|
Seismic Evaluation and Retrofit of Sacramento
River Bridge at Rio Vista
 |
| Sacramento
River Bridge at Rio Vista |
The Sacramento River Bridge at Rio Vista is a 2,500-foot
long, two-lane steel truss bridge with a lift span. The structure
was constructed in 1944 and 1958, and was awarded the American Institute
of Steel Construction “Most Beautiful Steel Bridge” award
in 1960. The bridge may be subjected to a maximum credible earthquake
of magnitude 6.75 from Coast ranges/Sierra Nevada Boundary Zone,
with a PGA of 0.5g. Seismic evaluation and retrofit studies were
conducted to investigate the bridge for a “No Collapse”
criteria in a maximum credible seismic event and to develop a retrofit
design.
Because of the complexity of the bridge, comprehensive
analyses of the structure were carried out using global and local
models. The seismic evaluation consisted of a force-and displacement-based
demand-to-capacity analysis. Global forces and displacement demands
were computed using linear elastic dynamic response spectrum analysis
(3D finite element models using SAP90 V6.0). Several local models
were developed to analyze the various structural elements such as
the pier bents, the foundations, the tower frames and base. Nonlinear
static and dynamic time history analyses were conducted using software
DRAIN-3DX and ABAQUS.
 The
seismic evaluation indicated that in the event of a major earthquake,
typical hinge and rocker bearings in truss approach spans and base
connections for tower columns could be severely damaged, leading
to possible collapse of the structure.
The selected retrofit strategy consists of seismic
isolation of east and west truss spans, and addition of passive
energy dissipators at the typical base connections of tower columns.
Seismic isolation of east and west truss spans incorporates replacement
of existing hinge and rocker bearings with seismic isolation bearings.
Passive energy dissipators are typically provided at tower column
base connections to control the uplift during rocking response.
>> Back
to Bridges and Transportation Services
|
