This research activity is being carried out in collaboration with the industrial partner Arian Sazeh Inc. and scientist from the Industrial Material Institute (IMI) of the NRC located at Boucherville, Montreal. It worth mentioning here that the manufacturing plant of Arian Sazeh Inc. for the development of FRP products is located inside the building facilities of the IMI, which offer a close collaboration with the experienced and knowledgeable scientists in this area and using the modern and heavy equipment of the IMI.
Canadian roads, especially in Québec, have a great number of wood bridges. Most of these bridges are structurally deficient. The design life of the wood bridge decks in the Canadian sever weathering conditions is approximately 15 years. The repair, rehabilitation, and replacement cost besides the damage due to traffic interruption is huge. Therefore, the need to have durable bridge decks with longer life span and with minimum maintenance is necessary. Fibre reinforced polymer FRP is a promising material system for use in bridge construction due to its lightweight, high-strength characteristics, in combination with durability and resistance to corrosion. As a result, the use of FRP in bridge applications has been a source of much investigation and experimentation in recent years. One of the most likely uses of this material in future bridges is FRP bridge decks over steel or concrete girders. In this application, FRP decks are used as a lightweight, corrosion resistant, replacement for traditional steel reinforced concrete decks. Often, due to unfavourable condition assessments, a particular bridge may be posted for reduced live-load capacity. FRP decks are attractive in these kinds of applications as they may be used in deck replacements to decrease the total dead load, which normally can be a significant percentage of the total load demand and hence increasing the live load capacity of the structure. FRP bridge decks offer a number of other advantages. For example, they are resistant to corrosion, placed very rapidly compared to typical cast-in-place reinforced concrete decks, and FRP also has excellent energy absorption characteristics.
In addition, based on the type of the polymer used, fibre composites can be either thermo-set or thermo-plastic, the latter type is superior since it needs lower production cycle time, produces non-volatile organic compound, can be re-shaped after processing, and is 100% recyclable. Thermoplastic composites are yet to be taken full advantage of in the construction industry. To-date, very limited research has been published on composite bridge decks, and none on thermoplastic type. Presently, the largest concern regarding FRP decks in the bridge industry involves the initial higher price of an FRP deck compared to that of a concrete deck. In the long run, the higher cost of FRP may be justified by considering life-cycle costs; the added durability and corrosion resistance will enhance the deck performance and reduce the need for deck replacements. Also, as FRP becomes more widely used, production quantities and manufacturing advances will help to reduce individual project costs. Furthermore, design provisions for this type of FRP bridge decks will be included in the amendment for the Canadian Highway Bridge Design Code CHBDC (CAN/CSA S6-00, Chapter 16 - dealing with FRP as reinforcement for concrete bridges) that will be published in the next Spring 2005.
The aim of this research activity is to develop through design, dimension and load test, a prefabricated bridge deck made of glass fibre woven roving reinforced polypropylene and polyurethane structural foam (sandwich panel) to replace the deficient wood decks (in collaboration with Arian Sazeh Inc). This research program involves several stages to develop a bridge deck prototype including the selection of the adequate design concept, fabrication process considerations, design objectives, structural shape through a parametric study involving finite element analysis (FEA) using a vertical load pattern prescribed by CHBDC. In the first phase of this research task, several mechanical and durability tests will be needed for the base material (thermoplastic glass fibre composite), which include cross-section properties, longitudinal tensile properties, shear strength, flexural tensile, thermal effects, fatigue resistance, creep rapture, wet-dry cycling, freeze-thaw cycling, contact with acid or alkali solutions, diesel fuel, exposure to UV radiation and humidity, the water absorption and adherence properties of the polyurethane foam to the GFRP.
In the second phase, prototype bridge decks will be fabricated afterwards and
testing under static and cycling loading. Two concentrated loads (each over
250x600 mm (representing the foot print of a truck wheel according to CHBDC)
will be applied to the deck. The static load test will evaluate the
load-deflection behaviour, the local deformations, and the mode of failure of
the deck, while the cycling load test will measure the performance under
sinusoidal loading at a frequency of 2 Hz till failure. These tests will reveal
the ability of the proposed system to support design loads. The results obtained
will be used to refine the design to fabricate the first composite bridge deck
for field evaluation.
The refined product will be installed in the field as a replacement of existing deteriorating bridge deck (in collaboration with the MTQ). This step will provide accurate data on the response of the system to actual field loads and environmental conditions. It will help promote the product and give the departments of transportation the confidence to use the proposed system to replace damaged bridge decks.
One issue that remains for the FRP bridge decks to be widely accepted is the need to develop an adequate and reliable connection between the deck and the steel girder. Current connection devices (shear stud connections, clamped connections, and bolted connections) are primarily proprietary in nature, developed by FRP bridge deck manufacturers, and the strength and long-term performance of these have not been deeply investigated. The primary purpose of this research task is to develop a universal connection for FRP decks to steel stringers. The goal is to develop an economical and durable means of providing a positive connection from the deck to the steel stringer and to thoroughly investigate the performance of this connection. During the development of this connection, composite action between the deck and supporting girder is neglected. This is appropriate due to the findings of limited studies focused on design economy indicating that, because of the high modular ratio between the FRP deck and the steel girder, even full composite action contributes negligible stiffness to the girder. Therefore, in practical applications, there is a little benefit to be gained by considering composite action.
The scope of this task includes the development of a new connection (in collaboration with Arian Sazeh Inc), followed by experimental and analytical evaluations of the proposed connection. Specifically, once a new connection is developed, component level testing of individual connections is performed. This includes experimental testing of several variations of the connection to determine the most appropriate design. Then system level tests are conducted, implementing the selected connection in a reduced-scale model bridge. This bridge system is loaded statically to assess the system performance of the selected connections, as well as investigate the load distribution characteristics. A finite element model of the scale model bridge is formulated to assist in future efforts related to investigating load distribution characteristics for other girder configurations. As a result of these efforts, it is expected that the reliable performance of the proposed connection will be experimentally and analytically verified, resulting in the possible implementation of this connection in future projects involving FRP bridge decks in collaboration with MTQ.