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Quick Details
Specifications
Highway bridge bearing:
1. We have more than 4000 staff
2. We have ISO,CE certificate
1. We have more than 4000 staff
2. We have ISO,CE certificate
Highway bridge bearing
1.Basic Design Consideration
For elastomeric bearing, the shear stiffness is an important parameter for design because it influences the force transfer between the bridge and its piers. In essence, elastomers are flexible under shear deformation but it is relatively stiff in compression. However, elastomeric bearings should not be used in tension.
Elastomeric bearing should be designed in serviceability limit state only. The cross sectional area is normally determined by the compressive stress limited under serviceability limit state. The shape factor, i.e. plan area of the laminar layer divided by area of perimeter free to bulge, affects the relation between shear stress and the compressive load. In essence, higher capacity of bearings could be obtained with higher shape factor.
The long side of the bearing is usually oriented parallel to the principle axis of rotation because it facilitates rotational movement. The thickness of bearings is limited and controlled by shear strain requirements. In essence, the shear strain should be less than a certain limit to avoid the occurrence of rolling over at the edges and delamination due to fatigue. Hence, it follows that higher rotations and translations require thicker bearing. On the other hand, the vertical stiffness of bearings is obtained by inserting sufficient number of steel plates. In addition, checks should be made on combined compression and rotation to guard against the possible occurrence of uplifting of corners of bearings under certain load combinations.
2.Services and Capabilities for Elastomeric Bridges Bearing Testing
- Fully equipped machine shops cut steel-laminated bearings to strict dimensional specifications
- Sectioned bearings conditioned and tested under controlled environmental conditions of 23°C and 50% relative humidity
- Elastomer sliced with surgical carbon steel at controlled pulling rates using pulley-equipped universal testing machine to provide smooth defect free surfaces and exact control of sample thickness
- Compression testing of full bearings up to 400,000 lb on bearing sizes up to a maximum of 550 mm x 450 mm
- All equipment calibrated and traceable. Quality systems conform to ISO 17025 requirements
- Reports contain full details of methods, test results and observations
3. Selection and Specification
Published standards, as well as road and infrastucture authorities and design engineers, have varying approaches to bearing specifications, but the following are provided as a general guideline:
• The vertical compression deformation should not exceed 15% of the initial bearing thickness.
• The horizontal displacement under shear should be lower than 70% of the total thickness of the rubber
• Total shear tension due to usual actions such as vertical, horizontal and rotations must be lower than five times G modulus.
• The maximum compression load should not be higher than 100-150 Kgs/cm2 .
• The minimum vertical load to avoid sliding in the structure should not be less than 30 Kgs/cm2 . If this condition cannot be satisfied, an anchored bearing should be used.
• For stability, the total effective height of the rubber should be lower than a fith of the smaller horizontal dimension, or if circular, a fith of the diameter and it should be greater or equal than a tenth of the smaller horizontal dimension.