ASTM D5977-03(2012)

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

ABSTRACT
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. The requirements of spherical bearings with a standard horizontal load (a maximum of 10 % of vertical) are discussed. The bearings are furnished in three types: fixed spherical bearing which is for rotation only, unidirectional sliding spherical bearing which is for rotation plus movement in one direction, and multi-directional sliding spherical bearing which is for rotation plus movement in all directions. The materials to be used in producing the bearings include: steel, stainless steel (flat sliding surface and convex surface), woven fabric polytetrafluoroethylene, and sheet polytetrafluoroethylene. The following different test methods shall be performed: proof load and rotation tests for fixed and expansion bearings, coefficient of friction test for expansion bearings only, PTFE (woven or sheet) bond test for expansion bearings only, and physical property test of both PTFEs for fixed and expansion bearings.
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 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: 14-Jul-2012
• ICS: 93.040 - Bridge construction
• Technical Committee: D04 - Road and Paving Materials
• Drafting Committee: D04.32 - Bridges and Structures

Relations

• Replaces: ASTM D5977-03(2007) - Standard Specification for High Load Rotational Spherical Bearings for Bridges and Structures
• Effective Date: 15-Jul-2012

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:D5977 −03(Reapproved 2012)
Standard Specification for
High Load Rotational Spherical Bearings for Bridges and
Structures
This standard is issued under the fixed designation D5977; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope A240/A240MSpecification for Chromium and Chromium-
Nickel Stainless Steel Plate, Sheet, and Strip for Pressure
1.1 This specification covers bridge bearings that consist of
Vessels and for General Applications
a spherical rotational element, where a stainless steel convex
A572/A572MSpecification for High-Strength Low-Alloy
surfaceslidesagainstaconcavecarbonsteelplatecoveredwith
Columbium-Vanadium Structural Steel
woven or sheet polytetrafluoroethylene (PTFE). The function
A588/A588MSpecification for High-Strength Low-Alloy
of the bearing is to transfer loads and to accommodate any
Structural Steel, up to 50 ksi [345 MPa] Minimum Yield
relative movement, including rotation between a bridge super-
Point, with Atmospheric Corrosion Resistance
structure and its supporting structure, or both.
A709/A709MSpecification for Structural Steel for Bridges
1.2 This specification covers the requirements of spherical
D638Test Method for Tensile Properties of Plastics
bearings with a standard horizontal load (a maximum of 10%
D792Test Methods for Density and Specific Gravity (Rela-
of vertical).
tive Density) of Plastics by Displacement
1.3 The requirements stated in this specification are the D1457 Specification for Polytetrafluoroethylene (Ptfe)
Molding and Extrusion Materials (Withdrawn 1996)
minima necessary for the manufacture of quality bearing
devices.Itmaybenecessarytoincreasetheseminimumvalues D1777Test Method for Thickness of Textile Materials
D2256Test 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.2.2-67Metalizing withAluminum and Zinc for Protection
test method portion, Section 7, of this specification: This
of Iron and Steel
standard does not purport to address all of the safety concerns,
D.1.5ANSI/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.
3.1.2 Uni-Directional Sliding Spherical Bearing—Rotation
2. Referenced Documents
plus movement in one direction.
2.1 ASTM Standards:
3.1.3 Multi-Directional Sliding Spherical Bearing—
A36/A36MSpecification for Carbon Structural Steel
Rotation plus movement in all directions.
A167 Specification for Stainless and Heat-Resisting
Chromium-Nickel Steel Plate, Sheet, and Strip
4. Material Specifications
4.1 Steel—The steel used for all major plates shall be
structural steel conforming to Specifications A36/A36M,
This specification is under the jurisdiction ofASTM Committee D04 on Road
and Paving Materials and is the direct responsibility of Subcommittee D04.32 on
Bridges and Structures.
Current edition approved July 15, 2012. Published July 2012. Originally The last approved version of this historical standard is referenced on
approved in 1996. Last previous edition approved in 2007 as D5977–03(2007). www.astm.org.
DOI: 10.1520/D5977-03R12. Available from American Association of State Highway and Transportation
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Officials (AASHTO), 444 N. Capitol St., NW, Suite 249, Washington, DC 20001,
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM http://www.transportation.org.
Standards volume information, refer to the standard’s Document Summary page on Available from American Welding Society (AWS), 550 NW LeJeune Rd.,
the ASTM website. Miami, FL 33126, http://www.aws.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5977−03 (2012)
A588/A588M, A572/A572M,or A709/A709M, as required. 4.4.1 The thickness of the sheet PTFE shall be a minimum
AllexposedsurfacesshallbezincmetalizedaccordingtoAWS of ⁄8in.(3.17mm)andshallberecessedatleastone-halfofits
C.2.2-67 (with no chipping), having a minimum thickness of 6 thickness.
mil (0.152 mm) or treated with other project-approved coating 4.4.2 ThePTFEfortheprincipalslidesurfaceandforguide
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:
NOTE 1—To Designer: The bearing details shall be designed in
4.2.1 Flat Sliding Surface—The sheet stainless steel used as
accordance with the requirements of the current edition with interims of
the mating sliding surface to the woven fabric PTFE or sheet the AASHTO Standard Specifications for Highway Bridges or other
governing design procedures.
PTFE in the sliding spherical bearings shall conform to
Specification A167 or A240/A240M, type 304, 20-µin. (0.5-
5.1 Rotational Elements:
µm) rms finish.
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
thegreatestratioofthehorizontalloadtoverticalloadunderall
surfacetothewovenfabricPTFEorsheetPTFEshallconform
loading conditions to prevent the unseating (separation at the
to Specification A167 or A240/A240M, type 304. The surface
edges) of the convex/concave elements.
shallbemachinedtoasurfacefinishof20-µin.(0.5-µm)rmsor
5.1.2 Unseating of the curved spherical surfaces relative to
less.
each other shall be prevented by transferring horizontal forces
through specifically designed restraints or by control of the
4.3 Woven Fabric Polytetrafluoroethylene (PTFE)—The
spherical radius.
woven fabric PTFE shall be made from virgin PTFE oriented
5.1.3 Acceptable spherical radius control shall be given
multifilament fibers with or without a high-strength backing.
when the configuration of the woven fabric PTFE concave
4.3.1 The thickness of the woven fabric PTFE in the free
3 radius follows the following design:
state shall be a minimum of ⁄32 in. (2.38 mm) when measured
in accordance with Method D1777.
ratio# tan α (1)
4.3.2 ThethicknessofthebondedwovenfabricPTFEunder
where:
the application of vertical load shall be a minimum of the
ratio = worst case ratio of horizontal to vertical loads.
following:
(1) ⁄16 in. (1.59 mm) from 0 psi (0 N/mm ) to 3500 psi
d/2
α 5 arcsin 2 ~designrotation! (2)
S S DD
(24.1 N/mm ).
Rmax
(2) ⁄64 in. (1.19 mm) from 3501 psi (24.1 N/mm ) to 4500
2 where:
psi (31.0 N/mm ).
d = projected diameter of the woven fabric
4.3.3 The woven fabric PTFE shall be mechanically inter-
PTFE,
locked and epoxy-bonded to the substrate using a system that
design rotation = design rotation of the bearing (in
prevents migration of the epoxy through the fabric. The use of
degrees), and
a mechanical interlock system along with the epoxy increases
Rmax = maximum allowable radius to prevent
thebondstrength,providingaredundancyforthepreventionof
uplift within the bearing during the worst
migration of the PTFE material. Any edges, other than the
horizontal to vertical load case.
selvedge (woven edge), shall be oversewn so that no cut fabric
edges are exposed. 5.1.4 Calculationsshowingdeterminationoftheradiusshall
4.3.4 The individual PTFE filaments used in making the
be submitted for approval.
wovenPTFEfabricshallconformtothephysicalrequirements 5.1.5 The radius of the convex plate shall be less than the
of Table 1.
radiuscalculatedforthewovenfabricPTFE(concaveplate)by
a value equal to the thickness of the PTFE.
4.4 Sheet Polytetrafluoroethylene (PTFE)—The sheet PTFE
5.1.6 The concave surface shall face down whenever the
shall be virgin material (not reprocessed) meeting the require-
resulting center of rotation is not detrimental to the system
ments of Specification D1457. The PTFE shall be resistant to
geometry. See Fig. 1
acids, alkalis, petroleum products, and nonabsorbtion of water.
5.1.7 The minimum thickness at the center of the concave
It shall be stable for temperatures up to 500°F (260°C) and
spherical element shall be ⁄4 in. (19 mm).
shall be nonflammable. When used in PTFE surfaces used for
guide bars only, filler material shall be composed of milled
glass fibers or carbon.
A
TABLE 2 Physical Property Requirements for Sheet PTFE
Physical Properties Test Method Requirement
Ultimate tensile strength, min, psi (MPa) D638 2800 (19.3)
TABLE 1 Physical Property Requirements for Woven PTFE
Ultimate elongation, min, % D638 200
Specific gravity, min D792 2.12
Physical Properties Test Method Requirement
A
Ultimate tensile strength, min, psi (MPa) D2256 24 000 (165.4) 15 % glass-filled PTFE may be used for guide bar surfaces (Specification
Ultimate elongation, min, % D2256 35
D1457).
D5977−03 (2012)
5.3.1 The woven fabric PTFE shall be mechanically inter-
locked to the steel substrate. An epoxy bond system shall be
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 10000 psi (68.8 N/mm ).
5.4 Sheet PTFE on Concave or Sliding Surfaces, or Both:
5.4.1 ThesheetPTFEshallbepurevirgin,unfilled,meeting
therequirementsofSpecificationD1457.ThesheetPTFEshall
berecessedtoone-halfofitsthicknessandepoxybondedtothe
steel substrate. The PTFE surface shall be smooth and free
from blisters or bubbles after completion of the bonding
FIG. 1 Views of a Spherical Bearing
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 ).
5.1.8 The minimum thickness at the edge of the convex
spherical element shall be ⁄2 in. (12.7 mm). 5.4.3 The maximum edge pressure on the sheet PTFE shall
5.1.9 Vertical and horizontal clearance between the rotating not exceed 5000 psi (34.4 N/mm ).
(attached to the superstructur
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