Section 27-635
§ 27-635 General requirements. The materials, design, and construction
of suspended structures shall meet the applicable requirements of the
code and the requirements of this article.
Section 27-636
§ 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
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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
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(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.
Section 27-637
§ 27-637 Tests of materials for bridge wire suspenders. The following
minimum quantities of bridge wire for suspenders shall be tested:
(1) Tensile strength tests of the wires shall be made of a specimen
cut from each coil of zinc coated wire.
(2) Tests for elongation and for yield strength shall be made on
samples from approximately ten percent of the coils of any one size
finished wire. If any of these tests fail to meet the specified
requirements, all the coils in that lot of finished wire shall be tested
and only coils that satisfactorily pass the test shall be used.
(3) Tests of the zinc coating shall be made of approximately five
percent of the coils of any one size of finished wire. If any of these
tests fail to meet the specified requirements, all the coils in that lot
of finished wire shall be tested and only coils that satisfactorily pass
the test shall be used.
Section 27-638
§ 27-638 Tests of materials for other types of suspenders. The
applicable provisions of reference standards RS 10-3 and RS 10-5 shall
apply.
Section 27-639
§ 27-639 Design. The following design requirements shall supplement
the applicable provisions of this subchapter.
(a) Flexibility. Suspenders, unless encased, may be considered as
perfectly flexible.
(b) Elastic stretch. The elastic stretch of the suspenders shall be
considered.
(c) Displacement. Displacement resulting from changes in magnitude and
position of load and its affects on stress shall be considered.
(d) Other considerations. Consideration shall be given to the effects
of temperature variations, partial and reversible wind loadings, and
vibration.
(e) Allowable working load. The allowable working load in suspenders
formed from bridge wire cable shall be computed on the basis of factors
equal to one and one-half times dead load plus two and one-half times
live load or one and two-tenths times dead load plus two times live load
plus two times wind load, applied to the specified, minimum, ultimate
strength of the suspender. The allowable working load in suspenders
conforming to the materials specifications or several reference
standards of this code shall be the allowable working stresses for
tension members as prescribed in the applicable reference standard or,
for those materials where allowable stresses for tension members are not
prescribed, on factors of one and one-half times dead load plus two
times live load or one and two-tenths times dead load plus one and
one-half times live load, plus one and one-half times wind load, also
applied to the specified minimum, ultimate strength of the suspender. In
no case, however, shall the factor, applied to the yield strength of the
material or to the prestretching or prestressing force, exceed one and
one-tenth times dead load plus one and one-quarter times live load.
Section 27-640
§ 27-640 Fittings for wire cable suspenders. Fittings for wire cable
suspenders shall be capable of developing the specified minimum ultimate
strength of the attached cable or strand without developing stresses in
the fitting equal to, or in excess of, the yield strength of the
material in the fitting. One end fitting, of each type and size to be
used, shall be tested to insure the adequacy of the fitting to develop
the ultimate strength of the cable or strand to which it is to be
attached.
Section 27-641
§ 27-641 Construction. (a) General. The general provisions of
reference standard RS 10-5 relating to erection of steel shall apply.
(b) Fitting for wire cable suspenders.
(1) Only fittings designed for use with the specific wire cable shall
be used.
(2) All fittings shall be galvanized in accordance with reference
standard RS 10-23.
(3) Zinc used for attaching all speltered fittings shall be at least
equal to the grade designated as "high grade" in reference standard RS
10-26.
Section 27-642
§ 27-642 Protection of suspenders. (a) Protected locations. All wires
in bridge strands, bridge ropes, or other wire rope or strand suspenders
placed on the interior of structures or concealed from exposure by
interior finish shall have at least a class A coating of zinc. Rods,
bars, plates, or shapes used for suspenders shall be given a protective
coating as specified for the protection of like material in the
applicable reference standard.
(b) Exposed locations. The outside wires of bridge strand or bridge
rope suspenders placed in locations exposed to the weather shall have at
least a class B coating of zinc and the inside wires shall have at least
a class A coating. Rods, bars, plates, or shapes used for suspenders
shall be given a protective coating as specified for the protection of
like material in the applicable reference standard.
To the extent possible under law, Friends of Devin Balkind for Public Advocate has waived all copyright and related or neighboring rights to New York City Administrative Code. This work is published from: United States.
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