Advantages of keeping the Middle Pier & Abutment as fixed piers in Bearing Articulation?

Symbols for common bearing types (from Table 1 of BS EN 1337-1)

What are the advantages of assigning the central pier and the abutment as fixed piers?

Bearing Articulation refer to the arrangement, configuration selection of bridge bearings inorder to facilitate force transfer from the superstructure to substructure by achieving predefined degree of freedom (Displacements or Rotations) at the support locations/bearings. Bearing articulation has a major impact on the design of substructure of bridges.

  1. For abutment pier to be assigned as fixed pier while the bridge is quite long, the longitudinal loads due to earthquake are quite large. As the earthquake loads are resisted by fixed piers, the size of fixed piers will be large and massive. In this connection, for better aesthetic appearance, the selection of abutment as fixed piers could accommodate the large size and massiveness of piers. Normally abutments are relatively short in height and for the same horizontal force, the bending moment induced is smaller.
  2. For the central pier to be selected as the fixed pier, the bridge deck is allowed to move starting from the central pier to the end of the bridge. However, if the fixed pier is located at the abutment, the amount of movement to be incorporated in each bearing due to temperature variation, shrinkage, etc. is more than that when the fixed pier is located at central pier. Therefore, the size of movement joints can be reduced significantly.
Symbols for common bearing types (from Table 1 of BS EN 1337-1)

Symbols for common bearing types (from Table 1 of BS EN 1337-1)

Typical Bearing articulation of a curved bridge

Typical Bearing articulation of a curved bridge

 

 

 

Thank you Vincent T. H. CHU