Gfrp seismic strengthening and structural health monitoring of portage creek bridge concrete columns

Abstract EN

Located in Victoria, British Columbia (BC), Canada, the Portage Creek Bridge is a 124 m long, three-span structure with a reinforced concrete deck supported on two reinforced concrete piers, and abutments on H piles.

The bridge was designed prior to the introduction of current bridge seismic design codes and construction practices.

Therefore, it was not designed to resist the earthquake forces as required by today’s standards.

The bridge is on a route classified as a Municipal Disaster Route scheduled to be retrofitted to prevent collapse during a design seismic event, with a return period of 475 years (i.e., an event with 10% probability of exceedance in 50 years).

Conventional materials and methods were used to retrofit most of the bridge.

The dynamic analysis of the bridge predicted the two tall columns of Pier No.

1 will form plastic hinges under an earthquake resulting in additional shear to the short columns of Pier No.

2.

A non-linear static pushover analysis indicated that the short columns will not be able to form plastic hinges prior to failure in shear.

The innovative solution of Fiber Reinforced Polymer wraps (FRPs) was chosen to strengthen the short columns for shear without increasing the moment capacity.

The FRP wraps and the bridge were instrumented as one of 36 demonstration projects across Canada sponsored by ISIS (Intelligent Sensing for Innovative Structures) Canada, a federally funded Network of Centres of Excellence, to assess the performance of FRP and the use of FOS (Fiber Optic Sensors) for Structural Health Monitoring (SHM).

The two columns of the bridge pier were strengthened with GFRP (Glass Fiber Reinforced Polymer) wraps with eight bi-directional rosette type strain gauges and four long gauge fiber optic sensors attached to the outer layer of the wraps.

In addition, two 3-D Crossbow accelerometers are installed on the pier cap above the columns and a traffic web-cam mounted above the deck at the pier location.

The data is collected through high speed internet line to an interactive web page at ISIS Canada’s web site.

The bridge can now be monitored from anywhere.

The data collected so far has proved the reliability of the instrumentation system.