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Texas HT Barrier ZOI

State IA
Description Text I am trying to establish a TL-5 ZOI chart for the Texas HT barrier, based on the 80,000 pound truck test that was performed by TTI back in 1984. Would you be able to provide me with such a chart, or supply me with the materials I would need to develop the chart on my own?
  • Permanent Concrete Barriers
Other Keywords none
Date November 15, 2010

Response The crash test for the 50 in. tall combination rail (test no. 2416-1) provides limited answers to the ZOI question. First, the barrier installation was not long enough to redirect the truck or allow it to stabilize before it reached the end of the system. As such, the cargo box continues to roll/ lean onto the barrier more and more until the barrier ends and the vehicle rolls onto its side. Thus, the maximum lateral extent can only be observed during the time of contact. Also, the camera views are not ideal as the overhead does not capture the downstream end of the barrier and the downstream camera is not directly in line with the barrier. This makes getting accurate distances from the test difficult and getting the vertical locations of the box as it rotates very difficult.

What I was able to gather from the test was a maximum lateral distance behind the barrier of approximately 4.5 ft. ZOI has typically been shown by dimension based on the top front of the barrier, so this extension would be 5.5 ft from the front of the steel tube (to be conservative you could use 6 ft).
Also, the height of the barrier prevented the bottom of the box from getting over and behind the rail, so the ZOI would not need to extend below the top of the rail as was recommended in the TL-4 ZOI.
Date November 29, 2010

Response Should I assume the 5.5-foot ZOI extends all the way up to 13.5 feet above the ground? Or do you think the maximum lateral extent of the truck occurred at some height below 13.5 feet?

We may consider limiting intrusion by raising the height to the top of the railing. Do you have any "rules of thumb" that we could use to estimate how much the intrusion would be reduced for each additional inch of barrier height?
Date November 30, 2010

Response The maximum lateral extent was lower than the top height of the box when the vehicle was at rest (I'm assuming that distance is the 13.5 ft you are referring to). However, the vertical position of the box is not easily obtainable from the test video. Also, since the box slid off the barrier and rolled onto its side before it had a chance to right itself (return to an upright position), the path of the box on its return is unknown " and very well could be more critical than the path to maximum extent. Therefore, I would recommend treating the max lateral distance as the boundary for all heights " ZOI would be a box of width 5.5 ft. We just don't have enough data to better define the ZOI.

There is not a rule of thumb to adjust the lateral extent of the box. We simply do not have the data from multiple TL-5 tests at multiple heights to establish such a relationship. Also, be carefull raising the height of the barrier. Extending the height of the steel rail without raising the height of the concrete parapet with it (extending the rail support posts) will reduce the strength of the rail and possibly lead to failure of the support posts and/or anchor bolts.
Date November 30, 2010

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