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Our structures department is in the process of developing guidance for their bridge designers. To comply with LRFD, the are asking me for a 54" tall TL5 barrier. Does MwRSF know of any TL5 crash tested barriers that are 54" tall?

Is it possible to modify the MwRSF TL5 barrier to be 54" tall? Does it make much sense to construct a 54" tall barrier verses a 42" barrier to protect a pier from a semi truck leaning over and striking the pier of a bridge? How far has TTI gotten with their research on the LRFD 400 KIP load requirement?

To date, I am aware of one TL-5 barrier that was 54 in. tall and one TL-6 barrier that was 90 in. tall. These barriers are described and referenced in MwRSF Research Report No. TRP-03-149-04. A copy of this report is included in this email. Other TL-5 barriers are noted in this report as well. MwRSF developed two TL-5 bridge railings and median barriers that are not included in this report. Those barrier systems and associated reports have been sent to you previously. If you need additional copies, I can send them to you in pdf format.

For the MwRSF barrier, a 54 in. median version could be developed as long as the additional height did not penetrate the head ejection envelope. This change would cause the barrier width to increase significantly and without knowledge as to how much trailer lean would still occur over the barrier.

The upper barrier section would also get more complex and costly. What distance is available from the front face of a barrier to the front face of a pier? Are you more concerned with vehicles hitting the piers head on or from allowing the box to lean over and snag on the pier? Remember that the box lean will not impart as high as a load as would a head-on impact. Head on impacts could be prevent using long TL-5 barriers that provide adequate length of need protection. I recall that we had 1 or 2 Pooled Fund problem statements that addressed this issue but were held back to wait for the TTI/TxDOT study to be completed.

I received a note from Gene Buth with regard to the site where updates can be found pertaining to the TTI/TxDOT pier protection project. See link below:

It is TPF-5(106) and it is at:

http://www.pooledfund.org/projectdetails.asp?id=338&status=6