Resumen de Recomendaciones para el proyecto de puentes de ferrocarril con aparatos de apoyo de núcleo de plomo (lrb) en zonas sísmicas
Railway bridges located at seismic zones are particularly complex structures that present exceptional difficulties due to the existence of the track and the phenomena associated to it called track-bridge interaction. The design of these bridges is only possible by using isolation and dissipation techniques that have been developed in the last years.
It is possible to choose among several protection schemes depending on the seismic design strategy. However, despite advances in seismic engineering, it has not been yet possible to define a protection scheme that verifies optimally the structural requirements given by the norms, as well as the requests in terms of profitability and reliability of the service that the railway administration expects.
In the market, it can be found a device whose features are really attractive for railway bridges. We are talking about elastomeric bearings with a lead plug called LRB (“Lead Rubber Bearings”). These devices are known by having both capacities of isolation and dissipation, and they are usually used in buildings, in highway bridges and even in railway bridges with rail expansion devices (where there are no problems of track-bridge interaction). A priori, these devices seem to gather all the features of an ideal antiseismic device for railway bridges: stiffness in service, seismic protection, recentering, no need for maintenance and low cost. However, the truth is that their behavior against horizontal railway actions is unknown, their recentering capacity is also unknown and it is not either known if they are capable of respecting the track-bridge interaction requirements.
On the other hand, due to the lack of norms that treat together the track-bridge interaction and the seismic situation, it is not clear which verifications have to be performed during the bridge design.
Therefore, in this investigation it is analyzed if the LRB bearings are able to verify the track-bridge interaction requirements, if they provide the structure with adequate seismic protection and if they satisfy the requirements of the railway administrations related to the reliability of the service.
