• DYMAT® Structural Bearings: Molded Steel Reinforced Bearings
  • Molded Steel Reinforced Bearings - Features
  • Molded Steel Reinforced Bearings - Design & Materials
  • Molded Steel Reinforced Bearings include steel plates & elastometric cover

Molded Steel Reinforced Bearings

DYMAT® Structural Bearings

30 Years Later and Still the Best

DYMAT® molded, steel reinforced bearings are manufactured of high quality neoprene or natural rubber with steel plates inside the elastomer and no steel exposed to the environment. This design has been performing excellently for over 20 years.

Design engineers should specify molded, steel reinforced bearings carefully to eliminate laminated bearings with exposed steel edges or laminated bearings with bonded elastomeric covers, since both have a record of field problem
 

 

Features

Versatility
The key feature of molded, steel reinforced bearings is their functionality in a wide array of uses and conditions.

Earthquake Bearing Designs
Custom designs are available with the following features: Structure supported on DYMAT® multi-directional bearings with no internal bearing guiding. Connection between the supports and concrete deck is made with a custom unit that disconnects at maximum design horizontal force. These are fixed and unidirectional connectors. When the horizontal force exceeds the maximum design force, as in an earthquake, large molded steel reinforced bearings support the structure and supply the horizontal returning force due to the shear stiffness of the material. DYMAT® offers a design service to incorporate this system into the structural design.  

Vibration & Acoustic Isolation Pads
The selection of vibration and acoustic properties of a pad is a special study and the material compound and exact shape of the pad must be carefully selected. DYMAT® offers the service of proposals of pad designs at no obligation. Special type “U” and “L” pad standards are available with reduced shape factors.
 

Design, Materials & Testing


Design
Elastomeric material meets all AASHTO and MTC specifications
Standard Durometer A 55±5 Durometer
Maximum dead plus live load 6.89 MPa (1,000 psi)
Maximum dead load 4.14 MPa (600 psi)

Per AASHTO Specifications
Initial deflection less than 7% between zero and 5.52 MPa (800 psi)
Allowable shear deflection ±25% of effective rubber thickness

Per MTC Specifications
Initial deflection less than 4% between 1.38 MPa (200 psi) and 6.89 MPa (1,000 psi)
Allowable shear deflection ±50% of effective rubber thickness

Materials
High quality neoprene and natural rubber elastomers are compounded to meet engineering requirements. Standard bearings in the table are compounded to meet current AASHTO and the Canadian MTC current specifications. Custom material specifications can be manufactured.
 

DYMAT® Plain Bearing Pads


Available in all Sizes and Thicknesses
The material is standard AASHTO and MTC neoprene or natural rubber in 50, 55, 60   and 70 Durometer A (±5).  DYMAT® will manufacture special material specifications on request.

Stability
The least plan dimension of the bearing must be equal to, or greater than, five times the thickness.

Compression - Deflection
The initial deflection due to load should not exceed 6% of the thickness when measured between 200 and 1,000 psi.

Abnormal Design Conditions
See Transport and Road Research Laboratory Report 708 (1976), Transport and Road Research Laboratory, Crow Thorne, Berkshire, England.

Design Criteria for Non-Standard Bearings
Design engineers should be knowledgeable in all aspects of the bearing design.
 
Reference is made to:
Design of Neoprene Bearing Pads, E.I. DuPont Company

Natural Rubber in Bridge Bearings, Technical Bulletin No. 7

Natural Rubber Bureau, 19 Buckingham Street, London, W.C.2
 
Since it is not possible to list all potential bearing sizes required for every structure, DYMAT® offers custom sizing service at no obligation to engineers.

Calculation of Shear Stiffness
DYMAT® has tested shear stiffness on the standard bearing. Use the following method.

KS = G x L x W per unit length / Et

KS = Shear Stiffness
G = Shear Modulus
L   = Length of Pad
W = Width of Pad
E   = Number of Internal Elastomeric Layers
t   = One Layer of Elastomeric Thickness
 

Typical Uses

  • Bridge bearings
  • Building bearings
  • Vibration pads
  • Acoustic isolation pads
  • Shock absorbers
  • Machinery mounting pads
  • Earthquake bearing design pads

Advantages

  • Lightweight, space saving, simple to install
  • No maintenance required
  • No moving parts. No friction or corrosion
  • Absorb movement of structure
  • Excellent shock absorbing and vibration damping
  • Initial and long term economy
  • Lightweight, space saving, simple to install

Data Sheets

Molded Steel Reinforced Bearing

Installation

Installation
Molded, steel reinforced, elastomeric bearings must be stable. The least plan dimension of the bearing must be equal to, or greater than, four times the effective rubber thickness

Concrete Structures
When the bearing is placed on rough concrete supports with a rough concrete cast over the bearing, adhesive is not normally required, provided the bearing operates within the shear deflection range. For supports with slippery grout or polished concrete, designer should specify a pintel or keeper design.

Steel Structures
Where the elastomeric bearing contacts the steel in the load areas, use of a steel pintel or keeper design is recommended.

Fixed Bearing
DYMAT® molded, steel reinforced bearings can be designed to allow the fixing of the structure through them. Fixed bearings are designed using rotation as the controlling factor for thickness (T).