Highway A20/A73 InterchangeOverview
A new highway viaduct was constructed in 2013, serving the city of Levis in Quebec, Canada. The viaduct, at an interchange between Highways 20 and 73, was constructed adjacent to an existing structure in order to increase highway capacity.
The viaduct is a six-span structure with a steel girder deck, with spans of between 40 m and 60 m and a total length of over 300 m. With a horizontal radius of 270 m, it has a prominent curve which heightens the risk of serious damage during an earthquake and thus increases the need for its deck to be seismically isolated from its supports.The planning phase took several years to find the best solution for integrating the new bridge into the protected and sensitive local environment with minimal impact. The new 9.3 km long bypass, constructed to motorway standard, shortened the old route by 12.8 km.
While the end spans of the deck are supported by conventional pot bearings, the central spans, which are more prone to damage from movements, are supported by mageba LASTO®LRB Lead Rubber Bearings (LRB). These LRBs will protect the structure during an earthquake by isolating it from destructive ground movements.
Each interior pier carries six LRBs, one supporting each of the deck’s main girders. Each LRB has a vertical load capacity of approximately 3,200 kN. Due to the structure’s location, the LRBs were designed for extreme temperatures from 104 °F (40 °C) to –22 °F (–30 °C).
LRB seismic isolators
For temperatures as low –30 °C (–22 °F)
Steel girder deck