January 26, 2009

In Reply Refer To: HSSD/SS-159

Mr. Donnie Lewis
Roadway Construction Products, Inc.
3645 Elizabethtown Road
Clarkson, Kentucky 42726

Dear Mr. Lewis:

This letter is in response to your request for the Federal Highway Administration (FHWA) acceptance of omni-directional slip bases for wide flange beams used as sign supports for use on the National Highway System (NHS).

You requested that we find this sign support system acceptable for use on the NHS under the provisions of the National Cooperative Highway Research Program (NCHRP) Report 350 “Recommended Procedures for the Safety Performance Evaluation of Highway Features.”

Requirements
The FHWA memorandum, “ACTION: Identifying Acceptable Highway Safety Features” of July 25, 1997, provides further guidance on testing requirements of sign supports and outlines procedures for pendulum testing and estimation of high-speed breakaway performance of sign supports from low-speed pendulum test results.

Product description
The two different sizes of posts with the Roadway Construction Products, Inc. Omni-Directional Slip Bases that were tested to evaluate impact performance were the S4x7.7 and the W12x26 posts. Intermediate sizes of posts including S5x10, W6x9, W6x12, W8x18, W8x21, W10x22, and W10x26 were not tested but will be considered for acceptance based on interpolation of the test results. Detailed drawings of the slip base assembly are enclosed.

The S4x7.7 size post was impacted by the pendulum to evaluate omni-directional crashworthy performance. One test was conducted in the strong axis direction and a subsequent test was performed in the weak axis direction. The bolt torque was 37ft/lb at the slip base and 85 ft/lb on the hinge plate for each test.

The W12x26 size post was impacted by the pendulum to evaluate omni-directional performance. One test was conducted in the strong axis and a subsequent test was performed in the weak axis direction. The bolt torque was 62-63 ft/lb at the slip base and 70 ft/lb on the hinge plate for each test.

Test article installations
Each tested post was installed with a surrogate sign attached that represented the largest sign configuration according to the Texas Department of Transportation Standards under a Zone 1 design wind condition. Calculations determined the weight and mounting height of the surrogate sign for each of the post sizes.

Testing
The test article installations were tested at the TTI outdoor pendulum testing facility. The pendulum bogie was built according to the specifications of the Federal Outdoor Impact Laboratory's (FOIL) pendulum, and the frontal crush of the aluminum honeycomb nose of the bogie simulated the crush of an actual vehicle. Tests with pendulums are acceptable for most breakaway supports with the exceptions of base bending or yielding supports. Pendulum testing can be used on your company’s sign support systems as a surrogate for a full crash testing.

In each of the four tests, the supports slipped away from the base as designed and came to rest near the impact location. No significant damage was noted to the support or the slip base. Results from testing the Omni-Directional Slip Base show the support slipped away from the base as designed. For the S4x7.7 size post the resulting maximum change in velocity was 1.8 ft/s in the strong axis direction and 1.9 ft/s in the weak axis direction. For the W12x26 size post the resulting maximum change in velocity was 4.5 ft/s in the strong axis direction and 6.0 ft/s in the weak axis direction. In addition, the TTI extrapolated the high speed performance from the low speed pendulum tests. The test articles appear to perform appropriately to make such high speed extrapolations. For the S4x7.7 size post the high speed extrapolations yield acceptable change in velocity values of 3.58 ft/s and 3.29 ft/s respectively in the strong and weak axis direction. For the W12x26 size post the high speed extrapolations yield acceptable change in velocity values of 11.36 ft/s and 12.24 ft/s respectively in the strong and weak axis direction. It is noted that the upper hinge plates did not activate during any of the pendulum tests and this does not result in a failure of the evaluation criteria. A summary of the test results are enclosed.

Based on the test results, the Roadway Construction Products, Inc. Omni-Directional Slip Base for Wide Flange Beams as described above meet the appropriate evaluation criteria for the NCHRP 350 Test Level 3 devices. The beam sizes tested represent the minimum (S4x7.7) and maximum (W12x26) sizes acceptable. Additionally, the post sizes are limited to the conditions and configurations stated in the FHWA’s previous acceptance letters, SS-25 and SS-36, addressing standard I-beam sign support sizes utilizing generic slipbases.

This FHWA acceptance applies to the Roadway Construction Products, Inc. Omni-Directional Slip Base for Wide Flange Beams. These devices may be used at all appropriate locations on the NHS when selected by the contracting authority, and subject to the provisions of Title 23, Code of Federal Regulations, Section 635.411, as they pertain to proprietary products. This acceptance is based on the reported crash performance of your device and is not meant to address the limitations of testing or the systems’ installation, maintenance, or repair characteristics.

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

• This acceptance is limited to the crashworthiness characteristics of the devices and does not cover their structural features, nor conformity with the Manual on Uniform Traffic Control Devices.
• Any changes that may adversely influence the crashworthiness of the device will require a new acceptance letter.
• Should the FHWA discover that the qualification testing was flawed, that in-service performance reveals unacceptable safety problems, or that the device being marketed is significantly different from the version that was crash tested, it reserves the right to modify or revoke its acceptance.
• You will be expected to supply potential users with sufficient information on design and installation requirements to ensure proper performance.
• You will be expected to certify to potential users that the hardware furnished has essentially the same chemistry, mechanical properties, and geometry as that submitted for acceptance, and that they will meet the crashworthiness requirements of the FHWA and the NCHRP Report 350.
• To prevent misunderstanding by others this letter of acceptance designated as number SS-159 shall not be reproduced except in full. This letter and the test documentation upon which this letter is based, is public information. All such letters and documentation may be reviewed at our office upon request.
• The Roadway Construction Products, Inc. Omni-Directional Slip Base for Wide Flange Beams are patented products and considered proprietary. If proprietary devices are specified by a highway agency for use on Federal-aid projects, except exempt, non-NHS projects, they: (a) must be supplied through competitive bidding with equally suitable unpatented items; (b) the highway agency must certify that they are essential for synchronization with the existing highway facilities or that no equally suitable alternative exists; or (c) they must be used for research or for a distinctive type of construction on relatively short sections of road for experimental purposes. Our regulations concerning proprietary products are contained in Title 23, Code of Federal Regulations, Section 635.411.
• This acceptance letter shall not be construed as authorization or consent by the FHWA to use, manufacture, or sell any patented device for which the applicant is not the patent holder. The acceptance letter is limited to the crashworthiness characteristics of the candidate device, and the FHWA is neither prepared nor required to become involved in issues concerning patent law. Patent issues, if any, are to be resolved by the applicant.

Enclosures

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