Refer to: HNG-14 

Dennis H. O'Brien, P.E. 

Manager, Product Planning 

Industrial & Construction Products Division 

Valmont Industries, Inc. 

Valley, Nebraska 68064 

Dear Mr. O'Brien: 

Thank you for your April 4 letter to Mr. Thomas 0. Willett requesting Federal 

Highway Administration's (FHWA) acceptance of your company's breakaway 

luminaire support. With your letter, you enclosed a Southwest Research 

Institute (SwRI) report (Project No. 06-3116-516) dated March 1990, containing 

results of pendulum tests on the Valmont Industries Model DS60-TOOE486-15D, 

pole mounted on a cast aluminum transformer base, Valmont Part Number 0283093, 

manufactured by Akron Foundry Company. The test was conducted to assess the 

compliance of this hardware with FHWA breakaway requirements, which cite 

Section 7 of the 1985 American Association of State Highway and Transportation 

Officials' (AASHTO) Standard Specifications for Structural Supports for 

Highway Signs, Luminaires and Traffic Signals. 

The test used an instrumented l,BOO-pound pendulum fitted with a 10 stage 

crushable nose, which simulates a 1979 Volkswagen Rabbit. Details of the 

tested hardware are shown on enclosure 1. The measured and extrapolated test 

results are summarized below: 

Base tested Valmont No. 0283093 

356-76 Aluminum Alloy. 15-inch bolt 

circle. l-inch diameter bolts. Nuts 

torqued to approximately 200 foot-pounds. 

Pole used 

Mast arm lengths 

DS60-TOOE486-150, steel 

15.0 feet (two mounted perpendicular to 

the direction of impact) 

Luminaire mounting height 55 feet 

Test article weight 950 pounds (excluding base weight) 

Test speed 20 mph 

Velocity change 9.5 fps 

Stub height (actual)* 6.7 inches 

Calculated velocity change 16.7 fps at 60 mph 

*The reported stub height was 3.3 inches which is the measurement to the 

top of the anchor bolt. A shard of aluminum from the transformer base 

remained in place to a height of 6.7 inches. We concur with the SwRI 

conclusion that the protrusion above the 4-inch maximum does not 

constitute "substantial remains" as referred to in Section 7 of the 

AASHTO Standard Specifications for Structural Supports for Highway 

Signs, Luminaires and Traffic Signals. 
2 

The above information shows that the test results of the subject pole-base 

combination meet the change in velocity and stub-height requirements adopted 

by the FHWA. The 16.7 fps calculated change in velocity exceeds FHWA 

requirements by 0.7 fps. However, as the evidence you presented in your 

submission indicated, calculated changes in velocities nearly always over 

estimate the 60 mph results. Therefore, we will consider the results as 

meeting the new FHWA requirements. 

Your letter requested that our acceptance be granted with several hardware 

parameters specified that do not conform with the tested hardware, such as the 

bolt diameter, weight of pole with mast arm and luminaire, mounting height, 

and pole wall thickness. The evidence presented suggests the hardware, as 

tested, is marginally acceptable. Therefore, without further crash testing, 

we cannot accept the hardware changes you propose because we believe they have 

the potential for reducing the breakaway performance of the pole-base 

combination. Specifically, our acceptance is limited to the use of l-inch 

diameter anchor bolts, a maximum anchor bolt nut tightening torque of 

200 foot/pounds, and a maximum weight of pole and appurtenances of 

950 pounds, and a maximum luminaire mounting height of approximately 55 feet. 

In the test, machined washers were used on the bolts attaching the bottom of 

the base to the test pad. As these smoother surfaced washers probably created 

less friction than typical galvanized cut washers would have, the breakaway 

performance may have been enhanced. Thus, our acceptance is also limited to 

the use of similarly machined washers for the use with the anchor bolts. 

In summary, the transformer base you have designated Valmont Part 

Number 0283093, as shown on the enclosed drawings and subject to the 

limitations described above, is acceptable for use on Federal-aid highway 

projects if proposed by a State. This acceptance is limited to breakaway 

characteristics of the base and does not cover its structural features. 

Presumably, you will supply potential users with sufficient information on 

structural design and installation requirements to ensure proper performance. 

We anticipate that the States will require certification from Valmont 

Industries that the castings furnished have essentially the same chemistry, 

mechanical properties, and geometry as the casting used in the test, and that 

the castings will meet the FHWA change in velocity requirements. 

Since your company's breakaway support design is a proprietary item, to be 

used in a Federal-aid highway project it; (a) must be supplied through 

competitive bidding with equally suitable unpatented items; (b) the State 

highway agency must certify that it is essential for synchronization with 

existing highway facilities, or that no equally suitable alternate exists; or 

(c) it must be used for research or for a distinctive type of construction on 

relatively short sections of road for experimental purposes. Our regulations 
3 

Concerning Proprietary products are contained in Title 23 Code of Federal 

Regulations, Section 635.411, a copy of whjch is enclosed'for your 

information. 

Sincerely yours, 

L. A. Staron 

Chief, Federal-Aid and Design Division 

Enclosures 

Endorsement to FHWA Field Offices: 

Geometric and Roadside Destgn acceptance letter number LS-14 

The cast aluminum transformer base yalmont Dart number 0283093 is nominally 

the same as the Akron Foundry 76-l base which is the subject of a same-dated 

letter to Robert Sik of Akron Foundry (Geometric and Roadside Design 

Acceptance letter LS-15). The TB-1 base was also the subject of letters to 

Akron Foundry dated 6/29/M (LS-2) and l/12/89 (LS-4). 
NUMBERED DAY NUMBERED DAY 

(CASTING DATE) (CASTING DATE) 

YEAR YEAR 

L 17.06 ,-I 

12.25. f0.25. 

1.x RAD. 

SECTION A-A 

0.31’ 

0.6r 

I 

b------ 11 15*oo” .ocf -~ z 2.36 

----.----_____ 

I 

I I 

I I 

01 

I I 

I 

I 1 

_k_______-_--_- - 

/ 

-x 

0.66. -I 

SEE NOTE 1 RAD. 

L- MIC 4043 WIRE 0.25 P WITH APPROXIMATELY 5” 

OF WELD ON EACH OF THE (4) INTERNAL CORNERS 

NOTES: 

1. WALL THICKNESS VARIES-MINIMUM 0.15. IN MIDDLE 

TO A MAXIMUM 0.31” AT WELDED END. 

2. BOLT SLOT DRAFT ANGLE IS 10.. 

SECTION B-B 

BREAKAWAY BASE 
__ _ __ b_. - .---. 

r OLTIrL 2 

EIJCLOSURE : 1 

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