Elastomeric Bearing Pads
Ref-Tro Enterprises productions of Elastomeric Bearing Pads have been recognized due to its quality and outstanding performance in long term.
Bearing support the bridge structure and accommodate expansion, contraction, and end rotation of the structure. The bearing must function properly in all regions of the world and under constantly changing temperature and weather condition. Prior to the development of elastomeric bearings, bridge engineers used mechanical devices such as sliding plates, rollers, rocker arms to accommodate structures. These devices required inspection and maintenance to prevent corrosion and seizing of bearings.
In contrast, elastomeric bearings are economical, effective and require no maintenance. They are simple solid pads, with no moving parts. The pads deflects in shear to accommodate expansion, contraction and end rotation of bridge structure , There is no need for lubrication, no need for cleaning, and no opportunity for bearing to seize.
Types of Elastomeric Bearings
There are three types of elastomeric bearings commonly used for supporting bridges and
other structures – Plain pads (unreinforced), Laminated pads reinforced with steel, and Laminated reinforced with fabric. Reinforced pads can support greater loads than plain pads of the same size.
1. Plain Pads – the most economical to produce, They consist of blocks of elastomer, compound, molded or extruded into large sheets, vulcanized, and then cut to sized. There use is generally
limited to smaller bridges where compressive stresses no higher than 2.8 – 3.4 Mpa (400-500 psi)
2. Laminated pads reinforced with steel – produced by plying alternate layers of elastomer and steel in a mold of the desired shaped. The elastomer is bonded to the steel during vulcanization under heat and pressure. A thin cover layer of elastomer encapsulates the steel during vulcanization under heat and pressure. The cross section of a typical steel – reinforced Neoprene bearing pad is shown in Figure 1. Three 12.7 mm (0.6 inch) layer of Neoprene compound are bonded top and bottom to steel shims; a minimum 3.2 mm (0.125 inch) cover layer of Neoprene is used around the perimeter of the bearing. Steel reinforced bearing pads are used on larger bridges where compressive loads up to 5.6 Mpa (800 psi) may be encountered.
3. Laminated pads reinforced with fabric – made by calendaring the elastomeric compound into large sheets, plying it with alternate layers of fabrics (usually fiberglass), and vulcanizing under heat and pressure. Bearings of any desired size can be cut to order from the large pad. The edge of the fabric reinforcement maybe left exposed, since it corrosion resistant. Fabric- reinforced bearings are not as stiff as steel reinforced bearings, and thus will comform more readily to surface irregularities in the bridge structure. Bearing of this type have been used on bridges where compressive loads up 5.6 Mpa (800 psi) have been encountered.
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