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                Safety Eligibility Letter B-96
  
  **Hardware Type:**
            Longitudinal Barriers and Bridge Rails
                          **Code:**
            B-96
                          **Date:**
            08/30/2002
                          **Testing Criteria:**
            NCHRP 350
                          **Manufacturer:**
            Marion Steel Company
                          **Device Description:**
            posts/attachment hardware for 3-strand cable g.r.@TL-3
                          **View PDF:**
            b96.pdf (498.24 KB)
    
    
August 30, 2002
HSA-10/B96
Mr. Rick Mauer
  National sales Manager
  Marion Steel Company
  Post Office Box 837
  Greenland, New Hampshire 03840-0837
Dear Mr. Mauer:
Your January 8 letter to Mr. Lawrence A. Staron, former Chief of the Federal 
  Highway Administration's Federal-Aid and Design Division, was forwarded to me 
  for a response.  Because you requested acceptance of a modified cable barrier 
  design that used a new anchoring system, you subsequently asked Mr. Richard 
  Powers of my staff to withhold action on the barrier proper until the new terminal 
  design was accepted.  An interim review of the test report also revealed some 
  discrepancies between the report text and figures. A revised report, dated February 
  2002 and entitled "NCHRP Report 350 Test 3-11 of the Wire Rope Barrier with 
  Marion Steel 6 Kg/M U-Channel Posts" was sent to Mr. Powers by Dr. Dean Alberson, 
  Texas Transportation Institute Research Engineer on March 4.  The proprietary 
  cable anchor was finally accepted on August 29, following additional tests and 
  significant design modifications.  However, the terminal changes would have 
  no effect on the performance of the length of need section of barrier that you 
  tested.
Your tested installation was a 3-strand cable guardrail installed as a median 
  barrier with the upper and lower cables on the field side of the posts and the 
  middle cable on the impact side.  The cables were 19-mm diameter 3 x 7 wire 
  rope and their heights above the ground were approximately 520 mm, 650 mm, and 
  775 mm.  The length-of-need posts were standard 1664-mm long 6 kg/m U-channel 
  posts installed on 2-meter centers with trapezoidal soil plates just below the 
  ground line.  The cables were attached to the line posts with proprietary 6.4-mm 
  diameter locking hook bolts.  The test installation was anchored at both ends 
  with TTI's proprietary Cable Guardrail Terminal and each cable was tensioned 
  to 25 kN (5600 lbs.) for the ambient temperature of 21 degrees C.   Design details 
  can be seen in Enclosure 1, but note that changes have been made to the terminal 
  itself and its final design is somewhat different from that shown on Enclosure 
  1A.
NCHRP Report 350 Test No. 3-11 was run on the 101.4 meter test installation, 
  with the pickup truck impacting approximately 20 m from the upstream anchor 
  at 25.3 degrees and 100.7 km/h.  The dynamic deflection of the cable barrier 
  was 1.99 m with the 2.0 m post spacing.  By comparison, the dynamic deflection 
  of the standard 3-cable median barrier in test 3-11 was 3.4 m.  The reduced 
  deflection seen in your test can be attributed to the combination of higher 
  cable tension, the reduced post spacing, and the use of locking hook bolts to 
  develop the full strength of each post before the cables disengage.  Summary 
  test results are shown in Enclosure 2.
Test 3-10, an 820-kg car impacting at 20 degrees, was not run.  However, based 
  on earlier tests of Washington State's cable median barrier that has cables 
  at the same heights (but with significantly less tension) and posts on 5.0 m 
  centers, I am willing to waive test 3-10.
The 3-strand cable barrier described above is acceptable for use on the National 
  Highway System as an NCHRP Report 350 test level 3 (TL-3) barrier.  Although 
  tested as a median barrier, this design may be used as a roadside barrier with 
  all three cables on the traffic side of the posts at heights of approximately 
  610 mm, 685 mm, and 760 mm above the ground.  Your posts and locking hook bolts 
  may also be used with the current NCHRP Report 350 concrete anchor block terminal 
  and the standard 3-strand cable rail with its reduced cable tension, 5.0-m post 
  spacing, and a dynamic deflection of 3.5 m. Use of the patented locking hook 
  bolts is likely to reduce the barrier dynamic deflection to some extent.
Since both the TTI anchor and the locking hook bolts at each line post are 
  considered proprietary, the provisions of Title 23 CFR, Section 635.411 apply 
  to the use of this system on federally funded projects.
Sincerely yours,
(original signed by Janet A. Coleman)
for
Carol H. Jacoby, P.E.
  Director, Office of safety Design
2 Enclosures U.S. DEPARTMENT OF TRANSPORTATION

**Federal Highway Administration**

1200 NEW JERSEY AVENUE, SE

WASHINGTON, DC 20590

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