Table of Contents
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Introduction
Design serves many different purposes in in structural aspects and for buildings. As society becomes more complicated, there are more factors that have to be considered when faced with unexpected scenarios. One of the concerns that have to be addressed for more buildings that is on the rise is prevention and protection against explosions, especially for government and military based buildings. Since terrorist attack cases have increased dramatically over the last few years, they are considered dynamic loads along with natural disasters like seismic design for earthquakes and require meticulous consideration and calculation [1]. Designing for Blast means incorporating the possibility for an explosion has become a primary objective for the scope of the building and requires a series of various steps and impacts to be addressed before any decisions can be made. Although protection of people within the building would be the main concern, there are numerous other trade-offs and criteria that have to be assessed to be able to conclude with the best design [2].
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| Building after explosion [3] |
Purpose
Threat
For terrorist activities, usually the two main considerations are for vehicles and weapons [2]. In terms of watching out for vehicles, the potential threat emerges from all sides of a building that is parallel to or facing a street. The vehicle is considered an air-blast load and decreases with distance so the primary danger is near the base of the building. For prevention of vehicle attacks apart from screening are intrusions such as anti-ram barriers along the perimeter of the building as well as utilizing the form of the landscape to create an obstacle course can be effective. However, oftentimes the vehicle itself is not the only threat because they can be used as a diversion or container for a secondary attack such as an explosive or hand-held weapons like a gun so further protection is needed.
There are a multitude of various weapons that produce a hazard to the lives of people but in regards to a building, the greatest pressure comes from explosives. Factors to be aware of are that the impact of explosives decrease very quickly with time and space and usually the pressure produced increases linearly with the size. Although the actual explosion only lasts a couple milliseconds, the area of the shock wave can hit the entire building and even the surroundings.
Effects of an explosion:
- The side of the building facing the initial source can be amplified up to ten times the pressure.
- Has a positive pressure phase and a negative pressure phase.
- During the negative pressure phase, regions with low pressure such as windows and sloped roofs to fail and collapse.
- Thin members like columns are impacted more by drag effects than direct pressure.
- Rebound is structures moving in the reverse direction due to vibration and can cause the exterior envelope to fall.
- Below the point of impact, an underground crater will form that damages the foundation and anything below grade.
- Any energy of the weapon that transfers through soil will create a small earthquake that can derange mechanical and electrical systems.
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| Vehicle weapon threat [2] |
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| Sequence of air-blast effects [2] |
Building Damage
Damage done to a building can be separated into two categories of direct air-blast and progressive collapse. Direct air-blast refers to the source of the explosion and takes into account the damage caused by the high-intensity pressures near the incident.
Structural Aspects and Specifications
Building Envelope
Walls
Roof
Below Grade
Windows/Fenestration
(Windows)Building Materials and Methods
Issues and Considerations
Additional Reading and Resources
Contributors:
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