The world of blast protection has been rapidly expanding and there are now numerous products and approaches to provide protection from explosive attack. Where there used to be two solutions, there may now be ten. It is critical that security and design professionals understand the strengths and limitations of the various mitigation measures, and how to select products appropriate for their project.
For exterior explosions, the most fragile and vulnerable elements make up the façade of the building: walls, windows, doors, louvers, etc. These elements are most often not critical for the structural integrity of the building (unless the façade consists of load-bearing walls), but they can represent significant hazards to occupants in the event of an explosion. For very large or close-in exterior or interior explosions, the structure of the building can be damaged as well.
The process of specifying blast resistant products can be simplified into 6 basic steps.
The following narrative provides a very brief description of each step.
Step 1: Is Blast Design Required?
While security consultants and blast engineers can make recommendations on this subject, it is the owner who must make the final determination. Project types that may require blast protection include:
The types of threats to be considered in the design should also be identified at this juncture. This includes the delivery methods (vehicle, backpack, package, etc.). These delivery methods will lead to the establishment of the locations of the threats.
Step 2: Identify Vulnerable Elements
Based on the types and locations of the blast threats, the vulnerable building elements can be identified. These elements may include:
Step 3: Develop Blast Design Criteria
For each type of building element, blast design criteria must be developed. The primary components of blast design criteria are:
Step 4: Identify Other Design Criteria
Other design requirements may be incompatible with certain approaches to blast resistance, and in other cases they may reduce the number of available products appropriate for a specific project. Other design criteria to consider may include:
Step 5: Supporting Structure Check
One of the critical things to remember when designing structures for blast resistance is that the individual building elements (e.g., door, window, wall, roof system) do not act alone. All building elements are supported in some manner, and those supportive systems must be able to withstand the blast loads transferred from the original building elements.
Step 6: Develop Specifications
Whether part of an overall construction document package or as a standalone document for one-off procurements, a well-written and complete specification is key to getting the proper blast resistant products. Specifications should include:
There are a number of changes between the previous (2007) version the current version (June 2015). These changes include:
Be sure to review the new version to understand how these changes may affect you!
With this year’s earthquakes in Southern California, Chili, and Mexico, and the the Fukashima earthquake and subsequent tsunami Japan still causing problems 3-years later, earthquake preparedness has – and should be – been on the minds of many.
The New York Times recently posted an article and accompanying video discussing past earthquakes and the damage they have caused. The video starts out with the Loma Prieta earthquake and its subsequent damage. It then shifts to Oregon and seismic studies that have been done in that area show that a large earthquake (between magnitude 8 and 9) on average every 240 years. The last one that struck was over 300 years ago. One of these studies, The Oregon Resilience Plan, concluded that without preparedness between 1,200 and 10,000 people would die in a tsunami and economic impact would be felt for decades.
The Los Angeles Times had a recent article discussing Mexico’s 21 year old earthquake warning system. The system provides warnings broadcast through air sirens, TV, and radio; providing valuable seconds of warning when an earthquake hits. The 7.2 earthquake that struck near Acapulco on April 18th,
triggered the system and gave Mexico City 71 seconds before the shaking began in the city. Many other countries, including Japan, also have seismic warning systems that alert residents, give bullet trains time to slow down, and even secure inventory before the shaking begins. The USGS has a prototype warning system, but lacks the funding needed to make the system functional.
What does the emergency plan in your state/city/town include?
Sources:
USGS Earthquake Interactive Map
