Advanced in Structures Steel, Concrete, Composite and Aluminum Sydney, 2325 June, 2003 BEHAVIOR OF H

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Advanced in StructuresSteel, Concrete, Composite
and AluminumSydney, 23-25 June, 2003BEHAVIOR
OF HIGH-STRENGTH CONCRETE COLUMNS SUBJECTED TO
BLAST LOADING

• by Tuan Ngo Priyan Mendis
• The University of Melbourne

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Outline
Blast Loading Blast Damage
Dynamic Response of RC Columns subjected to
blast loading
Comparison of Blast Resistance of NSC HSC
Columns
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EXTRME LOADINGS
Natural hazards - Earthquake, Cyclone, etc.
Impact Accidental - Light aircraft -
Fragments. Terrorist - Missile, aircraft.
Technical hazards
Blast Accidental - Gas explosion -
Chemical explosion, etc. Terrorist - Car
bomb, truck bomb, etc.
Fires Associated with explosions - Gas
fire - Chemical fire, bush fire etc.
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Blast loading
Equivalent TNT weights
Oklahoma 1814 kg
WTC (1993) 816.5 kg
Stand-off distance
Oklahoma 4.5m
Blast loads on a building
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Blast loading
Blast wave pressure Time history
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Blast loading
Peak reflected overpressures (MPa) with different
W-R combinations (TM5-1300, 1990)
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Bali Bombing
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Response of RC members under blast
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Blast Damage to RC members
Upward pressure
Punching shear of slabs
Slab damages due to blast
Column failures due to loss of lateral supports
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Blast 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

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Tall building under Bomb BlastGlobal Assessment
Blast pressure P(t)
Blast
Time-history analysis - blast loading
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Localised Failure of Columns Progressive Collapse
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Blast Loading vs Static Loading
Blast loading significantly influence dynamic
response of RC members. High loading rate
affect - strength ductility - bond
relationships for reinforcement - failure modes
- structural energy absorption capabilities.
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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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Experimental ProgramSplit Hopkinson Bar Test
(SHPB)
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Experimental ProgramSplit Hopkinson Bar Test
(SHPB)
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Experimental ProgramStress-strain relationship
at high strain-rates
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Constitutive model for concrete at different
strain-rates
Modified Scott Model (Mendis, 2000)
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Split Hopkinson Bar Test (SHPB) Computer
modelling
3D computer model using explicit code LS-DYNA
3D Concrete Model Smear Crack model
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HSC vs NSC Columns
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HSC vs NSC Columns
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HSC vs NSC Columns
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Conclusions

• Effects of Blast loading on RC structures are
  different from that caused by other types of
  loading (wind, earthquake).
• A strain-rates dependent constitutive model for
  concrete has been proposed.
• The experiment program using Split Hopkinson
  Bar to validate the model.
• The analytical program on RC columns shows that
  HSC columns have higher energy absorption
  capacity compared to NSC columns.
• This study is continuing at the University of
  Melbourne.

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Thank you !