Seismic evaluation of the Confederation Bridge

Abstract

The 12.9 km Confederation Bridge, crossing the Northumberland Strait in eastern Canada, is one of the longest reinforced concrete bridges in the world. The bridge was designed for a service life of 100 years, which is twice the service life considered in the Canadian codes for highway bridges that were in use at the time. Much higher safety factors than those for typical highway bridges were used. In the design of the bridge, the seismic hazard was represented by a seismic design spectrum. This spectrum was derived by applying spectral amplification factors to the peak ground acceleration, velocity and displacement, corresponding to the design service life and the required safety of the bridge. The design forces and displacements due to seismic loads were computed using the response-spectrum analysis method. This thesis presents results from a seismic evaluation study of the Confederation Bridge. The following seismic excitations were considered in the study: (i) excitations represented by the uniform hazard spectrum for the bridge location, (ii) ground motion records representative of seismic motions in eastern Canada, (iii) ground motion records representative of seismic motions from large earthquakes at large distances, (iv) records obtained during the 1988 Saguenay, Quebec earthquake, (v) records obtained during the 1982 Miramichi, New Brunswick earthquake, and (vi) simulated seismic ground motions for the bridge location. The bending moments and displacements obtained from the seismic analysis were compared with the design values. It was found that the seismic parameters used in the design are quite representative of the seismic hazard of the bridge location. (Abstract shortened by UMI.)