Section 27-636. Suspenders

(a) Bridge wire cable. Bridge wire cables used
  for suspenders shall be either bridge strand or bridge  rope  fabricated
  from galvanized bridge wire.
    (1)  WIRE.  Wire  shall  be produced from rods rolled from high carbon
  steel, the composition of which shall be controlled to provide  internal
  soundness,  uniformity  of chemical composition and physical properties,
  freedom  from  injurious  surface  imperfections,  and  shall  meet  the
  following requirements.
    a.  The minimum ultimate tensile strength of zinc-coated wire shall be
  as follows:
 
       Class A coating .............. two hundred twenty thousand psi
       Class B coating .............. two hundred ten thousand psi
       Class C coating .............. two hundred thousand psi
 
    b. Yield strength shall be one hundred fifty thousand psi minimum  for
  zinc-coated  wire  with  class  A  or class B coating, one hundred forty
  thousand psi minimum for zinc-coated wire with class C coating, based on
  the cross-sectional  area  of  the  coated  wire  when  loaded  to  0.7%
  elongation in a ten inch gage length. In determining the yield strength,
  an  initial  stress  equivalent  to  forty-two  thousand  psi,  based on
  cross-sectional area of the coated wire, shall be applied  to  the  wire
  sample.  At  this  loading,  the  entensometer  shall be attached and an
  initial dial reading set at the equivalent of 0.15% elongation.
    c. Elongation shall be four percent minimum in a ten inch gage length,
  determined as the permanent increase in length after failure of a marked
  section of the wire originally ten inch in length except that a value of
  two percent will be permitted for wires 0.110 in. or  less  in  diameter
  having a class A zinc coating.
    d.  The  zinc-coated  wire  must  withstand  wrapping  at  a  rate not
  exceeding fifteen turns per minute twice around a mandrel equal to three
  times the wire diameter without fracture of the steel.
    e. The wire used in bridge strand or bridge rope shall be  zinc-coated
  (galvanized)  in  accordance with the requirements of table 10-5. Weight
  of coating shall be determined in  accordance  with  the  provisions  of
  reference standard RS 10-24.
 
     Table 10-5  Minimum Weights of Coating -- Bridge Wire, Zinc-Coated,
               For Bridge Strand and Bridge Rope Constructions
  ========================================================================
                                                Minimum Weight of Coating
  Diameter of Coated Wire                         (Ounces per Sq. Ft. of
           (in.)                                  Uncoated Wire Surface)
                                               ___________________________
                                               Class A   Class B   Class C
  ________________________________________________________________________
  0.041 to 0.061 incl. .......................   0.40      0.80      1.20
  Over 0.061 to 0.079 incl. ..................   0.50      1.00      1.50
  Over 0.079 to 0.092 incl. ..................   0.60      1.20      1.80
  Over 0.092 to 0.103 incl. ..................   0.70      1.40      2.10
  Over 0.103 to 0.119 incl. ..................   0.80      1.60      2.40
  Over 0.119 to 0.142 incl. ..................   0.85      1.70      2.55
  Over 0.142 to 0.187 incl. ..................   0.90      1.80      2.70
  Over 0.187 .................................   1.00      2.00      3.00
  ========================================================================

    (2)  BRIDGE  STRAND. Bridge strands shall be made from wires complying
  with subparagraphs a through e of paragraph one of this subdivision, and
  shall meet the following requirements:
    a.  The  wires  shall  be made in such lengths that the strands can be
  manufactured with no splices in the outside  wires.  Splicing  of  inner
  wires  during  the  stranding  operation is permissible. When joints are
  necessary in any wires, they shall be electrically butt welded and shall
  be recoated in a workmanlike manner. Joints in the wires of strand shall
  be made and dispersed  in  a  manner  that  will  maintain  the  minimum
  specified breaking strength of the strand.
    b.   The  minimum  breaking  strength  shall  be  based  on  tests  to
  destruction and shall be certified by the manufacturer.
    c. Bridge strand shall be prestretched to produce a stable modulus  of
  elasticity  of  at  least  the  following values for strand wires having
  class A coating:
 
  one-half inch to two and nine-sixteenths
    inches dia. ................................. twenty-four million psi
  two and five-eighths inches and larger ........ twenty-three million psi
 
    For bridge strands that have classes  B  and  C  zinc-coating  on  the
  outside  wires,  the  modulus  of  elasticity shall not be more than one
  million psi less than the corresponding values for bridge strand with  a
  class  A  coating.  The  pre-stretching load shall not exceed fifty-five
  percent of the breaking strength of the strand.
    (3) BRIDGE ROPE. Bridge rope shall be made from wires  complying  with
  subparagraphs  a  through  e  of  paragraph one of this subdivision, and
  shall meet the following requirements:
    a. Joints are permissible in  inner  and  outer  wires  and  shall  be
  electrically  butt welded and shall be recoated in a workmanlike manner.
  Joints in the wires of strand shall be made and dispersed  in  a  manner
  that will maintain the minimum specified breaking strength of the rope.
    b.   The  minimum  breaking  strength  shall  be  based  on  tests  to
  destruction and shall be certified by the manufacturer.
    c. Bridge rope shall be prestretched to produce a  stable  modulus  of
  elasticity  of at least twenty million psi for rope wires having a class
  A coating. For bridge rope that has class B and C zinc-coatings  on  the
  outside  wires,  the  modulus  of  elasticity shall not be more than one
  million psi less than the corresponding value for  bridge  rope  with  a
  class  A  coating.  The  prestretching  load shall not exceed fifty-five
  percent of the breaking strength of the rope.
    (b) Other materials. Any structural material permitted for  use  under
  the  provisions  of  other  sections  of this subchapter may be used for
  support of a suspended structure including, but not limited to, types of
  steel permitted for use under the provisions of  reference  standard  RS
  10-5; reinforcing steel and wire, prestressing wire and strand, and high
  strength  alloy  steel  bars conforming to the requirements of reference
  standard RS 10-3; and steel conforming to the requirements of  reference
  standards  RS  10-66  and  RS 10-69. Prestressing wire and strand may be
  used for suspenders without the application of prestressing  force.  All
  such  suspenders  shall  be  protected as described in section 27-642 of
  this article.