Donner Bridge construction and rehabilitation
involved the restoration and seismic upgrade of a historic cast-in-place
arch bridge and the installation of 50-ton rock anchors into bedrock
at each abutment.
To ensure the stability of the superstructure
during construction, shoring was constructed from the canyon floor approximately
ninety feet below, consisting of four 100 KIP per leg towers. This temporary
support of the bridge was required to replace each column, one bent
at a time. Reinforcement and seismic stabilization of all four arch
bases was performed in addition to the conversion of column connections
from moment resisting to pinned connection.
Hydroblasting of the main bridge deck was
performed to remove deteriorated concrete and salvage the existing rebar.
The bridge deck was widened to accommodate upgraded barrier rails. Extensive
dental concrete repair involved hand chipping of deteriorated concrete
and replacing with reinforced shotcrete.
This project was completed on time in 1995
even though the site required the removal of twenty feet of snow in
June of the second construction year to gain access to the project at
7000' elevation.