Theme 3 Projects (2002-2006):
Structural Strengthening and Rehabilitation with FRPs
Director: Dr. Kenneth Neale, Université de Sherbrooke
Focus Area 3.1: Assessment of FRP Repairs in Canadian Environments
FRP Repair Systems for Cold Weather Conditions (3.1.1)
Project Leader: Dr. Mark Green, Queen's University
An important concern, of particular interest in Canada, is the behaviour and durability of FRP repair methods for concrete structures under cold weather conditions. Initial research conducted by ISIS and others indicates that FRP repair methods perform satisfactorily in cold climates. However, all of this research was conducted on small-scale specimens and, furthermore, the combined effects of cold climates and loads were not considered. Thus, the main research needs are to assess scale effects and the combination of loading with cold environments. In this research program, small-scale reinforced concrete columns and beams strengthened with FRP sheets are being subjected to various combinations of cold region conditions and loadings. Additionally, larger scale specimens are being subjected to similar environments to examine scale effects. Numerical models are being developed to predict the behaviour of the strengthened specimens under cold region conditions. The project also incorporates field applications of FRP rehabilitation of bridges.
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FRP Repair Systems for Corrosion Damaged Flexural Members (3.1.2)
Project Leader: Dr. Khaled Soudki, University of Waterloo
In Canadian climates, where the extensive use of de-icing salts leads to the rapid corrosion damage of our infrastructure systems, FRP repair systems can potentially provide significant benefits of (i) increased service lives of structures, and (ii) decreased negative environmental impacts. Although many FRP repair systems are being proposed to prolong the service life of corrosion-damaged flexural members, their behaviour under service conditions is not well understood. The focus of this project is the serviceability and durability of FRP repair systems for reinforced concrete flexural members subjected to aggressive corrosive environments and service loads. In this study, chloride-contaminated reinforced concrete beams are being subjected to accelerated corrosion by impressed current. The beams are being repaired following moderate or severe corrosion by externally-bonding FRP sheets, and the performance of the FRP repairs is being monitored over time. Prediction models are being developed for FRP repair systems of corrosion-damaged reinforced concrete beams. This project will result in more effective rehabilitation methods for concrete structures suffering from steel reinforcement corrosion.
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FRP Repair Systems for Corrosion Damaged Columns (3.1.3)
Project Leader: Dr. John Bonacci, University of Toronto
Standard options for the corrosion repair of load-bearing elements are either very expensive (e.g., reconstruction), or cheap but rather ineffective (e.g., patching). This research aimed for a middle-ground alternative, using externally bonded FRPs, that is both acceptably durable and relatively inexpensive. Advanced repair techniques of this kind will potentially have a profound effect on the infrastructure repair deficit, as well as broaden the role that FRPs can play in the infrastructure renewal market.
Recent studies have shown that FRP wraps are effective for restoring corrosion-damaged columns to better than original performance, even when corrosion is allowed to continue. These are promising indications from the point of view of economical approaches to infrastructure rehabilitation. However, more specific study is needed before these developments can have practical impact. The idea of rapid repair (wrapping over a damaged column) is being addressed. Monitoring data obtained during this study is being used to form a basis for a long-term structural health monitoring system as part of column wrap repairs.
To enable stakeholders to make the best choice of repair alternatives with varied performance lives and condition improvements, a performance-based life cycle comparison should be made. In this project, tools have been developed for carrying out these kinds of evaluations. Early versions of the software relied on empirical performance data. Development of mechanistic performance models is ongoing.
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Repair and Strengthening of Specialized Concrete Structures (3.1.4)
Project Leader: Dr. Shamim Sheikh, University of Toronto
This research is aimed at developing retrofitting techniques for concrete structures that are simultaneously subjected to extreme physical and environmental loads. These techniques must be able to impart strength and ductility to the members to dissipate energy from extreme loads and must be durable. Both the structural and durability aspects of FRP-retrofitting have experimental and analytical components.
The structural experimental work involves testing of large-size to full-size specimens of concrete columns, beams and slabs under normal and simulated extreme loads such as earthquake, blast and impact loads. The experimental work on the durability aspect of repair focuses on structures in extreme Canadian environments and in specialized industries such as nuclear and other power generating stations, cement manufacturing plants and oil and gas installations. The performance of FRP and FRP-concrete composites is investigated under environmental conditions such as high temperature, freeze-thaw, gamma (nuclear) radiation, etc., while most of the specimens are subjected to service loads. Field applications and monitoring are an important component of this program.
Analytical modeling of structural behaviour will be carried out with the aim of developing design procedures and guidelines, taking into account the structural and durability aspects. Models developed for steel reinforced concrete members have been investigated for their application to FRP reinforced members and new formulations will be and are being developed, where needed.
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Focus Area 3.2: Concrete Structures
Strengthening of Existing Structures (3.2.1)
Project Leader: Dr. Pierre Labossière, Université de Sherbrooke
This project addresses the following three issues related to the extension of the service life of reinforced concrete structures through: (i) the flexural and shear strengthening of concrete beams and slabs with FRP sheets, FRP laminates, or near-surface-mounted FRP rods, (ii) the confinement of columns with FRP wraps for axial and lateral load capacity improvements, and (iii) the integral study of complete structural systems consisting of FRP-strengthened elements of different types. Many results have been published on the first two of the above issues over the last few years; consequently, this project concentrates on questions related to complex loading conditions which have not been investigated so far. Fatigue and cyclic loading conditions and their effects on FRP strengthening schemes, in particular, are being studied in detail. For both beams and columns, a substantial portion of the research activities is experimental, and is complemented by finite element modelling and advanced statistical analyses.
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Sprayed FRPs for Rehabilitation (3.2.2)
Project Leader: Dr. Nemkumar Banthia, University of British Columbia
The ISIS research program at the University of British Columbia has taken a worldwide lead in the development of a unique method of repair using sprayed FRPs. Research so far has clearly shown that this method is highly cost-effective, simple to apply, and produces repair solutions with performances that equal or exceed other traditional techniques. The potential economical benefits of its continued development are numerous, and could translate into substantial savings for both private and government sectors.
To date, research on sprayed FRPs has focused on the development of the technique itself and towards demonstrating its effectiveness. The objective now is to fully optimize the spraying process to produce sprayed FRPs with a minimal rebound, maximum reinforcement efficiency, an optimal bond with the substrate, and an adequate long-term durability. Plans are underway to carry out damage-based modelling of these materials to further optimize their properties. With the bulk of the work done so far on concrete flexural elements, it is intended to extend this technique to concrete columns, to seismic retrofits and to timber, steel and masonry structures. The use of sprayed FRPs as protective coatings will be extended also to structures in extremely aggressive environments.
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Creep and Fatigue of FRP Strengthened Structures (3.2.3)
Project Leader: Dr. Kenneth Neale, Université de Sherbrooke
It is well known that the application of FRP sheets on the surface of a concrete element can increase its strength considerably. However, the extended use of a structure at loads that can be much greater than the original design loads may compromise the safety of the structure if no provisions are made with regard to creep and fatigue. The research includes experimental investigations on the long-term effects of various parameters such as the bonding polymer, the confinement or strengthening level, the FRP and steel reinforcement ratios, the concrete strength, the level of stress and the level of damage prior to rehabilitation. Creep and fatigue tests on columns will be performed, as will similar tests on beams in flexure. Theoretical analysis is also being performed in order to provide tools readily usable to prescribe load and strain limitations in design.
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Performance of Retrofitted Structures Under High Strain-Rate Loading (3.2.4)
Project Leader: Dr. Patrick Paultre, Université de Sherbrooke
The objective of the research is to develop simple, reliable and efficient methods using FRP materials for the rehabilitation of reinforced concrete bridges and buildings. These methods are being applied to full-size structures built in the structures laboratory. The structures are being tested under earthquake loading by pseudo-dynamic and substructure testing techniques, and will subsequently be rehabilitated with FRP materials. The performance of the retrofitted structures will be assessed by means of both experimental and analytical techniques.
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Effects of Low Temperature and High Strain Rate (3.2.5)
Project Leader: Dr. Robert Tremblay, École Polytechnique de Montréal
Considering that more than 75 percent of the bridges in Canada were built before modern seismic design requirements were implemented in bridge codes, there is an urgent need for retrofitting bridges located in active seismic regions. The seismic risk associated with reinforced concrete bridges in eastern Canada, particularly along the St-Lawrence Valley in Québec, is exacerbated by the fact that these bridges can experience earthquakes during winter conditions. If an earthquake occurs in winter, the structural elements could be subjected simultaneously to high strain rate and low temperature effects. These combined effects can change the mechanical properties of the materials (steel, concrete and FRP), and possibly alter the seismic behaviour and failure modes of these structures. The use of FRP for retrofitting seismically deficient structures has shown its efficiency. However, little or no research has been carried out on the combined effects of high strain rate and low temperature on the mechanical properties of the FRP. The objective of this research is to provide an understanding of these effects on reinforced concrete bridge columns retrofitted with FRP. A secondary objective is the evaluation of the performance and durability of fibre optic sensors for the seismic health monitoring of reinforced concrete bridges located in seismically active cold regions of Canada.
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Focus Area 3.3: Timber, Steel and Masonry Structures
Strengthening of Existing Timber Structures (3.3.1)
Project Leader: Dr. Ken Johns, Université de Sherbrooke
This project aimed to deepen the understanding of how FRP reinforcements contribute to the strengthening of timber beams. Work done at the Université de Sherbrooke and the University of Manitoba towards the end of the first phase of the ISIS Canada mandate has shown that there were much greater gains in strength for timber beams than what could be predicted by simple analysis models. More sophisticated behaviour models need to be formulated before reliable predictions of strength increase can be obtained. The objective of this project was to formulate and verify these models.
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Durability of FRP Strengthened Timber Bridges (3.3.2)
Project Leader: Dr. Dagmar Svecova, University of Manitoba
The use of FRPs as near-surface-mounted reinforcement for timber bridges has been shown to reduce the cost of bridge repairs by over 80 percent. As the strengthening is carried out while the bridge is open to traffic, traffic interruptions and public inconvenience are kept to a minimum. Manitoba has many timber structures, most of which need rehabilitation. If strengthening using FRPs can be shown to be a feasible solution in Manitoba, there can be an enormous economical potential in using this technique elsewhere in Canada, as well as internationally. This project will optimize the strengthening technique using near-surface-mounted FRP bars, or laminates, and the performance of strengthened creosote-treated timber beams under environmental conditions including temperature and humidity effects. The bond length of the bars is being determined for this application, together with the most effective configuration of the groove. Half-scale and full-scale beams are being tested to verify the effectiveness of the reinforcement schemes on the strength and mode of failure.
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FRP Strengthening Systems for Steel Structures (3.3.3)
Project Leader: Dr. J.J. Roger Cheng, University of Alberta
The use of FRPs in the repair/rehabilitation of steel structures is relatively unproven. The objective of this project is to develop such technologies using FRPs for aging/damaged steel structures, in particular, steel pipelines, and railway and highway bridges in cold regions. Structural rehabilitations can generally be classified into four types of enhancement: strength, stiffness, toughness, and ductility. By contrast with other conventional construction materials such as concrete and timber, steel itself is a high performance material but difficult to construct and susceptible to buckling, corrosion, or brittle fracture and fatigue. In this project, the use of FRPs on steel structures focuses on the last three types of enhancement to fully utilize the unique material characteristics of FRPs over steel. Fundamental research covers the bond behaviour between FRPs and steel, the stress distribution in FRP patches and wraps, the fatigue and corrosion resistance of FRPs on steel, the toughness and durability of the repair, and the optimum design of FRP patches and wraps. Applied research focuses on the application and transfer of the technology to industry-related projects, mainly on aging pipelines and railway and highway bridges, and the fracture and fatigue control of steel structures in cold regions.
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Rehabilitation of Masonry and Historical Brick Structures (3.3.4)
Project Leader: Dr. Alaa Elwi, University of Alberta
Older masonry structures have the characteristic of being lightly reinforced. They have well-defined joint patterns that provide distinct failure planes detailed to withstand only wind and gravity loads. These structures are thus highly susceptible to damage caused by either out-of-plane or in-plane loading during a storm or seismic event. Recent research conducted at the University of Alberta and elsewhere has demonstrated the potential of using FRPs in the repair and rehabilitation of masonry structures for strength and ductility enhancements. With strategic and adequate application of FRPs, increases in strength of several times the flexural capacity of existing masonry walls have been demonstrated.
This research project is a continuation of existing work to systematically study and optimize the use of FRPs in the repair/rehabilitation of masonry structures. The research focuses on flexural, axial and shear strengthening, ductility enhancement, and the improvement of structural performance necessitated by functional requirements (e.g., openings in walls) in existing masonry structures. The projects include fundamental analytical and experimental research, as well as practical applications with possibilities of field implementations. Full-scale tests with realistic loadings have been conducted on tall bearing walls under eccentric axial compressive forces as well as on masonry shear walls with openings. In addition, small detailed specimens have been tested to map out bond interface behaviour between masonry blocks and CFRP sheets. This is all backed by nonlinear finite element simulation intended to give an insight into the behaviour as well provide extensive parametric information for design purposes.
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Design Manual Update (3.3.5)
Project Leader: Dr. Kenneth Neale, Université de Sherbrooke
One of the major accomplishments and tangible results of Phase I of the ISIS mandate was the publication of four design manuals in 2001. These manuals were developed over a two-year period by Network participants under the leadership of the ISIS Theme Directors. These manuals were prepared for two reasons. The first is to provide practicing engineers with detailed guidelines regarding the use of FRPs and FOSs in the design and construction of civil engineering structures. The second is to provide a credible reference for the Code Committees to facilitate and accelerate changes to existing codes which did not envisage the use of advanced composite materials such as FRPs.
New chapters are being added and the manuals are in the process of being updated with additional case studies.
 More information on Design Manuals
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Completed Research 1995 to 2006
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