8.2.13 Expedient Barrier Systems. Common construction items, such as large diameter concrete
and steel pipes, and large construction vehicles (i.e., dump trucks and earth moving equipment)
that have heavy mass and size can be used, or modified for use, as expedient barrier systems.
Some examples are:
a) Three-foot (0.9-m) sections of large-diameter, corrugated metal or reinforced
concrete pipe can be placed on end and filled with sand or earth.
b) Steel pipe can be stacked and welded together in a pyramid.
c) Construction vehicles can be anchored together with cable or chain.
These expedient measures can provide effective protection against vehicle bomb
attacks. Because no testing has been done on these systems, it is important that, if used, these
barriers be stabilized and anchored to prevent displacement by a threat vehicle.
Vehicle Barrier Performance. Full-scale testing of vehicle barrier systems is only one
way to obtain information on the performance capabilities of vehicle barriers. Testing provides
evidence that the selected barrier will effectively absorb the impact of a threat vehicle. Tests
may be conducted by independent testing laboratories, government agencies, or the
manufacturer. Some tests are properly documented and/or witnessed by authorities, while others
are not. Only tests by independent testing laboratories or government agencies should be
It is important to correctly interpret the test results. For example, full penetration
could mean the vehicle passed through a barrier and was still capable of movement after
penetration. Or, it could mean the vehicle payload penetrated through a barricade, but the
vehicle was incapacitated. Whenever possible, carefully review the actual test report before
selecting a barrier system. For commercially available active barriers, these reports are usually
available from the manufacturer. Such review may not always be possible. In this situation, it
may be necessary to make judgments based on experience.
Selection of vehicle barriers can also be based on engineering analysis. Finite
element analysis and computer models specifically designed to analyze barrier impact, such as
the BIRM computer model (PDC-TR90-2), have been successfully used and correlated to actual
test results. Using this method is much more cost-effective than full-scale testing. Before
accepting the results of an engineering analysis from a manufacturer, have the calculations
carefully checked by a qualified structural engineer.
For the most current information available on vehicle barriers, contact NFESC,
Security Engineering Division, Code ESC66, 1100 23rd Avenue, Port Hueneme, California,
93043-4328, or call DSN 551-1581, or commercial (805) 982-1581.