Federal Highway Administration
400 Seventh St., S.W.
Washington, D.C. 20590
April 6, 2006
In Reply Refer To:HSA-10/B-145
Ronald K. Faller, Ph.D., P.E.
Midwest Roadside Safety Facili ty
University ofNebraska, Linco ln
527 Nebraska Hall
P.O. Box 880529
Lincoln, Nebraska 68588-0529
Dear Dr. Faller:
Thank: you for your letter of December 16, 2005. requesting the Federal Highway Administration (FHWA) acceptance ofa Test Level 5 (TL- 5) Bridge Rail developed in cooperation with the Nebraska Department of Roads. Accompanying your letter were reports of crash testing you conducted at the Midwest Roadside Safety Facili ty along with video and photographic documentation of the test s. You requested that we find this railing acceptable for use on the National Highway System (NHS) under the provisions of the National Cooperative Highway Research Program (NCHRP) Report 350 "Recommended Procedures for the Safely Performance Evaluation of Highway Features."
The FHWA guidance on crash testing of roadside safety hardware is contained in a memorandum dated July 25, 1997, lilled "INFORMATION: Identifying Acceptable Highway Safety Features."
A briefdescription of the barrie r follows:
The 121-ft 6-in.long, aesthetic post and beam concrete bridge rail con sisted of a "ribbed" reinforced concrete beam 14-in. wide by 3D-in. deep with a 42-in. top mounting height which was cast in place with a 2-in. overhang on the front face of the posts parallel to the roadway and flush with the backs ide of the posts. The two " ribs" extend l-½ in. from the face of the beam. Both upstream and downstream edges of the posts were tapered back 2 in. from the face of the post to minimize tire snagging of passenger vehicles. Fifteen bridge posts, measuring 1O.5-in. wide by 30-in. long by 12-in. high. were used to support the bridge rail. Bridge posts were spaced 8 ft - 6 in. on centers along the length of the bridge railing. The concrete used for the bridge rail and posts had a minimum compressive strength of 5.000 psi.
A minimum concrete cover of 2 in. was used for all the rebar placed within the bridge rail and posts. All steel reinforcement in the bridge rail and posts was Grade 60 epoxy-coated rebar. The bridge rail and post dimensions, including reinforcement details. arc shown in the enclosed drawings for reference.
Full-scale tractor-semi trailer testing was conducted on the barrier. The report explai ns that concrete barriers with similar features have been successfully crash tested with 820C and 2000P vehicles . We concur that the single TL-5 test is the only one requ ired to qualify this barrier.
|NCllRP Report 350 Test 5· 12|
|Report Number||TRP 03·1 48·05|
|Mass of Test Vehicle||35,822 kg (78,975 pounds)|
|Impact Speed||79.6 km/h 149.4 mph)|
|OIV Longitudinal||0.91 m/s (2.99 ft/s )|
|OIV Latera||5.50 m/s (18.05 ft/s)|
|Ridedown Longitudinal||8.05 g's/-6.98 g's|
|Ridedown Lateral||6.06 g's/-7.91 g's|
|Dynamic Deflection||285 mm (11.2 in.)|
|Working Width||1916 mm(75.4 in.)|
The test showed that the aesthetic open concrete bridgerail adequately contain ed and redirected the vehicle with controlled lateral displacements of the rail. There were no detached elements or fragmen ts which showed pote ntial for penet rating the occupant compartment nor presented undue hazard to other tra ffic. There were no deformations or intrusions into the passenger compartment that cou ld have caused serious injury. The test vehicle did not penetrate or roll over the barrier, and it remained upright without intruding into adjacent traffic lanes. Vehicle roll, pitch, and yaw were good to moderate. As shown above, while the dynamic deflection was about 11 in., the Working Width (deflect ion plus vehicle overhang plu s width of the rail system) was slightly over 6 ft.
The results of the testing met the HCHRP Report 350 requirements and, therefore, the device described above and detailed in the enclosed drawings is acceptable for use on the NHS as a TL-5 bridge rail, under the range ofconditions tested, when proposed by a State.
Please note the following standard provisions that apply to the FHWA letters of acceptance:
John R. Baxter, P.E.
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