12 Collapse
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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