IABSE Symposium Melbourne Sep' 2002 Organized by International Association of Bridge and Structural

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IABSE Symposium - Melbourne Sep. 2002Organized
by International Association of Bridge and
Structural Engineering (IABSE) Institution of
Engineer Australia (IEAust)Tall buildings
subjected to blast loading aircraft impact

• A/Prof. Priyan Mendis
• Tuan Ngo
• The University of Melbourne

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Extreme loads
Blast Accidental - Gas explosion -
Chemical explosion, etc. Terrorist - Car
bomb, truck bomb, etc.
Impact Accidental - Light aircraft -
Fragments. Terrorist - Missile, aircraft.
Fires Associated with explosions - Gas
fire - Chemical fire, etc.
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Blast loading
Equivalent TNT weights
Oklahoma 1814 kg
WTC (1993) 816.5 kg
Stand-off distance
Oklahoma 1.5m
Blast loads on a building
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Blast loading
Blast wave pressure Time history
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Impact loading
F(t) Fc ? m(t) V(t)
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Impact loading
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Impact loading
F(t) Airframe impact Engine impact
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Case study (typical building in Australia)
Boeing 767
Impact
Blast
Structural configuration
Point of detonation Stand
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Global Assessment - Types of analysis
Implicit FE Time history Nonlinear Dynamic
Analysis
Explicit FE - Transient Nonlinear Dynamic Analysis
Vb
Push-over Curve Load vs Deflection
Static Nonlinear Push-over Analysis
UN
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Nonlinear Analysis Blast load
Blast pressure P(t)
Time-history analysis - blast load condition
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Nonlinear Analysis Blast load
Distribution of Peak Pressure on elevation
Push-over curve of the blast load condition
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Nonlinear analysis Impact load
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Nonlinear Analysis Impact load
Aircraft impact
Blast load
Push-over curve of the aircraft impact
Bending moment diagrams of the core walls
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Concrete at high loading-rates
Concrete strength is highly sensitive under high
rates of loading
Dynamic Magnification Factor for peak stress of
concrete (CEB-FIP model)
Stress-strain behaviour of concrete at different
strain-rates
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High velocity impact Advanced Modelling
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Damages by light aircraft impact
Impact Assessment using Modified Compression
Field Method
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Detailed Impact Analyses (FE Explicit code -
LSDYNA)
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Blast Impact Resistant Design
Design objectives

• to provide sufficient ductility to enable the
  element to deflect with acceptable degree of
  damage
• while deforming, the element should not fail
  prematurely due to other load effects (shear,
  local instability) -gt preventing progressive
  collapse

Failure of Floor trusses (WTC)
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Slab subjected to blast
Upward pressure
Punching shear of slabs
Slab damages due to blast
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Blast impact resistance
Column failures due to loss of lateral supports
Upward pressure
Collapse of transfer girders
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Progressive collapse
World Trade Centre (2001)
Oklahoma (1995)
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Progressive collapse of RC building
Oklahoma (1995)
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Column Failure - Progressive collapse
Oklahoma (1995)
Differential pressure between the front and rear
of column G24 caused its failure 3.75
milliseconds after blast arrival
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Slab Failure - Progressive collapse
Oklahoma (1995)
Differential upward pressure on 5th floor slab
caused its failure along after the blast loads
disminished
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Progressive collapse Case study
Direct column loading (Blast pressure)
Uplifting of floor slabs (Blast pressure)
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Progressive collapse Blast load
Progressive collapse analysis of perimeter frame
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Progressive collapse Slab detailing
Initial Failure - Punching shear
Initial Failure - Punching shear
Final state - Total collapse
Final state - Slab hanging by bottom bars
The role of Bottom Reinforcement Anchored into
Supports
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Progressive collapse Aircraft impact
Progressive collapse analysis of perimeter frame
(damaged by aircraft impact)
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Improve ductility to prevent collapse
Plastic hinge formation and collapse mechanism of
HSC frames under extreme lateral loads
50MPa concrete frame
100MPa concrete frame
Idealised moment-curvature (M-?) relationship
Moment-curvature diagram of spandrel beams
Moment-curvature diagram of core walls less
ductile
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Protective technologies the road ahead
With SFRC
Without SFRC
Failure patterns of RC slabs subjected to blast
with and without steel fibres
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MBT FRP Tecnologies
Confinement of columns using SP A-Sheet strips
Bonding of the laminate using SP Resin 220
Impregnation of the sheet with SP Resicem
(vapour permeable)
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Protective technologies
Crushing
Spalling
Shear failure
Rehabilitated column
Glass fibres (GFRP)
Failure patterns of RC columns and the
rehabilitation using GFRP