Structural Bearing
Assemblies
D.S. Brown Stuctural Bearing Assemblies
Since 1963, The D.S. Brown Company has
provided bearing assemblies and joint seals
for bridges around the globe. Bridges and
other large structures are supported on
bearing assemblies to transmit forces while
accommodating all structural movements.
The selection of an appropriate bearing
assembly is based on the magnitude of
vertical and horizontal forces transmitted
through the bearing assembly, as well as the
amount of displacement and rotation of the
superstructure elements. In addition, special
attention to the bearing assembly design may
be necessary when, for example, larger than
normal horizontal loading or uplift situations
exist. Walt Whitman Bridge, Philadelphia, PA - Versiflex™ Elastomeric Bearing Assemblies.
D.S. Brown is one of the leading suppliers of structural bearing assemblies. With extensive experience and utilizing the
latest technologies, D.S. Brown can efficiently design, manufacture and test Versiflex™ high-load multi-rotational (Versiflex™
HLMR) pot and disc style, spherical, seismic isolation and elastomeric bearing assemblies for all types of construction.
D.S. Brown is available to work closely with bridge owners and engineering design consultants to assist in the design,
selection and testing of the proper structural bearing assemblies.
Structural Bearing
Assemblies
Table of Contents
Versiflex™ HLMR Bearing Assemblies.................3-5
Versiflex™ Elastomeric Bearing Assemblies...........6
Versiflex™ HLMR Disc Bearing Assemblies............7
Seismic Isolation Bearing Assemblies....................7
D.S. Brown Signature Projects...............................8
Cover Bridge Photo: Veterans Memorial Bridge, Portland, ME - Versiflex™ HLMR Disc Bearing Assemblies by The D.S. Brown Company
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Versiflex™ HLMR Bearing Assemblies
Typical Applications
Versiflex™ HLMR pot-style bearing assemblies are suitable at locations where low-profile, high-load bearing devices are
required. Versiflex™ HLMR bearing assemblies are especially suited for curved or skewed bridges and other complex
structures where the direction of rotation varies or cannot be precisely determined.
Design Criteria Components
Required information for the proper design of a Versiflex™ As shown in the illustration, the Versiflex™ HLMR bearing
HLMR bearing assembly includes: assembly consists of a shallow steel cylinder, or pot, which
contains a tight-fitting elastomeric disc thinner than the depth
• Vertical Load
of the cylinder. The pot is a one-piece machined component.
• Horizontal Load
A machined steel piston fits inside the cylinder and bears
• Rotation
directly on the elastomeric disc.
• Translational Movements
Flat brass rings are used to
The plan area of a bearing seal the elastomer between the
assembly is usually controlled by piston and pot components. This
the average vertical stress on the assembly resembles a hydraulic
elastomeric disc. cylinder where the elastomer
Rotations of up to ±0.03 behaves like a viscous fluid,
radians can be accommodated flowing as rotation occurs.
by Versiflex™ HLMR bearing Structural Steel
assemblies. Design rotation is a
combination of the effects of live Components are typically
load and construction tolerances. fabricated from either 50 ksi
(345 N/mm2) or 36 ksi (250 N/
The use of polytetrafluoroethylene mm2) material. All exposed steel
(PTFE) as the low-friction sliding surfaces are to be metalized or
surface in bearing guide systems painted to prevent corrosion.
was previously the standard.
With the increased use of seismic Elastomeric Disc
design in the bridge industry, Typically manufactured from 50
larger horizontal loads must pass durometer neoprene.
through the bearing assembly’s
guide system. Alternative low-
friction materials, which provide much higher allowable Sealing Rings
bearing pressures than PTFE, are recommended for cases Rectangular in shape and manufactured from half-hard
where horizontal loads exceed 50 percent of the vertical brass.
design load.
PTFE
For curved bridge structures, the theoretical direction of
movement is a chord projected from the mid-point of the Low-friction material stable to 500ºF (260ºC).
deck at the expansion bearing line to the mid-point of
Stainless Steel
the deck at a fixed bearing line. Finite element analysis
may also be used to determine a more precise movement Polished to a 10 micro inch or less RMS (mirror) Finish.
direction. All bearing assemblies at any pier or abutment line
must be oriented in the same direction.
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Versiflex™ HLMR Bearing Assemblies
Fixed Design
(PF Series)
Fixed bearing assemblies are designed to transmit
horizontal forces in any direction through contact
between the piston and the inside of the pot wall.
Horizontal movement is restricted in all directions
while accommodating rotational movement of the
bridge superstructure.
Multi-Directional Design
(PM Series)
The addition of a PTFE and stainless steel sliding
surface between the piston and the sole plate creates
a bearing assembly that allows horizontal movement
in any direction. A multi-directional bearing assembly
does not resist externally-applied horizontal forces.
Uni-Directional Design
The addition of guide bars to the multi-directional
bearing device allows for horizontal movements in a
single direction and the capability to resist externally-
applied horizontal forces in the orthogonal direction.
Orientation of the guide bars in a direction parallel to
the structural movement is critical.
Center-Guided
(PMCG Series)
The Center-Guided system consists of a single
guide bar along the centerline of the bearing
assembly. Center-Guided gearing devices are not
recommended where the horizontal force exceeds
30 percent of the vertical force.
Edge-Guided
(PMG SERIES)
The Edge-Guided system utilizes two (2) guide
bars which are external to the rectangular pot plate.
An inverted pot assembly is typically detailed to
economically provide uniform bearing along the
guide bars.
*NOTE: Masonry plate excluded for clarity.
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Versiflex™ HLMR Bearing Assemblies
Manufacturing Capabilities Installation Considerations
High-load bearing assemblies require precision machining Versiflex™ HLMR bearing assemblies must bear on an even
to provide long-term, maintenance-free performance. and level surface. The two most common ways to achieve
The D.S. Brown Company utilizes state-of-the-art CNC a level bearing seat are:
machining equipment in its manufacturing process to assure • Grout the bearing into place
that manufacturing tolerances are maintained. • Provide a lead or fabric underlayment between the
bridge seat and the masonry plate
Load Testing Capabilities
When the grouting method is not utilized, the use of metal
Bridge owners often require the use of proof testing to
shims or blocks to adjust the level or elevation of the bearing
verify performance. Proof tests commonly specified include
assembly is to be avoided. Careful attention should be given
vertical and horizontal load testing, rotation testing and
to the strength of concrete and reinforcement around the
coefficient-of-friction testing.
bearing because of the large concentration of load carried
The D.S. Brown Company utilizes some of the largest, by the bearing devices.
most versatile calibrated test presses in the United States.
In some cases, the masonry plate size will be increased to
Vertical forces up to 5 million pounds (2270 tonnes) can be
meet required concrete pressure limits. Where required,
achieved, and bearing assemblies up to 75 inches (1900
expansion bearing assemblies may be provided with an
mm) by 65 inches (1700 mm) in plan and 18 inches (455
initial offset, so the slide plate can be set to allow structure
mm) in height can be tested.
shortening due to post-tensioning, creep or other causes.
Horizontal load tests and coefficient of friction tests are
Unless strictly supervised by a D.S. Brown representative,
conducted using a double-acting hydraulic cylinder with a
bearing assemblies should not be dismantled on-site.
capacity of 1.3 million pounds (590 tonnes) in tension. The
maximum horizontal displacement is ±18 inches (455 mm)
at a maximum travel speed of 6 inches (150 mm) per minute.
Static and dynamic coefficients of friction are determined
by recording horizontal force and displacement on an X-Y
plotter.
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Versiflex™ Elastomeric Bearing Assemblies
Typical Applications Sliding Design
For nearly 50 years, elastomeric bearing assemblies have For applications where horizontal displacements exceed
been used in the construction of new bridges and the ±2 inches (50 mm), sliding elastomeric bearing assemblies
rehabilitation of existing structures. may provide an economical solution. The addition of a
Other applications include: buildings and arenas, shear-key low-friction sliding surface allows a standard laminated
bumpers, seismic isolation protection and vibration devices elastomeric bearing device to accommodate unlimited
for machinery. horizontal displacement without increasing the height of the
bearing assembly.
General
Versiflex™ elastomeric bearing assemblies are custom
molded using neoprene or natural rubber and are categorized
into three basic designs: non-reinforced, laminated and
sliding bearing assemblies. Rotation and displacement
of elastomeric bearing devices are accommodated by
deformation of the elastomer. Bearing assemblies may be
molded with holes, slots, skewed ends, clipped corners and/
or sealing ribs and may also be circular in shape.
Non-Reinforced Design
Non-reinforced bearing devices are best specified when
the load, rotation and horizontal deflection are minimal.
Top and/or bottom steel load plates can be vulcanize-
bonded to the bearing device during the molding process.
Laminated Design
The addition of internal steel plates (or laminates) increases
the vertical load bearing capacity and the amount of hori- A slide bearing assembly consists of an upper and lower
zontal deflection which can be accommodated by the component. The upper component consists of a steel load
bearing device. plate attached to the superstructure and a polished stainless
steel sheet welded to the load plate. The lower component
consists of a low-friction PTFE sliding surface, steel backer
plate, molded elastomer and bottom steel load plate. All
components of the bottom assembly are vulcanize- bonded
during the molding process. Slide bearing devices may be
guided or free to move in any direction.
Manufacturing Capabilities
Versiflex™ elastomeric bearing assemblies and all associated
Laminated bearing assemblies are molded to any shape steel components are molded and manufactured to precise
or size. The internal steel plates are vulcanize bonded to tolerances. Versiflex™ elastomeric bearing assemblies can
alternating layers of elastomer during the molding process. be produced up to 75 inches (1900 mm) by 65 inches (1700
Laminated bearing assemblies may also be manufactured mm) in plan and 18 inches (455 mm) in height. In addition to
with top and/or bottom steel load plates which are also physical property tests on the polymer compounds, specified
vulcanize-bonded. An elastomer cover layer is necessary testing is also performed in-house, including vertical and
to protect the internal plates from the environment. horizontal load testing, rotation testing, peel testing and
coefficient-of-friction testing.
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Versiflex™ HLMR Disc Bearing Assemblies
General
Versiflex™ HLMR Disc Bearing Assemblies consist of an elastomeric disc made of unconfined polyether-urethane polymer
to accommodate rotation between two metal plates. The vertical loads are transferred by the elastomeric disc. Horizontal
shear forces are transmitted between upper and lower plates by a dowel pin mechanism in the center of the bearing.
Advantages
• Multi-rotational
• Lower Profile (Vertical Height)
• Cost Efficient
Seismic Isolation Bearing Assemblies
Typical Applications
D.S. Brown Seismic Isolation Bearings are ideal for
protecting critical structures from ground movement in all
seismic zones and soil types. These proof-tested lead-core
elastomeric bearings are maintenance-free and designed
to operate throughout the full lifecycle of bridges, buildings,
towers and piers.
General
Lead-Rubber Isolation Bearings consist of three
Advantages
components: rubber, steel plates and a lead core. Rubber
provides flexibility allowing deformation of the bearing and • Maintenance-free
memory to allow the bearing to recover after deformation. • Proven performance (shake-table + real earthquakes)
The internal steel plates provide vertical stiffness to handle • Effective isolation in all seismic zones and soil types
the dead and live loads of the structure but their horizontal
The isolation bearing system works by lengthening the
orientation allows movement in the lateral direction. The
fundamental period of the structure, thereby reducing the
lead core provides damping by deforming plastically when
acceleration input into the building, bridge or equipment. The
the isolator moves laterally. The lead core also dissipates
damping achieved by the isolation system further reduces
kinetic energy of an earthquake by transferring into heat
the acceleration input and reduces the displacements
energy during deformation. Lead is capable of multiple
across the isolation system.
deformations without failing.
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Dolphin - Palmetto Interchange Project
FL, USA
Versiflex™ HLMR Pot Bearings
Assemblies
D.S. Brown Signature Projects
The following list highlights some signature projects by The D.S. Brown Company.
Blennerhassettt Bridge, Parkersburg, WV High Five Interchange, Dallas, TX
Bobsled and Luge Facility, Lake Placid, NY Hollywood International Airport, Fort Lauderdale, FL
Boston I-93 Central Artery “Big Dig”, Boston, MA Pearl Harbor Memorial Bridge, New Haven, CT
Champlain Bridge, Chimney Point, VT San Rafael Bridge, Richmond, CA
Dolphin-Palmetto Interchange, Miami-Dade County, FL Throgs Neck Bridge, Queens, NY
Eggner’s Ferry Bridge, Trigg County, KY Veterans Memorial Bridge, Portland, ME
Golden Gate Bridge (South Approach), San Francisco, CA Walt Whitman Bridge, Philadelphia, PA
Golden Gate Bridge (South Approach)
CA, USA
Lead Rubber Seismic Isolation
Bearings
