High Rise Buildings and  Large fires  Structural loads  thermal strain What can happen

High Rise Buildings and Large fires Structural loads thermal strain What can happen PowerPoint PPT Presentation


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. . Probable Maximum Loss. PML assumes a fire scenario with a loss of one suppression system and a delay in manual fire fighting.The 9/11 Commission report ignores the collapse of WTC 7The NIST Report on WTC 1,2

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High Rise Buildings and Large fires Structural loads thermal strain What can happen

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1. High Rise Buildings and Large fires Structural loads & thermal strain What can happen? As presented to the Northern California-Nevada Chapter of the Society of Fire Protection Engineers On April 21, 2006 in Walnut Creek, California. by Edward Munyak, P.E. [email protected] The talk is about modern steel frame buildings with and without fire proofing. Building codes categorize them as type 1 and type 2 in descending order of fire resistance. Different parts of the structure are required to have varying degrees of fire resistance in each category. Both types are composite structures in terms of strength and heat flux. Thermal strains will be superimposed on structural loads such as mass, seismic and wind forces. The talk is about modern steel frame buildings with and without fire proofing. Building codes categorize them as type 1 and type 2 in descending order of fire resistance. Different parts of the structure are required to have varying degrees of fire resistance in each category. Both types are composite structures in terms of strength and heat flux. Thermal strains will be superimposed on structural loads such as mass, seismic and wind forces.

2. Probable Maximum Loss PML assumes a fire scenario with a loss of one suppression system and a delay in manual fire fighting. The 9/11 Commission report ignores the collapse of WTC 7 The NIST Report on WTC 1,2 & 7 implies that global collapse was inevitable for these steel structures. Such was the case in all examples of high rise fires picked for this study. The NIST report gives contradictory conclusions regarding fire proofing Such was the case in all examples of high rise fires picked for this study. The NIST report gives contradictory conclusions regarding fire proofing

3. Is there a new paradigm for building collapse? What follows is a study of steel frame building response to maximum fire conditions based on: Historical catastrophic fires in high rise buildings from 1986 to 2005 Actual fire tests in steel frame buildings in the UK Thermodynamic simulations The collapse of a modern steel frame building has not happened before or after 9/11/2001 Modern high rise buildings have excellent fire safety records. The collapse of a modern steel frame building has not happened before or after 9/11/2001 Modern high rise buildings have excellent fire safety records.

4. Fire Resistance Unprotected steel that resists high winds and seismic forces has considerable fire resistance. Adding dead weight at a cost of 20% ? Structures need to be designed to resist higher wind, seismic loads and increased fire resistance will automatically follow. SFRM = spray applied fire resisting material such as asbestos fibers and Intumescent coatings retard the transmission of heat Gypsum and concrete protect steel by insulation and chemical transformation- water vapor is driven off and absorbs heat A large mass of steel or reinforced concrete simply takes longer to heat up when exposed to standard oven temperatures. SFRM = spray applied fire resisting material such as asbestos fibers and Intumescent coatings retard the transmission of heat Gypsum and concrete protect steel by insulation and chemical transformation- water vapor is driven off and absorbs heat A large mass of steel or reinforced concrete simply takes longer to heat up when exposed to standard oven temperatures.

5. Inherent fire resistance “In many instances, particularly in tall buildings or massive structures, the mass of steel required to support loads and resist moments is very large and thus the thermal mass of the steel itself provides inherent resistance to weakening by fire fire exposure for periods of time that can be determined by engineering analysis” page 17 NIST structural steel report GCR 04-872 7/2004

6. ASTM E-119 is the standard test for full size structural components. Oven temperature(not structure) versus time. One side of the structure is exposed to heat. If temperature on unexposed side is excessive or if deflection is above a certain limit after the test duration, the component fails. Structure is always within the elastic range

7. ASTM vs “Real” fires Recent and historical large fires in steel frame buildings have demonstrated that actual fire performance of the structural system is much better than results of the test of a single component. Broadgate Fire in UK occurred prior to fire proofing. Structure exceeded 650 degree C. but did not collapse. Ductility of steel allowed thermal strains to be safely absorbed. Floor loads were more efficiently carried by membrane and catenary action. Floor slabs=trampoline, beams=clothsline. Structures with less thermal diffusivity between composite structure performed better Ductility of steel allowed thermal strains to be safely absorbed. Floor loads were more efficiently carried by membrane and catenary action. Floor slabs=trampoline, beams=clothsline. Structures with less thermal diffusivity between composite structure performed better

8. Simulations of Standard Fires on whole frame design Performance based approach deleted fire proofing on most secondary steel. Catenary action on beams and Tensile membrane action of floor slabs compensated for the reduction of strength at higher temperatures Done in the UK, Euro fire = ASTM fire Done in the UK, Euro fire = ASTM fire

9. High rise Building fires 20 year time span Montreal, Canada 1986, 15 stories Los Angeles, 1988, First Interstate Bank One Meridian Plaza, Philadelphia, 1991 WTC 1, 2 & 7, NYC. 9/11/2001 Parque Central, Caracas, Venezuela 2004 Edificio Madrid, Spain 2005

10. 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 multiple floor levels due to vertical openings. A 30ft x 40ft section on the 11th floor fell to the 10th floor when welded clips failed. No inelastic deformation noted on surrounding structure. Loss demonstrated the need for automatic sprinkler protection and protection of vertical openings. Interesting example of girder to column failure of weld clip.

11. First Interstate Bank Fire Los Angeles, May 4, 1988 62 story type II. SFRM steel frame, open floor plan Fire duration was 3 1/2 hours Fire spread vertically from 12 th to 15th floors internally and externally. Many broken windows resulted in a severe fire and auto-ignition Smoke spread throughout building but there was no structural frame damage. Fire damper in HVAC failed at critical point Vertical openings at perimeter of floor slab, stairways and HVAC ducts. No sprinklers on upper floors. Typical office fire loading of approximately 5 lbs/ sq ft with workstations similar to WTC. Spray on fire proofing on steel 3 hour primary, 2 hour secondary. One 6 inch standpipe system with diesel and electric fire pumps with 87,500 water tank in basement which was nearly depleted. Power and water supplies were lost,elevator cause one fatality and could not be used by FD. Fire was stopped at the 16th floor with difficulty. Flames from windows extended several floors high from the non-compartmented 12 th floorVertical openings at perimeter of floor slab, stairways and HVAC ducts. No sprinklers on upper floors. Typical office fire loading of approximately 5 lbs/ sq ft with workstations similar to WTC. Spray on fire proofing on steel 3 hour primary, 2 hour secondary. One 6 inch standpipe system with diesel and electric fire pumps with 87,500 water tank in basement which was nearly depleted. Power and water supplies were lost,elevator cause one fatality and could not be used by FD. Fire was stopped at the 16th floor with difficulty. Flames from windows extended several floors high from the non-compartmented 12 th floor

12. 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 the 30th floor. Vertical columns were not damaged, horizontal beams sagged as much as 3 feet.

13. WTC 1 and 2 NYC Sept 11, 2001 Applying the equal-area principle for the time-temperature curve, fires were not as severe as ASTM standard and less than all other examples. Each tower was more massive than other high rise examples. NIST report, page 77, estimates a fuel loading of 4 lbs/ sq ft or 60 tons of combustibles per floor. This was cross checked with data from the NIST reportThis was cross checked with data from the NIST report

14. WTC 1 & 2 Structure Designed in accordance with the 1968 NYC building code with a 50 year wind storm of just under 100 mph which exceeds existing and current codes. Designed to resist the impact of a Boeing 707@ 600 mph Originally designed with gypsum board and SFRM to protect core. Building core supported gravity load, external high strength columns could be under compression or tension

15. ASTM vs WTC South After the initial fireball 1050 C for 2min. Fuel burns off in 10 minutes 4 lbs/ ft fire load equates To 30-40 min duration.

16. NIST analysis of WTC collapse “The towers withstood the impact and would have remained standing if not for the dislodged insulation(fire proofing) and subsequent multi-floor fires.” Towers were built in accordance with 1968 NYC Building Code. Recommended objective should be survival of an uncontrollable fire without local or global collapse.

17. WTC Tower structure Gravity loads were supported by 47 steel columns in the core. Wind loads were resisted by 59 columns on each of 4 sides that could be in compression or tension. The floors were composite concrete and steel. Steel trusses had viscoelastic dampers on bottom chord.

18. Thermal simulation of south tower A steel frame building with the mass of WTC 1 or 2 could have partial structural collapse after aircraft impact only if the heat output was at least 100 times the 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 broken and providing plenty of oxygen as in the Edificio Windsor fire in Madrid. This most severe fire would need to burn for at least 12 hours before loss of strength from heat; and thermal strains from expansion and contraction caused partial collapse. The south tower was chosen because it had the most spectacular fireball The Edificio Windsor fire in Madrid, Spain confers this. This 32 story charcoal lighter had a fire in the “ballpark” range of this heat release.. The south tower was chosen because it had the most spectacular fireball The Edificio Windsor fire in Madrid, Spain confers this. This 32 story charcoal lighter had a fire in the “ballpark” range of this heat release..

19. Anomalies within an Anomaly Unprecedented total collapse of a steel frame building. The tower with the least structural damage and 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 to the verge of collapse.

20. WTC 7 WTC 7 was one city block away from Towers No damage to fire proofing Small fires were observed Global collapse was initiated on the lowest level Different structure Building collapse was a free fall lasting less than 7 secondsBuilding collapse was a free fall lasting less than 7 seconds

21. Parque Central Office Building Caracas, Venezuela October 15, 2004 South America’s Tallest building at 56 stories Automatic sprinkler system impaired The fire burned for over 24 hours and consumed 17 floors at a rate one floor every 2 1/2 hours. Five spray fire proofed structural steel sections were sandwiched between concrete protected steel macro slabs that were supported by exterior reinforced columns Fire spread by auto-ignition and through unrated floor panels in the two hour rated floors. Total glass breakage on fire floors.. Two floor areas partially collapsed, fire chief ordered fire fighters to abandon interior fire fighting but there was no further collapse. All combustibles were consummed.All combustibles were consummed.

22. Edificio Windsor Madrid, Spain 12 Feb, 2005 Fire started on the 21 st floor of a 32 story concrete core column building with unprotected steel beams on perimeter with unprotected perimeter columns Building was being renovated; there were large unprotected vertical openings. Unknown fire load but judging by the 18- 20 hour fire duration, and massive flames, the fire load must have been high. The suspicious fire spread from the 21 floor to the top 32nd floor within one hour and then downward to the lowest floor(4th) within the next 10 + hours. Property was valued at 72 million Euros before the fire that gutted it. A portion of the floor slabs above the 17th floor that was supported by unprotected steel beams collapsed but the reinforced concrete core columns performed well. http://www.mace.manchester.ac.uk/project/research/structures/strucfire/CaseStudy/HistoricFires/BuildingFires/default.htm

23. Madrid,Spain12/2/2005

24. Edificio Windsor Madrid, Spain

25. Edificio Windsor, Madrid 2/12/2005

26. Edificio Windsor After 20 + hour fire Edificio Windsor Fire, Madrid, Spain 13 Feb 2005 after a 20 hour duration severe fire at 100 times more heat output than the under control fire in the South Tower WTC of 9/11/2001. Every single glass window is destroyed which is an indication of fury of this fire with unlimited ventilation and adiabatic fire temperatres of at least 1260 degrees C. In contrast, my simulations of WTC South indicate fire temp. before collapse of less than 920 degree C. with decreasing heat output. No additional windows were being broken and fire was limited to impact floors. Edificio Windsor Fire, Madrid, Spain 13 Feb 2005 after a 20 hour duration severe fire at 100 times more heat output than the under control fire in the South Tower WTC of 9/11/2001. Every single glass window is destroyed which is an indication of fury of this fire with unlimited ventilation and adiabatic fire temperatres of at least 1260 degrees C. In contrast, my simulations of WTC South indicate fire temp. before collapse of less than 920 degree C. with decreasing heat output. No additional windows were being broken and fire was limited to impact floors.

27. Theorem of Castigliano Elements of Strength of Materials by Timoshenko & Young 4th edition page, p. 246-263 Strain energy that must be overcome before limit collapse is complete is proportional to all forces squared and inversely proportional to high strength modulus of elasticity. Integration of area under the stress-strain curve represents a massive amount of strain energy that must be overcome before collapse is complete in the case WTC 1, 2 & 7. The only available source of energy of that magnitude is the potential energy of at least 10 floors and it had to be released in a sudden impulse. Ductile steel absorbs more strain energy before limit collapse than high strength steel. Although there were 14 grades of steel used in WTC, the columns were all the lowest yield strength but the highest in strain energy. The core columns had to be severed first with thermite and the exterior perimeter columns would shatter more easily.Ductile steel absorbs more strain energy before limit collapse than high strength steel. Although there were 14 grades of steel used in WTC, the columns were all the lowest yield strength but the highest in strain energy. The core columns had to be severed first with thermite and the exterior perimeter columns would shatter more easily.

28. Energy available for release Fire tests in the UK shown the structure under load at very high temperatures slowly releasing potential energy of mass and height by plastic deformation of the heated steel. Chemical energy in the fuel and potential energy (mass x height) is released by plastic deformation where temperatures are hottest. The load path then shifts to surrounding structures in rather slow process. The failure mode that would act quicker would be local buckling of a single element column under load. Center core with perimeter columns such as WTC have each floor level acting as a diaphragm to prevent buckling.The failure mode that would act quicker would be local buckling of a single element column under load. Center core with perimeter columns such as WTC have each floor level acting as a diaphragm to prevent buckling.

29. Steel in plastic range

30. Magnitude of Available Energy sources Chemical energy in jet fuel(2 planes)=6.9.e+10 metric 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)  Physics professor Frank Moscatelli states that the gravitational potential energy was the largest available source of energy. His calculations are accurate to within 25%Physics professor Frank Moscatelli states that the gravitational potential energy was the largest available source of energy. His calculations are accurate to within 25%

31. Releasing Gravitational Energy Collapse in WTC was initiated near the floors of Impact. The center core suddenly dropped without any resistance from the structures below. If column severing energy was sequentially timed so that as the total mass accelerating down met minimal resistance for 2 or 3 floor enough potential energy will be converted into downward momentum so that in the words of the NIST report “global collapse was inevitable.” All potential energy was suddenly released and available for inelastic deformation of steel and simultaneous pulverizing of concrete within a time span of about 10 seconds All official reports indicate that the buildings suddenly collapsed with no structural resistanceAll official reports indicate that the buildings suddenly collapsed with no structural resistance

32. Recommendation Reimbursement of any loss must be contingent upon access to and analysis of fire damaged structure: The wreckage of WTC 1, 2 & 7 was worth hundreds of millions of dollars in terms of research and practical knowledge. There was evidence of sulfadation on beams from explosive material The severed ends of beams were observed to be partially molten for days after clean-up. This is characteristic of thermite.

33. WTC Collapse Professor 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 due to conservation of momentum-one of the foundational laws of physics” Understanding of large mass momentum-linear and rotationalUnderstanding of large mass momentum-linear and rotational

34. http://www.implosionworld.com/cinema.htm What is incredible in the fire effects continua is routine in the world of controlled demolition. “Even with explosives, achieving such results requires a great deal of pre-planning and expertise” “The explosive demolition hypothesis better satisfies tests of repeatability and parsimony” states Professor Steven Jones http://www.physics.byu.edu/research/energy/htm7.html

35. To be continued For additional information contact Edward Munyak, P.E. esmunyak@ earthlink.net (650)948-8035

36. References NFPA Journal, March/April 2005 “Fire Unchecked” page 47 Caracas, Venezuela Fire Culver, Charles, “Characteristics of fire loads in office buildings” Fire Technology 1978, 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/historic fires/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

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