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High Rise Buildingsand

Large firesStructural loads & thermal strainWhat can happen?

As presented to the Northern California-Nevada Chapter of theSociety of Fire Protection Engineers

On April 21, 2006 in Walnut Creek, California.

by Edward Munyak, P.E.esmunyak@earthlink.net

mailto:esmunyak@earthlink.netmailto:esmunyak@earthlink.net

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Probable Maximum Loss

PML assumes a fire scenariowith a loss of one suppressionsystem and a delay in manualfire fighting.

The 9/11 Commission reportignores the collapse of WTC 7

The NIST Report on WTC 1,2 &7 implies that global collapsewas inevitable for these steelstructures.

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Is there a new paradigm

for building collapse? What follows is a study of steel frame

building response to maximum fireconditions based on:

Historical catastrophic fires in high rise buildingsfrom 1986 to 2005

Actual fire tests in steel frame buildings in the UK

Thermodynamic simulations

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Fire Resistance

Unprotected steel that resists high windsand seismic forces has considerable fireresistance.

Adding dead weight at a cost of 20% ?

Structures need to be designed to resisthigher wind, seismic loads and increasedfire resistance will automatically follow.

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Inherent fire resistance

In many instances, particularly in tallbuildings or massive structures, the mass ofsteel required to support loads and resistmoments is very large and thus the thermal

mass of the steel itself provides inherentresistance to weakening by fire fire exposurefor periods of time that can be determined byengineering analysis page 17 NISTstructural steel report GCR 04-872 7/2004

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ASTM E-119 is the standard test for fullsize structural components.

Oven temperature(not structure) versustime.

One side of the structure is exposed toheat.

If temperature on unexposed side isexcessive or if deflection is above a

certain limit after the test duration, thecomponent fails.

Structure is always within the elasticrange

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ASTM vs Real fires

Recent and historical large firesin steel frame buildings havedemonstrated that actual fireperformance of the structuralsystem is much better thanresults of the test of a singlecomponent.

Broadgate Fire in UK occurredprior to fire proofing. Structureexceeded 650 degree C. but didnot collapse.

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mu a ons o an arFires

on whole frame designPerformance based approachdeleted fire proofing on most

secondary steel.Catenary action on beams and

Tensile membrane action offloor slabs compensated for thereduction of strength at highertemperatures

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High rise Building fires

20 year time spanMontreal, Canada 1986, 15

stories

Los Angeles, 1988, FirstInterstate Bank

One Meridian Plaza,Philadelphia, 1991

WTC 1, 2 & 7, NYC. 9/11/2001

Parque Central, Caracas,Venezuela 2004

Edificio Madrid, Spain 2005

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Montreal, Canada

October 26, 1986 15 story SFRM Steel frame building with a

fire load estimated to be at least twice WTC (10 - 11 lbs/sq ft vs 4 lbs/ sq ft in WTC)

Fire burned for over 13 hours on multiplefloor levels due to vertical openings.

A 30ft x 40ft section on the 11th floor fell tothe 10th floor when welded clips failed. Noinelastic deformation noted on surroundingstructure.

Loss demonstrated the need for automaticsprinkler protection and protection of verticalopenings.

Interesting example of girder to columnfailure of weld clip.

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First Interstate Bank Fire

Los Angeles, May 4, 198862 story type II. SFRM steel frame,

open floor plan

Fire duration was 3 1/2 hours

Fire spread vertically from 12 th to15th floors internally and externally.

Many broken windows resulted in asevere fire and auto-ignition

Smoke spread throughout buildingbut there was no structural framedamage.

Fire damper in HVAC failed at

critical point

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One Meridian Plaza, Philadelphia,Pa

February 23, 1991 Fire gutted 8 floors of a 38 story building

3 fire fighters died,$100 million in direct fire loss,$ 4 billion civil damage

Fire burned for over 19 hours Major power and water supply failure

Severe fire broke most windows on the fire floors

Fire spread externally by auto-ignition

Fire was stopped by automatic sprinklers on the30th floor.

Vertical columns were not damaged, horizontalbeams sagged as much as 3 feet.

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WTC 1 and 2

NYC Sept 11, 2001

Applying the equal-area

principle for the time-temperature curve, fires werenot as severe as ASTM standardand less than all otherexamples.

Each tower was more massivethan other high rise examples.

NIST report, page 77, estimates

a fuel loading of 4 lbs/ sq ft or60 tons of combustibles er

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WTC 1 & 2 Structure

Designed in accordance with the 1968 NYCbuilding code with a 50 year wind storm ofjust under 100 mph which exceeds existingand current codes.

Designed to resist the impact of a Boeing707@ 600 mph

Originally designed with gypsum board andSFRM to protect core.

Building core supported gravity load, external

high strength columns could be undercompression or tension

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ASTM vs WTC South

0

200

400

600

800

1000

1200

1400

0 100 200 300 400 500 600

temperature

WTC South Temperature

After the initial fireball1050 C for 2min.

Fuel burns off in 10 minutes

4 lbs/ ft fire load equates

To 30-40 min duration.

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NIST analysis of WTC

collapseThe towers withstood the

impact and would haveremained standing if not for thedislodged insulation(fireproofing) and subsequent multi-floor fires.

Towers were built in accordancewith 1968 NYC Building Code.

Recommended objective shouldbe survival of an uncontrollablefire without local or globalcollapse.

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WTC Tower structure

Gravity loads were supported by47 steel columns in the core.

Wind loads were resisted by 59columns on each of 4 sides thatcould be in compression ortension.

The floors were compositeconcrete and steel. Steel trusseshad viscoelastic dampers onbottom chord.

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Thermal simulation of south

tower A steel frame building with the mass of WTC 1 or 2

could have partial structural collapse after aircraftimpact only if the heat output was at least 100 timesthe heat release rate of the accountable fuel load and

ventilation conditions in the south tower. This fire would need to involve every floor from

impact floor to the roof with most windows brokenand providing plenty of oxygen as in the EdificioWindsor fire in Madrid.

This most severe fire would need to burn for at least12 hours before loss of strength from heat; andthermal strains from expansion and contractioncaused partial collapse.

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Anomalies within an Anomaly

Unprecedented total collapse of a steelframe building.

The tower with the least structural damageand smallest fire collapsed first.

If lack of fire proofing brought down WTC 1& 2 why did intact fire proofing not help

WTC 7? On the scene professional fire fighters

knew that the building was not damaged tothe verge of collapse.

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WTC 7

WTC 7 was one city blockaway from Towers

No damage to fire proofing

Small fires were observed

Global collapse was initiatedon the lowest level

Different structure

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Parque Central Office BuildingCaracas, Venezuela

October 15, 2004 South Americas Tallest building at 56 stories

Automatic sprinkler system impaired

The fire burned for over 24 hours and consumed 17floors at a rate one floor every 2 1/2 hours.

Five spray fire proofed structural steel sections weresandwiched between concrete protected steel macroslabs that were supported by exterior reinforced columns

Fire spread by auto-ignition and through unrated floorpanels in the two hour rated floors. Total glass breakageon fire floors..

Two floor areas partially collapsed, fire chief ordered fire

fighters to abandon interior fire fighting but there was nofurther collapse.

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Edificio Windsor

Madrid, Spain 12 Feb, 2005 Fire started on the 21 st floor of a 32 story

concrete core column building with unprotectedsteel beams on perimeter with unprotectedperimeter columns

Building was being renovated; there were largeunprotected vertical openings.

Unknown fire load but judging by the 18- 20 hourfire duration, and massive flames, the fire loadmust have been high.

The suspicious fire spread from the 21 floor to the

top 32nd floor within one hour and then downwardto the lowest floor(4th) within the next 10 +hours.

Property was valued at 72 million Euros before thefire that gutted it.

A portion of the floor slabs above the 17th floor

that was supported by unprotected steel beamscollapsed but the reinforced concrete core

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Madrid,Spain12/2/2005

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Edificio Windsor Madrid, Spain

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Edificio Windsor, Madrid 2/12/2005

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Edificio Windsor

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Theorem of CastiglianoElements of Strength of Materials by Timoshenko & Young 4th edition

page, p. 246-263

Strain energy that must be overcome beforelimit collapse is complete is proportional toall forces squared and inversely

proportional to high strength modulus ofelasticity.

Integration of area under the stress-straincurve represents a massive amount ofstrain energy that must be overcomebefore collapse is complete in the caseWTC 1, 2 & 7.

The only available source of energy of thatmagnitude is the potential energy of atleast 10 floors and it had to be released in

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Energy available for

releaseFire tests in the UK shown the

structure under load at veryhigh temperatures slowlyreleasing potential energy ofmass and height by plasticdeformation of the heated steel.

Chemical energy in the fuel andpotential energy (mass xheight) is released by plasticdeformation wheretemperatures are hottest.

The load path then shifts to

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Steel in plastic range

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Magnitude of Available Energysources

Chemical energy in jet fuel(2 planes)=6.9.e+10metric joules

(applied over 5 -10 minute time duration)

Kinetic energy (2 planes) = 1.9 e+9 metric joules(less than one second)

Potential energy (2 towers) =6.8 e=11 metric joules

(controlled demolition can release this in less than

one second)

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Releasing Gravitational

Energy Collapse in WTC was initiated near the floors of

Impact.

The center core suddenly dropped without anyresistance from the structures below.

If column severing energy was sequentially timed sothat as the total mass accelerating down met minimalresistance for 2 or 3 floor enough potential energywill be converted into downward momentum so thatin the words of the NIST report global collapse was

inevitable. All potential energy was suddenly released and

available for inelastic deformation of steel andsimultaneous pulverizing of concrete within a timespan of about 10 seconds

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RecommendationReimbursement of any loss must be

contingent upon access to and analysis offire damaged structure:

The wreckage of WTC 1, 2 & 7 was worthhundreds of millions of dollars in terms ofresearch and practical knowledge.

There was evidence of sulfadation on beamsfrom explosive material

The severed ends of beams were observedto be partially molten for days after clean-

up. This is characteristic of thermite.

WTC C ll

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WTC CollapseProfessor Steven Jones of BYU

Department of Physics and Astronomy

WTC 7 collapsed rapidly and symmetrically-even though fires were randomly scattered in

the building

Where is the delay that must be expected dueto conservation of momentum-one of thefoundational laws of physics

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http://www.implosionworld.com/cinema.htm

What is incredible in the fire effectscontinua is routine in the world ofcontrolled demolition.

Even with explosives, achieving suchresults requires a great deal of pre-planning and expertise

The explosive demolition hypothesisbetter satisfies tests of repeatability andparsimony states Professor Steven Jones

http://www.physics.byu.edu/research/energy/htm7.html

http://www.physics.byu.edu/research/energy/htm7.htmlhttp://www.physics.byu.edu/research/energy/htm7.htmlhttp://www.physics.byu.edu/research/energy/htm7.htmlhttp://www.physics.byu.edu/research/energy/htm7.html

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To be continued

For additional informationcontact

Edward Munyak, P.E.

esmunyak@ earthlink.net

(650)948-8035

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References NFPA Journal, March/April 2005 Fire Unchecked page 47 Caracas, Venezuela Fire

Culver, Charles, Characteristics of fire loads in office buildings Fire Technology1978, Vol 14, No.1 pages 51-60

NFPA investigation of High Rise office Building Fire, Montreal, Canada, October 26,1986

NFPA investigations of May 4, 1988 First Bank Building Bank Fire, Los Angeles, Ca

WWW. Implosionworld.com

http://911reserach.wtc7.net

Building Regulatory Systems in a post-September 11 World by Richard Bukowski,P.E. NIST Building and Fire Research Laboratory

http://www.mace.manchester.ac.uk/project/research/structures/casestudy/historicfires/building fires/default.htm

http://www.physics.byu.edu/research/energy/htm7.html

Fire Protection of Structural Steel in High Rise Buildings, NIST GCR 04-872

Moscatelli, Frank, WETC energy calculations

9/11 Commission Report, Omissions and Distortions. David Ray Griffin

9/11 Synthetic Terror-Made in the USA, Webster Griffin Tarpley

http://www.mace.manchester.ac.uk/project/research/structures/casestudy/historichttp://www.physics.byu.edu/research/energy/htm7.htmlhttp://www.physics.byu.edu/research/energy/htm7.htmlhttp://www.mace.manchester.ac.uk/project/research/structures/casestudy/historic