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                Safety Eligibility Letter SS-05A
  
  **Hardware Type:**
            Sign Supports, Mailboxes, and Delineator Posts
                          **Code:**
            SS-05A
                          **Date:**
            07/18/1996
                                  **Manufacturer:**
            Marion Steel Company
                          **Device Description:**
            Redesigned Rib-Bak
                          **View PDF:**
            ss05a.pdf (79.98 KB)
    
    
United States Department of Transportation - Federal Highway AdministrationJuly 18, 1996
  Refer to: HNG-14/SS-05A
  Mr. Rick Mauer
    National Sales Manager
    Marion Steel Company
    912 Cheney Avenue
    Marion, Ohio 43302
  Dear Mr. Mauer:
  This is in reply to your June 24 letter to Mr. Nicholas Artimovich regarding 
    your company's Rib-Bak u-channel signposts.  Various sizes of Rib-Bank posts 
    have been crash tested and found acceptable as breakaway sign supports when 
    buried directly in the soil, when used with the Lap-Splice system, or when 
    used with the Minuteman Breakaway System.  You requested that FHWA acceptance 
    be continued if the shape of the post cross-sections is changed.  To increase 
    the steel mill's rolling efficiency, you propose to remove the two outermost 
    ribs (at the edge of the "flanges" of the u-channel) while retaining the two 
    ribs on either side of the web, adjacent to the row of holes.
  In support of this request you provided section data via facsimile on July 
    9 on both the original and proposed post cross sections.  The net effect of 
    revising the Rib-Back cross section is a slight change to the Moment of Inertia 
    and the Section moduli of some of the posts (4 percent +/-).  The cross-section 
    area and the mass per meter of the posts will not change since our revision 
    will redistribute the metal that was formerly rolled into the ribs.  This 
    metal will remain in the flanges or, in some cases; a small portion will be 
    redistributed to the sidewalls.
  Because the section properties of the proposed posts are very close to those 
    of the crash tested posts, and the mill's rolling tolerance on the dimensions 
    of u-channel posts is +/- five percent, we find the proposed revised designs 
    acceptable for use on the national highway system, if requested by a state.  
    Conditions regarding steel quality, spacing, splice details, stub height, 
    etc, that were discussed in our acceptance of the original Rib-Bak design 
    remain in effect.
  Sincerely yours,
  Seppo I. Sillan, Acting Chief
                                                                                        
    Federal-Aid and Design Division
  
  Geometric and Roadside Design Acceptance Letter Number SS-64
    Supplement: SS-5A, SS-13D, SS-18A, SS-56B, SS-57A
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