12 Collapse

Objectives

• Identify the various types of collapse

• Apply risk analysis to fire-ground safety

• Identify the specific basic competencies all fire fighters should have to perform at a structural collapse

• Explain the essential elements of the collapse of the World Trade Center twin towers on September 11, 2001

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Collapse: The Greatest Threat on the Fire Ground (1 of 2)

• How fire fighters die

– Heart attacks (the greatest killer today)

– Smoke inhalation

– Falls

– Building collapse

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Collapse: The Greatest Threat on the Fire Ground (2 of 2)

• Building collapse represents the greatest threat to kill in number

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Anticipating Collapse

• Responsibility of the incident commander, the operations chief, and the safety officer

• Responsibility of each fire fighter

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Risk Analysis (1 of 2)

• After fire fatalities

– Questions are asked

– Were fatalities caused by antiquated macho attitude?

– Taxpayers saddled with unnecessary expenses

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Risk Analysis (2 of 2)

• Professional fire services

– Analyze the relationship between risk incurred and benefits obtained

– Are well informed about construction features of buildings that have been available for study for many years

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Types of Collapse (1 of 2)

• Global

• Partial collapse

• Progressive collapse

• Secondary collapse

• Pancake collapse

• Lean-to-floor collapse

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Types of Collapse (2 of 2)

• V-shaped floor collapse

• Cantilever floor collapse

• Frame floor collapse

• Inward outward collapse

• 90-degree wall collapse

• Lean over collapse

• Curtain fall wall collapse

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Establish Collapse Zones

• Fire fighters and fire apparatus must be kept out of collapse zones

• “Staying back one third the height of the wall is safe” is untrue

• Fire fighters must remain at least the full height of the wall away

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Minimum Collapse Competencies for Fire Fighters

• Identified by National Fire Protection Association (NFPA) 1670: Standard on Operations and Training for Technical Search and Rescue Incidents

• Higher competency levels require higher training

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Our Worst Collapse Tragedy

• History of the World Trade Center

– Two of the tallest and largest buildings ever built

– Each tower was 110 stories high and each floor was 40,000 square feet

– Each side of the building measured 210 feet in length

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Major Structural Components of the Towers

• Exterior walls

• A series of columns in the center core

• Lightweight steel floor trusses forming a composite floor

• Hat truss

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Mechanism of Collapse

• Studied by the National Institute of Standards and Technology (NIST)

• Used visual evidence of the exterior damage and computer modeling

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The North Tower (Tower 1)

• Structural damage from the planes

• Jet fuel and dislodged fireproofing

• Open paths for fire spread

• Weakened core columns

• Sagging of the “south floors”

• Bowed south perimeter columns

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The South Tower (Tower 2)

• Damage to the center core columns

• Jet fuel and dislodged fireproofing

• Sustained fires had an ample air supply

• Weakened core columns

• Sagging of the “east floors”

• Bowed east perimeter columns

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Questions

• How many trusses were destroyed in the initial impact?

• How many failed in the subsequent fires?

• How much fireproofing was knocked off by the plane impact?

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Questions for the Future

• Should lightweight trusses be used in high-rises?

• Should spray-on fireproofing come under more scrutiny?

• What role should fire services have in construction and regulation?

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In the End

• Be proactive role in securing your safety and the safety of others

• Get involved in the construction of a new building

• Get involved in the code development and adoption process

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Summary

• All fire fighters have the responsibility to know the conditions for collapse in different types of buildings

• Fire fighters and fire apparatus should be kept out of collapse zones

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