Civil Engineering Reference
In-Depth Information
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NORTH APPROACH VIADUCT
APPROACH TRUSS SPANS
NORTH ANCHOR
NORTH
SUSPENDED
SOUTH
SOUTH ANCHOR
SPAN 142.15m
CANTILEVER
SPAN
CANTILEVER
SPAN
328.27m
116.28m
102.72m
116.28m
141.77m
SLOPE 5%
NORTH
VANCOUVER
SOUTH
VANCOUVER
1290.82m
Fig. 6.1
General configuration and bent designation of the IMSNC
Fig. 6.2
Approach truss spans, (
a
) Deck floor and steel warren trusses, (
b
) Bent 14: south end of the approach truss spans
Since the original construction of the bridge, two significant seismic retrofit projects have been completed. The first was
applied in 1994; this was a structural retrofit which involved the piers on the viaduct, strengthening both at the base and at the
pier cap; the steel truss sections where several details were upgraded including adding isolation bearings and bumpers
between individual truss spans, and at the anchor span tie-downs where the maximum longitudinal clearance at the top of the
pier and abutment was increased. The second retrofit was applied in 2001 involving ground improvements on the north end
of the bridge. This retrofit in general involved installing drains, ground densification and installing timber compaction piles.
6.3 Real-Time Seismic Monitoring System
A real-time monitoring system (RTMS) was installed on the IMSNC over several months, completed in May 2011. The
monitoring system is a part of a province wide network, with its central hub located at the University of British Columbia in
Vancouver. The monitoring system provides real-time information regarding structural performance and safety, primarily
for seismic, but also applicable for a variety of load types. The monitoring system will be implemented in two phases: first to
install the on-site hardware and second to implement a customized software and data processing system unique to the MoT/
UBC network.
The general purpose of the system is to monitor the structural health of the bridge for seismic, impact and deterioration
effects. This considers two loading levels: severe infrequent events, such as seismic and impact/collision; and frequent long-
term effects, such as wind, traffic, etc. The system instrumentation consists of:
1. Tri-axial accelerometers on pier footings using 4 g force-balance EpiSensors
2. Tri-axial accelerometer at each abutment (2 in total) using 4 g force-balance EpiSensors
