A well-constructed building is a collective effort of a hundred people involved in the project. An architectural project involves a team of masons, specialists, engineers, structural engineers, interior designers, electrical team, architects, and many more. Every entity plays an eminent role in the configuration of the structure.
Architects not only aim to design a building catering to client’s requirements but incorporate solutions to real-time problems. Architects strive for space optimization, less carbon footprint, net-zero building design, fire-resistant, well-ventilated and climate-responsive structure, and many more.
One of these key factors is Blast Resistant Building.
What is a blast-resistant building?
Several loads like earthquake loads or wind loads act upon a building. In such loads, the structural integrity of the building is affected by naturally occurring agents like tremors or wind. But other than earthquake load or wind load, a building can undergo a manmade attack. Man-made attacks can be employed by intruding explosives in a building. Blast attacks can not only affect the structural integrity but in worse scenarios can even lead to a collapse.
To prevent the collapse and reduce the damage, the building design is oriented towards a Blast Resistant Building. The intruding agents vary from an airborne chemical to a missile. A good blast-resistant building design procures maximum safety for the occupants. A blast-resistant building can be achieved by mitigating certain measures. Architects adopt certain measures at varying levels of designing a structure.
The spatial arrangement contributes to the protection of the building from explosives and chances of attack aftereffects. Architects decide the spatial movement of the occupants of the building. At the time of an attack, occupants are evacuated to the refugee area. Refugee areas are allocated by the architects in an established evacuation plan of the blast-resistant building.
All the points of exit are placed such that the travel distance is minimized. Structural elements like stairwells are required to be located remotely and not discharged in lobbies, loading areas, or parking. While designing the spaces, avoid collocating high-risk facilities with low-risk occupancy. In other words, avoid placing a control room or supply room near a childcare facility.
There are certain mitigation measures (based on Building profile) for blast-proof buildings which architects keep in mind.
For low, large footprint building:
- Distribution of people and assets over a larger area to reduce the damage
- Use of green elements and landscaping and incorporate protective screens to maintain a hostile surrounding
- Managing the Solar Heat Gain Coefficient of the building by maximizing the effect of green roof in design
Tall, small footprint building:
- Vertical profiled structures have a large percentage of risk for facades and interiors. To overcome collateral damage or a collapse, blast-resistant building designs need to incorporate the collapse prevention techniques
- Reducing the number of impervious surfaces to minimize the use of drain water pipes or sewage pipes helps to reduce site access opportunity
Form of the Building
The Shape of the building is also associated with the attack. Usually ‘U’ and ‘L’ shaped forms trap the shock waves and intensify the damage. Therefore it is recommended to avoid sharp-edged corners in the built form.
For instance: a circular building reduces the air blast pressure because the angle of incidence of the shock waves increases rapidly compared to a rectangular form.
Simpler the form, the more Blast resistant the building is. Studies recommend opting for simpler forms and avoiding ornamentation as it invites opportunities for attacks.
The HVAC of a building plays a huge role in stimulating an attack as it determines the air circulation and distribution system. Hazardous gases are released through ducts. Additional measures are required to prevent the intrusion of harmful agents.
Architects are required to consider the following design recommendations for a blast-resistant building:
- Earth-sheltered design to be incorporated for minimizing the effect of an attack
- Low, large footprint buildings bear less effect. It is recommended to orient buildings in a horizontal profile rather than a vertical profile.
- Ground floor level is recommended to be placed at a plinth of 4 feet above the grade to prevent the vehicle-ramming effect.
- Overhangs and eaves are considered points of local pressure and suction during a blast; hence these should be avoided or designed withstanding specifications.
- Structural elements like columns should not be placed externally or left exposed.
Elements of the Interior
Not just the Building Envelope but Interior spaces are also designed in particular ways for a blast-resistant building. The building material used and interior finishes are chosen according to the specification. Material of door, windows, and internal walls is chosen according to the fire-resistant rating. Internal spaces are to be segregated in compartments using fire-resistant barriers.
A blast-resistant building aims to prevent damage and the collapse of the structure in case of an attack. As the magnitude and intensity of the attack are not predefined, the architects and structural engineers incorporate the techniques based on the possible scenarios to achieve a blast-resistant building design.
While designing a blast-resistant building, primarily the inhabitant’s safety is considered. The movement through the spaces, structural integrity, site constraints, and architectural factors are considered to attain an optimum building design.
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