Skellerup Rubber Service’s (SRS) Elastomeric Bearing Pads, or Bearing Strips, comply with standard AS5100.4 as they are pressure moulded from a high quality 60 IRHD hardness natural rubber compound. NATA and NATA MRA Certification on hardness, tensile strength, compression set and ozone resistance is available.
SRS Elastomeric Bearings Pads & Strips
| SRS Part Number | Cross Section (mm) | Length (mm) | Maximum Working Load (kN/m) SLS | Maximum Shear Deformation (mm) | Compressive Stiffness (kN/mm per metre strip) | Shear Stiffness (kN/mm per metre of strip) | Rotation (Rads.) Maximum # |
|---|---|---|---|---|---|---|---|
| THBS10100 | 10 x 100 | 2000 | 500 | 5 | 500 | 9.0 | 0.03 |
| THBS10125 | 10 x 125 | 2000 | 625 | 5 | 750 | 11.3 | 0.02 |
| THBS10150 | 10 x 150 | 2000 | 750 | 5 | 1050 | 13.5 | 0.014 |
| THBS10200 | 10 x 200 | 2000 | 1000 | 5 | 1800 | 18 | 0.008 |
| THBS13100 | 13 x 100 | 2000 | 385 | 6.5 | 296 | 6.9 | 0.039 |
| THBS13125 | 13 x 125 | 2000 | 600 | 6.5 | 462 | 8.7 | 0.031 |
| THBS13150 * | 13 x 150 | 2000 | 750 | 6.5 | 648 | 10.4 | 0.023 |
| THBS13200 * | 13 x 200 | 2000 | 1000 | 6.5 | 1101 | 13.8 | 0.013 |
| THBS15100 | 15 x 100 | 2000 | 333 | 7.5 | 222 | 6.0 | 0.045 |
| THBS15125 | 15 x 125 | 2000 | 521 | 7.5 | 347 | 7.5 | 0.036 |
| THBS15150 * | 15 x 150 | 2000 | 750 | 7.5 | 500 | 9.0 | 0.030 |
| THBS15200 * | 15 x 200 | 2000 | 1000 | 7.5 | 844 | 12.0 | 0.018 |
| THBS20100 | 20 x 100 | 2000 | 250 | 10 | 125 | 4.5 | 0.06 |
| THBS20125 | 20 x 125 | 2000 | 390 | 10 | 195 | 5.6 | 0.048 |
| THBS20150 * | 20 x 150 | 2000 | 560 | 10 | 281 | 6.8 | 0.04 |
| THBS20200 * | 20 x 200 | 2000 | 1000 | 10 | 500 | 9.0 | 0.03 |
| THBS20250 | 20 x 250 | 2000 | 1250 | 10 | 750 | 11.3 | 0.02 |
| THBS25100 | 25 x 100 | 2000 | 200 | 12.5 | 80 | 3.6 | 0.075 |
| THBS25125 | 25 x 125 | 2000 | 310 | 12.5 | 125 | 4.5 | 0.06 |
| THBS25150 | 25 x 150 | 2000 | 450 | 12.5 | 180 | 5.4 | 0.05 |
| THBS25200 | 25 x 200 | 2000 | 800 | 12.5 | 320 | 7.2 | 0.037 |
| THBS25250 | 25 x 250 | 2000 | 1250 | 12.5 | 500 | 9.0 | 0.03 |
| THBS25300 | 25 x 300 | 2000 | 1500 | 12.5 | 696 | 10.8 | 0.021 |
Other thicknesses, sizes and lengths available upon request.
Properties for bearing pads and strips are derived from AS 5100.4. Design is based on AS 5100.4. Compressive stiffnesses are indicative only. Refer later notes.
* Stock readily-available ex from our Auckland Warehouse
# This is the maximum rotation capacity when bearing strip is under maximum working load.
Compound Characteristics Bearing Pads & Strips
| Material Properties | Specification |
| Hardness (IRHD) | 60 ± 5 |
| Elongation at break | 450% min |
| Tensile Strength | 17.0 MPa min |
| Compression Set at 22hrs 70°C | 30% max |
| Applicable Standard | AS5100.4:2017 |
Design Parameters
The design of elastomeric bearing pads and strips is largely empirical. In the determination of the shape factor used in the computation process, a safety factor is incorporated in order to ensure a reasonable correlation between the calculated compressive stiffness value and the actual test value. This is largely an attempt to compensate for variations of compressive stiffness as will be experienced in practice, due to the friction that will occur when different surfaces are in contact with the rubber.
Material Lengths
Standard segment lengths are 2 metres. Custom lengths can be cut on request. By placement “end to end” on the headstock / corbel the support conditions become referred to as “continuous”.
Holes
SRS provides hole-cutting on bearing pads and strips to your specifications. Specially moulded modules with countersunk or counterbored holes are also available on special request. These are sometimes used as a means to hold vertically orientated buffer bearing pads and strips in position.
If you are requiring holes in bearing pads/strips please clearly dimension these on the project drawings.
Vertical Loads
Loads shown in table are the maximum recommended working/ serviceability loads, at the maximum shear deformation shown. Elastomeric bearing pads and strips are selected based on serviceability loads rather than ultimate design loads. The bearing pads and strips can tolerate significant overloading during ultimate limit state cases without harm hence this criteria does not govern.
Compressive Stiffness
Values shown in table are theoretical calculated values. They are considered as reasonable average values for the determination of rotational capacity. Actual values achieved in service will be influenced by the frictional characteristics of the contact surfaces against which the pad is placed, eg. rough concrete, galvanised steel etc.
The addition of a hole(s) into the pad or strip will cause a significant increase in compressive deflection at the rated load together with a corresponding decrease in load capacity, ie. The pad or strip will be softer, and thus, to keep within the design code for total strains, load carrying capacity is reduced. Consult with AS5100.4 for detailed calculation methods. A factor of 25% reduction would be a reasonable assumption in many cases.
Shear Deformation/Movement
Shear stiffness values shown are +/- from neutral position. It may be assumed that a pad or strip with dowel pin holes and thus not subject to shear deformation, has a load carrying capacity in order of values shown in table for bearing pad or strip considered.
Properties of Elastomer
“Temperature Effect” – Within the range of -20°C to +80°C no significant variation in performance will occur.
“Ozone” – Ozone cracking in any elastomer will occur where there are surface tensile forces. If cracking does occur, it is frequently harmless. It is simply relieving the surface tensions and further, deeper, cracking is unlikely.
“Longevity” – Due partly to their small surface area to volume ratio, and in particular the small surface area exposed to the atmosphere during service, plus the location where such pads or strips are used, bearing pads or strips of high quality natural rubber will give an extremely long life – typically longer than the structure.
“Fire Resistance” – Blocks of natural rubber do not burn easily. However, if fire resistance is considered essential, then in order to eliminate softening problems, sheathing with a suitable fire retardant, or insulating material, foam etc, is suggested. Alternatively, design to minimise any settlement if destruction by fire would cause structural problems.
Rotation
Tilting of the load bearing surfaces relative to one another, is referred to as “rotation”. The criteria for rotational capacity is that the trailing edge of the pad or strip does not go into tension, ie. No gap, but that it is always under a degree of compression. Rotational capacity listed in the table is that applicable at recommended maximum load.
The relationship LOAD / ROTATIONAL CAPACITY is reasonably linear. Additionally, constructional errors of the seating and / or camber, hog etc., of beams should be considered in determining the required rotational capacity of the bearing pad or strip.
Whilst with laminated elastomeric bearing pads or strips is undesirable to have “lift-off” or loss of full contact due to rotational effects, with plain elastomeric bearing pads or strips a degree of “lift-off”, provided it is minimal, will not damage the product.
Slippage
Non reinforced bearing pads or strips will spread when loaded. This is referred to as a “squirming”. The type of seating, steel, concrete, wood float / steel trowel finish rough / smooth, dry or wet, will all have an influence on the degree of squirming of the pads or strips under a compressive load. Part recessing of the pad or strip or the use of an adhesive can reduce this problem, but not eliminate it. However, it is recommended that adhesives not be used as if they are used and fail, then the squirming and slippage could get worse. “Slippage” is the term used to describe the actual displacement of the pad or strip from its initial placement. This can occur at one or both faces. It is also referred to as “walking out” of the pad or strip. NOTE – Where mechanical devices such as dowel studs are used to restrain the bearing pad or strip, these devices may limit the depth of the elastomer available to accommodate shear deformation movement.
Installation
Non-reinforced pads and strips will spread when loaded. Thus, the support area must be greater than the nominal plan size of the pad or strip. We would recommend a minimum value of 25mm on all edges of the pads or strips, particularly if the structure is steel. If concrete, then the recommendation is 25mm all around. If a mortar pad is used, then minimum thickness is suggested as 10mm together with a 45° chamfer on the mortar pad sides. If the mortar pedestal is greater than 25mm, reinforcement may be necessary. Surfaces should be flat, free from cavities / projections, and preferably rough “wood float finish” in texture.
Use of adhesives is not recommended.