Bridges & Structures

Bearing Design Example

1. Obtain Design Criteria Design Step 6.1

   Commentary for 1: Includes: Movement (longitudinal and transverse), Rotation (longitudinal, transverse and vertical), Loads (longitudinal, transverse, and vertical)

2. Select Optimum Bearing Type S14.6.2 Design Step 6.2

   Commentary for 2: See list of bearing types and selection criteria in AASHTO Table 14.6.2-1

3. Steel reinforced elastomeric bearing?

4. Select Preliminary Bearing Properties Design Step 6.3

   Commentary for 4: Includes: Pad length, Pad width, Thickness of elastomeric layers, Number of steel reinforcement layers, Thickness of steel reinforcement layers, Edge distance, Material properties

5. Design selected bearing type in accordance with S14.7.

6. Select Design Method (A or B) S14.7.5 or S14.7.6 Design Step 6.4

   Commentary for 6: Method A usually results in a bearing with a lower capacity than Method B. However, Method B requires additional testing and quality control (SC14.7.5.1).

7. Compute Shape Factor S14.7.5.1 or S14.7.6.1 Design Step 6.5

   Commentary for 7: The shape factor is the plan area divided by the area of perimeter free to bulge.

8. Check Compressive Stress S14.7.5.3.2 or S14.7.6.3.2 Design Step 6.6

   Commentary for 8: Limits the shear stress and strain in the elastomer.

9. Does the bearing satisfy the compressive stress requirements?

10. Check Compressive Deflection S14.7.5.3.3 or S14.7.6.3.3 Design Step 6.7

    Commentary for 10: Includes both instantaneous deflections and long-term deflections.

11. Does the bearing satisfy the compressive deflection requirements?

12. Check Shear Deformation S14.7.5.3.4 or S14.7.6.3.4 Design Step 6.8

    Commentary for 12: Checks the ability of the bearing to facilitate the anticipated horizontal bridge movement. Shear deformation is limited in order to avoid rollover at the edges and delamination due to fatigue.

13. Does the bearing satisfy the shear deformation requirements?

14. Check Rotation or Combined Compression and Rotation S14.7.5.3.5 or S14.7.6.3.5 Design Step 6.9

    Commentary for 14: Ensures that no point in the bearing undergoes net uplift and prevents excessive compressive stress on an edge.

15. Does the bearing satisfy the compression and rotation requirements?

16. Check Stability S14.7.5.3.6 or S14.7.6.3.6 Design Step 6.10

17. Does the bearing satisfy the stability requirements?

18. Check Reinforcement S14.7.5.3.7 or S14.7.6.3.7 Design Step 6.11

    Commentary for 18: Checks that the reinforcement can sustain the tensile stresses induced by compression in the bearing.

19. Does the bearing satisfy the reinforcement requirements?

20. Method A or Method B?

21. Design for Anchorage S14.7.6.4 Design Step 6.12

22. Design for Seismic Provisions S14.7.5.3.8 Design Step 6.12

23. Is the bearing fixed?

24. Design Anchorage for Fixed Bearings S14.8.3 Design Step 6.13

25. Draw Schematic of Final Bearing Design Design Step 6.14

26. Return to Main Flowchart

Flow:

1 go to 2
2 go to 3
3 if yes go to 4
3 if no go to 5
4 go to 6
6 go to 7
7 go to 8
8 go to 9
9 if yes go to 10
9 if no go to 4
10 go to 11
11 if yes go to 12
11 if no go to 4
12 go to 13
13 if yes go to 14
13 if no go to 4
14 go to 15
15 if yes go to 16
15 if no go to 4
16 go to 17
17 if yes go to 18
17 if no go to 4
18 go to 19
19 if yes go to 20
19 if no go to 4
20 if method A go to 21
20 if method B go to 22
21 and 22 go to 23
23 if yes go to 24
23 if no go to 25
24 go to 25
25 go to 26

Note:

Method A is described in S14.7.6
Method A is described in S14.7.5