Jul 26, 2013. EXPLOSIVE BLAST 4. EXPLOSIVE BLAST. This chapter discusses blast effects, building damage, inju- ries, levels of protection, stand-off distance, and predicting blast effects. Specific blast design concerns and mitigation measures are discussed in Chapters 2 and 3. Explosive events have historically. Atrium In ancient Roman times, the atrium was the central open area of a house, but today the term atrium is typically associated with commercial and public buildings.

The objective of this study is to shed light on blast resistant building theories, the enhancement of building security against the effect of explosives in both architectural and structural design process and the design techniques that should be carried out. Firstly, explosives and explosion type have been explained briefly.

In addition, the general aspects of explosion process have been presented to clarify the effect of explosives on buildings. To have a better understanding of explosives and characteristics of explosions will enable us to make blast resistant building design much more efficiently. Essential techniques for increasing the capacity of a building to provide protection against explosive effects is discussed both with an architectural and structural approach. Architectural And Structural Design Of Blast Resistant Buildings - PRESENTATION • 1.

WELCOME 1 • Blast Resistant Buildings • Guide: Mr. Arun.K.A Asst. Professor Civil Engg SIMAT • Presented By: Paul Jomy SYAKECE033 Civil Engg SIMAT 2 • 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 3 • 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. 4 • 5 • 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 6 • 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 7 •  Minimize the quantity and hazard of broken glass and blast induced debris.  Facilitate rescue and recovery operation with adequate time of evacuation of occupants. 8 • 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. 9 • Effects of Blast On The Structure 10 • 11 • 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, 12 • 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.

13 • Treatments Provided To Various Parts Of A Structure To Improve Blast Resisting Mechanism 14 • 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.

15 • 16 • 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 17 • 18 • Roofs • Arches and domes are the types of structural forms that reduce the blast effects on the building compared with a cubicle form.

19 • Floorings • They must be prevented from ‘falling off' their supports. Pre-cast flooring is to be avoided in case of blast resistant structures. 20 • Beam-to-column Frame structures Connectionsare 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.

21 • Side plate connection for a steel structure Beam to column connection in Reinforced concrete structure 22 • 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). 23 • Wrapped Columns 24 • 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. 25 • 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. Download Film Keramat Full Movie 480p more. 26 • 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.

27 • 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. Case Study – WTC Collapse two passenger • On 11 September 2001, 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. 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 30 • Conclusion 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 31 • Thank You 32 • 33.

The arc blast (what results from the arc flash) will likely vaporize all solid copper conductors, which will expand up to 67,000 times its original volume when it is vaporized. The arc blast releases fire, intense light, and pressure waves in an explosion of flying shrapnel. An arc flash happens without warning. This typically results in the complete destruction of equipment involved and severe injury or death to people inside the arc flash boundary at the time of the incident.

The energy released by an arc flash is a function of system voltage, available fault current at the location, and duration of the arc. Should you be concerned about Arc Flash Hazards on Low Voltage Equipment? The theory that Arc flash hazards are greater at higher voltages is a common misconception.

It is far more common for low voltages, such as 480v, to have much more significant arc flash hazard levels because the fault currents are much higher. Most recorded arc flash accidents happen at lower voltages as a fault is created from a technician working on electrical equipment. It is not uncommon to have an arc flash hazard Category 3 or Category 4 on low voltage systems due to the long clearing time of the protective devices and high fault currents. What causes an Arc Flash? When significant fault currents are flowing through several conductors that are in close proximity of each other, the differences in potential, among other factors, will ionize the air, allowing a low resistance path between the conductors.

Improper tools, improper electrical equipment, corrosion of electrical equipment, improper work techniques, lack of electrical safety training, and a lack of preventative maintenance are just some of the events that make an arc flash more likely. What sort of injuries can happen from an Arc Flash? It is estimated that 5 to 10 arc flash and blast explosions occur in electrical equipment every day in the United States with 2,000 people each year being admitted to burn centers for severe burns (CapSchell Inc.) The degree of injury is directly related to the power of the arc flash, the distance the person is at the time of the arc flash and the protective equipment (PPE) worn by an individual during an arc flash.

Due to the force from the explosion of energy (the blast) and the intense heat, burns, concussions, collapsed lungs, hearing loss, shrapnel injuries, and broken bones are the common injuries. What are the costs associated with an Arc Flash accident?

Total costs of arc flash accidents have been estimated to be between $12 and $15 million, and can include medical expenses, down time,, lawsuits, and insurance and litigation fees. OSHA has fined some facilities over $500K for not being compliant with electrical safety regulations (www.osha.gov). The biggest costs are the probable lawsuits, because the employer did not properly identify the hazards, train employees and provide proper warnings, procedures and protective equipment (PPE). It is widely recommended to outsource arc flash analysis to trained experts, with the knowledge and experience needed to determine all hazards. Destroyed low voltage switchboard due to the arc flash. Does Proper PPE Protect me from Injury? Protective equipment is designed to limit burns to second-degree burns.

Those who experience an arc flash and are wearing the proper equipment can still be seriously injured or even killed from the force of the arc blast. An arc blast can or blow doors or shrapnel across the room, to which the proper arc flash PPE provides little to no protection!

In an ideal situation, the operator would utilize safety equipment, such a Remote Racking device, that would allow them to stand outside of the arc flash boundary. How is the correct level of PPE determined? In order to select the proper PPE (personal protective equipment), incident energy must be known at every point where workers may be required to perform work on electrically energized equipment. These calculations are determined in an arc flash study and need to be performed by a qualified person such as an electrical engineer. Offers a guide to proper protection. All parts of the body that may be exposed to the arc flash need to be covered by the appropriate type and quality of PPE.

Proper PPE can include Arc Resistant clothing, hardhat, hood, face shield, safety glasses, gloves, shoes, etc. Depending upon the magnitude of the incident energy present. An example of proper PPE (personal protective equipment). Can an Arc Flash incident be prevented? There is no way to completely prevent an arc flash from happening in electrical distribution systems. The best one can do is to mitigate or reduce the risk. Below is a prioritized list, based off of The Risk Control Hierarchy by NIOSH, which describes ways to systematically reduce risk to its lowest practicable level by mitigating a given risk. Higher priority and weight are given to methods that seek to control risk by proactive means as close as possible to the root cause.

Meanwhile lower priority is placed on reactive methods of controlling damage after an incident has occurred. Elimination // Remove the hazard • Only work on energized electrical equipment, when absolutely necessary. De-energizing equipment removes the arc flash hazard, although there is some risk of arc flash and blast when testing to make sure that the equipment is de-energized, as well as when re-energizing. • Removing the personnel from the arc flash boundary eliminates the risk of human injury.

Equipment such as Remote Racking devices allow users to stand outside of the arc flash boundary, while operating breakers. Substitution // Replace higher risks with lower risks This can be done with two methods: • Arc Flash Study with short circuit study and protective device coordination study can identify how to reduce an arc flash hazard category for some equipment. • Technologies can be implemented to reduce risks. This includes equipment such as arc limiting fuses and remote racking technologies. Engineering Controls // Reinvent ways to limit and (or) prevent the risk This can be done by replacing it with equipment that will lower the incident energy, including but not limited to: adjusting breaker settings and redesigning electrical distribution systems. Awareness // Raise knowledge of risks and consequences thereof • Train all workers on the hazards of arc flash.

Although this is #4 on the Risk Control Hierarchy, it should be the first thing done and is mandated by OSHA regulations. It is only through training that workers will understand how to eliminate, substitute or otherwise lower the risk.

• Conduct an arc flash study to properly identify the hazards, boundaries and required PPE. Administrative Controls // Create regulations, work processes, etc. • Make sure that you have a written electrical safety program AND that it is understood by everyone AND that it is enforced.

• Allow only Qualified Persons wearing the proper PPE and using the correct tools to work on or around electrically energized equipment. • Implement a preventive maintenance plan for electrical systems based on NFPA 70B. A proper preventive maintenance program will help identify or fix electrical hazards before they become big problems. Does Preventive Maintenance reduce the potential for an Arc Flash? Preventive maintenance should be conducted on a routine basis to ensure safe operation.

A preventive maintenance program not only ensures that the equipment is functioning properly, but it also identifies potential hazards before they cause an accident. As part of a preventive maintenance program, electrical equipment should be thoroughly cleaned and routine inspections should be conducted by qualified personnel who understand how to uncover loose connections, overheated terminals, discoloration of nearby insulation, and pitted contacts. NETA states, “The ideal maintenance program is reliability-based, unique to each plant and to each piece of equipment.” NETA offers a frequency of maintenance tests matrix and table available here and is recognized as a guide only.

How can system design impact Arc Flash hazards? System configuration plays a key role in arc flash calculations.

Lowering leads to either transformer replacement or reactor installations, which generally is a high long-term expense. Trip times can be improved more cost efficiently. The system configuration, system fault levels, and exposure time can affect the incident energy exposure caused by an arc flash. Se_ttsystem 8.010 9369 Rar. System fault levels can be reduced by changing the system configuration to reduce available fault current and limit trip time.