Disc Bearings

DYMAT® Structural Bearings

Design coefficient of friction between bright annealed stainless steel and PTFE at design load is less than 3% at less than 25.4mm (1 in) per minute sliding speed.

The pressure on the Virgin PTFE horizontal surface in contact with the stainless steel is a maximum of 24.1 MPa (3500 psi).  The force on the mechanically fastened PTFE guides is designed for 45 MPa (6,526 psi) maximum. Special PTFE composite guides can be used for higher pressures.

Dimples can be added in the PTFE if specified by the engineer. Typical pockets are 7mm (0.275 in) in diameter, 2mm (0.078 in) deep, and occupy greater than 20% of the PTFE surface area.  Add 0.4mm (o.016 in) to the overall bearing thickness for use of dimples. High quality silicone grease shall be used. The working compressive stress on the DYMAT® disc is up to 35 MPa (5,076 psi).

​Long term deflection of the DYMAT® disc is less than 7% of element thickness. See test report for initial load deflection characteristics.

Plate Design
The standard lower bearing plate is designed for 20.68 MPa (3,000psi) pressure on the concrete or grout. Add-on masonry plate sizing is available upon request.


Design Features

​​Simple Design
Rotation element does not have critical tolerances compared to pots with sealing ring or curved, mating, sliding surface bearings. No greasing or PTFE lining needed to accommodate rotation.

Simple Installation
Alternate anchorage details are provided for all structure types. Jacking ports are standard and flexible guides are available. The designer selects the features desired. ​

​Simple Inspection
Rotation element visible from all sides.

Simple Modification
The shear restriction mechanism is easily modified to allow lateral movement for a series of fixed and uni-directional bearings. Seismic and base isolation designs also available.


Performance Features

​Confined Virgin PTFE Horizontal Sliding Surface
PTFE provides low coefficient of friction against the bright annealed finished stainless steel (less than 0.127 µm (5 µin) root mean square finish). Less than 0.03 coefficient at 10.4 MPa (1508 psi). Test reports available for friction values at dynamic seismic cycling.

​High Rotational Capacity
Designed to rotate up to 4º. The shift in center of gravity is low within structural design guidelines of less than 3% of the column diameter at 1% rotation. Full rotation at low loads is accommodated within the bearings.

Unique Shear Restriction
The unique shear restriction mechanism uses DYMAT® alloy to allow rotation with uniform distribution of forces between bearings in the structure.

Compact Design
The shear restriction mechanism eliminates shear on the disc due to horizontal forces, while allowing high vertical loading on the unique disc material.  The result is a compact bearing.

Easy Design for High Horizontal Force
A larger shear restriction mechanism is introduced when the horizontal force is above 25% of the total vertical load.
Internal Uplift Restraint. Special bolts with DYMAT® alloy rotation elements provide uplift restraint while allowing rotation at the same time.

​Unique Disc Shape
Eliminates stress point “V” used in older designs.


Material Specifications

Steel Components
All steel plate, G40.21M, 300W or A572 (grades 36, 42 or 44) minimum specification. Custom steel available on request.DYMAT® disc meets requirements of AASHTO specifications.

​Stainless Steel Components
Sheet shall conform to ASTM A-240, Type 304. Stainless steel in contact with PTFE sheet shall be less than 5µin (0.127µm) root mean square finish. Thickness of stainless steel shall be 0.063 in (1.6mm) minimum.

​Exposed Steel Surfaces
Steel surfaces exposed to the environment are painted with structural primer to design authority specifications. Surfaces can also be galvanized or Metalized if required.

Polytetraflouroethylene (PTFE) Sheet and Strip PTFE is pure virgin (unfilled) polymer. Properties conform to the following:

Requirement:  Tensile Strength MPs (psi)
Test Method:  ASTM D-638
Value:  19.3 (2800) min.

Requirement: Elongation
Test Method:  ASTM D-638
Value:  200% min.

Requirement: Specific Gravity
Test Method: ASTM D-792
Value: 2.13 ± 0.03

​Reinforced PTFE can be used in higher load applications. Different thicknesses are available. PTFE with grease retention cavities is available.

​PTFE to Steel Bonding
Special etched, one side virgin PTFE is bonded with DYMAT® adhesive to grit blasted steel using special bonding procedures. Virgin PTFE guides are bonded and mechanically fixed in place.


Manufacturing Tolerances

​± 0.125 in (3mm)
Overall plan sizes

​± 0.125 in (3mm)
Overall height (except for very large bearings)

​Standard machined surfaces to finish ASA 125

​0.625 in (1.6mm)
Standard total gap on guide bars

​± 0.0312 in (0.8mm)
Standard tolerance on guide bars

​These are normal tolerances for DYMAT® bearings unless designer specifies other requirements.


Specially compounded PTFE is available for minimal wear when a higher coefficient of friction is tolerable.

Test reports available to 500,000 cycles.

Design Features

  • Simple Design
  • Simple Installation
  • Simple Inspection
  • Dynamic absorption
  • Vibration isolation
  • Simple Modification

Performance Features

  • Confined Virgin PTFE, Horizontal Sliding Surface
  • High Rotational Capacity
  • Unique Shear Restriction
  • Compact Design
  • Easy Design for High Horizontal Force
  • Internal Uplift Restraint
  • Unique Disc Shape

The DYMAT® disc bearing using the DYMAT® element concept has evolved from years of research and development, and field observation. Testing has been carried out on the bearing elements to 20 times the design load with full material recovery. Where testing is required, testing the production bearings is recommended. This could be carried out on the DYMAT® Load Test Machines.

High Load Test Machine at LeTourneau University

2,000 kips (8,896 kN) Vertical Load Capacity   |   380 kips (1,690 kN) Horizontal Load Capacity  |   18 in (45.7cm) Horizontal Displacement


​Cast in Place Structure

​Cast or grout the lower central anchor or lower add-on distribution plate on the support to provide level bearing. Alternate method is to grind the concrete flat with ± 0.1º from horizontal.

Set theDYMAT® bearing on support (arrives completely assembled from plant).

Remove all shipping clamps or steel bands before pouring concrete. Engineer must specify shipping clamps since slings are normally used.

For uni-directional and multi-directional bearings, adjust upper plate to proper setting as instructed by the engineer and then cast in place.


Precast Structure

Place a plate as detailed on drawing into the precast member at the casting plant. This plate should be larger than the upper plate of the bearing to allow for field tolerances and welding of this plate to upper plate.

Remore all shipping clamps from bearings just before setting precast member in place. ​


Steel Structure

Weld or bolt upper plate of bearing to the steel structure.  Engineer must approve welding details near or on bearing. Place protective materials over bearings to protect against spark and flash.

Items 1&2 apply to all structures with concrete supports. Leave bearings and surroundings clean after installation. Engineer specifies when to remove temporary clamps.


Jacking Ports

If replaceable bearings are desired, the designer must allow space to set a hydraulic jack.  Too much space may necessitate expensive shims.  Too little, and an expensive frame support may be needed to remove concrete or support jacks on foundations.If the structure is not jackable, lifting should be at the owner’s expense. Conventional, low profile hydraulic jacks are recommended for control on both up and down lifts.

Required Space for Low Jacks

Load up to 500 kips (2,224 kN)   
4.72 in (120mm) vertical by 15.75 in (400mm) in plan

Load up to 1,000 kips (4,448 kN)  
4.72 in (120mm) vertical by 23.62 in (600mm) in plan

See standard jack catalogs for standard height jacks.


Slideshow: Connecting to any structure