ASTM D5977-96

Standard Specification for High Load Rotational Spherical Bearings for Bridges and Structures

SCOPE
1.1 This specification covers bridge bearings that consist of a spherical rotational element, where a stainless steel convex surface slides against a concave carbon steel plate covered with woven or sheet polytetrafluoroethylene (PTFE). The function of the bearing is to transfer loads and to accommodate any relative movement, including rotation between a bridge superstructure and its supporting structure, or both.  
1.2 This specification covers the requirements of spherical bearings with a standard horizontal load (a maximum of 10% of vertical).  
1.3 The requirements stated in this specification are the minima necessary for the manufacture of quality bearing devices. It may be necessary to increase these minimum values due to other design conditions.  
1.4 The values stated in both inch-pound units are to be regarded as the standard. The values given in parentheses are for information only.  
1.5 The following safety hazards caveat pertains only to the test method portion, Section 7, of this specification: This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 31-Dec-1995
• ICS: 93.040 - Bridge construction
• Technical Committee: D04 - Road and Paving Materials
• Drafting Committee: D04.32 - Bridges and Structures

Relations

• Replaced By: ASTM D5977-03 - Standard Specification for High Load Rotational Spherical Bearings for Bridges and Structures
• Effective Date: 10-Feb-2003

Standards Content (Sample)

NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: D 5977 – 96
Standard Specification for
High Load Rotational Spherical Bearings for Bridges and
Structures
This standard is issued under the fixed designation D 5977; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope A 588/A 588M Specification for High-Strength Low-Alloy
Structural Steel with 50 ksi [345 MPa] Minimum Yield
1.1 This specification covers bridge bearings that consist of
Point to 4 in. [100 mm] Thick
a spherical rotational element, where a stainless steel convex
A 709/A 709M Specification for Carbon and High-Strength
surface slides against a concave carbon steel plate covered with
Low-Alloy Structural Steel Shapes, Plates, and Bars and
woven or sheet polytetrafluoroethylene (PTFE). The function
Quenched-and-Tempered Alloy Structural Steel Plates for
of the bearing is to transfer loads and to accommodate any
Bridges
relative movement, including rotation between a bridge super-
D 638 Test Method for Tensile Properties of Plastics
structure and its supporting structure, or both.
D 792 Test Methods for Density and Specific Gravity (Rela-
1.2 This specification covers the requirements of spherical
tive Density) of Plastics by Displacement
bearings with a standard horizontal load (a maximum of 10 %
D 1457 Specification for Polytetrafluoroethylene (PTFE)
of vertical).
Molding and Extrusion Materials
1.3 The requirements stated in this specification are the
D 1777 Method for Measuring Thickness of Textile Mate-
minima necessary for the manufacture of quality bearing
rials
devices. It may be necessary to increase these minimum values
D 2256 Test Method for Tensile Properties of Yarns by the
due to other design conditions.
Single-Strand Method
1.4 The values stated in inch-pound units are to be regarded
2.2 AASHTO Standard:
as the standard. The values given in parentheses are for
AASHTO Standard Specifications for Highway Bridges
information only.
2.3 AWS Standards:
1.5 The following safety hazards caveat pertains only to the
C.2.2-67 Metalizing with Aluminum and Zinc for Protec-
test method portion, Section 7, of this specification: This
tion of Iron and Steel
standard does not purport to address all of the safety concerns,
D.1.5 ANSI/AASHTO/AWS Bridge Welding Code
if any, associated with its use. It is the responsibility of the user
of this standard to establish appropriate safety and health
3. Classification
practices and determine the applicability of regulatory limita-
3.1 The bearings are furnished in three types, as follows:
tions prior to use.
3.1.1 Fixed Spherical Bearing—Rotation only.
2. Referenced Documents 3.1.2 Uni-Directional Sliding Spherical Bearing—Rotation
plus movement in one direction.
2.1 ASTM Standards:
3.1.3 Multi-Directional Sliding Spherical Bearing—
A 36/A 36M Specification for Carbon Structural Steel
Rotation plus movement in all directions.
A 167 Specification for Stainless and Heat-Resisting
Chromium-Nickel Steel Plate, Sheet, and Strip
4. Material Specifications
A 240/A 240M Specification for Heat-Resisting Chromium
4.1 Steel—The steel used for all major plates shall be
and Chromium-Nickel Stainless Steel Plate, Sheet, and
3 structural steel conforming to Specifications A 36/A 36M, A
Strip for Pressure Vessels
588/A 588M, A 572/A 572M, or A 709/A 709M, as required.
A 572/A 572M Specification for High-Strength Low-Alloy
2 All exposed surfaces shall be zinc metalized according to AWS
Columbium-Vanadium Structural Steel
C.2.2-67 (with no chipping), having a minimum thickness of 6
1 4
This specification is under the jurisdiction of ASTM Committee D-4 on Road Annual Book of ASTM Standards, Vol 08.01.
and Paving Materials and is the direct responsibility of Subcommittee D04.32 on Annual Book of ASTM Standards, Vol 07.01.
Bridges and Structures. Available from The American Association of State Highway and Transportation
Current edition approved July 10, 1996. Published September 1996. Officials, 441 N. Capitol St., N.W., Washington, D.C. 20001.
2 7
Annual Book of ASTM Standards, Vol 01.04. Available from American Welding Society, 550 N.W. Lejeune Rd., Miami, FL
Annual Book of ASTM Standards, Vol 01.03. 33135.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D5977–96
mil (0.152 mm) or treated with other project-approved coating 4.4.2 The PTFE for the principal slide surface and for guide
systems such as coal tar or inorganic zinc paint. The dry film bars shall conform to the physical requirements listed in Table
thickness (DFT) of the approved paint system must be speci- 2.
fied by the owner.
5. Design Requirements
4.2 Stainless Steel:
4.2.1 Flat Sliding Surface—The sheet stainless steel used as
NOTE 1—To Designer: The bearing details shall be designed in accor-
the mating sliding surface to the woven fabric PTFE or sheet dance with the requirements of the current edition with interims of the
AASHTO Standard Specifications for Highway Bridges or other govern-
PTFE in the sliding spherical bearings shall conform to
ing design procedures.
Specification A 167 or A 240/A 240M, type 304, 20-μin. (0.5-
μm) rms finish. 5.1 Rotational Elements:
5.1.1 The spherical radius shall be determined such that the
4.2.2 Convex Surface—The solid stainless steel plate or
resulting geometry of the bearing is capable of withstanding
sheet stainless steel used as the mating rotational convex
the greatest ratio of the horizontal load to vertical load under all
surface to the woven fabric PTFE or sheet PTFE shall conform
loading conditions to prevent the unseating (separation at the
to Specification A 167 or A 240/A 240M, type 304. The
edges) of the convex/concave elements.
surface shall be machined to a surface finish of 20-μin.
5.1.2 Unseating of the curved spherical surfaces relative to
(0.5-μm) rms or less.
each other shall be prevented by transferring horizontal forces
4.3 Woven Fabric Polytetrafluoroethylene (PTFE)—The
through specifically designed restraints or by control of the
woven fabric PTFE shall be made from virgin PTFE oriented
spherical radius.
multifilament fibers with or without a high-strength backing.
5.1.3 Acceptable spherical radius control shall be given
4.3.1 The thickness of the woven fabric PTFE in the free
when the configuration of the woven fabric PTFE concave
state shall be a minimum of ⁄32in. (2.38 mm) when measured
radius follows the following design:
in accordance with Method D 1777.
ratio # tan a (1)
4.3.2 The thickness of the bonded woven fabric PTFE under
the application of vertical load shall be a minimum of the
following:
where:
(1) ⁄16 in. (1.59 mm) from 0 psi (0 N/mm ) to 3500 psi
ratio = worst case ratio of horizontal to vertical loads.
(24.1 N/mm ).
d/2
a5 arcsin 2 ~design rotation! (2)
S S DD
(2) ⁄64 in. (1.19 mm) from 3501 psi (24.1 N/mm ) to 4500
Rmax
psi (31.0 N/mm ).
4.3.3 The woven fabric PTFE shall be mechanically inter-
where:
locked and epoxy-bonded to the substrate using a system that
d = projected diameter of the woven fabric
prevents migration of the epoxy through the fabric. The use of
PTFE,
a mechanical interlock system along with the epoxy increases
design rotation = design rotation of the bearing (in de-
the bond strength, providing a redundancy for the prevention of
grees), and
migration of the PTFE material. Any edges, other than the
Rmax = maximum allowable radius to prevent
selvedge (woven edge), shall be oversewn so that no cut fabric
uplift within the bearing during the
edges are exposed.
worst horizontal to vertical load case.
4.3.4 The individual PTFE filaments used in making the
5.1.4 Calculations showing determination of the radius shall
woven PTFE fabric shall conform to the physical requirements
be submitted for approval.
of Table 1.
5.1.5 The radius of the convex plate shall be less than the
4.4 Sheet Polytetrafluoroethylene (PTFE)—The sheet PTFE
radius calculated for the woven fabric PTFE (concave plate) by
shall be virgin material (not reprocessed) meeting the require-
a value equal to the thickness of the PTFE.
ments of Specification D 1457. The PTFE shall be resistant to
5.1.6 The concave surface shall face down whenever the
acids, alkalis, petroleum products, and nonabsorbtion of water.
resulting center of rotation is not detrimental to the system
It shall be stable for temperatures up to 500°F (260°C) and
geometry. See Fig. 1
shall be nonflammable. When used in PTFE surfaces used for
5.1.7 The minimum thickness at the center of the concave
guide bars only, filler material shall be composed of milled 3
spherical element shall be ⁄4in. (19 mm).
glass fibers or carbon.
5.1.8 The minimum thickness at the edge of the convex
4.4.1 The thickness of the sheet PTFE shall be a minimum
spherical element shall be ⁄2in. (12.7 mm).
of ⁄8 in. (3.17 mm) and shall be recessed at least one-half of its
thickness.
A
TABLE 2 Physical Property Requirements for Sheet PTFE
Physical Properties Test Method Requirement
TABLE 1 Physical Property Requirements for Woven PTFE
Ultimate tensile strength, min, psi (MPa) D 638 2800 (19.3)
Ultimate elongation, min, % D 638 200
Physical Properties Test Method Requirement
Specific gravity, min D 792 2.12
Ultimate tensile strength, min, psi (MPa) D 2256 24 000 (165.4)
A
Ultimate elongation, min, % D 2256 35 15 % glass-filled PTFE may be used for guide bar surfaces (Specification
D 1457).
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D5977–96
used for additional security. After completion of the bonding
operation, the PTFE surface shall be smooth and free from
blisters, bubbles, and evidence that any epoxy has migrated
through the woven fabric PTFE.
5.3.2 The area of the woven fabric PTFE shall be designed
for a maximum average working stress of 4500 psi (31.0
N/mm ).
5.3.3 The maximum edge pressure on the woven fabric
PTFE shall not exceed 10 000 psi (68.8 N/mm ).
5.4 Sheet PTFE on Concave or Sliding Surfaces, or Both:
5.4.1 The sheet PTFE shall be pure virgin, unfilled, meeting
the requirements of Specification D 1457. The sheet PTFE
shall be recessed to one-half of its thickness and epoxy bonded
to the steel substrate. The PTFE surface shall be smooth and
free from blisters or bubbles after completion of the bonding
operation.
5.4.2 The area of the sheet PTFE shall be designed for a
maximum average working stress of 3500 psi (24.1 N/mm ).
FIG. 1 Views of a Spherical Bearing
5.4.3 The maximum edge pressure on the sheet PTFE shall
not exceed 5000 psi (34.4 N/mm ).
5.1.9 Vertical and horizontal clearance between the rotating
5.4.4 The surface of the PTFE sheet to be epoxy bonded
(attached to the superstructure) and non-rotating (attached to
shall be etched using the sodium naphthalene or sodium
the substructure) spherical bearing components, including
ammonia etching process.
fasteners, shall be no less than ⁄8 in. (3.17 mm) when rotated
5.5 Sheet PTFE Guiding Surfaces:
to 150 % of the design rotation.
5.5.1 Attachment of the sheet PTFE to the steel substrate of
the guiding surface shall be performed by epoxy bonding and
NOTE 2—To Designer: The spherical PTFE pad may be damaged at
mechanical fastening. The mechanical fastening shall consist
150 % of the design rotation.
of a minimum of two stainless steel screws (Specification
5.1.10 The concave radius shall be machined to a tolerance
A 304) located on the centerline of the strip of PTFE and
of − 0.000, + 0.010 in. (−0, + 0.25 mm).
located ⁄2 in. (12.7 mm) from each end of the PTFE strip. The
5.1.11 The convex radius shall be machined to a tolerance
top of the screws shall be recessed a minimum of 50 % of the
of − 0.010, + 0.000 in. (−0.25, + 0 mm).
amount of protrusion of the PTFE above the steel substrate.
5.2 Stainless Steel Sliding Surface:
5.5.2 The surface of the PTFE sheet to be epoxy bonded
5.2.1 The thickness of the stainless steel sheet shall be 11
shall be etched using the sodium naphthalene or sodium
gage, with a manufacturer’s minimum thickness of 0.059 in.
ammonia etching process.
(1.5 mm).
5.6 Guide Bars:
5.2.2 Fixing of the Stainless Steel Sheet—The stainless steel
5.6.1 Each guide bar shall be manufactured from a mono-
sheet shall be attached to its backing plate by continuous fillet
lithic piece of steel. Guide bars may be made integral by
welding along its edges. It is essential that the stainless steel
machining from the solid shape or fabricated from solid bars
sheet remain in contact with the base metal throughout its
that are welded, bolted, or recessed into the guiding plate, or
service life and that interface corrosion cannot occur. The
some combination thereof.
attachment of the stainless steel to its back-up plate shall be
5.6.2 Guided surfaces shall be faced with opposing strips of
capable of resisting the frictional force set up in the bearing.
stainless steel and sheet PTFE. No metal-to-metal contact shall
Welding must be in accordance with ANSI/AASHTO/AWS
be permitted. The sheet PTFE may be fastened to either the
D1.5.
concave plate or guide bars, with opposing stainless steel on
5.2.3 The backing plate shall extend beyond the edge of the
the guide bars or concave plate, respectively. The sheet PTFE
stainless steel sheet to accommodate the weld; also, the weld
shall be bonded as well as fastened mechanically with stainless
must not protrude above the stainless steel sheet. TIG welding
steel screws (see 5.5.1). The maximum total gap allowed
of the stainless steel sheet is highly recommended to achieve
between the guiding surfaces shall be ⁄16in. (1.59 mm).
this connection.
5.2.4 The flat horizontal stainless steel sliding surface shall 5.6.3 The guide bars and their connections to the sliding/
sole plate shall be designed for the horizontal forces on the
cover the PTFE surface completely in all operations, plus one
additional in. (25.4 mm) in all directions of movement. For a bearing but not less than 10 % of the maximum working stress
load on the bearing.
guided bearing with which there is no transverse movement,
this requirement does not apply in the transverse direction. 5.6.4 Guiding arrangements shall be designed so that the
5.3 Woven Fabric PTFE Concave or Sliding Surfaces, or PTFE-covered guide surface is kept parallel a
...