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                Safety Eligibility Letter B-112
  
  **Hardware Type:**
            Longitudinal Barriers and Bridge Rails
                          **Code:**
            B-112
                          **Date:**
            03/14/2003
                          **Testing Criteria:**
            NCHRP 350
                          **Manufacturer:**
            Midwest Roadside Safety Facility
                          **Device Description:**
            Steel strap tie-down system for PCB on bridge decks @ TL-3
                          **View PDF:**
            b112.pdf (54.36 KB)
    
    HSA-10/B112

March 14, 2003
HSA-10/B112
Ronald K. Faller, Ph.D., P.E.
Research Assistant Professor
Midwest Roadside Safety Facility
P.O. Box 880601
Lincoln, NE 68588-0601
Dear Dr. Faller:
In your letter dated October 24, 2002, you requested formal
Federal Highway Administration acceptance of a steel strap tie-down system
designed to limit the deflection of temporary concrete barrier when used on a
bridge deck or in other locations where the barrier's normal design deflection
would not be tolerable.
The proposed design was tested using a total of sixteen
3.8-m long sections of the Iowa pin and loop F-shape barrier that was formally
accepted as an NCHRP Report 350 barrier at test level 3 (TL-3) in Mr. Dwight A.
Horne's October 10, 1997 letter (acceptance letter B-41). These barriers were set 305 mm from the
outside edge of the simulated bridge deck.
The tie-down system consisted of a trapezoidal-shaped 6.4-mm thick A36
steel strap at each barrier joint through which the connecting pin between
adjacent barrier segments is inserted.
This strap, shown in the enclosure to this letter, was then attached to
the concrete bridge deck with two 19-mm diameter x 57-mm long ISO Class 8.8
bolts set into 19-mm diameter Red Head drop-in anchors. These anchors were embedded 81mm into the
concrete deck. Eleven tie-down straps
were used. The test vehicle impacted the barrier 1.2 upstream of the gap
between segments 8 and 9. At that point,
there were four strap anchors upstream of the impact point and seven anchors downstream. The first three joints upstream of the
impact and the last downstream joint were not anchored. Thus, the impact point
was approximately 30 m downstream from the approach end of the test
installation and approximately 14 m downstream from the first strap anchor
As noted in your August 16, 2002 report entitled
Development of a Tie-down System for Temporary Concrete Barriers, the design
was successfully tested to NCHRP Report 350 TL-3. Dynamic deflection of the barrier was 960 mm, with one segment
deflected over the edge of the bridge deck and the two adjacent segments
partially deflected over the edge.
However, the pin and loop connections and the intact tie-down straps
along the rest of the barrier segments held the deflected segments in place on
the bridge as desired. Two tie-down straps in the immediate impact area were
pulled out of the deck and three adjacent straps showed extensive deformation,
as did several of the connecting pins and barrier loops. However, none of the
barrier pin and loop connections failed.
Impacts closer to the unanchored segments at either end of the bridge
can be expected to result in larger
lateral barrier deflections.
Based on staff review and recommendations, I agree that the
tested design satisfies NCHRP Report 350 evaluation criteria at TL-3 and that
this design may be used on the National Highway System to limit the deflection
of temporary concrete barriers located on a concrete surface.

Sincerely
yours,
(original signed by Michael S. Griffith)
Michael
S. GriffithActing
Director, Office of Safety DesignOffice
of Safety
Enclosure U.S. DEPARTMENT OF TRANSPORTATION

**Federal Highway Administration**

1200 NEW JERSEY AVENUE, SE

WASHINGTON, DC 20590

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