Now a days very less research is going on for this topic. I have tried to design G+1 building using STAAD Pro as per IS Code 4991-1968.

1. Birla Vishvakarma Mahavidyalaya (Engg. College)
[An Autonomous Institution]
Seminar On:
DESIGN OF BLAST RESISTANCE BUILDING
Guided by : Prof. Vishal B. Patel
Prepared by : Mehul Doshi (16SE818)
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2. CONTENTS
• Introduction
• Literature Review
• Observations
• References
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3. Introduction
• Civil structures are exposed to threats
• New chemicals – Higher Magnitude
• Need of blast resistance design
• Required attention as very less research is going on
• Blast load very different from other load – Impact load
• Cannot be assessed true value for blast magnitude
• Probability of this type of load – very less for a particular building
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4. Blast Loading
• First step is to know how to decide the blast load for the blast
resistance design
• Near range region- blast loading made up of blast pressure, ground
shock & fragment impact
• Far field region- blast loading made up of only blast pressure
• Ideal blast wave representation &
its characteristics = f (R, t)
• Ideal blast wave is a curve as shown
but for simplicity it is considered
triangle.
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5. Blast Loading
• Combined effect of stand off distance in meter & amount of TNT in kg
is expressed by scaled distance Z = R/W^(1/3)
• For combination of load wind load & earthquake load – not take into
account only dead load & live load – live load not at the roof
• There is more pressure
at the exterior portion
& at corner
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6. Effects of shock-waves
• This travels away from explosion faster than the speed of sound
poses threat in close location.
• Shock front is similar to “moving wall” of highly compressed air
accompanied by blast wind.
• It causes sudden rise in ambient pressure. This is called ‘over-
pressure’. Pressure caused by blast wind is called ‘dynamic
pressure’.
• Both these pressure decay rapidly with time.
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7. • Pressure and overpressure sinks below
ambient pressure before equalizing back to
atmospheric pressure.
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8. Blast response mitigation
• Main objectives: (1) acceptable damage limit to the structure
(2) functionality requirement after blast
• Most effective strategy is
- to increase the stand off distance – Blast wave decay very fast with
distance – Leads to economical design
- Distributed mass will help in absorbing of blast wave
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9. Blast response mitigation
• Important buildings are designed for all possible combination of
different load
• To meet different criteria of loading, design requirement may be
different & some times contradictory
• Like for seismic behavior - lighter section
• For good blast resistance behavior – should posses adequate mass
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10. Sacrificial blast wall against Explosion
• Significance level of hardening – In new structure
• Making existing structure resist blast – Expensive
• Protection strategy – is to construct defense barrier all around the
existing structure – which dissipate the energy & increases stand off
distance
• Wall performs roll of mitigation device
• This wall may damage permanently – but structure should be
functioning well after blast
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11. Building performance goal
• Building may subjected to different hazards:
(1) low hazards : No need of blast resistance design
(2)moderate hazards: Structural configuration & detailing measure
should be improved like preference of single storey buildings, no heavy
load on the roof & enhance the ductile behavior with that large
deformation before collapse.
(3) high hazards : stress in the structural limits are permitted to
exceed but there is some level of damage but by controlling inelastic
behavior so acceptable performance of the building can be achieved.
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12. Ductile design consideration
• Structure response beyond elastic limit – but no brittle behavior &
abrupt collapse
• Greatest blast resistance – use of Reinforced concrete or Reinforced
masonry shear wall – do not use unreinforced concrete, brick &
timber
• Very less geometric irregularities give less stress concentration
• Connection between two structural member stronger than member
itself so more ductile behavior of member govern the design over
brittle behavior of connection
• Provide sufficient shear transfer to floor slabs so that directly applied
blast loads can be restricted by the diaphragms rather than weak axis
bending. 12

13. Literature Review (IS 4991 – 1968 guidelines)
• Blast wave loads the exposed surface elements which transfer load to the
other connected members – needed to analyze individual member
• Strain is greater than the static load so reducing required design strength
as more energy is absorbed during this.
• Longer the natural time period of the structure lesser design load is taken
account Wn=(k/m)^(1/2)
• For reinforcing steel & for concrete dynamic strength will be 25% more
than the static strength
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14. Literature Review (IS 4991 – 1968 guidelines)
• Roofing & cladding material :
- tiles & corrugated asbestos sheets- not used
- corrugated galvanized iron sheet are used – connected very well with
the formwork
• For wall thickness against blast splinters:
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15. • Designed on shear wall concept with roof acting as a
diaphragm that transfers the transverse loads to the side shear
walls and columns.
• R.C.C. blast wall shall be taken 1.5 m below G.L
• Roof slab shall be doubly reinforced. Minimum reinforcement on
top and bottom shall be 1% of gross cross sectional area.
• Maximum spacing of bars in walls as well as roof slab shall not
exceed 150 mm c/c. minimum bar diameter shall be 12 mm
Literature Review (IS 4991 – 1968 guidelines)
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16. Literature Review
• Zeynep Koccaz et. al. (2008) said arches and domes are the types of
structural forms that reduce the blast effects on the building
compared with a cubicle form
• Complex shapes that cause multiple reflections of the blast wave
should not be designed
• Single story buildings are more blast resistant compared with multi-
story buildings
• Cast-insitu reinforced concrete floor slabs are the preferred option
• Lightweight roofs should be avoided and a reinforced concrete or
precast concrete slab is to be preferred.
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17. Literature Review
Zac Liskay et. al. (2014) has given following details
• Phase duration of blast > natural period  static behavior of building
• Phase duration of blast < natural period  impulsive loading behavior
• Phase duration of blast = natural period  max. deformation
behavior
• Floor slabs are typically designed with a downward
gravity loading
• When the moments change direction, the flexural
reinforcement is no longer resisting the bending.
This reverse loading may cause shear cracking in the
slabs.
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18. Literature Review
• Exterior walls must be designed to fail in a ductile manner rather
than in a brittle manner. Because of this, the preferred material for
exterior wall construction is poured-in-place reinforced concrete.
• This reinforced concrete wall should give ductile behavior
• Ductile failures also produce less shrapnel, which can reduce the
injuries caused.
• Exterior walls should have less window as possible & equipped with
shard reduction technique.
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19. Example : Analysis of the structure
• Stand off distance: 10m
• 2 bay of 3m in X & Z direction
• 200kg TNT
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20. Example : Analysis of the structure
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21. Example : Analysis of the structure
• Peak side over pressure calculation from IS 4991:1968 is 890 kN/m2
• Equivalent time duration = 3.88 millisec
• Load is given in any one surface of the building
• This data is used in load application to the building in form of time
history
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22. Reference
• IS 4991:1968
• http://skghoshassociates.com
• https://redguard.com/blog/discovering-1001-ways-to-build-
a-blast-proof-building/
• https://www.researchgate.net
• http://onlinelibrary.wiley.com
• Blast and progressive collapse Kirk A Marchand and Farid
Afawakhiri AISC
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23. THANK YOU
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