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                Safety Eligibility Letter CC-98
  
  **Hardware Type:**
            Barrier Terminals and Crash Cushions
                          **Code:**
            CC-98
                          **Date:**
            04/09/2007
                          **Testing Criteria:**
            NCHRP 350
                          **Manufacturer:**
            Armorflex
                          **Device Description:**
            Armorwire Terminal End for cable barriers
                          **View PDF:**
            cc98.pdf (1.56 MB)
    
    
Skip to contentSkip to contentUnited States Department of Transportation - Federal Highway AdministrationDOT logo
U.S. Department of Transportation
**Federal Highway Administration**
400 Seventh St., S.W.
Washington, D.C. 20590April 9, 2007
In Reply Refer To: HSSD/CC-98
Mr. Dallas James
Managing Director
Armorflex Ltd.
P.O. Box 303 177
North Harbor,  Auckland, 1330, New Zealand
Dear  Mr. James :
Thank you for your letter requesting the Federal Highway  Administration’s (FHWA) acceptance of your company’s Armorwire Terminal End  (ATE) for Wire Rope Barrier Systems for use on the National Highway System  (NHS). Accompanying your letter were  reports of crash testing conducted by the University of Canterbury  and video of the tests. You requested  that we find this device acceptable as a Test Level 3 (TL-3) and TL-4 device  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.”
**Introduction**
  The FHWA guidance on crash testing of roadside safety  hardware is contained in a memorandum dated July 25, 1997, titled “INFORMATION:  Identifying Acceptable Highway Safety Features.”
A description of the ATE follows:
**Trigger Release Head and Post**
  The trigger  release head is fabricated from hot rolled steel galvanized after fabrication in  accordance with AS/NZS 4680.  The hot rolled steel complies with the following specifications; ASM  A36, AS 3678-250, JISG3101 – SS400, and BS4360 – 43A. The trigger release head is attached to the  top of the first post (same section as Steel Line Post) by a weld around the  back side of the post only. This head  effectively joins the two cables that are attached to the ground strut to the  three cables forming the barrier.
**Steel Line Posts**
  These posts  are fabricated from 42 x 97 x 3 mm flat sided oval “Yard rail.” Standard grade for this section is:  Ptd/NOPC:AS 1163. Three notches are cut  into the sides of the posts to hold and retain the three cables. The posts are 1220 mm long and Hot Dip  Galvanized after cutting in accordance with AS/NZS 4680. The cable heights are 530, 640 and 750 mm above  ground level.
**Plastic socket**
The sockets  are molded from high density polyethylene (HDPE) and form a 350 mm deep socket  in the concrete foundation that is 5 mm larger than the post outside  dimensions.
**Plastic post cap and cable retaining strips**
  The cap and  retaining strips are molded from PVC with UV stabilizers. The cap is fitted into the top of the posts  with two 350 mm long strips of plastic protruding down the inside of the post  to help retain the cables.
**Barrier Cables**
  The three  cables are constructed using 19 mm 3 x 7 strand galvanized cable, pre-stretched  by 
  35 percent. The cable specification is DSR Galvanized  320, lay – RHRL. The cables are  tensioned to a nominal 25 kN at an ambient temperature of 21 degrees  Celsius. The cable heights are 530, 640  and 750 mm above ground level. The cable  breaking strain has an ultimate tensile capacity of 110kN.
**Cable Fittings**
  All cable  terminations are achieved with self-swaging fittings. These fittings consist of three tapered  "jaws" that fit inside a tapered casing and a tail piece that is  screwed into the rear of the casing.  These fittings have been failure tested to 240 kN.
**Cable Adjustment**
  The cable tension  is adjusted using turnbuckles fabricated from 10x20mm low tensile steel side arms, and welded to  30mm thick end "washers.”
**Terminal End Anchor Foundation**
  The anchor  point foundation consists of three 300 x 1000 mm deep holes at 1000 mm centers  filled with 25 MPa concrete. The rebar  cages are constructed from D12 rebar, complete with M24 studs, and are inserted  into the concrete so that the ground strut can be bolted to the protruding  studs. The ground strut connects all  three foundations together to form one unit.
**Ground Strut**
  The ground  strut is fabricated from RHS and Angle sections of mild steel made to match the  dimensions of the anchor foundations.  The mild steel conforms to the following specifications ASTM A36, AS  3678-300, JISG3101 – SS400, BS4360 - 43A.
**Terminal Cables**
  The  terminal cables are two 2000 x 19 mm wire rope assemblies complete with M24 x  345 mm HDG swage fittings. The wire rope  is 19 mm 6x9/9/1 IWRC Galvanized.
**Line Post Foundation**
  The line  post foundations consist of 300 x 750 mm deep holes at various centers filled  with 
  25 MPa  concrete (see figure 2.1.1). One  D10x175 diameter rebar ring is placed in each foundation 100 mm  down from the top. One plastic socket is  pushed into the concrete so that the top lip of the socket sits flush with the  top of the concrete.
**Fasteners**
  The ATE is  assembled with standard galvanized fasteners.  The bolts and studs are galvanized
Grade 4.6  with matching nuts and heavy washers.
The key  element of the ATE terminal end is the trigger post assembly. This assembly connects the terminal cables  and the barrier cables by placing the adjustment nuts on the rope fittings into  slots located in the trigger release head.  When a vehicle impacts on the end of the barrier, the two terminal  cables projecting from the ground strut are forced downward out of their slot  in the terminal head. This allows the  trigger post to bend backward under the tension of the barrier cables, thereby  releasing the tension from the barrier.  The trigger release head is welded to the back of the trigger post allowing  the head to detach on impact and ensuring the barrier cables are fully released  when a vehicle impacts at the end of the terminal.
**Testing**
  Three different test article installations were used for the Armorflex  ATE test program.
The installation details are as follows:
**Test  057053302 (Test 3-30) and Test 057053351 (Test 3-35)**
  The test article installation for these two tests consisted of 68 meters  of barrier installed in prepared and existing soils at the high speed vehicle  test facility, running parallel to the main test track. The first 38 meters of the barrier was  installed standard soil conforming to the NCHRP 350 specifications. The last 30 meters of the installation was  located in the in situ soil. All of the  impacts occurred on posts installed in the prepared ground. The upstream end of the installation was  fitted with the ATE, and the downstream end fitted with a plain ground anchor  that did not form part of the product test.
**Test  057053321 (Test 3-32)** 
  The test article installation for this test consisted of 35.5 meters of barrier  installed in prepared and existing soils at the high speed vehicle test  facility, and laid out at an angle of 15 degrees to the main test track. The first 25.5 meters of the barrier was  installed in the prepared ground. The  last 7 meters of the installation was located in the in situ soil. All posts were installed with 
  2 metre post spaces. The distance  between posts 2 and 3 (not counting the trigger post) was 
  2.96 meters and the gap between posts 4 and 5 was 3.9 meters. All of the impacts occurred on posts  installed in the prepared ground. The  upstream end of the installation was fitted with the ATE, and the downstream  end fitted with a plain ground anchor that did not form part of the product  test.
**Test  057053392 (Test 3-39)**
  The test article installation for this test consisted of 15.8 meters of  barrier installed in prepared soils at the high speed vehicle test facility, and  laid out at an angle of 20 degrees to the main test track, with the terminal  end located at the downstream end. The entire  length of barrier was installed in standard soil conforming to the NCHRP 350  specifications. All posts were installed  with approximately 2 metre post spaces.  The three cables at the upstream end of the installation were attached  to a section of concrete median barrier, acting as an anchor. The concrete anchor was remote from the point  of impact on the terminal end and barrier.
**Design Changes During Test Program**
  There were several design changes made to the Armorflex ATE during the  testing program. The NCHRP 350 allows  changes to be made to a test article during the testing program provided good  engineering judgment indicates that the design change would not adversely  affect the outcome of a test that has already been passed. Under these circumstances it is considered  reasonable not to repeat that test.
The chronological order of testing was as follows - Test 057053392, Test  057053321, 
  Test 057053351, Test 057053302.  All of the design changes were made after Test 057053321 and before Test  057053351. The design changes were as  follows:
**Trigger  Post** - To prevent the vertical strain plates (Part 1 of figure 2.1.2) of the  trigger post spreading during impact, the top of the trigger post was notched  and a M8x75mm grade 
  4.6 bolt was fitted. The anchor  cable connection to the trigger post was modified by slotting the top plate to  allow the common washer for the two front cables to sit higher relative to the  ground strut cable plates (Part 4 of figure 2.1.2). This increases the bearing area for the  washer and allowed a retainer pin to be fitted to prevent the cables dropping  when the terminal end is assembled.
This modification was implemented as it was felt that the vertical  strainer plates may bend under high impact loads on the wire rope barrier. No damage was observed to the vertical  strainer plates of the trigger head in the test completed prior to the  modification.
**Ground  Strut** - The ground strut was changed from a 75 x 50 x 5mm RHS with the cables  placed on top to a strut manufactured from 50 x 100 x 5mm RHS and angle with  the cables located inside of the RHS.  The angles at which the cables come up from the strut to the trigger  post were not altered. This design  change was made to reduce the height of the strut and simplify its construction.
**Post 1  ‘J’ Bolts** - Line post was modified from a notched post to a plain post with M8,  4.6 grade, J bolts fitted to capture the barrier cables. The expectation was that the modification  would prevent the released cable fittings from being carried along with the  impacting vehicle in end-on impacts.  This modification did not prevent the release of the cable fittings, as  evidenced by Test 057053302. All  production barriers will use standard line post for post1.
**Cable  Retaining Strips** – The retaining strips are used as part of the top  cap fitted to the top of the line posts.  The strips 340 mm long and are made from white, 1 mm thick PVC  plastic. The strips act to both cover  the notches in the posts, and to help prevent the cables from  "unzipping" in side impacts.
The design changes would have no adverse effect on the tests completed  before the changes were made and no tests were repeated following the design  changes.
The Test Data Summary Pages are attached to this letter for  reference.
**Findings**
The  Armorflex ATE was judged to have satisfied the NCHRP 350 evaluation criteria  for Test Level 3 when installed on Armorflex Armorwire wire rope barrier  embedded in a standard soil foundation. Test  057053302 (3-30) allowed controlled penetration of the vehicle and brought it  to rest, while incurring localized damage near the occupant compartment. The ATE gated cleanly for tests 057053321(3-32)  and 057053392 (3-39). For Test 057053392  (3-39) the vehicle impact point was closer to the end of the terminal than is  generally recommended, however developmental testing showed a design flaw that  the reverse-direction test is supposed to expose. We concur that the impact  point of the successful 3-39 test was appropriate. For Test 057053351 (3-35), the ATE  successfully redirected the vehicle from the length of need.
You also requested that the Armorflex ATE be an acceptable  terminal for other cable/wire rope systems where the number of cables, the  cable heights and tension are the same as Armorwire. We concur in this request.
Although the barrier performed well under ideal test impact conditions  the likelihood of passenger car  underrides of any cable system may increase as the post spacing increases,  particularly when the barrier is installed on non-level or slightly irregular  terrain and the cables are not restrained from lifting at each post.  Consequently, some transportation agencies have limited post spacing to  approximately 6 m for cable barriers. The dynamic deflection of the barrier is  likely to increase when it is installed along the convex sides of horizontal  curves, and when distances between anchorages exceed the normal 100 m test  length.
The results of the testing met the FHWA requirements and,  therefore, the devices described in the various requests above and detailed in  the enclosed drawings are acceptable for use on the NHS under the range of  conditions tested, when proposed by a highway agency.
Please note the following standard provisions that apply to  the FHWA letters of acceptance:
Our acceptance is limited to the crashworthiness  characteristics of the 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 CC-98, 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 Armorwire ATE is a patented device and is considered  "proprietary." The use of  proprietary devices *specified by a highway agency* for use on Federal-aid  projects must meet one of the following criteria: (a) it must be supplied  through competitive bidding with equally suitable unpatented items; (b) the  highway agency must certify that it is essential for synchronization with  existing highway facilities or that no equally suitable alternative 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 concerning proprietary  products are contained in Title 23, Code of Federal Regulations, Section 635.411,  a copy of which is enclosed.
  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.Sincerely yours,
			Signature of John R. Baxter
			John R. Baxter, P.E.
				Director, Office of Safety Design
				Office of Safety2 Enclosures

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