Lead Rubber Bearings for Seismic Isolation of Structures in Cold Climates - New Developments

Nowadays, even in areas that have not been well known for the application of seismic protective measures, there is a growing tendency to design highway bridges, especially curved ones, to withstand strong seismic demands. This paper describes the challenge faced in the seismic isolation using LRBs of a curved highway viaduct where low temperatures must be considered in the design. Specifically, the LRBs must be able to withstand temperatures as low as -30 °C for up to 72 hours, while displaying only minor variations in their effective stiffness. This extreme condition required the development of a new rubber mixture, and the optimization of the general design of the isolators. Since the relevant specifications such as AASHTO Guide Specifications for Seismic Isolation Design and EN 15129: Anti-Seismic Devices contain only limited test data relating to low- temperature performance, extensive full-scale low-temperature dynamic testing was carried out.