The seminar presented by Mehul Doshi at Birla Vishvakarma Mahavidyalaya discusses the design of blast-resistant buildings, emphasizing the need for such designs due to rising threats from blasts. It covers various aspects including blast loading, effects of shock waves, mitigation strategies, ductile design considerations, and guidelines from IS 4991-1968. The document highlights the importance of material selection, structural forms, and design modifications to enhance safety and functionality post-blast.

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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