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WELCOME

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Blast Resistant Buildings

• Guide : Mr. Arun.K.A Asst.

Professor Civil Engg SIMAT

• Presented By :

Paul Jomy SYAKECE033

Civil Engg SIMAT

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Introduction• One of the most popular design issue.• Increase in number of Terror attacks and accidents.• Subject is popularly applied in modern and important buildings.• Emerging branch in the field of structural engineering

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Objective Of The Blast Design

The primary objectives for providing blast resistant design for buildings are:• Reduce the severity of injury• Facilitate rescue• Expedite repair• Accelerate the speed of return

to full operations.

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Major Causes Of Life Loss After The Blast

• Flying Debris• Broken glass• Smoke and fire• Blocked glass• Power loss• Communications breakdown• Progressive Collapse of

structure

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Principles of Blast Resistant Design

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

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Minimize the quantity and hazard of broken glass and blast induced debris.

Facilitate rescue and recovery operation with adequate time of evacuation of occupants.

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Blast Load Definition

• 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.

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Effects of Blast On The Structure

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Basic Requirements To Resist Blast Loads

• The first requirement is to determine the threat. The major threat is caused by terrorist bombings. • The threat for a conventional

bomb is defined by two equally important elements,

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The bomb size (or) charge weight, The standoff distance – the

minimum guaranteed distance between the blast source and the target

• Another requirement is to keep the bomb as far away as possible, by maximizing the keep out distance.

• No matter what size the bomb, the damage will be less severe the further the target is from the source.

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Treatments Provided To

Various Parts Of A Structure To

Improve Blast Resisting

Mechanism

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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.

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Stand Off Distance• Blockades, planters, fountains,

fences as obstacles to ramming vehicles or truck bomb.• Allow only emergency vehicle

access. • Raise the building 2m above

ground level

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Roofs• Arches and

domes are the types of structural forms that reduce the blast effects on the building compared with a cubicle form.

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Floorings• They must be

prevented from ‘falling off' their supports. Pre-cast flooring is to be avoided in case of blast resistant structures.

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failure of beam to column connections

Inability of the structure to tolerate load reversal

providing additional robustness to these connections can be significant enhancement.

Frame structures are deficient in 2 aspects:

Beam-to-column Connections

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Side plate connection for a steel structure

Beam to column connection in Reinforced concrete structure

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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).

24Wrapped Columns

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Shear Walls• Use a well

distributed lateral load resisting mechanism in the horizontal floor plan.

• Shear plan around the plan will improve the overall seismic as well as blast behaviour of the building.

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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.

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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.

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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.

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1. Case Study – WTC Collapse

• On 11 September 2001, two passenger planes were hijacked by terrorists and crashed into the WTC Towers in New York.

• The impact of the plane crashes directly caused significant structural damages to both World Trade Center towers.

•  The multiple floors fires ignited by the jet fuel finally weakened the remaining structures and the towers collapsed.

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2. Israel as a Case Study

• Israel has adapted military blast design to blast design to be used as a part of civilian structures.

• In the 1970s civilians in Israel were being threatened along its border with Lebanon.

• Throughout northern Israel rooms designed to protect a buildings inhabitants from an explosion were included in most homes as well as schools and public buildings

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ConclusionIt 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.

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Thank You

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