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FHWA Home / Safety / Roadway Departure / Safety Eligibility Letter

Safety Eligibility Letter B-190

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U.S. Department of Transportation
Federal Highway Administration

1200 New Jersey Ave. S.E.
Washington, D.C. 20590

March 20, 2009

In Reply Refer To: HSSD/B-190

Mr. Jorge D. Hinojosa, P.E.
Bexar Concrete Works I, Ltd.
P.O. Box 700250
San Antonio, TX 78270

Dear Mr. Hinojosa:

This letter is in response to your request for the Federal Highway Administration (FHWA) acceptance of a roadside safety system for use on the National Highway System (NHS).

Name of system:MF-Shape Concrete Traffic Barrier with Quick-Bolt Connection
Type of system:Portable concrete barrier system
Test Level:MASH-08 Test Level 3
Testing conducted by:Texas Transportation Institute
Date of request:November 19, 2008

You requested that we find this system acceptable for use on the NHS under the provisions of the proposed American Association of State Highway and Transportation Officials’ Manual for Assessing Safety Hardware 2008 (MASH-08).

Requirements
Roadside safety systems should meet the guidelines contained in the NCHRP Report 350. The FHWA Memorandum “Identifying Acceptable Highway Safety Features” of July 25, 1997, provides further guidance on crash testing requirements of longitudinal barriers. You have chosen to anticipate the adoption of the MASH-08, an option that FHWA has offered with the understanding that additional testing may need to be done if changes to the test criteria are made before MASH-08 is formally adopted.

Description
The precast segments used in the construction of the test installation were 30 feet in length and had a standard F-shape profile. The barrier segments were 32 inches in height, 24 inches wide at the base, and 9-1/2 inches wide at the top. Horizontal reinforcement consists of eight #5 bars placed symmetrically about the vertical centerline of the barrier. Vertical reinforcement consists of #4 bars spaced 12 inches on center. Spacing of the vertical bars is reduced to provide additional strength within 5 feet of the barrier ends.

Ten inch long sections of 1 1/2-inch diameter PVC pipe are horizontally cast into the end of each segment that provide access for feeding the threaded rod from one barrier into another and for securing the nuts and washers once the rod is in place. A 3-inch diameter, 12-inch long bolt retraction cavity extends from the hand hole further into the barrier. Two #5 “hairpin” shaped bars extend horizontally along the top and bottom of the PVC sleeve, hand hole, and bolt retraction cavity. Three #5 stirrups enclosed these hairpins bars to provide further strength to the connection. The barrier connection is made with two 7/8-inch diameter, 2 ft 1-inch long steel rods. A 3-inch square x 3/8-inch thick plate washer and nut are used on each end of the threaded rod.

The completed test installation consisted of eight barrier segments connected together for a total length of approximately 240 ft. The concrete was specified to be 3600 psi and reinforcing steel was grade 60. The threaded rods were fabricated from SAE Grade 5 or equivalent steel, and the plate washers were A-36 steel. Details of the barrier segment are shown in the enclosure for reference.

Crash Testing
Two full-scale crash tests are required under the proposed Manual for Assessing Safety Hardware. Test 3-10 using a 2420-pound passenger car has already been conducted on the New Jersey safety shape concrete barrier under NCHRP Project 22-14(2) at the Midwest Roadside Safety Facility. As the Jersey shape is known to be a “worst case scenario” among rigid barriers, Test 3-10 will be waived for the Bexar concrete traffic barrier. Test 3-11 using a 5000-pound quad-cab pickup was conducted to evaluate the strength of the barrier connection and for determining the maximum barrier deflection or working width.

The Test Data Summary Sheet for test 4000001-BCW1 is enclosed for reference and shows the maximum occupant impact velocity was 22.3 feet per second (40 fps is allowed) and the maximum ridedown acceleration was 13.1 G’s (20 G’s is allowed.) Both of these maximum values were the lateral components. The maximum dynamic deflection was 31.0 inches. The maximum roll angle was 17 degrees and the vehicle exited the barrier within the “exit box” limits.

Findings
The MASH-08 Test 4000001-BCW1 met the appropriate evaluation criteria, therefore, the Bexar Concrete Traffic Barrier described above and detailed in the enclosed drawings is acceptable for use on the NHS under the range of conditions tested, when such use is acceptable to a highway agency.

Please note the following standard provisions that apply to the FHWA letters of acceptance:

 

Sincerely yours,

Signature of David A. Nicol

David A. Nicol, P.E.
Director, Office of Safety Design
Office of Safety

Enclosures

Page last modified on June 24, 2011.
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