THEME 2 PROJECTS

Materials Science and Innovative Structures

Director: Dr. Nemkumar Banthia, University of British Columbia

THEME 2 OVERVIEW

Materials Science

One of the objectives is to understand concrete-FRP bond at high strain rates and to develop bonding agents that enhance such a bond. Another is to study the improvements in the impact resistance of reinforced concrete beams and plates by applying an externally bonded FRP. The project includes full scale blast tests and the development of structural health monitoring to mitigate damage during severe blast conditions.

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The project consists of developing techniques for the manufacture of composite rebar using the new improved polymer resin with glass fibre using pultrusion and in the process determine the effect on the nanoclay particles in the polymer. Determination of the resultant bond strength, flammability resistance and water/alkali-water absorption of the composite components also form part of the research.

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The first goal of this project is to establish the optimization of the bond performance of FRP strengthening systems for reinforced concrete structures. The second is to better understand and improve the durability of FRP/concrete interfaces. The objective is to develop reliable numerical tools and experimental techniques for predicting bond behavior and to exploit these tools to analyze and enhance bond performance for concrete structures. Design guidelines will be developed regarding durability of FRP strengthening techniques.

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The objective is to develop prediction models (simple and sophisticated) to predict the service life of components associated with concrete structures in their natural environment. These will be used to estimate the advantages and disadvantages of using FRPs for reinforcement compared to other alternatives. Decision analysis will be incorporated in the prediction models as it affects the life cycle cost prediction of a structure. Eventually the research results will be used to enhance the ISIS technology transfer program to the user sector.

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This project will extend the current research on Fire Resistance of FRP Systems to include new concrete structures constructed with internal FRP reinforcement and existing structures repaired with near-surface mounted FRP reinforcement. The focus will be on beams and slabs, since these are the most relevant applications for internal FRP reinforcement. The experimental program will be complimented with the development of numerical models to predict the behaviour in fire of concrete beams and slabs containing FRP reinforcement. The outcome will be design recommendations for practicing engineers.

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The project consists of investigating the durability and serviceability performance of FRP reinforced concrete deck slabs subject to real operational environments. This includes the quantification of the different design parameters on their behaviour and to define acceptable ranges (design factors) for glass and carbon bars based on the design of FRP reinforcement for concrete bridges.

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Establishing Serviceability Stress Limits for GFRP Reinforcement in Natural Weathering Environments (F2.1.7)
Project Leader: Dr. John Newhook, Dalhousie University

Fibre reinforced polymer (FRP) reinforcement is now permitted by code documents in Canada as internal reinforcement for concrete components. A long-standing issue with the user sector though has been questions related to the potential alkaline-based deterioration of glass fibres in concrete. The recent round-robin durability study undertaken by ISIS through tests facilities at the University of Manitoba, University of British Columbia, Universite de Sherbrooke and the University of Saskatchewan has demonstrated to the world that durability problems observed in some aggressive conditioning environments in the laboratory are not observed in field structures. This work has gained world-wide attention and increased the acceptance of GFRP. In the forthcoming edition of the Canadian Highway Bridge Design Code, the results of this study were instrumental in convincing the code committee to permit GFRP as primary reinforcement. While this is an important step forward, a significant limitation on the use of GFRP still remains. The permitted service stress level for GFRP will be 25% of ultimate. This stress limit inhibits the designer’s ability to optimize the use of GFRP in certain components, particularly if a level of prestressing is desired. A second and equally important issue is the question of whether the service stress limit is influence by the exposure environment. For example, does GFRP have different durability performance in a marine environment then it has in a cold dry environment. The limit on service stress in GFRP stems from earlier laboratory research in which the durability of GFRP was linked with the level of sustained stress. Based on the realization that actual field performance of GFRP is much better than predicted by aggressive laboratory experiments, it is proposed that this stress limit may be very conservative. While the structures used in the previous core extraction study were in different exposure environments, unfortunately the cores were extracted from portions of the structures which were not highly stressed regions of the structure and therefore did not directly address the service stress limit issue specifically. To investigate this issue, new long-term testing is required in which the natural conditioning environments cover a wide range of exposure conditions found
across Canada and the level of GFRP service stress is known. The objective of this project is to establish safe serviceability stress limits for GFRP based on long-term behaviour in natural conditioning environments. The results should be applicable to both non-stressed (concrete tension field) and prestressed (concrete compression field) applications. It is hoped that the results will be influential in the next revision of relevant codes.

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Innovative Structures

Investigation of Fatigue-Durability Interaction in Bridge Deck Slabs (F2.2.1)
Project Leader: Dr. Aftab Mufti, University of Manitoba

One objective of this project is to establish the relationship between fatigue damage in the cantilever overhang of a concrete bridge deck slab. Another is to determine the durability of GFRP bars in the slab that is exposed to a salt-laden environment as compared to steel bars in the same condition. Another objective is to study the relative effectiveness of GFRP and steel bars in controlling cracks under repeated loads in a well confined cast in place deck slab that is exposed to de-icing salts. Additional investigations related to fatigue and durability are also planned for other structural components and configurations.

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The objective is to develop durable and innovative precast bridge modules for rapid erection using concrete-filled FRP tubes. Circular tubes will be used for pier columns and rectangular tubes for the cap beam of the piers and girders. A lightweight GFRP deck will be supported by the rectangular girders. The project has four sub-themes with the first three conducted at Queen’s and the fourth carried out at the University of Manitoba. The composite action will be examined using a full scale composite system tested in bonding.

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Sandwich FRP/Foam Cladding Panel (F2.2.3)
Project Leader: Dr. Amir Fam, Queen's University

Traditionally, architectural precast wall panels have been fabricated using reinforced or prestressed concrete. While these panels have been successful for years, advances in composite materials have now made it possible to develop a new generation of superior panels that overcome a number of shortcomings of conventional concrete panels. The new panels are composed of high density yet lightweight foam, sandwiched between two thin layers of high performance carbon fibre reinforced polymer (CFRP) laminates. The self weight of the composite panel is substantially lower than conventional concrete panels. Since self-weight is essentially the largest component of the loads that buildings are designed for, it is expected that composite panels will lead to significant costs savings in the structural system of a building (beams, columns and foundation), as well as savings in the costs of transportation, handling, lifting and installation. Another major feature of composite panels is that they are immune to aggressive environments due to their non-corrosive characteristics. This research program is geared towards understanding the structural behaviour and various failure mechanisms of the composite panels under loading conditions designed to simulate the actual environment.

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