Pot bearings behavior after 32 years of service: In situ and laboratory tests

In order to extend the Swiss railway grid in the 1960s and 70s, many railway bridges were constructed for which pot bearings were taken for the supports. It is essential that the long-term behavior of these pot bearings is examined, as their life expectancy is, in most cases, much more limited than that of the associated superstructure. In this study, the operational condition of the pot bearings from a prestressed concrete girder bridge was investigated through in situ measurements and by evaluating the accumulated sliding path due to traffic loads and temperature impacts. It was found that long-term effects in relation to the traffic loads affect minimally the fatigue behavior of the bearings. Within extensive laboratory test series, the influence of parameters such as the lubrication condition, rotation angle, pressure acting on the elastomer pad and temperature on the restoring moments of the pot bearings was studied. Results of this study indicate not only that the condition of the pot bearings has deteriorated, but also that they were still in reasonable working condition after 32 years of service.