Design of blast resistance structures

DESIGN OF BLAST RESISTANT STRUCTURES
Sneha
09011A0135

AGENDA:
Need
Types of blasts
Principles
Effects on the structure
Preventive measures:
(i) Measures to be taken while planning
(ii) Measures to be taken while construction
Installations
Bomb shelter areas
conclusion

Need:
Increase in number of terrorist attacks.
To minimize damage to the assets
To minimize the loss of life.
To protect historical monuments and important buildings
To subside social panic

Moving
vehicle
attack
Stationary
vehicle
bomb
Exterior
attack
Arsons
Others
Ballistic
attacks

 Maintain safe separation of attackers and targets i.e.
STAND-OFF zones.
 Design to sustain and contain certain amount of bomb
damage. Avoid progressive collapse of the building.
 Allow for limited localized damage of members
 Minimize the quantity and hazard of broken glass and
blast induced debris.
 Facilitate rescue and recovery operation with
adequate time of evacuation of occupants.

Effects of blast on the structure:
An explosion is a rapid release of potential energy
characterized by eruption enormous energy to the
atmosphere.
A part of energy is converted to thermal energy radiation(flash)
and a part is coupled as air blast and shock waves which expand
radially

How to safeguard the structure from
these effects

Design of blast resistance structures

Planning and layout:
 Sufficient stand-off distance
must be provided.
 In case of congested areas
where there is no provision
for stand off distance,
bollards, trees or street
furniture are to be provided
as obstacles.

Structural Solutions for Blast Resistant Buildings:
Roof: Arches and domes are the types
of structural forms that reduce the
blast effects on the building compared
with a cubicle form.
Flooring: They must be prevented
from ‘falling off' their supports. Pre-
cast flooring is to be avoided in case
of blast resistant structures

Beam-to-column connections:
Frame structures are deficient in 2
aspects:
 failure of beam to column
connections
 Inability of the structure to
tolerate load reversal
 providing additional
robustness to these
connections can be significant
enhancement.
Side plate connection for a steel structure

Beam to column connection in Reinforced
concrete structure

 The use of extra links and the location of the starter bars in the
connection reduce the collapse and damages.
 In critical areas full moment-resisting connections are
made in order to ensure the load carrying capacity of
structural members after an explosion

 The need for fire resistance, strength and ductility favors
reinforced concrete as a construction material for floors.
Blast-resistant design philosophy allows structural
elements to undergo large inelastic (plastic) deformations
in response to blast loading.
• A ductile structure that undergoes large deformations
without failure can absorb much more energy than a
brittle structure of the same static strength

 Tensile reinforcement between 0.5 and 2 percent of the cross-
sectional area of the concrete element will usually insure
ductile behavior while providing the required strength.
 Compression steel in flexural members serves two purposes.
After a structural member is deflected by blast loads, it
attempts to spring back or rebound. Dynamic rebound causes
load reversal and, under certain circumstances, can result in
catastrophic failure

Wrapping of columns:
Wrapping is done to
done for external
protection of columns
and also to protect the
column from shock
waves. Two types of
wrapping can be
applied. Wrapping
with steel belts or
wrapping with carbon
fiber-reinforced
polymers (CFRP).

Miscellaneous measures:
 Partially or fully embed buildings are quite blast resistant.
 Projected roofs and floors are undesirable
 Single story buildings are more blast resistant than multi story
buildings
 Double-Dooring should be used.

Installations:
Gas, water, steam installations, electrical connections,
elevators and water storage systems should be planned to
resist any explosion affects.
Bomb shelter areas:
The bomb shelter areas are specially designated within the
building where vulnerability from the effects of the explosion
is at a minimum and where personnel can retire in the event
of a bomb threat warning.

Glazing and cladding:
 Glass from broken and shattered windows could be
responsible for a large number of injuries caused by an explosion in
a city centre. The choice of a safer glazing material is critical and it
has been found out that laminated glass is the most effective in this
context.

 It is not practical to design buildings to withstand
any conceivable terrorist attack.
 It is possible to improve the performance of
structures should one occur in the form of an
external explosion.
 Design process to ensure that appropriate threat
conditions and levels of protection are being
incorporated.
Conclusion:

References:
 Structural design for external terrorist bomb attack by Jon A. Schmidt
structure® magazine march issue (2003)
 Structure to resist the effects of accidental explosions U.S army nov 1990
 Blast resistant design technology by Henry Wong WGA Wong Gregerson
architects Inc.
 Constructing and deigning blast resistant buildings by G. Gehring and P.
Summers MMI engg Texas
 Design of structure for blast related progressive collapse resistance by
Ronald Hamburger and Andrew
 Blast and progressive collapse Kirk A Marchand and Farid Afawakhiri AISC
Inc.
 Blast resistant design of R C structures by Dennis M. McCann and Stevan
J. Smith an internet webpage in dmccann@exponent.com

Design of blast resistance structures

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