Spherical bearings are the result of the most up to date technology. They have been developed for the bridges of the high speed railways, but they are suitable for all kinds of structures.
The spherical bearings are provided with a special sliding material, called ISOGLIDE, which is an innovative patented product, whose material characterization tests have been performed at Politecnico di Milano laboratory.
The use of this product, instead of PTFE, allows the following great advantages:
v The service life of the bearings is extended by a factor at least 5. It is well known that for bridges subjected to heavy traffic the sliding material will continuously slide and will wear out after a certain period. ISOGLIDE has a resistance to wear at least 5 times greater than PTFE
ISOGLIDE has been successfully tested in particular for the long term resistance up to 50.000 meters.
v The range of temperature f the bearings is extended from -50°C up to +90°C, instead of the -35°C and +48°C range of the PTFE
v The dimensions of the bearings may be reduced because the characteristic compression strength of ISOGLIDE is more than twice that of PTFE.
The design rotation of the spherical bearings is normally ± 3 (0,05 rad). This allows the compensation not only of the elastic rotations of the bridge, but also those due to the inclination of the beams or the manufacturing and installation tolerances of the prefabricated beams. With such an allowable rotation the installation of prefabricated beams is greatly simplified, avoiding the use of expensive tapered plates. It is possible to achieve a considerable saving and to speed up the erection of the beams.
The fixed bearings may be equipped with a damping ring that will equalize the horizontal loads when it is necessary to install 2 or more fixed bearings on the same bearing axis. The damping ring avoids the uncertainty of the repartition of the horizontal load allowing it to be shared in equal parts between the different bearings.
The spherical bearings, provided with ISOGLIDE, are CE marked covered by ETA 17/0808.