Field Demonstration Projects
Alberta

Beddington Trail Bridge

The Beddington Trail highway bridge in Calgary is one of the first in Canada to be outfitted with FRP tendons and a system of structurally integrated optical sensors for remote monitoring. The bridge opened to traffic in 1993, prior to ISIS Canada’s existence. It is significant to the ISIS network because, for the group of researchers involved, it confirmed the need for an organization that could spearhead transferring the new technology to industry.

The Beddington bridge is a two-span, continuous skew bridge of 22.83 and 19.23-m spans, each consisting of 13 bulb-Tee section, precast, prestressed concrete girders. Two different types of FRP tendons were used to pretension six precast concrete girders. Carbon fibre composite cables produced by Tokyo Rope of Japan were used to pretension four girders while the other two girders were pretensioned using two Leadline rod tendons produced by Mitsubishi Kasei.

Fibre optic Bragg grating strain and temperature sensors were used to monitor the behaviour during construction and under serviceability conditions. The four-channel Bragg grating fibre laser sensing system was developed at the University of Toronto Institute for Aerospace Studies.

An experimental program was conducted at the University of Manitoba's W.R. McQuade Laboratory prior to constructing the bridge to examine the behaviour of 1:33 scale model beams pretensioned by the same type, size, and anchorage of the two different tendons used for the bridge girders. The tests also used the same optic sensor as used for the bridge, in addition to electric resistance strain gauges to compare the results.

Prestressing of carbon fibre reinforced polymer (CFRP) was adapted to the practice of the precasters by coupling the carbon fibre composite cables and Leadline rods to conventional steel strands. Couplers helped to minimize the length of CFRP tendons, and were staggered to allow use of the same spacing for the conventional steel reinforcing tendons.

The Leadline rods were cut at the site and two rods were used for each tendon. The carbon fibre composite cables were delivered precut to the specified length with 300-mm die cast at each end to distribute the stresses at the anchoring zone. Construction of the bridge and handling of the girders at the site were typical.

A four-channel Bragg grating fibre laser sensor system was used at different locations along the bridge girders pretensioned by the carbon FRP. The system involves four independent Bragg grating tuned fibre lasers that are multiplexed in order to be pumped by one semiconductor laser. Each fibre laser was attached to the surface of the tendon to serve as a sensor. The sensors were connected, through a modular system, to a laptop computer used at the construction site to record the measurements at different stages of construction and after the completion of the bridge.

The optic sensor system measures the absolute strain rather than a strain relative to an initial calibration value, similar to the electric resistance strain gauges and mechanical gauges.

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Centre Street Bridge

Centre Street Bridge in Calgary has undergone an extensive rehabilitation. Deterioration has been repaired and structural strength has been raised to current load standards. The City of Calgary utilized GFRP grid as top reinforcement instead of conventional steel rebar in approximately two-thirds of one span of the lower deck. The aim of this project is to complement this effort by providing an intelligent sensing system to monitor the performance of this innovative repair.

In cooperation with the City of Calgary and the FRP supplier, strain gauges were glued in key locations of the FRP reinforcement. In addition, conventional steel reinforcement in similar parts of the bridge deck was instrumented as a control and to provide additional information on structural behaviour. The instrumentation was installed during construction and the leads run to a central monitoring cabinet at the structure. The data acquisition, processing and communications equipment is installed such that the bridge can be monitored from the University of Calgary, the University of Alberta, the City engineer's office and from any other appropriate location. The project utilizes remote monitoring technology developed by ISIS.

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Country Hills Boulevard Bridge

In 1996, CH2M Gore & Storrie Limited, with the assistance of Dr. Gamil Tadros of ISIS Canada, began a material testing program at the University of Calgary to review the strengthening effects of carbon fibre reinforced polymer (CFRP) strips on existing bridge beams. In 1997, CH2M Gore & Storrie Limited was appointed by the City of Calgary to strengthen the bridge carrying Country Hills Boulevard over the Deerfoot Trail in north-east Calgary.

One of the main problems with the bridge was that its thin deck would be over-stressed in lateral bending under full CS-600 loading due to the skew angles at the abutments and pier. Conventional strengthening with the addition of reinforcement would have required breaking the deck into strips, adding reinforcement, and re-concreting each strip. Hit and miss strip construction would have been required since the bridge had to have one lane open at all times and it was feared that to do otherwise would weaken the deck such that failure could occur. To avoid this problem and to strengthen the deck in a non-destructive way, the contract alternative of applying CFRP strips was chosen.

Sika Carbodur strips were installed in eight areas of the slab found to be in need of strengthening. Strips were installed at 500-mm centres. The hydromilled deck surface was rough and an initial levelling course of Sikadur 30 epoxy was applied. A 2-mm layer of Sikadur 30 was also applied to each strip using a convex application tool so that, initially, more epoxy was applied to the middle of the strip, after which it was rolled to remove the excess. One day later, the strip's back, which would be in contact with the new deck overlay, was cleaned, sanded and given an application of Sika Armatec 110 binding agent approximately four hours prior to installing the overlay.

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Crowchild Trail Bridge

Many of Canada’s bridges require upgrading because they were not built to handle the weight of today’s increased traffic loads. Calgary’s Crowchild Trail Bridge is one such case. The 90-m long, 11-m wide bridge carries two lanes of traffic over its three continuous spans. While the deck slab itself is free of reinforcing, it is supported by five steel girders and external steel straps. Glass fibre reinforced polymer (GFRP) C-bars were used to provide the continuity and to minimize the transverse cracks of the steel-free deck over the intermediate bridge piers. Based on the results of a full-scale model test at the University of Manitoba, GFRP C-bars were also used to reinforce the cantilever slabs of the bridge. On a tendered basis it proved to be the least costly option.

The deck has cantilevers on either side, reinforced with GFRP rods. To reduce surface cracks, the bridge deck concrete contains short random polypropylene fibres. This bridge is stronger, more resistant to corrosion and less expensive to maintain than if it had been constructed using traditional methods and materials. The bridge is also outfitted with remote monitoring technology: 81 strain gauges, 19 embedded gauges, five thermisters, three smart glass rebars and two fibre optic gauges.

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Inuvik Timber Piles

Buildings in the Arctic are typically supported using untreated timber piles. A recent study has revealed that decay is present in a large percentage of existing piles, potentially causing buildings to become unstable. In response to this problem, a method for the repair of existing heavily decayed timber piles using glass fibre reinforced polymer (GFRP) sheets and grout injection was examined. Typically, the use of GFRP sheets provides an advantage over other conventional materials due to their high strength, light weight and ease of installation. In this application, the use of a lightweight material such as GFRP may also reduce the significant cost of transporting materials to remote regions in the Arctic. The use of fibre optic sensing technology will also be implemented to monitor the success of this repair technique in service.

A program for development of the repair technique was recommended, beginning with an initial feasibility study to determine the cost and structural reliability of the technique. The first phase would involve experimental testing of repaired pile specimens, followed by a freeze-thaw durability study in the laboratory.  The research program would culminate with the repair and monitoring of severely decayed piles in the field.

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