Seismic isolation of highway bridges: Effective performance of LRBs at low temperatures

ABSTRACT: Curved highway bridges are widely used in modern highway systems, often being the most viable option at complicated interchanges or other locations where geometric restrictions apply. Among the great variety of seismic isolation systems available, the lead rubber bearing (LRB), in particular, has found wide application in highway bridge structures. However, conventional LRBs, which are manufactured from standard natural rubber and lead, display a significant vulnerability to low temperatures. 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 acceptable 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.