In most concrete and steel structures accomodation must be made for relative movement between structural members in order to avoid the build-up of dangerous stresses. The source of this movement may be:

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

It is usually desirable to minimise the resistance forces and moments resulting from these movements and this is the primary function of Structural Bearings.

Bearing Technologies range of Line Rocker Bearings provide this function by the most efficient method using well proven concepts combined with modern manufacturing technology and advanced materials.

This is achieved by exploiting the unique low-friction sliding properties of PTFE (polytetrafluoroethylene) and a simple line contact rocker for rotation.


PTFE is a well known polymer which possesses some remarkable properties. The coefficient of friction when sliding against a polished surface can be as low as 0.01 which compares with ice sliding on ice. In addition, its coefficient of friction is the lowest at highest specific pressures which make it particularly suitable for use in structural bearings.


Glacier DU is a proprietary composite material comprising a PFTE mixture impregnated into a metallic structure. It is capable of withstanding extreme pressures whilst possessing similar friction properties to those of pure PTFE. It is used in Bearing Technologies Line Rocker Bearings for side restraints.

Line Rocker Principle

The main feature of Line Rocker Bearings is their ability to provide relatively large amounts of rotation about the transverse axis whilst constraining rotation of the superstructure about its longitudinal axis. The bearings are relatively narrow in the longitudinal direction and wide in the transverse direction. This feature makes them particularly suitable for precast beam constructions not only because of their minimum width requirements on the piers but also for their inherent transverse stability during erection.

© GLACIER DU is the registered trademark of Dana Inc