The document discusses the impact of blast loading on structures. It defines blast loading as short duration explosive loads that can cause significant damage to buildings. The key effects are primary effects from the blast wave, shock wave, heat and fragments. Secondary effects include debris impact. Response depends on the natural period of the structure and blast wave duration. The document recommends blast resistant design features like continuity of beams and columns to improve structural performance during explosions.

2. Impact of blast loading on
structures

3. Group Members
Group 06
ABBAS KHAN UW-14-CE-BSC-017
Habib Ur Rehman UW-14-CE-BSC-001
Shafiq Ur Rehman UW-14-CE-BSC-008
M Hamza Tariq UW-14-CE-BSC-015
Muhammad Ali UW-14-CE-BSC-016
Muhib Ullah UW-14-CE-BSC-04
WAH ENGINEERING COLLEGE WAHCANTT

4. • Introduction
• Blast Loads
• Blast Waves
• Effects on Structures
• Expected Damage Levels
• Response of Structure
• Blast Resistant Buildings
• Solutions for Blast Resistant
Buildings
• Conclusions
• References

5. • The increase in the number of terrorist attacks especially in the last few
years has shown that the effect of blast loads on buildings is a serious
matter that should be taken into consideration in the design process.
• The blast explosion nearby or within structure is due to pressure or
vehicle bomb or quarry blasting.
• These causes catastrophic damage to the building both externally and
internally (structural frames).
• Collapsing of walls, blowing out of windows, and shutting down of
critical life-safety systems.

6. • Buildings, bridges, pipelines, industrial plants dams etc are the lifetime
structures and they play an important role in the economy of the
country and hence they have to be protected from dynamic and wind
loading.
• Structures should be protected from the blast effects, which are likely
to be the targets of terrorist attacks.
• The dynamic response of the structure to blast loading is complex to
analyze, because of the non-linear behavior of the material.

7. • 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.

9. • Blast loads on structures can be classified into two following main group
 confined Explosions
 Unconfined Explosions

10. confined Explosions
• An explosion occurring within a vessel or building. These are most
common and usually result in injury to the building inhabitants and
extensive damage.
• There are two types involving explosive vapors and explosive dusts.

12. Unconfined Explosions
• Unconfined explosions occur in the open. This type of explosion is
usually the result of a flammable gas spill. The gas is dispersed and
mixed with air until it comes in contact with an explosion source.
• Unconfined explosions are rarer than confined explosion.
• These explosions are very destructive since large quantities of gas
and large areas are often involved.

14. To be an explosive, the material will have the following
characteristics :
• Must contain a substance or mixture of substances that remains
unchanged under ordinary conditions.
• This reaction must yield gases whose volume at the high temperature
is much greater than that of the original substance.
• The change must be exothermic in order to heat the products of the
reaction and thus to increase their pressure.

15. Common types of explosions include :
• Construction blasting to break up rocks,
• Blasting to demolish buildings and their foundations,
• Accidental explosions resulting from natural gas leaks or other
chemical/explosive materials.

16. • The rapid expansion of hot gases resulting from the detonation of an
explosive charge gives rise to a compression wave called a shock
wave, which propagates through the air is known as blast wave.

17. Blast effects on building structures can be classified as :
• Primary effects and Secondary
effects.
• Primary effects include ;
 Air Blast
 Ground Shock
 Heat
 Fragments

19. • The blast wave causes a pressure increase of the air surrounding a
building structure and also a blast wind.
• For example, the blast may deflect structural steel frames,
collapse roofs, dish-in walls, shatter panels and break windows.

20. • An explosive which is buried completely or partly below the ground
surface will cause a ground shock.
• This is a horizontal vibration of the ground, similar to an earthquake
but witha different frequency.

21. • A part of the explosive energy is converted to
heat.
• Building materials are weakened at increased
temperature.
• Heat can cause fire if the temperature is high
enough.

22. • Fragmentsfrom the explosive sourcewhichare thrown into the air at high
velocity.
• Forexample wall fragments of an exploded gas tank.

23. • Secondary Effects can be fragments hitting people or buildings near
the explosion.
• They are not a direct threat to the bearing structure of the building,
which is usually covered by a facade.
• However, they may destroy windows and glass facades and cause
victims among inhabitants and passers-by.

24. • Minor :
• Non-structural failure of building elements such as windows,
doors & cladding.
• Injuries may be expected and deaths are possible but unlikely.

26. • Moderate :
• Structural damage is confined to a localized area and is usually
repairable.
• Structural failure is limited to secondary structural members, such as
beams, slabs &
non load bearing walls.
• Injuries and deaths are expected.

28. • Major :
• Loss of primary structural members such
as columns.
• In this case, extensive deaths are
expected.
• Building becomes non repairable.

30. • Blast loading is a short duration load also called impulsive loading.
• Mathematically blast loading is treated as triangular loading.
• The ductility and natural period of vibration of a structure governs its
response to an
explosion.
• Ductile elements, such as steel and reinforced concrete, can absorb
significant amount of strain energy, whereas brittle elements, such as
timber, masonry, and monolithic glass, fail abruptly.

31. • In the investigation of the response of a building structure to
bomb blast, the following procedures are followed :
• The characteristics of the blast wave must be determined;
• The natural period of response of the structure must be determined;
• The positive phase duration of the blast wave is then compared with
the natural period of response of the structure.

32. The response of structure due to blast loadings can be as
follows :
• Impulsive
• Quasi-static
• Dynamic

33. • Impulsive
• If the positive phase duration of the blast pressure is shorter than the
natural period of vibration of the structure, the response is described
as impulsive. In this case, most of the deformation of the structure
will occur after the blast loading has diminished.

34. • Quasi-Static
• If the positive phase duration of the blast pressure is longer than the
natural period of vibration of the structure, the response is defined as
quasi-static. In this case, the blast will cause the structure to deform
while the loading is still being applied.

35. • Dynamic
• If the positive phase duration of the blast pressure is close to the
natural period of vibration of the structure, then the response of the
structure is referred to as dynamic. In this case, the deformation of
the structure is a function of time and the response is determined by
solving the equation of motion of the structural system.

36. • Explosions and blasts can produce, in a very short time, an overload
much greater than the design load of a building.
• Nothing can be guaranteed to eliminate all risks; but if the following
blast resistant design features were to be incorporated, many lives
could be saved and many structures and businesses would survive.

38. • Floors :
must be prevented from ‘falling off' their supports. If pre-cast concrete
planks are used they should have sufficient bearing; but they should not
depend on bearing and gravity to stay in place, they should be made
continuous with rebars between adjacent planks and preferably be
made continuous with the supporting beams.
• Joists :
should be made continuous themselves, through every main beam
and wherever they coincide with outer columns.

39. • Main Beams :
shouldbe continuousacrossthe structure and shouldhaveconnectionsto the outer
columns
whichexceed the plastic capacity of the main beam.
This means that in the case of overload the beamsdeform, forming hinges,
absorbing energy and taking time. Blastor shockloads will diminishin a veryshort
time.
• Main OuterColumns :
should remain elastic and strong enough to carry likely loads even when main
beamsattached to themform plastic hinges.

40. • The ground to first floor columns carry the heaviest loads. They are
always more vulnerable to attack. They are almost always longer than
columns on other floors. So special care has to be taken: they need to
be stronger; to have barriers to protect them; to have continuity at
footings level with ground beams or slabs.
• If all this continuity is achieved, even if a column or two are cut or
deformed, the grillage of beams and joists and slabs at each floor
throughout the building will continue to carry the loads.

42. • It is not economical to design all buildings for blast loading.
• Public buildings, tall structures and city centers have to be designed
against terrorists
attacks and sudden explosions.
• It is recommended that guidelines on abnormal load cases and
provisions on progressive collapse prevention should be included in
the current Building Regulations and Design Standards.

43. • Requirements on ductility levels will also help to improve the building
performance under severe load conditions.
• Evaluation of the results due to blast loading under several conditions have
to be included in the design procedure to get into the correct evaluation of
the stress characteristics of the material under consideration.

44. • T. Ngo, P. Mendis, A. Gupta & J. Ramsay, "Blast Loading and Blast Effects on
Structures – An Overview", The University of Melbourne, Australia, EJSE
Special Issue: Loading on Structures (2007).
• N. Munirudrappa, Professor, Civil Engineering department,
Dayananda Sagar College of
Engineering, , Bengaluru, Blast Loading and Its Effects on Structures A
Critical Review.
• http://www.nbmcw.com/articles/miscellaneous/others/29110-blast-loading-and-its-
effects- on-structures.html
• http://www.slideshare.net/sitaramayya/blast-resistant-structures
• http://www.docstoc.com/docs/73460939/BLAST-LOAD-AND-
EFFECTS-OF-BLAST-ON- STRUCTURES#
• http://www.reidsteel.com/information/robust_resilient.html