Federal Highway Administration
1200 New Jersey Ave. S.E.
Washington, D.C. 20590
August 17, 2007
Mr. Jeff Tumlinson
530 Jesse Street
Grand Prairie, Texas 75051
Dear Mr. Tumlinson :
In your letters of June 4 and June 20 2007, you requested the Federal Highway Administration (FHWA) acceptance of your company’s Fiberglass Sign Support Systems and Bolt Down Breakaway Slip Base Assembly 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 Safety Performance Evaluation of Highway Features.” To support your request, you provided copies of the Texas Transportation Institute’s (TTI) pendulum test reports entitled “Pendulum Testing of the International FiberLok Fiberglass Sign Support System.”
Sign supports should meet the guidelines contained in the NCHRP Report 350, “Recommended Procedures for the Safety Performance Evaluation of Highway Features.” 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.
Three International FiberLok Fiberglass Sign Support Systems were tested.
The 6 inches by 6 inches (152 mm x 152 mm) I-beam system consists of:
The inclined 3 inches by 3 inches (76 mm x 76 mm) I-beam system consists of:
The International FiberLok Bolt Down Breakaway Slipbase Assembly consists of:
Sample drawings that show the design details of the International FiberLok Fiberglass Sign Support System and Bolt Down Breakaway Slipbase Assembly are enclosed. It is noted that bracing is added to the composite I-beams at the bottom of the sign support.
Test article installations
The 6 inches by 6 inches (152 mm x 152 mm) I-beam system was installed with 57-1/2 inches by 24 inches by 3/4 inch (1460 mm x 610 mm x 19 mm) steel plated sign panel mounted at 7.6 ft (2.3 m) to the bottom of the sign panel. The 3 inches by 3 inches (76 mm x 76 mm) system was installed with a 48 inches by 48 inches by 5/8 inch (1219 mm x 1219 mm x 16 mm) plywood sign panel mounted at 7.6 ft (2.3 m) to the bottom of the sign panel. Both systems were mounted on a steel reaction plate. The Bolt Down Breakaway Slipbase Assembly with an 8 inch by 5 inch (203 mm x 127 mm) I-beam was installed with a 57 inches by 24 inches by 3/4 inch (1460 mm x 610 mm x 19 mm) steel plated sign panel mounted at 7.6 ft (2.3 m) to the bottom of the sign panel.
The test article installations were tested at the TTI outdoor pendulum testing facility. The pendulum bogie was built according 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. I agree that pendulum testing can be used on your company’s Sign Support Systems as a surrogate for a full crash testing. In addition, TTI extrapolated the high speed performance from the low speed pendulum tests. I agree that the test articles appear to perform appropriately to make such high speed extrapolations. The high speed extrapolations yield acceptable change in velocity values.
In each of the three tests the supports slipped away from the base as designed and came to rest near the impact location. No damage was noted to the support or the slipbase casting in the test with the 6 inch I-beam system. In the test with the inclined 3 inch I-beam system, no damage was noted to the slipbase stub and there was a vertical hairline fracture on the impact face of the support. Results from testing the Bolt Down Breakaway Slipbase show the support slipped away from the base as designed. For each of the three tests the entire systems could be reused after the impact. A summary of the test results are enclosed.
Based on the test results, I agree that the International FiberLok Fiberglass Sign Support Systems and the Bolt Down Breakaway Slipbase Assembly as described above meet the appropriate evaluation criteria for NCHRP 350 TL-3 devices. The I-beam sizes tested represent the minimum size acceptable for each mounting type. The maximum size acceptable is limited to the conditions and configurations stated in 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 Fiberlok’s steel and fiberglass composite systems but is limited to bi-directional impacts on the Bolt Down Slipbase Assembly and the composite fiberglass system. Also, this FHWA acceptance limits the inclined base systems as crashworthy in one direction. 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.
Please note the following standard provisions that apply to the FHWA letters of acceptance:
George E. Rice, Jr.
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