Bridges · Bearings & joints
Elastomeric bearing (Method A) calculator
Shape factor, compressive stress limit 1.0·G·S (≤ 7 MPa), shear deformation limit Δs ≤ hrt/2 and rotation sense check.
Standard: AASHTO LRFD 14.7.6 Method A (shape factor) · cf. AS 5100.4
Inputs in the worked example
The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.
| Input | Value | Unit |
|---|---|---|
| Pad length (along bridge) | 300 | mm |
| Pad width | 400 | mm |
| Internal layer thickness | 12 | mm |
| Internal layers | 4 | |
| Shear modulus G | 0.9 | MPa |
| Service load (total) | 650 | kN |
| Shear displacement | 20 | mm |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Shape factor LW/(2 hri (L + W)) | 7.14 | |
| Compressive stress | 5.42 | MPa |
| Limit min(1.0 G S, 7) | 6.43 | MPa |
| Total elastomer | 48.00 | mm |
| Shear limit hrt/2 | 24.00 | mm |
- ✓ Compressive stress
- ✓ Shear deformation
Method, formulas and assumptions
- Shape factor LW/(2 hri (L + W)) = 300*400/(2*12*(300+400)) = 7.1429
- Compressive stress = 650*1000/(300*400) = 5.4167 MPa
- Limit min(1.0 G S, 7) = MIN(0.9*7.1429,7) = 6.4286 MPa
- Total elastomer = 4*12 = 48 mm
- Shear limit hrt/2 = 48/2 = 24 mm
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.