A footbridge basically consists of bridge deck supported by piers. In order to avoid damage by movements of thermal expansion, vehicular movement, loading to piers, footbridge bearings are used to accommodate these movements so as to reduce reaction forces and bending movement to within safety limits of the structure. Footbridges, unlike vehicular and rail bridges, often present an unusual combination of having to bear relatively low loads while at the same time experiencing large movements. This is especially true in the case of single span structures crossing a freeway, and footbridge bearings must be designed accordingly. The stresses that can be built up in a footbridge can be caused by:

• Thermal expansion and contraction
• Permanent creep and shrinkage
• Post tensioning strain
• Live load deflections
• Earth movement

It is necessary to minimise the resistance forces and moments resulting from these movements and this is the primary function of footbridge bearings.

Laminated rubber footbridge bearings are often used in these applications but they do not always provide the best solution. This is because in order to accommodate the relatively large movements usually experienced in footbridges, the footbridge bearings need to be relatively thick and at the same time have a small cross-section due to the low vertical loads. If the plan dimension is less than four times the height, a condition of instability will arise, and so a bearing with a larger than normal plan dimension would be required, raising further issues. In order to address this problem BAR series footbridge bearings utilising low friction PTFE/Aluminium alloy sliding surfaces in combination with an elastomeric layer should be utilised. If you would like further clarification please call us at +27 (0) 11 605 2434