
wide flange steel members. Transfer seconds later the penthouse on the west trusses except for pipes carrying diesel
trusses spanned the 5th to 7th floors to side disappeared. Immediately after the fuel to and from the generators. While
transition from the structure for the sub- disappearance of the west penthouse, some fuel was found in the under-
station to that for the office floors. The the progressive collapse started, appar- ground tanks once they were recovered,
positions of the transfer trusses are indi- ently at a low floor. On the videotape the role of the diesel fuel was ques-
cated in Figure 8. record of the collapse from the news tioned by the BPAT.
The fire resistance design was be- media, the upper 30 to 35 stories appear
lieved to be similar for this building as to descend intact, indicating the collapse OTHER OBSERVATIONS
for WTC 1, 2, and 5, though using a ce- was initiated on a lower floor. In addi-
mentitious SFRM for three-hour fire re- tion, just prior to collapse, a crack or The FEMA report1 was intended to
sistance rated column designs and two- “kink” (as referred to in the FEMA provide a compilation of the facts, as
hour fire resistance-rated floor-ceiling report1) becomes evident on the north could be best accumulated during the
assemblies. The trusses were presum- wall in the vicinity of the east pent- seven-month period. The FEMA report
ably protected in a manner similar to house. did not recommend any immediate code
that followed for the columns. The east penthouse is located over changes based on the limited analysis
Fires were observed on multiple transfer trusses 1 and 2. One proposed conducted in the BPS. Certainly, as re-
floors in WTC 7 following the collapse mechanism of the collapse was a failure search continues to identify probable
of WTC 2.2 Photographs of the south of transfer truss 1 or 2 due to fire expo- collapse mechanisms in WTC 1, 2, 5,
face of the building indicate fires were sure on that level. Fuel loads were re- and 7 as well as to understand why col-
located on many of the floors. Fire fight- portedly light in the vicinity of the lapse was arrested in WTC 5, possible

S PRING 2003 www.sfpe.org

 ■ Study of Building Performance

Figure 8. Position of Transfer Trusses in WTC 7

recommendations for code changes • Tools to predict performance of 3 Zalosh, R., “Explosion Protection,” SFPE
Handbook of Fire Protection Engineering,
could become apparent. buildings to actual fires need to be de-
3rd Edition, P.J. DiNenno, (Ed.), NFPA:
Areas recommended for further study veloped, including the role of connec-
Quincy, MA, 2002.
include: tions (results from standard fire resis-
• Are there details of the structural tance tests cannot be used to predict 4 Babrauskas, V., “Heat Release Rates,” SFPE
design of WTC 1, 2, 5, and 7 that made performance). Such tools are needed Handbook of Fire Protection Engineering,
3rd Edition, P.J. DiNenno, (Ed.), NFPA:
them more susceptible to collapse? Are for conducting performance-based de-
Quincy, MA, 2002.
there subtle changes in the design that sign of structural fire protection systems
could have prevented the collapse of and would be essential in providing 5 Rehm, R., “Modeling Fires In the World
these buildings? real-time information for fire service of- Trade Center Towers,” Fire Risk & Hazard
Assessment Research Application
• What is the role of connections in ficers directing emergency operations
Symposium, Fire Protection Research
fire-resistant assemblies? Connections in high-rise buildings subjected to seri-
Foundation, Baltimore, MD, 2002.
are not included in standard fire resis- ous fires. ▲
tance tests. Thus, protection of connec- 6 Clifton, G., “Collapse of the World Trade
tions is often done simply by continuing James Milke is with the University of Center Towers,” Structures in Fire ’02,
University of Canterbury, New Zealand,
the same protection as for the con- Maryland.
2002.
nected structural member.
• Can the durability of fireproofing 7 Routley, J., Jennings, C., and Chubb, M.,
REFERENCES
materials to impact loads be improved? “High-Rise Office Building Fire, One
Meridian Plaza, Philadelphia, Pennsylvania,”
• Critical elements whose failure
1 World Trade Center Building FEMA Report 049, Federal Emergency
would lead to progressive collapse need Performance Study: Data Collection, Management Agency. Washington, D.C., 1991.
to be identified. Such is reportedly com- Preliminary Observations, and
mon practice in the U.K., but not the 8 Kirby, B., “Large Scale Fire Tests: The
Recommendations, FEMA Report 403,
U.S. Policy needs to be established on British Steel European Collaborative
Federal Emergency Management Agency,
Research Programme on the Building
how such critical elements should be Washington, D.C., 2002.
Research Establishment 8-storey Frame.”
protected, i.e., is additional fire resis- 2 Smith, D., Report from Ground Zero: The Fire Safety Science – Proceedings of the 5th
tance needed, should special inspection Story of the Rescue Efforts at the World Intl Symposium, International Association
programs be established to confirm Trade Center, Putnam Publishing Group, for Fire Safety Science, Melbourne,
proper protection of such elements? 2002. Australia, 1997.

0 Fire Protection Engineering N UMBER 18

 By Robert Berhinig, P.E.

Restructuring T he attack on the World Trade

Center (WTC) in New York City
has raised concerns regarding the
fire safety of high-rise structures. Until
Sept. 11, 2001, few people envisioned

Confidence in
the total collapse of a high-rise building
except under controlled conditions such
as an implosion for demolition purpos-
es. Today, the public’s concerns are
heightened.
These concerns can be reduced by

the Fire Safety recognizing that the Sept. 11 attack on

the WTC was an extreme act of terrorism.
Also, fires in high-rise structures are not
unexpected events. Fire-testing proce-
dures are in place to determine a build-

of Buildings ing assembly’s ability to resist structural

collapse when exposed to fire. Structures
that consist of fire-resistive building as-
semblies have functioned well under se-
vere fire conditions. In fact, the Federal
Emergency Management Agency (FEMA)
report, “World Trade Center Building Per-
formance Study,”1 states the collapse of

S PRING 2003 www.sfpe.org 1

■ Restructuring Confidence

these structures is particularly significant the most recent edition published in rorist attacks. It is implied that because
in that, prior to these events, no protected 2000. Throughout the world, similar fire- the standard was originally developed
steel-frame structure, the most common test methods are published by interna- 80 years ago and because relatively
form of large commercial construction in tional organizations such as the Interna- “low-tech” equipment such as kiln-type
the United States, had ever experienced a tional Organization for Standardization furnaces is used for the test, the result-
fire-induced collapse. The overall perfor- (ISO). These basic fire-test standards are ing data may be inadequate.
mance of structures during fires is a credit the foundation for many other test meth- At the heart of this debate is the time-
to the entire fire-protection community, ods that focus upon fire containment temperature curve that controls the tem-
which includes engineers, product de- within building structures. Technical perature conditions within the test
signers, architects, testing organizations, committees with membership extending chamber. The time-temperature curve is
code bodies, inspection agencies, and the throughout the global fire-protection intended to represent an intense, fully
fire services. community develop these test standards, developed fire within a building. Does
which are consistently reviewed and up- the time-temperature curve perfectly
HOW ARE FIRE-TESTING dated as technology changes. While to- represent every fully developed fire in
METHODS USED? day’s test is similar to the test devised in every location? No. The actual heat and
1918, the quantity and the accuracy of temperature conditions generated from
The nationally recognized standard the data obtained during the tests have a fire in a particular location is depen-
used to conduct tests in the United advanced greatly. It is important to keep dent upon many variables such as build-
States is the American Society for Testing in mind that the testing chamber that is ing contents, materials of construction,
and Materials Standard Fire Test Meth- used in the fire test is only a tool – it is and ventilation conditions.
ods of Building Constructions and Mate- used to determine that a fire will be con- The value of the time-temperature
rials,2 also known as ASTM E119. It is tained by fire-resistance building assem- curve in ASTM E119 is its reproducibility
used to generate data to measure the in- blies within a laboratory environment. and its relationship to the previously ref-
tegrity of building assemblies subjected Several published stories have ques- erenced variables. This standardization
to fire exposure. The first edition of this tioned the reliability of the ASTM E119 enables the building code community to
standard was published in 1918, with fire test standard in light of the WTC ter- specify a minimum fire-resistive rating

Fire Protection Engineering N UMBER 18

 ■ Restructuring Confidence

for the performance of these building als for Structural Steel,3 specify fire test- The ASTM fire-test standard is a living
assemblies. chamber temperatures that rise at a document that undergoes constant review
In recent years, some fire conditions quicker rate than those specified in ASTM by the ASTM technical committee respon-
have been identified as sufficiently differ- E119. The time-temperature curve in UL sible for its content. Discussions regarding
ent from those represented by the time- 1709 represents the conditions associated the merits of the ASTM standard among
temperature curve in ASTM E119, thus with burning pools of hydrocarbon fuels. fire science professionals are similar to
meriting an additional time-temperature At the other end of the spectrum, discus- the discussions among professionals in
curve. As a result, several fire test stan- sions have cited the need for a time-tem- other sciences on topics in their special-
dards, including UL 1709, Standard for perature curve that has a slower rate of ized field. It is telling to note that, in the
Rapid Rise Fire Tests of Protection Materi- rise than specified in ASTM E119. FEMA report,1 an observation on the con-
dition of the structural steel in WTC 5
states that the structural damage due to
the fires closely resemble that commonly
observed in test assemblies exposed to
the ASTM E119 Standard Fire Test.

ARE BUILDINGS SAFE FROM FIRE

TODAY?

This is an appropriate question to

raise as a result of the collapse of the
buildings at the WTC site. The FEMA re-
port has taken the initial step in focusing
upon opportunities to enhance high-rise
building safety. Items cited in the report
include:
• the durability of materials used in
passive fire-protection systems,
• the lack of data on the performance
of structural connections when exposed
to fire, and
• a need for additional data describing
the physical characteristics of materials
used in passive fire-protection systems.
These material characteristics are re-
quired for a broad temperature range.
Since fires do occur in high-rise build-
ings, building codes typically require a
combination of both active systems
(smoke alarms and sprinklers) and pas-
sive systems (building assemblies with
hourly fire-endurance ratings) as a
means to protect public buildings. The
construction of the WTC and all typical
high-rise buildings is based upon re-
quirements in the applicable building
codes. The WTC was exposed to condi-
tions far beyond the scope of the build-
ing codes. Yet, at the WTC, the FEMA
report1 states that almost everyone be-
low the points of impact was able to
safely evacuate the buildings. More than
30,000 people evacuated the WTC.

CAN BUILDINGS BE SAFER IN THE

FUTURE?

As with any engineering challenge,

the resulting solution depends heavily
upon the assumptions made during the

3 Fire Protection Engineering N UMBER 18

evaluation process. With respect to the WTC, does one assume fire-resistive materials. This includes items such as the adhesion
the fire origin will be the result of careless housekeeping or the of coatings to structural steel, the securement of gypsum board,
deliberate impact of a highly combustible object such as an air- and the performance of an acoustical ceiling system with re-
plane? Each scenario requires a different fire-protection solution. spect to the acoustical panels remaining within the steel sus-
In the area of passive fire protection, the FEMA report1 fo- pension system.
cuses upon three items where action is recommended: Data from full-scale fire tests, such as ASTM E119, provide
• Develop additional data on the fire resistance of structural this type of physical performance information. Data from full-
connections. scale fire tests may also be used to validate the accuracy of the
• Improve the durability of fire-resistant materials. computer models for the material properties and fire conditions
• Develop data describing the characteristics of materials provided as input to the model. This can be accomplished only
used in passive fire-protection systems. because of the reproducibility of the ASTM E119 fire test cham-
The fire resistance of structural connections is not within the ber conditions. ▲
current scope of ASTM E119. This does not mean that data on
the fire resistance of structural connections could not be ob- Robert Berhinig is with Underwriters Laboratories, Inc.
tained using existing test equipment.
With respect to the durability of fire-resistive materials, the REFERENCES
ASTM E119 standard test method assumes that the systems
tested are located within environmentally controlled areas of a 1 “World Tracde Center Building Performance Study: Data Collection,
building. By contrast, for more than 20 years, UL has certified Preliminary Observations, and Recommendations.” FEMA 403,
fire-resistive materials intended for exterior use. Before a fire Federal Emergency Management Agency, May, 2002.
test, samples of the materials intended for exterior applications 2 ASTM E-119, “Standard Test Methods for Fire Tests of Building
are subjected to various exposures, which include accelerated Construction and Materials,” American Society for Testing and
aging, wet-freeze-dry cycling, high humidity, salt spray, and ul- Materials, West Conshohocken, PA, 2002.
traviolet light. 3 UL 1709, “Standard for Rapid-Rise Fire Tests of Protection Materials
Furthermore, all intumescent-type materials certified by UL for Structural Steel,” Underwriters Laboratories, Northbrook, IL,
for use in fire-resistive assemblies have been subjected to ad- 1994.
verse conditions to measure their durability. These conditions
include exposure to accelerated aging and high humidity.
These durability tests on intumescent materials are conducted
to evaluate the ability of these products to perform as intended
after being exposed to harsh environmental conditions.
Similar types of requirements can be developed for all types
of fire-resistive materials for which a higher degree of durability
is desired. Another consideration could be the expanded use of
a hose stream test that is part of the ASTM E119 standard. The
hose stream test subjects fire-resistive assemblies to impact and
erosion effects. An alternate method of applying the hose
stream test, or establishing new acceptance criteria intended for
highly durable materials, might be a desirable approach to en-
hance the level of safety for these products and systems.
As in almost all fields, the growth of computer-related applica-
tions has been enormous since the WTC was constructed. The
application of computer models in fire protection engineering is
an example of this growth. Today, computer models are avail-
able that will predict temperatures of building materials, such as
structural steel, during a fire. Computer models that will predict
the performance of multistory structures under varying tempera-
ture conditions are also available. These computer programs are
available to the fire protection engineering community. How-
ever, the input data required for these programs to function are
not readily available for most fire-resistive materials.
As stated in the FEMA report,1 standardized test methods are
needed for fire-resistive materials to determine their physical
characteristics such as density, conductivity, and specific heat
for temperature ranging from 70°F to 2,000°F (20°C-1100°C).
The material properties are known for common construction
materials such as concrete and steel but not for most propri-
etary materials. In addition to the need for material properties,
the results from computer models require validation. Today’s
computer models cannot predict the physical performance of

S PRING 2003 www.sfpe.org 1

 Consequences of
Imperfect Insulation –

Figure 1: View of the Building

Numerical
Modeling
Fire Protection Engineering N UMBER 18
Figure 2: The Protected Steel Columns

By Jean-Marc Franssen, Ph.D.

A
13-story high-rise office building in Germany was
undergoing refurbishment (see Figure 1). In order to
enlarge the area of some individual offices, some load-
bearing concrete walls were being replaced with steel frames
consisting of one steel beam and two steel columns. This modifi-
cation extended from the second floor to the top of the building,
with 24 steel columns at each floor.
In order to achieve the required fire resistance time of 90 minutes
to the standard ISO 834 fire curve, the columns were thermally pro-
tected by a box protection made of gypsum-type fire protection
boards (see Figure 2).

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■ Numerical Modeling

After the work was completed, the thermal protection

did not totally cover the horizontal steel plates upon
which the columns were placed; some 40 mm or 50 mm
of this steel plate was exposed and could be susceptible
to fire attack (see Figure 3).
The control authority questioned whether the exposed
steel could significantly reduce the fire resistance of the
columns. Figure 4 shows one of the columns that under-
went a tentative repair.
The University of Liege was commissioned to investi-
gate potential fire exposures to the bottom region of the
columns.

DATA AND HYPOTHESES

Each column is made of a hot rolled H profile of the

heavy HEM 160 type (166 mm x 180 mm x 76.2 kg/m). It
is placed on a 330 mm x 300 mm x 35 mm steel plate. The
steel plate comes on a 140 mm thick concrete slab, with a
35 mm intermediate layer of mortar. Steel is assumed to
have the thermal properties of Eurocode 3.1
The thermal insulation is made of 25 mm boards a den-
Figure 3: Imperfect Detailing sity of 900 kg/m3; a specific heat of 1700 J/kg-K, and a
thermal conductivity of 0.20 W/m-K. The high value of
the specific heat accounts for the energy absorbed by the
evaporation of the moisture and for the endothermic
chemical reactions of the gypsum-type board.
A 70 mm topping layer was added on the concrete slab.
The concrete of the slab, the topping, and the mortar
layer are assumed to have the thermal properties of Eu-
rocode 22 with a density of 2,300 kg/m3 and a moisture
content of 46 kg/m3.
This heat transfer involves not only conduction, but
also radiation in the chambers of the H profile created by
the box insulation. Different materials are involved, with
nonlinear temperature-dependent properties, and a tran-
sient situation has to be taken into account. Strictly
speaking, this was a 3D problem. The software SAFIR,3,4
established at the University of Liege for the analysis of
structures subjected to fire, can treat 3D conductive prob-
lems. Internal cavities with radiation inside can be taken
into account, but only in 2D sections. This is because the
algorithms for evaluating the view factors in the cavity
are quite complex, even in 2D, particularly if the cavity is
a complex shape, if there is partial visibility within the
cavity, or if there are objects within the cavity. The possi-
Figure 4: One “Repaired” Column bility of internal cavities in 3D structures has thus not
been programmed in the code. In order to have an
indication of the solution, it was decided to treat the
problem as a series of uncoupled 2D problems and then
to exercise some engineering judgment in order to reach
a conclusion.

Fire Protection Engineering N UMBER 18

 ■ Numerical Modeling

It is assumed in the analyses that no RESULTS OF THE MODELS ison with other results obtained by nu-
contact resistance exists at the interface merical methods.
between two adjacent different materi- Simple calculation model
als. Eurocode 3, and many other text- 2D numerical model at mid-level
The heat flux from the fire environ- books, gives a simple differential equa- At mid-level, the situation is purely
ment to the boundaries of the column is tion that allows calculating the temper- 2D and the “exact” solution can be ob-
calculated accorded to the recommen- ature evolution in a protected steel tained numerically using the discretiza-
dation of Eurocode I:5 see equation 1. profile on the hypothesis of uniform tion shown on Figure 5. Only one-
temperatures of both the steel profile fourth of the section is analyzed owing
( ) ( )
•
9" = α c Tg − Tm + σ ε res Tg4 − Tm4 (1) and surrounding gases. With the ther- to symmetry.
mal massivity of the box-protected pro- The isotherms after 90 minutes of fire
where file being equal to 71.3 m-1, this equa- are shown on Figure 6. This Figure in-
tion yields temperatures in the profile deed confirms that, in this well-pro-
•
9" heat flux at the boundary, W/m tected profile, the temperature distribu-
2
of:
hc coefficient of convection, 25 W/m2-K 127 °C after 30 minutes, tion in the steel is nearly perfectly
Tg gas temperature according to the 263 °C after 60 minutes, uniform. Minimum and maximum steel
ISO 834 standard fire curve, K 383 °C after 90 minutes. temperatures at that time are 337 °C in
Tm temperature at the surface of the the center of the web (node 1) and
material, K This uniform temperature is an ap- 349 °C in the corner of the profile
σ Stefan-Boltzman constant, 5.67 10-8 proximation of the situation prevailing (node 105).
W/m2K4 at mid-level of the column, i.e., far The average temperature obtained by
εres resultant emissivity, 0.56 away from the perturbation existing at the numerical model is 40 °C cooler
the bottom. It can be used as a compar- than the uniform temperature given by

8 Fire Protection Engineering N UMBER 18

 the simple model. This difference can be attributed to
the two simplifying hypotheses made in the simple
model:
1. The heat transfer between the hot gases and the
section is neglected in the simple model; it is assumed
that the temperature at the edge of the section is equal
to the temperature of the gas, and this is not exactly the
case.
2. The thermal massivity is calculated with the inside
surface of the insulating box as the surface of heat trans-
fer. In the present case, the thickness of the insulation
board is not small compared to the dimensions of the
profile. If, for example, the external surface of the insu-
lating box is taken into account, this yields a thermal
massivity of 91.9 m-1, and the uniform temperature calcu-
lated by the simple model after 90 minutes is then
435 °C. The value obtained by the numerical analysis is
between the two extreme values given by the simple Figure 5: Discretization of the Section
method, which gives some confidence in the results of
the numerical analysis.

2D discretisation perpendicular to the web

A 2D analysis is then performed in a vertical plane
passing through the center of the section and perpen-
dicular to the plane of the web (A-A’ on Figure 5). The
discretization is shown on Figure 7. The first material is
the concrete slab; material 2 is the mortar layer; mater-
ial 3 is the concrete topping; material 4 is the steel of
the web and of the horizontal plate (with 42 mm ex-
posed to the fire); and material 5 is the insulation
board. Figure 7 is a zone near the bottom of the col-
umn; a 1.040 m height of the column was modeled. A
450 mm width of the slab is represented because the
thermal field through the slab becomes uniaxial at
greater distance from the column. An axis of symmetry
Figure 6: Isotherms After 90 Minutes
exists on the left edge of the section.
Figure 8 shows the isotherms in the section after 90
minutes of the ISO 834 fire. The temperature in the
web is nearly uniform from the bottom to the top. It is
slightly colder at the bottom than in the current section,
416 °C versus 420 °C, because the heat flux to the web
is higher due to radiation from the insulation rather
than due to conduction via the horizontal steel plate.
During the first minutes of the fire, the contrary situa-
tion prevails: The temperature increases faster at the
bottom of the web than in the current section. This is
because the temperature wave needs some time to
travel through the insulation before it can attack the
web by radiation (as a function of the fourth power of
the temperature in the inside of the insulation),
whereas the heat transfer through the plate by conduc-
tion is more a linear function of the temperature differ-
ence. The linear function has a steeper slope at the be-
Figure 7: Discretization Perpendicular to the We
ginning, but at the end, the fourth power function
prevails.

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 ■ Numerical Modeling

2D discretization through the web

A 2D analysis is then performed in a vertical plane paral-
lel to the plane of the web and passing at one-fourth or
three-fourths of the width of the section (B-B’ on Figure 5).
The discretization is shown on Figure 9.
50 mm of the horizontal steel plate are exposed to the fire.
The insulating board is in contact with the flange of the pro-
file that is visible on this Figure.
Figure 10 shows the isotherms in the section after 90 min-
utes of the ISO 834 fire. In the flange, the temperature is
somewhat higher at the bottom of the column than in the
current section (392 °C versus 356 °C). This is not because a
bigger surface of the horizontal plate is exposed to the fire,
but more likely because the flange is located closer to the
exposed surface. The length for conduction through the
plate has been reduced, and this overwhelms the fact that
Figure 8: Isotherms in the Section the radiation resistance has disappeared between the insula-
Perpendicular to the Web tion and the flange.
This temperature increase has yet a limited extension
along the height of the column. Figure 11 shows that the af-
fected zone does not extend further than 400 mm above the
slab after 90 minutes of fire.

CONCLUSIONS

Two main observations emerge from the analyses.

1. The local temperature at the foot of the column is
slightly higher than the average uniform temperature
that can be calculated by the simple method of Eu-
rocode 3. The difference increases in time but is lim-
ited to 35 °C in the web and to 10 °C in the flange af-
ter 90 minutes of ISO fire.
2. The region that is influenced by the local effect has a
very limited extension, in the order of 400 mm
Figure 9: Discretization Parallel to the Web after 90 minutes of fire.
Because the local temperatures at the bottom of the col-
umn hardly exceed 400 °C, the temperature at which the
yield strength of steel starts to decrease according to the
Eurocode model, a failure by local crushing of the section
is not likely.
The Young’s modulus of steel starts decreasing at tem-
peratures as low as 100 °C. There will thus be a local de-
crease of the stiffness of the column, but this decrease acts
over too short a distance to increase significantly the buck-
ling length of the column.
As a consequence, it was judged that the consequences of
the apparently improper detailing could be neglected. Al-
though the software SAFIR is able to perform a mechanical
analysis of the column under a transient and nonuniform
temperature distribution, it was estimated that such a nonlin-
ear structural analysis was not necessary. ▲
Figure 10: Isotherms in the Section
Jean-Marc Franssen is with National Fund for Scientific
Parallel to the Web
Research Belgium.

0 Fire Protection Engineering N UMBER 18

 2 Eurocode 2: Design of concrete struc-
tures. Part 1.2: General rules. Structural
fire design. ENV 1992-1-2, CEN, Brussels,
1995.

3 Nwosu, D. I., Kodur, V. K. R., Franssen, J.

M., and Hum, J. K., User Manual for
SAFIR. A Computer Program for Analysis
of Structures at Elevated Temperature
Conditions, National Research Council
Canada, int. Report 782, 1999.

4 Franssen, J. M., Kodur, V. K. R., and

Mason, J., User’s Manual for SAFIR 2002.
A Computer Program for Analysis of
Structures subjected to fire, Univ. of
Liege, Dpt M&S, 2002.

Figure 11: Evolution of the Temperature Along the Height of the Flange 5 Eurocode 1: Basis of design and actions
on structures – Part 2-2: Actions on struc-
Note: A free demonstration version REFERENCES tures – Actions on structures exposed to
of the SAFIR software can be ordered 1 Eurocode 3: Design of steel structures. fire. ENV 1991-2-2, CEN, Brussels, 1995.
on the FTP site msmpc27.gciv.ulg.ac.be; Part 1.2: General rules. Structural fire
userid and password: SAFIR design. ENV 1993-1-2, CEN, Brussels, 1995.

S PRING 2003 www.sfpe.org 2

Accuracy, Precision, Resolution, and Uncertainty in

FIRE PROTECTION ENGINEERING

M uch of the work done by fire
protection engineers involves
computations using data gath-
ered during experiments. Those data
were gathered by making measure-
Significant Figures: The number of
digits needed to express the number to
within the uncertainty of the measure-
ment. Only figures or digits which are ac-
tually measured are said to be significant.
ments, and there is always some uncer- Significant figures include the uncertain
tainty when making a measurement. DEFINITIONS digit that is estimated when a measure-
Therefore, there is uncertainty in any ment is made (observed). For example,
computations using that data. This article Accuracy: How close a measurement when a scale is graduated in grams and
offers a brief refresher on accuracy, pre- or statement is to the true value. Of the display shows that the value lies be-
cision, resolution, and uncertainty, and course, when measuring something, the tween 5 and 6 grams, we may estimate
challenges the fire protection community true value can never be known. the value to be 5.2, 5.5, or 5.9 grams.
to take the next great step for an evolv- Precision: The degree of agreement Thus, the last digit is uncertain but is sig-
ing discipline: recognition and public between individual measurements of a set nificant.
reporting of our uncertainty. Whether a of measurements. This is the most com- Numbers other than measured values
model or a calculation method is accu- mon use of the term. Sometimes, preci- also have significant digits. These include
rate or not requires careful analysis and sion or the word “precise” is used when integers, such as the number of smoke
study, and is beyond the scope of this describing the resolution of an instrument. detectors used in a battery calculation.
article, which is intended to focus on Resolution: The smallest interval that With defined numbers such as π, square
how to properly report data and the an instrument can actually measure. A roots, or unit conversions, every digit you
results of calculations. meter stick with 1 mm gradations has a choose to use is significant.
“In physical science, the first essential resolution of 1 mm even though accepted Determining the number of significant
step in the direction of learning any sub- practice is to estimate one additional sig- figures in a number can be tricky. For ex-
ject is to find principles of numerical nificant figure. ample, if you are told that the tempera-
reckoning and practicable methods for Uncertainty: An interval around a ture is 20°C, does that number have one
measuring some quality connected with measured value such that repeated mea- or two significant figures? Our experience
it. I often say that when you can measure surements will lie within this interval. tells us that most thermometers are grad-
what you are speaking about and express Repeatability: Close agreement be- uated in single degrees, not 10-degree in-
it in numbers, you know something tween the results of successive measure- crements. So it would be safe to say that
about it; but when you cannot measure it, ments carried out under the same condi- the resolution is one degree, and that our
when you cannot express it in numbers, tions of measurement.1 Repeatability uncertainty is one degree and the number
your knowledge is of a meagre and un- conditions include: of significant digits is two. However, if
satisfactory kind; it may be the beginning • the same measurement procedure; you are given heat release rate datum
of knowledge, but you have scarcely in • the same observer; such as 2,579 kW you should question
your thoughts advanced to the state of • the same measuring instrument, used whether that datum really has four signifi-
Science, whatever the matter may be.” under the same conditions; cant figures as reported. Was it really
Lord Kelvin, 1824 – 1907 (Sir William • the same location; and measured (or calculated) with that level
Thomson, Baron Kelvin of Largs) • repetition over a short period of time. of resolution? Similarly, if the datum is
Many fire protection engineers and sci- Reproducibility: Close agreement be- listed as 2,000 kW, is it really only certain
entists use fire models. Calculations are tween the results of measurements car- to within 1,000 kW or is it better reported
made using data whose uncertainty is un- ried out under changed conditions of as 2.0 x 103 kW, thereby confirming two
known – or at least not reported. Clients measurement.1 The changed conditions significant digits?
and courts are given results by experts may include: Most engineers are familiar with the
that imply the work has a degree of accu- • principle of measurement; rules for rounding to the correct number
racy and precision that it may not have. • method of measurement; of significant figures after making a calcu-
The experimenter must determine and re- • observer; lation using multiple pieces of data.
port the uncertainty interval for measured • measuring instrument; However, recent work shows that the
data, and the engineer that uses the data • reference standard; standard rule for rounding after multipli-
in calculations or models is responsible • location; cation and division can result in errors
for informing their audience of the uncer- • conditions of use; and and the loss of data.2, 3
tainties inherent in the analysis†. • time. The standard rule for addition and sub-

Fire Protection Engineering N UMBER 18

traction is that the number of significant What is the uncertainty associated with reporting of engineering analyses.
figures is determined by the smallest res- our results? It depends on the uncertainty
* Here, “reliable” is used to mean a result that is least
olution or uncertainty (lowest precision) of the data used to get the results. When likely to contain an error or to lose data when a
of all the quantities involved. For exam- making measurements to obtain data, it is rounding rule is applied. For more information on
ple, 1.413 + 9.2 = 10.613 and should be best to make several measurements and the reliability of the standard rule and the alternate
rounded to 10.6. The standard rule for calculate the mean and the average devia- rule, see references 2 and 3, which can accessed at
http://www.angelfire.com/oh/cmulliss/.
multiplication and division states that the tion. For example, the following table lists
results should be written using the same many measurements made of the length
REFERENCES
number of significant digits as the least of a sample:4
precisely known number used in the 1 Taylor, B.N., and Kuyatt, C.E., “Guidelines
computation. For example, 5.60 x 3.7524 Length Deviation
(cm) from mean for Evaluating and Expressing the
= 21.01344 should be reported as 21.0 Uncertainty of NIST Measurement Results,”
since 5.60 has only three significant digits. 15.39 0.012 NIST Technical Note 1297, U.S.
The alternate rule states that the results 15.37 0.008 Government Printing Office, Washington,
should be reported using one more sig- 15.37 0.008 DC, 1994.
nificant figure than the standard rule.2 15.39 0.012 2 Mulliss, C., and Lee,W., “On the Standard
Thus, for this example, the results would 15.38 0.002 Rounding Rule for Multiplication and
be reported as 21.01. 15.37 0.008 Division”, Chinese Journal of Physics, 1998,
When combining addition, subtraction, 36(3), 479-487.
15.37 0.008
multiplication, and division, determining 3 Lee,W., Mulliss, C., and Chiu,H., “On the
15.38 0.002
the number of significant digits in the fi- Standard Rounding Rule for Addition and
nal result is more difficult. The proper The mean is calculated to be Subtraction”, Chinese Journal of Physics,
method, which preserves the integrity of 123.02/8=15.378 cm. The average devia- 2000, 38(1), 36-41.
the data, is to apply the rules at each step. tion is 0.060/8=0.008 cm. The results, in- 4 Example from Bellevue Community
For example: cluding uncertainty, would be reported as Collage Physics Department Web site,
15.378 +/- 0.008 cm. A simpler approach is http://scidiv.bcc.ctc.edu/Physics/Measure&si
X = 5.60(1.413 + 9.2)3.7524
to make only one measurement and to ap- gfigs/Measure&sigfigsintro.html.
X = 5.60(10.6)3.7524 ply the general rule for uncertainty, which Additional Information:
X = 222.706 is to use one-half the smallest scale divi-
ISO, Guide to the Expression of Uncertainty
X = 222.7 by the alternate rule sion of the measuring instrument as the
in Measurement, International Organization
X = 223 by the standard rule uncertainty. For this example, assume the
for Standardization, Geneva, Switzerland,
scale is in mm and that last digit in the data 1993.
However, using a calculator, spread- is the observer’s estimate. If they measured
sheet, or computer model, intermediate 15.38, it should be reported as 15.38 +/- Eric W. Weisstein, Wolfram Research, Inc.:
results are not rounded, and the user (or 0.05. Consult the references for how un- http://mathworld.wolfram.com/S/SignificantD
igits.html
the person who wrote the spreadsheet or certainties propagate through calculations.
program) must determine how to present This article has only touched on a few Purdue University, Chemistry primer on
the results. For the above example, the of the issues related to accuracy, preci- Significant Digits: http://chemed.chem.purdue.
following results might be displayed: sion, resolution, and uncertainty. It is in- edu/genchem/topicreview/bp/ch1/sigfigs.html
X = 5.60(1.413 + 9.2)3.7524 cumbent on the engineering practitioner World of Chemistry: The Home Page of
to be both accurate and precise, as well Ralph Logan: http://members.aol.com/
X = 223.01564
as honest in their work. For example, a profchm/sig_fig.html
How should this be rounded? If the calculation may indicate that the time to
Interactive (JAVA) site to test your knowl-
least number of significant digits in the egress a space is 2 min., 30 seconds, and
edge of significant digits: http://brad.tcimet.
data (two) is used, it would be written as the minimum time for untenability, based
net/java_samples/sigfigs/autogen_SigFigs.html
220 without a decimal point. If the least on a series of realistic design fires is 3
level of precision is used, it would be minutes. It is insufficient, even dangerous, Significant Figures, by Timothy C.K. Su,
written as 223.0. Neither matches the to say that a protection plan is good if the Professor, Chemistry Department, UMass
most reliable answer, 222.7, which is egress time includes a detection compo- Dartmouth: http://www.umassd.edu/
1Academic/CArtsandSciences/Chemistry/Cata
found by intermediate rounding using the nent with an uncertainty of 1 minute.
lyst/sf.html
alternate rule*. Nor do they match the It is only through careful, disciplined
next most reliable answer, 223, reached practice that the fire protection commu-
using the standard rounding rules. Wher- nity will correctly present its work to
Editor’s Note – About This Article
ever possible, models should use inter- peers and other more established disci-
mediate rounding. If this is not possible, plines, and gain recognition and respect This is a continuing series of articles that is
the easiest method is to round using ei- for its engineering and scientific efforts. supported by the National Electrical
ther the lowest precision or the least Manufacturer’s Association (NEMA), Signaling
number of significant digits plus one, † This article address only measurement uncer- Protection and Communications Section, and
whichever results in the least number of tainty. Chapter 5-4, “Uncertainty,” by Dr. Kathy No- is intended to provide fire alarm industry-
tarianni, in the SFPE Handbook of Fire Protection related information to members of the fire
digits. This would cause the results to be Engineering, 3rd ed., addresses other types of un-
reported as 223 or 2.23 x 102. certainty that are important for honest and complete
protection engineering profession.

S PRING 2003 www.sfpe.org 2

By Robert H. Iding, Ph.D.1

CALCULATING
INTRODUCTION

A performance-based approach to
designing structures for fire resis-
tance is gradually gaining favor
as an alternative to traditional prescrip-
tive requirements such as hourly ratings
and tables of required fireproofing
thicknesses. The basic concept underly-
STRUCTURAL
RESPONSE
ing performance-based fire analysis is
that a building should be designed for
the fire severity that might actually
occur in the building rather than for a
code-specified “one-size-fits-all” fire
such as ASTM E-119. Using factors such
as fuel load and ventilation, the maxi-
mum credible fire in different locations
in the building is calculated, and the
structural response to these fires is cal-
culated.
TO FIRE
S PRING 2003 www.sfpe.org 2
■ Calculating Structural Response to Fire

Typical Ratio of the Eleveated-Temperature

1.2

to Room-Temperature Yield Strength

1

0.8

0.6

0.4
Q̇
0.2

0
0 200 400 600 800 1000 1200 1400 1600 1800 2000
5
T (°F) = (T (°C) − 32) Temperature, ˚F
9

Figure 1. Effect of Temperature on the Yield Strength

of Steel3

Basic heat conduction theory can N = convection power factor

predict temperature history in fire-ex- V = radiation view factor
Calculating a structure’s response to posed structures when thermal material σ = Stefan-Boltzmann constant
fire is a three step process: properties of concrete, steel, and insu- α = absorption of surface
1. Fire Hazards Analysis to identify lation are known. The heat conduction εf = emissivity of the flame associ-
all credible fire scenarios and deter- field equation for a three-dimensional ated with fire
mine the impact of each scenario on body is: εs = surface emissivity
adjacent structural members. ∂T Tf = fire exposure temperature
2. Thermal Analysis to calculate tem- ρCp + K∇ 2 T = Q˙ Ts = surface temperature
∂t
perature history in each member. where
3. Structural Analysis to determine ρ = density of material There are a number of finite element
forces and stresses in each member and Cp = specific heat capacity of computer codes that solve the heat
whether local or progressive structural material conduction field equation with this fire-
collapse would occur during any of the T = temperature distribution in boundary condition. Two of the most
fire hazard scenarios. member commonly used are FIRES-T31 and
t = time TASEF2. All of these codes discretize the
THERMAL ANALYSIS K = heat conductivity of material field equations into a set of linear equa-
= heat input into member per tions expressed by the matrix relation-
Structural members exposed to hot unit time ship:
gases from fires gradually heat up and
∂2 ( ) ∂2 ( ) ∂2 ( ) [C]{T } + [ K ]{T } = {Q}
can reach very high temperatures. The ∇2 ( ) = + +
temperature rise always lags the fire ∂x 2
∂y 2
∂z2 where
temperature because of the thermal in- [C] = capacity matrix (temperature-
ertia inherent in the material and the Heat input is due to a combination of dependent)
tendency for heat to flow to cooler ma- convection and radiation into the fire- [K] = conductivity matrix (tempera-
terial adjacent to the heated area. Insu- exposed surfaces. This heat flow can be ture-dependent)
lation can greatly slow the temperature calculated using the equation: {Q} = external heat flow vector (de-

[( )]
rise in protected members. When the pends on exothermic reac-
) (
N
fire starts to cool, the temperature drop Q̇ = A h Tf − Ts + Vσ αε f Tf 4 − ε s Ts 4 tions and fire-boundary con-
in a structural member will lag the where ditions)
falling gas temperature, again because A = surface exposed to fire {T} = temperature vector (time-de-
of thermal inertia and insulation. h = convection coefficient pendent)

Fire Protection Engineering N UMBER 18

■ Calculating Structural Response to Fire

Plume Time-Temperature Profile

2000
Target
1800 Elevation
1600 1 ft (0.3 m)
2 ft (0.6 m)
Temperature (F)

1400
3 ft (0.9 m)
1200 4 ft (1.2 m)
5 ft (1.5 m)
1000
6 ft (1.8 m)
800 8 ft (2.4 m)
10 ft (3.0 m)
600 12 ft (3.6 m)
400 14 ft (4.2 m)
200
0
0 5 10 15 20 25 30
5
T (°C) = (T (°C) − 32) Time (min)
9

Figure 2. Column Exposure Temperatures from Maintenance Refuse Fire.9

All thermal analyses start with dis- analysis methods and computer models
cretizing the structural members into fi- can be used, but they must take into
nite elements and defining boundary account the special characteristics of
conditions, both fire-exposure bound- materials at high temperatures:
aries and other boundaries where heat • Thermal expansion (coefficient of
may escape from the member into ad- expansion multiplied by temperature
joining parts of the structure or into the change), which can be very large in a
environment. The thermal material fire. When there is restraint acting, very
properties are defined for all compo- large stresses can be generated by this
nents of the model, and the time-de- thermal expansion. Steel W14 90
pendent fire curve (gas temperature Tf) • Effect of temperature on material column
from the particular fire scenario to be properties, such as modulus of elastic-
considered is specified. The equations ity, yield point, and ultimate strength.
are then solved to obtain the tempera- For example, when steel becomes hot
ture history in all parts of the structural enough, the yield point can drop so
member during the fire. Such tempera- much that the member cannot support
tures form the basis for a structural gravity loads during the fire and col-
analysis of each member and the struc- lapse will occur. The degradation of
ture as a whole. yield strength with temperature for A36
mild steel is shown in Figure 1.3 It can
STRUCTURAL ANALYSIS be seen that between 1000°F and
1100°F (500°C-600°C) the yield point
Once the maximum temperature has fallen to only 60 percent of its
Line of symmetry
loading in each structural member is room-temperature value. Typical maxi-
known, calculations to determine the mum design loads produce about 60 Concrete slab
structural response of these members percent of yield stress, so collapse of a
to the fire can be made, particularly to fully loaded member could occur once Figure 3. Column, Adjacent Base
determine whether any member will this temperature is reached, although Plate, and Floor Slab Discretized
fail during the fire. Standard structural most steel structures would be much into Finite Element Mesh.

S PRING 2003 www.sfpe.org 2

■ Calculating Structural Response to Fire

Steel Time-Temperature Profile

2000
1800
1600 FIRES-T3
T avg
Temperature (F)

1400
FIRES-T3
1200 T max
1000
800
600
400
200
0
0 5 10 15 20
5
T (°C) = (T (°F) − 32) Time (min)
9

Figure 4. Steel Temperature History for Maintenance Refuse Fire.

more lightly loaded during a fire and properties as the analysis proceeds. EXAMPLE – TRANSIENT TRASH
would fail at higher temperatures. Con- Simplified approaches are also possi- FIRE IN POWER PLANT
crete loses strength more slowly at ele- ble. For example, in relatively unre-
vated temperatures than steel does,3 strained steel members, a temperature The particular fire hazard to be ex-
but it is susceptible to spalling, which threshold can be set (typically 800°F- amined here is a transient trash, or
may expose reinforcing steel to fire 1000°F [400°C-500°C]) at which the refuse, fire in a large steel-framed
and loss of strength. yield point is well above the stresses power plant. This is an important sce-
• Nonlinear behavior. Structural re- the member must carry during the fire, nario to consider since there are many
sponse during a severe fire can quickly and the member can be considered ac- places in such a structure that could be
lead to high stresses, yielding, creep, ceptable. This is the type of acceptance impacted by a fire of this type. If the
and local or general failure. A com- criterion used in ASTM E-119 furnace refuse is placed directly against an un-
plete analysis must take these nonlin- tests when assemblies are not loaded fireproofed steel column, and the fire
ear effects into account. during the test. were large enough, the structural in-
Several computer models were The emphasis of a structural analysis tegrity of that column might be af-
specifically designed to model these should be on examining the fire safety fected.
special high-temperature phenomena, of the building as a whole. The re- The first step in the analysis is to
including FIRES-RC II,4 FASBUS II 5 ,6 sponse of each member is calculated, conservatively estimate the quantity of
and SAFIR.7 Other nonlinear structural and local failures are identified. But transient material that could be adja-
programs such as ABAQUS and DIANA then it is important to continue the cal- cent to a column. The fuel package se-
have been modified and utilized for culations in order to determine lected is typical maintenance refuse
fire analysis.8 General-purpose linear whether these local failures could lead composed of a cardboard box,
programs can sometimes also be used, to progressive collapse of the entire Kimwipes™, acetone, and a plastic
particularly if member temperatures building. Increasing structural redun- wash bottle. The burning characteristics
are not very high or if there is little re- dancy in the fire-affected area may be of this fuel package (about 120 kW
straint to thermal expansion. When us- necessary if analysis indicates progres- heat release rate) were calculated, from
ing a linear program, the analyst must sive collapse is likely. This is one way which the gas temperatures of the fire
account for any yielding or other non- structural engineers can make an im- plume impacting the surface of the col-
linear behavior by modifying material portant contribution to fire safety. umn were also calculated,9 as shown in

Fire Protection Engineering N UMBER 18

■ Calculating Structural Response to Fire

Figure 2. Note that for this fuel load, temperatures. use. Ideally, fire should be treated as an
the fire duration is about 13 minutes The performance-based analysis for additional design load case, just as other
and the peak plume temperature is this typical transient trash fire shows infrequent loading conditions such as
1600°F (870°C). Also note in Figure 2 that such fires are too small to signifi- wind or earthquake are. ▲
that the temperature of the gas en- cantly affect the load-bearing capacity
veloping the column decreases at of columns anywhere in the steel Robert H. Iding is with Wiss, Janney,
higher elevations above the fire, so that frame, even if they are uninsulated. Elstner Associates.
only the first few feet of column above Therefore, spray-on insulation is not
the refuse pile are exposed to very high necessary for this fire hazard. REFERENCES
temperatures.
The next step in the analysis is to THE FUTURE 1 Iding, R.H., Bresler, B., and Nizamuddin,
determine the temperature rise in the Z., “FIRES-T3-A Computer Program for
steel column itself during the trash fire. Performance-based fire codes and the Fire Response of Structures-Thermal
(Three-Dimensional),” UCB-FRG Report
A three-dimensional heat conduction associated analysis will eventually find
77-15, Fire Research Group, Department
analysis using FIRES-T3 was performed universal acceptance, but not as
of Civil Engineering, University of
for a typical uninsulated W14 x 90 col- quickly and easily as other types of California, Berkeley, October 1977.
umn, which is the smallest size column performance-based codes have in the
in the steel frame and, therefore, past. For example, earthquake codes 2 Sterner, E., and Wickström, U., “TASEF -
Temperature Analysis of Structures
would be most severely affected by the and seismic structural analysis were
Exposed to Fire,” SP Report 1990:05,
trash fire. Also modeled is the base quickly accepted since they arose un- Swedish National Testing and Research
plate and adjacent concrete slab. It is restrained by previous practice. Build- Institute, Borås, 1990.
assumed that the trash is piled at ings had essentially not been designed
3 ASCE/SFPE 29 “Standard Calculation
ground level against one side of the specifically for earthquakes, and engi-
Methods for Structural Fire Protection,”
column’s web and adjacent flanges, neers, architects, and building officials
1999.
thereby exposing these surfaces to the gratefully adopted the new methods as
full radiation from the fire. The finite they found their way into engineering 4 Iding, R.H., Bresler, B., and Nizamuddin,
element model is shown in Figure 3 literature and the building codes. Per- Z., “FIRES-RC II – Structural Analysis
Program for the Fire Response of
and makes use of the symmetry of the formance-based fire analysis methods,
Reinforced Concrete Frames,” UCB-FRG
fire and associated heat flow. however, find the field already occu- Report 77-8, Fire Research Group,
Calculated temperatures within the pied by a long-established prescriptive Department of Civil Engineering,
hottest cross-section of the column code based on a hundred years of fur- University of California, Berkeley, July
(about 18 inches [460 mm] from the nace tests and engineering practice. 1977.
floor) are plotted in Figure 4. Maximum The new methods must be highly de-
5 Iding, R.H., and Bresler, B., “FASBUS II
steel surface temperature of 900°F veloped, extensively verified, and care- User’s Manual” prepared for the American
(500 °C) is reached after 13 minutes of fully peer-reviewed before they can Iron and Steel Institute, Wiss, Janney,
fire exposure, after which the fire be- supplement or replace the traditional Elstner Associates, Inc., April 30, 1987.
gins to cool. Average temperature methods. The following types of efforts
6 Iding, R.H., and Bresler, B., “Effect of
within the hottest steel cross-section would aid in this process: Restraint Conditions on Fire Endurance of
peaks at 715°F (380°C), also at 13 min- * Development of peer-review proto- Steel-Framed Construction,” Proceedings
utes of fire exposure. cols for the transitional period when of the 1990 National Steel Construction
The final step in the analysis is a performance-based analysis is first be- Conference, AISC, Chicago IL, March 14,
structural evaluation of the ability of ing presented to building officials. 1990.
the steel column to support superposed * More exposure of engineering stu- 7 Nwosu, D.I., Kodur, V.K.R., Franssen,
load when subjected to these tempera- dents and practitioners to the basics of J.M., and Hum, J.K., “User Manual for
tures. In this case, temperatures are so structural fire performance and analyti- SAFIR: A Computer Program for Analysis
low that complex nonlinear failure cal methods to predict it. Sponsorship of Structures at Elevated Temperature
analysis is not needed. At 715°F of workshops and seminars for non- Conditions,” National Research Council
(380°C), the A36 steel columns retain specialists. Canada, int. Report 782, 1999.
more than 90% of their room-tempera- * Some sort of codification of meth- 8 Sanad, A.M., Rotter, J.M., Usmani, A.S.,
ture yield strength (Figure 1), so there ods to calculate fire curves for the most and O’Connor, M.A., “Finite Element
can be no significant weakening of the common fire scenarios so design engi- Modeling of Fire Tests on the Cardington
frame from this fire scenario. In addi- neers do not have to engage a special- Composite Building,” Proceedings of
tion, the configuration of this frame and ist for routine structural design. An ef- Interflam ’99, Interscience
its connections will not offer much re- fort in this area is currently being made Communications, London, 1999.
straint to the thermal expansion in the by SFPE and ASCE. 9 Lee, John A., et alia, “Fire Hazards Analysis
columns, and thermal stresses would * Incorporation into commercial struc- and Fire Structural Analysis of the Healy
not be important. Therefore, these tural computer codes the basic capabili- Clean Coal Plant-Technical Report to Stone
columns will continue to support full ties to conduct fire analysis, especially as and Webster Engineering Corporation,”
design loading demands at these steel nonlinear programs come into greater SAIC Corporation, February 1996.

S PRING 2003 www.sfpe.org 2

 INTEGRATING STRUCTURAL
FIRE PROTECTION
INTO THE
By Harold A. Locke, P.Eng.

T he building design process has

become more complex with the
introduction of new technolo-
gies and materials. This has impacted
the architectural profession, but as
well, many new tools have been made
DESIGN
PROCESS
available to the engineering profes-
sion.
Fire protection engineering has made
great strides in recent years, which has
enabled building designers to provide
greater fire safety in buildings. How-
ever, this presupposes that the design
team avails itself of the most current
technical information applicable to the
building design.

BUILDING CODES

The starting process of any building

design is guided by the requirements of
the local building code. Any building
design is influenced by a number of fac-
tors. In the first place, the architect has
to capture the purpose’s of the building
together with the owner’s needs, and
interpret them architecturally. This usu-
ally occurs during the initial planning
process or schematic design phase. It is
also usual at this time for the prelimi-
nary design to be subject to review by a
Planning Board. This review process
may also ultimately have an impact on
the form of the building in “fitting” into
the built environment. Site conditions
may also be a factor in dictating the
need for a different approach for fire
department access and evacuation of
the building occupants.

Fire Protection Engineering N UMBER 18

 Building codes contain requirements Modern building codes address pub- Appendix D provides a method for the
that typically are considered to repre- lic health, safety, and welfare under user to develop fire-resistance ratings
sent a minimum level of performance many hazard conditions, including of generic materials without the need
necessary for the health and safety of structural stability under various load for a fire test.
the building occupants and emergency conditions, in addition to addressing Fire-resistance testing has been con-
responders, and public welfare. The re- fire hazards through regulating fire en- ducted in North America since the
quirements generally are based on a durance, flammability of surface fin- 1890s.2 ASTM adopted a standard time-
combination of factors, including the ishes, safety within floor areas, exiting, temperature curve in 1917 that to this
hazard represented by the uses and oc- fire department access, special mea- date has remained essentially un-
cupancy types, the type of construction sures to address high-rise buildings, changed. The fire test method (e.g.,
materials, fire department access, and and building exposure. In the area of CAN/ULC-S-101-M893 or ASTM E119)
the building exposure. structural design, reliability-based per- requires that the structural component
formance design has been intro- or assembly of materials be exposed to
duced, particularly for wind and a fire condition represented by the
earthquake design. The typical standard time-temperature curve for the
design team would be com- period for which the fire-resistance rat-
prised of the architect and other ing is required. In the case of a struc-
key professionals representing tural member, the rating is based on
structural, mechanical, electrical, meeting specific temperature criteria as
and geotechnical expertise. En- well as the ability to carry the design
couragingly, the fire protection load for the specified period.
engineer is being included more The standard time-temperature
frequently as one of the key curve, while providing a convenient
professionals on the design method for comparing the performance
team, which is essential to en- of structural members under standard
sure that protecting the building laboratory conditions, as well as
structure from fire exposure be- demonstrating compliance with build-
comes an integral part of the de- ing code requirements, is not represen-
sign process. tative of “real” fire conditions.4 It is sim-
ply a method of establishing a rank
STRUCTURAL STABILITY ordering of different assemblies ex-
UNDER FIRE CONDITIONS posed to the same fire conditions, the
severity of which is represented by the
The design team has the re- fire-resistance rating at a point in time
sponsibility to design the build- on the curve. Nevertheless, the results
ing to provide the degree of of such tests provide a source of infor-
structural fire resistance re- mation helpful to the practitioner in un-
quired by the building code. dertaking a fire hazard or risk assess-
According to ASTM 176, Stan- ment of a specific end use.
dard Terminology of Fire Stan- However, the standard fire test has
dards,1 fire resistance (en- been widely criticized as not being rep-
durance) is defined as “the resentative of real fires. Although the
property of a material or assem- fire test method was developed to en-
blage to withstand fires or give sure the structural integrity and com-
protection from it... As applied partmentation within buildings under
to elements of a building, it is post-flashover conditions, this ap-
characterized by the ability to proach is inherently conservative inso-
confine a building fire or to con- far as limiting the flexibility of designs
tinue to perform a given struc- desired by architects and engineers.
tural function.” According to the Some of the concerns with the fire
National Building Code of test method include the following:
Canada, fire-resistance ratings • The cost and time required to con-
must be established by one of duct tests;
two methods, using either a pre- • Reproducibility between testing
scriptive determination as out- laboratories;
lined in Appendix D of the • The testing of single structural ele-
building code or by physical ments do not take account of the
testing in a calibrated furnace. beneficial effects of adjacent struc-

S PRING 2003 www.sfpe.org 3

■ Integrating Structural Fire Protection

tural components; duction of a more rational approach to related to the design or use of a build-
• The size of structural elements is developing the structural fire protection ing that warrant consideration beyond
limited by the size of the test fur- of a building. Opportunities for devel- the minimum standards of the local
nace; oping a fire engineering approach at an building code. With design-build pro-
• The time-temperature curve repre- early stage may have a profound im- jects in particular, this may not be real-
sents only a fully developed fire; pact on the feasibility, costs, and archi- ized until after the commencement of
• The benefits of sprinkler protection tectural design of the building. construction and the ordering of long-
are not taken into account in the All too frequently, the architect will term delivery materials, such as struc-
fire test; and take a simplistic approach to fire safety tural steel. This often leads to costly de-
• The test does not evaluate the in a building, assuming that the require- lays in the completion of the project as
durability of fire-protective treat- ments of the local code will address all the matter is resolved, which at this
ments under anticipated service of the concerns related to the intended stage will not only be a challenge to
conditions. use of the building. This approach fails the fire protection engineer, but at best
As a result, considerable efforts have to recognize that the requirements of will likely be a compromise in order
been directed towards the development the local code are a minimum safety make use of the existing design ap-
of more rational design approaches for standard. In other cases, the owner may proach as much as possible. Such a
the determination of fire endurance of adopt an attitude towards fire as being compromise may still not be as cost-ef-
building elements.5 something that will not happen to them fective a solution as could have been
and take comfort from fire insurance found had the initial design taken into
PERFORMANCE-BASED and public fire protection. account the problem encountered or
STRUCTURAL FIRE PROTECTION Thus, to begin with, there has to be a had it been identified during the initial
willingness on the part of the owner design phase.
The involvement of the fire protec- and the architect, as well as other mem- The prescriptive approach to devel-
tion engineer early in the design of a bers of the design team, to recognize oping fire-resistance ratings does not
project is crucial to the successful intro- that there may be other considerations take account of the various factors that

Fire Protection Engineering N UMBER 18

influence fire growth. Such factors in- as part of the team so that input and fire and structural loads, model the
clude the fire load, distribution of the feedback can be provided as the per- thermal response of the structural
fire load, ceiling heights, ventilation, formance solutions are developed. members, and assess the results against
geometry of the room or space, the in- The performance-based design ap- the acceptable performance criteria.
herent fire resistance of the structure, proach will likely consider the desired Integrating structural fire protection
and whether or not the space is pro- time for which structural stability is re- into the design process at an early
tected by an automatic sprinkler sys- quired, consider the likely fire load as- stage using a performance-based solu-
tem. As a result, the prescriptive ap- sociated with the use of the building, tion allows for greater flexibility in
proaches for structural fire protection select a suitable model to model the achieving an optimal design solution. A
required by codes in North America are
the same, for example, regardless of
the room size. In reality, fire severity
will vary from compartment to com-
partment and will depend on the fac-
tors above. Thus it can be readily seen
that simply meeting the code require-
ment often results in overdesigning the
protection of the structural elements of
the building and limits design flexibil-
ity.
While there are well-established ana-
lytical methods for developing fire-re-
sistance ratings of traditional building
materials, such as those included in Ap-
pendix D to the National Building Code
of Canada and the Guidelines for De-
termining Fire Resistance Ratings of
Building Elements,6 the North American
regulatory system does not generally
recognize the use of a performance-
based approach for this purpose, even
though the concept of performance-
based design has existed for many
years.7 However, relatively new codes
such as the International Performance
Code8 and NFPA 5000,9 Chapter 5, hold
some promise in this area.
Nevertheless, fire protection engi-
neers are more frequently using a per-
formance-based design approach in or-
der to achieve the design objectives of
a building, where it is recognized that it
is impractical to comply literally with
the prescriptive requirements of the lo-
cal building code.10 However, such an
approach requires the agreement and
participation of the Authority Having
Jurisdiction in order to be successful.
The starting point in the process is to
first identify the applicable prescriptive
code requirements. Acknowledging
that performance-based design solu-
tions will be necessary, the next step in
the process will be to define and agree
upon acceptable performance criteria.
Obviously, this requires a collaborative
effort of all stakeholders to be success-
ful; in some situations it may also be
appropriate to appoint peer reviewers

S PRING 2003 www.sfpe.org 3

 ■ Integrating Structural Fire Protection

recent case study11 demonstrated that of structural design can be inefficient. Harold A. Locke, P.Eng. is with Locke
such an approach could also provide The concept of integrating structural MacKinnon Domingo Gibson & Associ-
significant cost savings, both in capital fire endurance into structural limit ates Ltd.
and life-cycle costs, while yielding a states design with defined strength and
more rational basis for the design of the serviceability limits in fire conditions al- REFERENCES
fire and life safety systems. lows for more efficient and reliable
The traditional approach of specify- building designs, with the potential for 1 ASTM E-176,Standard Terminology of Fire
ing fire endurance as an attribute to be more accurate optimization of life-cycle Standards, American Society for Testing
specified and achieved independently costing. ▲ and Materials, West Conshohocken, PA,
2002
2 The Behaviour of a Multi-storey Steel
Framed Building Subjected to Fire Attack-
Experimental Data, British Steel, Swindon
Technology, 1998.
3 CAN/ULC-S101, Standard Methods of Fire
Endurance Tests of Building Construction
and Materials, Underwriters Laboratories
of Canada, 1989.
4 Ingberg, S.H., “Tests of the severity of
building fires”, NFPA Quarterly, Vol. 22,
No. 1, 1928.
5 Gilvrey, K.R., and Dexter, R. J.,
“Evaluation of Alternative Methods for
Fire Rating Structural Elements”, NIST-
GCR -97-718.
6 Guidelines for Determining Fire
Resistance Ratings of Building Elements,
Building Officials and Code
Administrators, International, Country
Club Hills, IL, 2001.
7 Meacham, B. J., The Evolution of
Performance- Based Codes and Fire
Safety Design Methods, Society of Fire
Protection Engineers, Bethesda, MD,
1996.
8 International Performance Code for
Buildings and Facilities, International
Code Council, Falls Church, VA: 2003.
9 NFPA 5000, Building Construction and
Safety Code, National Fire Protection
Association, Quincy, MA, 2003.
10 Gibson, G. A. and Locke, H. A., “A
Performance-Based Approach to Exiting
of the Proposed Vancouver Convention
and Exhibition Centre Utilizing Fire
Modelling,” Proceedings of the
International Conference on Engineered
Fire Protection Design, Society of Fire
Protection Engineers, Bethesda, MD,
June 2001.
11 Locke, H. A., et al., “Hotel Fire Safety
Case Study – A Canadian Approach,”
Proceedings of the 4th International
Conference on Performance-Based Codes
and Fire Safety Design Methods, Society
of Fire Protection Engineers, Bethesda,
MD, March 2002.

3 Fire Protection Engineering N UMBER 18

 Resources UPCOMING EVENTS
May 8-10, 2003
Strategies for Performance in the Aftermath of the
World Trade Center
Designing Structures for Kuala Lampur, Malasia
Info: www.cibklutm.com

Fire Conference May 13-16, 2003

Fire Guangdong 2003
China Foreign Trade Center, Guangzhou China
September 30-October 1, 2003 Info: www.unionft.com

May 18-22, 2003

Radisson Plaza Lord Baltimore Hotel NFPA World Safety Conference and Exposition
Dallas, TX
in Baltimore, MD Info: www.nfpa.org

June 8-13, 2003

Third Mediterranean Combustion Symposium
Marrakech, Morocco
Info: www.combustioninstitute.it

June 22-25, 2003

13th World Conference on Disaster Management
Toronto, Canada
Info: www.wcdm.org
Intended for:
Provision of appropriate fire resistance to structural members is one of June 24-27, 2003
the major safety requirements in building design. However, evaluating Scientific Program of ITEE 2003
fire resistance of a structure is very complex and requires significant ef- The Technical University of Gdansk, Poland
Info: www.icsc-naiso.org/conferences/itee2003
fort. While there has been advancements in developing new approaches
for evaluating fire resistance, much of this knowledge has been applied August 20-22, 2003
by true “fire specialists.” In the aftermath of the September 11 terrorist 2nd International Conference in Pedestrian and Evacuation
incidents, resulting in significant damage and destruction to buildings and Dynamics (PED)
infrastructure in the WTC vicinity and Pentagon, building performance Greenwich, London
under fire conditions has received significant attention of the research Info: http://fseg.gre.ac.uk/ped2003/
and engineering community. This conference is aimed at sharing the September 8-12, 2003
recent advancements in fire resistance design with researchers, engineers 4th International Seminar on Fire and Explosion Hazards
and practitioners. The conference is of particular interest to scientists, fire Northern Ireland, UK
protection/structural/material engineers, architects and regulators. Info: www.engj.ulst.ac.uk/4thisfeh/

September 22-25, 2003

Description:

Seminar Themes:
6th Asia-Oceania Symposium on Fire Science and Technology
• Current methodology of fire resistance evaluation – merits Info: yhpark@office.hoseo.ac.kr
and drawbacks
• Fire resistance evaluation through testing March 2004
International Fire Safety Engineering Conference
• Fire resistance evaluation through numerical modeling Sydney, Australia
• Fire resistance evaluation through simplified (calculation) Info: www.sfs.au.com
methods March 2-4, 2004
• Material performance and properties under fire Use of Elevators in Fires and Other Emergencies
• Performance based fire safety engineering Atlanta, Georgia
• WTC and Pentagon disaster – fire resistance issues Info: www.asme.org/cns/elevators/cfp.shtml

• Fire resistance case studies of actual buildings March 17-19, 2004

• Integrating fire and aesthetics Fire & Safety At Sea
• Strategies for complying with fire resistance requirements Melbourne, Australia
Info: conference@rocarm.com
in codes and standards
May 2-7, 2004
For more information visit: www.sfpe.org CIB World Building Congress 2004
Toronto, Ontario, Canada
www.cibworld.nl

Fire Protection Engineering N UMBER 18

 Evaluation of the Computer Model DETACT-QS
SFPE’s New Technical Guidance Document
December 2002
The Society of Fire Protection Engineers is pleased to offer the fourth in its series of Technical Guides for the
practicing fire protection engineer. This guide, an evaluation of the computer model DETACT-QS, a model for
predicting thermal detector response, is the first in a series of evaluations undertaken by SFPE’s Computer
Model Evaluation Task Group. The evaluation document is intended to supplement the model’s original docu-
mentation by demonstrating the capabilities and limitations of the model and by highlighting underlying as-
sumptions that are important for users to consider when applying the model.

The evaluation addresses the model definition and evaluation scenarios, verification of theoretical basis and
assumptions used in the model, verification of the mathematical and numerical robustness of the model, and
quantification of the uncertainty and accuracy of the model predictions. This evaluation is based on comparing
predictions from DETACT-QS with results from full-scale compartment fire experiments.

Practicing fire protection engineers rarely have the opportunity to compare computer model predictions used
in fire safety designs with actual fire test data. This evaluation is intended to provide limited comparisons for
several geometries that might be similar to those found in the field. DETACT-QS is based on one set of algo-
rithms developed by industry experts for predicting ceiling jet velocities and temperatures. An extensive set of
references and background on the technical basis of the model is provided.

The price is $35 for SFPE Members, $50 for Non-members,

plus $6.00 for domestic shipping.
To order, contact SFPE or return (mail or fax) the order form below.

Please forward _______ copies of the Evaluation of the Computer Model DETACT-QS at $___________ (including shipping) to:
Name: __________________________________________________________________________________________________________

Address: ________________________________________________________________________________________________________

City: _______________________________________State/Prov. _________________________ Zip/Postal Code ____________________

Country: _________________________________________________________________________________________________________

Method of Payment: ❑ Check for_________________is enclosed. ❑ MasterCard ❑ VISA ❑ American Express

Name on Card:____________________________________________Card #: _________________________________________________

Expiration date: _____________________________________Signature ______________________________________________________

Today’s date: _______________________________________Daytime Phone Number: __________________________________________

7315 Wisconsin Avenue

Suite 1225W
Bethesda, Maryland 20814 USA
301-718-2910 Fax: 301-718-2242

S PRING 2003 www.sfpe.org 3

 Resources
An Historic Event – SFPE’s
Annual Meeting Moves to SFPE Invites your
Participation in the
Fall 2003 Corporate 100 Program
Mark your calendars for an historic Join the leading corporations in the fire
event – the SFPE Annual Meeting and protection industry who support SFPE’s mis-
Awards Banquet, September 29 sion to advance the science and practice of
through October 3 at the Radisson Lord fire protection engineering. The benefits of
Baltimore Hotel, in Baltimore, MD. For membership:
the first time, SFPE will combine its An-
nual Meeting with a series of education Recognition
programs for the practicing fire protection engineer and will not be meet- ...through prominent placement on the
ing in conjunction with the NFPA World Fire Safety Congress. Following SFPE website, magazine, annual meeting
in the path of the successful year 2000, 2001 and 2002 Professional Devel- and exhibit booth
opment Week activities in Baltimore, the new Annual Meeting format will
Information and referrals
include a complimentary one day professional program with the latest up-
…free library copies of SFPE Publications
dates on the science and practice of fire protection engineering, and the
…annual access to the SFPE chapter
professional issues of concern to the practicing FPE, as well as the familiar president contact information
ice cream social. This will be followed by the traditional Awards and …listing on the referral and recruitment
Honors Banquet, and by four days of education events, including 6 semi- portions of the SFPE Web site
nars, and an international conference on Design of Structures for Fire. …referrals from phone inquiries to SFPE
Visit www.sfpe.org for more information.
Leadership
...through periodic leadership Summits
on issues of concern to the industry
Industrial Fire Protection For more information on Corporate 100
Engineering membership. Please contact Kathleen Almand
at kalmand@sfpe.org
Robert G. Zalosh
Kathleen H. Almand, P.E.
NEW! This text covers general considera- Executive Director
tions that relate to the application of all fire Society of Fire Protection Engineers
protection engineering. The text also exam- 7315 Wisconsin Ave., #1225W
ines specific problem areas such as ware- Bethesda, MD 20814
housing, storage of flammable liquids and
safety of electrical equipment and comput- 301-718-2910
ers. The text includes a variety of up-to- Fax: 301-718-2242
date and international case studies. Refer- www.sfpe.org
ences are made to both European and domestic codes and
standards. Some of the latest research in the field such as protec-
tion of cabling from fire is explored.

Visit www.sfpe.org to order.

Fire Protection Engineering N UMBER 18

Products/Literature
Sealants Unobtrusive Sidewall Sprinklers
New GE Fire Stop™ products include an intumescent Tyco’s new concealed, horizontal,
water-based sealant (rated for use in 21 UL firestop sys- extended coverage (CHEC) sidewall
tems) and a 100% silicone joint sealant (rated for use in sprinkler is designed to incorporate
4 UL firestop systems). Designed primarily for multiunit an unobtrusive, aesthetically pleasing,
dwellings with firewalls, the products meet stringent “push-on, thread-off” cover combined
ASTM test standards and building code requirements. with a horizontal sidewall that is
www.gesealants.com capable of providing a quick-
—GE Sealants & Adhesives response, extended coverage rating
from 16 ft. x 14 ft., to a maximum 16 ft. x 22 ft. area per single sprinkler.
Listed for the protection of light hazard occupancies.
www.tyco-fire.com
—Tyco Fire & Building Products

New FP Piping Systems Catalog Flexhead Commercial Ceiling Sprinklers

Victaulic presents a new catalog for fire pro- Flexhead systems, which have been
tection piping systems. It highlights the com- used to protect semiconductor manu-
pany’s grooved-end piping system, including facturing facilities including clean-
IPS carbon steel couplings, fittings, valves, rooms for many years, are now avail-
and accessories; FireLock® Automatic able for commercial markets. Every
Sprinklers and accessories; FireLock system begins with stainless steel
Automatic Devices including the Series 745 hose rated up to 300 psi. Hoses are
Fire Pac; IPS carbon steel Pressfit® systems; available in 2-ft. to 6-ft. lengths and
CPVC FireLock piping products; and more. can be fitted with any standard sprinkler head. Features include easy
www.victaulic.com installation and flexibility.
—Victaulic www.flexhead.com
—Flexhead Industries

Smoke Beam Guards Fully Integrated Security Monitoring

Available in three sizes, these guards are The ADPRO® FastTrace™ is a digital
designed to protect costly sensor units of recorder with rapid remote access and
beam-type smoke detectors from damage video alarm verification and control. It is
leading to misalignment and false alarms in a fully integrated solution for remote
large-area applications such as warehouses storage and protection – an evidential
and auditoriums. Features include tough con- quality digital storage and remote video
struction, resistant coating, easy installation, transmission system. Features include
and lifetime guarantee against breakage in extended duration recording, simultaneous user access, and superior
normal use. image quality.
www.sti-usa.com www.visionusa.com
—Safety Technology International, Inc. —Vision Fire & Security

Gas/Fire Monitoring System Underground Water Tank

The Vortex multichannel gas and fire Xerxes Corporation provides custom man-
monitoring system is available in four ufactured underground water tanks that
configurations. The standard version is a are designed to each customer's specific
wall-mounted unit in its own enclosure; requirements. These tanks are ideal for
modular versions may be specified for a long-term, watertight storage. Carver
variety of specialist enclosures or larger County, Minnesota, Public Works new facility: 35,000 gallon under-
cabinet-based safety systems. All provide ground fiberglass tank to store water for fire protection. Site was too far
up to 12 gas-detection channels (including up to three for fire) and 24 from city-supplied water, therefore the county's engineer specified this
user-configurable relay outputs to drive external alarms and safety strong, fiberglass tank. Best tank choice for rust-proof, long term storage.
equipment. www.xerxescorp.com
www.crowcon.com —Xerxes Corporation
—Crowcon Detection Instruments

Fire Protection Engineering N UMBER 18

 Photoelectric Smoke Detectors Protective Covers Receive UL Listings
System Sensor announces six new i3™ UL Hazardous listing has been granted for both
Series photoelectric smoke detectors. STI NEMA 4X-rated protective covers for strobe
Available with an 85 dB sounder, a Form fire alarm signal units: the STI-1229 Stopper®
C relay, or an isolated thermal sensor, Dome and the STI-1229HTR Environmental
these detectors are ideal for residential, Enclosure for Strobes model with an integral
auxiliary control, or other specialty heating system. Both models just add “-HAZ”
applications. Designed based on i3 principles: installation ease, intelli- to the part number to indicate the hazardous
gent features, and instant inspection. model.
www.systemsensor.com www.stopper.com
—System Sensor —Safety Technology International, Inc.

Linear Heat Sensors Fire Protection Fluid Gets SNAP Approval

The new LHS™ Linear Heat Sensor is a flexi- 3M Performance Materials announces
ble fire detector cable designed to protect a that 3M™ Novec™ 1230 Fire Protection
wide range of commercial and industrial fire Fluid, a C6-fluoroketone halon alterna-
applications. Typical applications include tive, has received Significant New
areas where spot-type heat detectors are not Alternatives Policy (SNAP) approval
effective such as belt conveyors, tunnels, air- from the U.S. Environmental Protection
craft hangars, and classified hazardous areas. Agency. The SNAP approval lists the
Available in five alarm temperatures: 155°F, agent as an acceptable halon 1301 replacement in flooding applications
185°F, 220°F, 350°F, and 465°F. and as an acceptable halon 1211 replacement for nonresidential stream-
www.kiddefiresystems.com ing applications.
—Kidde Fire Systems www.3M.com/novec1230fluid
—3M

Intelligent Addressable Control Panel UV Pigment for Paints and Coatings

The MS-9200UD intelligent addressable control New Optically Active Coating System
panel, built upon a platform common to the MS- (OACS) uses an ultraviolet light-sensitive
9200 and MS-9600, features advanced autopro- pigment, easily added to a wide range of
gramming capabilities to help reduce installation paints and coatings. It allows thorough,
time and overall cost. It includes an integral timesaving, in-process applications and
remote upload/download communicator, which inspections of coatings, substrate cover-
allows for reporting of all system activity to a age, and structural analysis on metal and
remote monitoring location. Installers may command it to program itself nonmetal materials with visual documen-
in less than one minute. tation not previously available to the human eye.
www.firelite.com www.ncpcoatings.com
—Fire-Lite Alarms, Inc. —NCP Coatings, Inc.

Self-Contained Fire Suppression Network Solutions

Self-contained Firetrace® automatic fire NOTIFIER’s new eight-page, Network Solutions
suppression systems incorporate a brochure highlights the company’s NOTI-FIRE-
flexible polymer tubing that may be NET™ fire system network and UniNet™ 2000
installed and routed anywhere within facility monitoring network. It illustrates how
an enclosure where the threat of fire NOTI-FIRE-NET, a peer-to-peer fire alarm net-
exists to instantly detect and extin- work, allows each fire alarm control panel to
guish fires inside equipment, enclosed maintain its own area of protection, while mon-
spaces, or cabinets up to 250 cu.ft. itoring and interacting with other nodes. It also
Systems may be customized to dis- outlines how the UniNet 2000 network seamlessly integrates diverse
pense specific suppression agents. fire and security systems into a single graphics-oriented platform.
www.firetrace.com www.notifier.com
—Firetrace International —NOTIFIER

S PRING 2003 www.sfpe.org 3

 FIRE PROTECTION

B R A I N T E A S E R
Sales
Offices

HEADQUARTERS
A train traveling 80 km/h leaves Chicago heading for New York at 8:00 AM.
TERRY TANKER Publisher
Another train, also headed for New York, leaves Chicago on a parallel 1300 East 9th Street
track one hour later. If the second train is traveling at 100 km/h, at what Cleveland, OH 44114-1503
time will it pass the first train? 216.696.7000, ext. 9721
fax 216.696.3432
ttanker@penton.com

Solution to last issue’s brainteaser NORTHEAST

Water discharges through an Underwriters Playpipe with a 29 mm diameter nozzle. The TOM CORCORAN District Manager
playpipe is oriented at a 45° angle to the horizontal. A pitot gauge measures the velocity 929 Copes Lane
pressure at the nozzle discharge as 200 kPa. If the playpipe is located on a level surface, West Chestor, PA 19380
610.429.9848
how far from the nozzle will the stream land?
fax 610.429.1120
The discharge through the playpipe can be calculated by the following formula:1 tomcorcoran@penton.com

Q = 0.0666cd 2 p NORTH CENTRAL

JOE DAHLHEIMER District Manager
Where c is the discharge coefficient, d is the inside diameter of the orifice in mm, and
p is the velocity pressure in kPa. Using a discharge coefficient of 0.97 for an Underwriters 1300 East 9th Street
Cleveland, OH 44114-1503
Playpipe,1 The flow is 768 liters per minute or 0.768 m3/min.
216.696.7000, ext. 9279
fax 216.696.3432
Since Q=AV, this results in a discharge velocity of 1160 m/min or 19.4 m/s. Given that jdahlheimer@penton.com
the discharge is oriented at a 45° angle to the horizontal, the vertical component of veloc-
ity is 19.4 m/s x sin(45°) = 13.7 m/s. Similarly, the horizontal component of velocity is CENTRAL / WEST
19.4 m/s x cos(45°) = 13.7 m/s. AMY COLLINS District Manager
The time that the stream is in the air can be calculated with the following formula: 3240 Shadyview Lane North
Plymouth, MN 55447
D = V1t + 1 2 At 2 763.404.3829
fax 763.404.3830
Where D is the distance traveled, V1 is the initial velocity, A is the acceleration, and t is acollins@penton.com
the time. Substituting D = 0, A = -9.8 m/s2, and solving for t, we obtain values of zero and
2.8 seconds (the calculated time = zero corresponds to the instant the stream leaves the SOUTHEAST
nozzle.) DEBBIE ISGRO District Manager
707 Whitlock Avenue SW
During the 2.8 seconds that the stream is in the air, the stream travels a horizontal dis-
tance of 13.7 m/s x 2.8 s = 38 meters. Suite B-24
Marietta, GA 30064
1 Linder, K., “Hydraulics for Fire Protection.” Fire Protection Handbook, 19th Ed. National Fire Protection 770.218.9958
Association, Quincy, MA, 2003. fax 770.218.8966
disgro@penton.com

3M (Fire Protection Fluid) .............................Page 5 OCV Control Valves .....................................Page 28

AGF Manufacturing........................................Page 2 Potter Electric Signal Company...................Page 14
Index of Advanced Fire Technologies .......................Page 20 Reliable Automatic Sprinkler.......................Page 59
Advertisers Ansul Incorporated ......................................Page 40 Ruskin ...........................................................Page 23
BlazeMaster® Fire Sprinkler Systems .........Page 27 Siemens Building Technologies, Inc.
Chemguard..................................Inside Back Cover Fire Safety Division ...................................Page 55
Commercial Products Group.........................Page 9 SimplexGrinnell............................................Page 44
DecoShield Systems, Inc..............................Page 49 System Sensor ..............................................Page 39
Edwards Systems Technology ................Page 30-31 The RJA Group...........................Inside Front Cover
Fike Corpooration ........................................Page 18 Tyco Fire Products.................................Back Cover
Fire Control Instruments..............................Page 17 University of Maryland ................................Page 48
FlexHead Industries .....................................Page 50 Victaulic Company of America ...................Page 21
Gast Manufacturing......................................Page 20 Vision Fire & Security ..................................Page 43
Grice Engineering ........................................Page 22 Wheelock, Inc. .............................................Page 36
Koffel Associates, Inc...................................Page 10 Worcester Polytechnic Institute ...................Page 33
NOTIFIER Fire Systems ...............................Page 13

Fire Protection Engineering N UMBER 18

from the technical director

Tragedy in Rhode Island

Prescriptive codes typically contain safe than a nightclub built right next
thresholds before certain requirements door one year later.
take effect. For example, according to Prescriptive requirements are written
the National Fire Protection Associa- based on broad classifications of occu-
tion’s Life Safety Code,1 a door is typi- pancy or building use. They are written
cally not required to swing in the direc- such that, for any combination of ac-
tion of egress travel if the area served ceptable features, the resulting building
has an occupant load of less than 50. or structure will present an acceptable
The performance intended by this re- level of safety. Performance-based re-
quirement is to protect against a hazard quirements, on the other hand, require
where opening a closed door could that the design engineer develop an ac-
impede egress or could be hindered by ceptable solution based on engineering
egress. Presumably, the writers of this and science.
requirement felt that limiting the occu- A goal of the Life Safety Code is the
pant load served to less than 50 would protection of occupants who are not in-
meet the intended performance while timate with initial fire development. The
providing a sufficient safety margin and Life Safety Code further elaborates upon
providing for flexibility in areas where this goal through objectives and perfor-
Morgan J. Hurley, P.E. it would not be practical to require that mance requirements. Thus, any combi-
Technical Director a door swing in the direction of egress nation of fire protection features and
Society of Fire Protection Engineers travel. systems that can be shown to meet the
Prescriptive codes have the benefit of goals, objectives, and performance cri-
being easy to apply and enforce. In the teria of the Life Safety Code would be
previous door example, it would be acceptable. Performance-based codes,
much more difficult to apply a require- such as the performance option in the
ment that stated that “doors shall swing Life Safety Code, allow for the design of
in the direction of egress where neces- buildings which present an acceptable
sary to prevent the door from impeding level of safety, allow for the provision
egress travel.” While a performance- of an integrated package of fire protec-
based requirement such as this and the tion systems and features based on the
prescriptive requirement contained in hazards that exist within a building or
the Life Safety Code have the same ob- structure, while leaving code writers

O n February 20, 2003, a fire in

a Rhode Island nightclub
killed almost 100 people, and
injured almost twice that many, rank-
ing the fire as one of the deadliest
jective, the prescriptive requirement
could either unnecessarily limit flexibil-
ity or provide for situations that are un-
safe for occupant loads close to 50.
and legislators free to simply state what
constitutes an acceptable level of safety.
There is some degree of hazard or
risk present in any activity, and accord-
Similarly, the sprinkler provisions in ingly, accidents will still occur in build-
nightclub or social establishment fires Rhode Island are intended to provide ings designed on a performance basis.
in U.S. history. The fire was reportedly for safe buildings, while not imposing However, performance-based codes
caused by pyrotechnic devices inside an undue burden on existing buildings. will allow for an increased application
the nightclub, which ignited expanded However, prescriptive requirements of science in the design of buildings
thermoplastic sound insulation. The such as this or the door-swing require- and structures, while allowing those re-
nightclub, which was originally con- ment in the Life Safety Code place code sponsible for regulating safety to explic-
structed in 1950 as a restaurant, was writers and legislators in the difficult itly state what level of safety would be
not required to install sprinklers since position of making decisions that have “acceptable.”
it was built before 1974. While a broad impact without a firm basis in
tragedy of monumental proportions, engineering or science. Unfortunately, 1 NFPA 101, Life Safety Code. National Fire
this fire demonstrates some of the the result is that a door arrangement in Protection Association, Quincy, MA, 2000.
challenges that prescriptive codes pose a room that serves 49 occupants may
to code writers and regulators, and be less safe than a door that serves 50
shows some potential benefits of per- occupants. Similarly, a nightclub built
formance-based codes. in 1973 in Rhode Island may be less

Fire Protection Engineering N UMBER 18