Sandia LabNews

Sometimes walls aren't the answer

Sandia group provides access delay options for high-value facilities

When most people think about physical security, they think about building walls to keep outsiders out of an area. Turns out walls aren’t always the answer.


“Solid walls aren’t always a good solution,” says Dave Swahlan, manager of Active Response and Denial Dept. 6475. “Any kind of solid barrier can provide cover for bad guys,” he says, which can make it harder to distinguish the early stages of an attack in time to mount a response.

In the past four and a half years, Sandia has conducted some 28 vehicle barrier-type tests at the Texas Transportation Institute in College Station, Texas. Sandia conducts tests for the Department of State on systems intended for perimeter security, checkpoints, and other security concerns.

Sandia has tested many different items and configurations such as barriers using large concrete blocks, ballards, sections of walls, Jersey barriers in multiple variations, and trucks configured and parked to serve as temporary barriers.

The Department of State has many facilities that require physical security specialized for their location and for the unique concerns of the facility and area. “Some facilities may only have a sidewalk-sized area for a barrier,” Dave says. “In others, utilities and footings in already-existing locations can impact how large a barrier can be.” He says that even facilities with limited space must still try to prevent facility breaches from big vehicles such as dump trucks.

The barrier system most recently tested used a modified box beam with additional items inside the beam to provide additional delay should an adversary try to breach the barrier by cutting it open.

During the test, a large truck was pulled forward and up to speed using a tow truck and pull system that disengaged at the last second after the vehicle had reached its target speed. Instruments and video footage are later used to analyze how the barrier behaves during an attempted breach.

Sometimes a barrier’s movement is an important part of the design. “Most people don’t realize that movement is important in barriers,” Dave says. “High deceleration loads with a rigid barrier can still sometimes bring the load into the area you’re trying to protect.” Stopping a truck too quickly, he says, can lead to bed-shearing, where the load continues forward from the truck.

Test engineer Mark McAllaster (6475) has been integrally involved in all the tests at College Station, from the design process to the logistics of arranging, funding, and purchasing testing equipment. He’s also responsible for assuring the test components were correctly manufactured, installed, and tested according to the proper protocol to make the design eligible for certification according to an ASTM F2656-07 standard.

“Each test allows engineers to modify designs to potentially improve a barrier’s performance,” Mark says.

Mark says the most recent barrier tested met its design goal, adding that “engineers always hope that a design can be improved upon.” Mark says the test’s biggest surprise happened after the crash test, when the barrier proved more resistant to common cutting techniques than originally estimated.

Sandia is contracted by the Department of State through FY09 for both new design and testing. The State Department is interested in creating a portfolio of generic designs that it can contract out and have built for deployment. Sandia expects to design six generic barriers and test each one. Those designs may be gateway designs or perimeter designs depending on what the State Department decides it needs for the near future.

Another purpose of the tests is to create a collection of barrier designs that are precisely understood, so that the Department of State can have them built any time it requires new barriers, rather than relying on off-the-shelf systems.

In the past, the Department of State ranked barriers using “K-ratings,” which set up criteria for a barrier’s breachability. But the Department is replacing the “K-ratings” with the ASTM standard so many organizations can compare barriers using the same standards and the results of tests will be interpreted the same way. Right now, that testing information is not all kept in the same place. Sandia hopes the standardization of information will create a single standard and a single repository for all the information.

The testing group had company for its most recent test. More than 40 home-schooled students observed the testing. Mark says the kids wanted to know the purpose for the testing. “They asked many very good questions,” Mark says, “and we talked about the purpose and the logistics of setting up the tests.”

The test was explained to them in advance so students would know what to look for. Mark also wanted the students to know how the truck was being propelled, so they would be assured there was not a driver who could be injured. Mark says the most enjoyable part was telling them “do not do this at home with your Dad’s truck.”

Mark says the kids were amazed by the crash of the truck into the barrier, adding that there was a lot of yelling and clapping as the truck plowed into the barrier. After the test, the students yelled, “Cool, we want to see you do it again!”