Terrorism has threatened the internal security of many countries, including the US. In the last decade, Americans have seen numerous terror attacks in their country, among which 9/11 was the most devastating. The threat of terrorism has forced governments and construction companies to pay special attention to design buildings that are capable of absorbing blasts or at least minimizing and containing the destruction caused by the blasts so that loss of life can be brought under control.
Controlling the catastrophic collapse of a building by means of structural, architectural, and emergency envelope systems are among the best techniques to minimize blast effects. Terrorist organizations have become advanced and they may use the best materials available on the market, which means the governments and the designers have to be extra cautious while designing and testing blast containing buildings. In a terrorist attack, most of the fatalities occur because of sudden collapse. For instance, in the 1987 Oklahoma city bombing, more than 80 percent of the overall deaths were because of building collapse.
Designing Blast Containment Structures
The following factors should be taken into account while designing a safe building that can contain and minimize bomb hazards.
The main building and any unsecured areas must be separated from each other to minimize damage. For example, the parking lot should be outside the main building area so that catastrophic damage is minimized. Functional and structural layout of the building need to be reworked to make it blast containing. Internal buffer zones, adding hard lines to the design, and including secondary staircases and elevator shafts in the main design of the building will ensure that the main and secondary portions of the building remain fully functional yet separate from each other.
- The configuration of the building also plays a vital role in blast containment design. Convex shapes of buildings should be preferred over concave shapes as air blast pressure is minimized because shock waves travel at higher angles of incidence than in a rectangular building. Horizontal orientation of the building will reduce its profile and exposure. To avoid vehicle ramming or suicide vehicle bombing, ensure that ground floor elevation is at least 4 feet above the grade. Providing pitched roofs, avoiding exposed structural elements, and using earth sheltered design are some of the aspects of safe building design to avoid blast injuries.
- Using Green roof technology ensures that the visual profile of your building is reduced. It also reduces the heat signature of your building. Use of vegetation across the building, especially on its front, helps a great deal to keep a check on hostile surveillance activities.
- Safe havens must be designed within the building, and these should be accessible to the occupants of the buildings in less time than the attackers. This indirectly means that safe havens should not be placed near the entrance or possible infiltration zones like ventilation ducts and sewer pipes (in case of multistory buildings).
- Stairwells should be practically far away from the main building area. In emergency situations like a terrorist attack, people use stairwells and not the lifts. If bombing has already occurred, only separated stairwells from the main building will enable people to escape.
- The non-structural elements like lighting, false ceilings, and duct work should be minimized. If you are designing an office, keep it as simple as possible because in blast bombing scenarios, these aesthetically fascinating objects act as flying debris.
- To avoid chemical, biological, or radiological (CBR) threats, advanced HVAC and filtration technologies should be adopted because chemical warfare agents have far more dangerous consequences than physical injuries. Filter placement, sealing of open spaces in the ventilation chambers, monitoring and checking entry point of CBR agents are some of the other important aspects of avoiding CBR threats.
- To avoid progressive collapses, cladding, exterior window systems, and redundant mechanical and electrical systems must be used.
Strengthening the Security Components
Terrorists have become smart and they often make use of the weak links in our society. Strengthening the security components has become very important to avoid loss of life and property. Following are the four important aspects of our building security that need to be made foolproof to avoid terrorist activities and minimize blast injury and damage.
Deception Be as smart as the terrorists; use deceptive cover techniques to protect your building from unwanted surveillance.
- Intelligence means acting street smart in case any emergency situation arises. It not only means employing security guards, but it also includes organizing disaster mitigation workshops for the occupants of buildings so that they know about safe havens, how to use stairwells, and other safe practices.
- Structural Hardening of vulnerable components of the building will also help in minimizing blast damage.
- Operational Protection includes perimeter protection and equipping buildings with surveillance technology.
Risk Management Series, FEMA 427, Dec 2003, http://www.fema.gov/pdf/plan/prevent/rms/427/fema427.pdf
Risk Management Series, FEMA 428, Dec 2003, http://www.madcad.com/media/fema/fema428.pdf
Filtration and Air-Cleaning Systems to Protect Building Environments, http://www.cdc.gov/niosh/docs/2003-136/pdfs/2003-136.pdf