Key Research Accomplishments

Theme 2 (2002-2005):
Materials and Innovative Structures

Director: Dr. Nemkumar Banthia, University of British Columbia

Focus Area 2.1:  Materials Science

Integrated Durability and Fundamental Materials Assessments (2.1.1)
Project Leader: Dr. Nemkumar Banthia, University of British Columbia

2002-03

The primary objective of this project is to assess durability performance of commonly applied polymer and fibre reinforced polymer systems in civil engineering applications. In the first year, the focus has been repair system. In the subsequent years, the investigation will be expanded to include FRPs used in new construction. In the context of FRP repairs, chemical, thermal, UV, and mechanical degradation processes are being investigated with possible combinations of agents responsible. Throughout, 150 mm x 300 mm concrete cylinders have been chosen as a medium for these studies. Cylinders are given one of the three surface preparations and wrapped with commercially available FRP using the epoxy systems supplied by the manufacturers. Some new bi-functional bonding agents are also being investigated. Some cylinders have been pre-stressed to various levels of stress. Cylinders are subjected to various combinations of chemical, thermal; UV and mechanical deterioration and their performances are being monitored via periodic cyclic compressive tests in a closed-loop environment. From the resulting cyclic stress-strain responses, damage parameters are being calculated. In a separate series, samples have been pre-damaged by loading them to approximately 60% of their ultimate load capacity and then exposed to a deleterious environment. Accomplishments include:

• Fundamental understanding of research needs in the field of FRP durability.
• Development of rational test procedures for a comprehensive assessment of durability characteristics of FRP-concrete repair systems.
• Comprehensive understanding of materials science issues involved in FRP durability.

2003-04

• Development of an extensive database of publication related to FRP durability.
• Development of rational test procedures for a comprehensive assessment of durability characteristics of FRP-concrete repair systems.
• Comprehensive understanding of materials science issues involved in FRP durability.
• Studies of shear crack growth at interface between concrete and FRPs.
• Study of the influence of various surface preparation techniques and bonding agents on the short term and long term performance of the shear interfacial bond.
• Studies of interfacial fatigue crack growth under repeated flexural load at FRP-Concrete interface.

2004-05

• Development of rational test procedures for a comprehensive assessment of durability characteristics of FRP-concrete repair systems.
• Comprehensive understanding of materials science issues involved in FRP durability.
• Studies of shear crack growth at interface between concrete and FRPs.
• Study of the influence of various surface preparation techniques and bonding agents on the short term and long term performance of the shear interfacial bond.
• Studies of interfacial fatigue crack growth under repeated flexural load at FRP-Concrete interface.

2005-06

The primary objective of this project was to assess the durability performance of commonly applied polymer and fiber reinforced polymer systems in civil engineering applications. In the context of FRP repairs, chemical, thermal, UV, and mechanical degradation processes were investigated with possible combinations of agents and stress.

The key accomplishments include:

Development of rational test procedures for a comprehensive assessment of durability characteristics of FRP-concrete repair systems.

• Comprehensive understanding of materials science issues involved in FRP durability.
• Studies of shear crack growth at interface between concrete and FRPs.
• Study of the influence of various surface preparation techniques and bonding agents on the short term and long term performance of the shear interfacial bond.
• Studies of interfacial fatigue crack growth under repeated flexural load at FRP-Concrete interface.

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Durability of Polymer Interfaces (2.1.2)
Project Leader: Dr. Suong Van Hoa, Concordia University

2002-03

External reinforcement of concrete using composite:

1. The effect of the presence of water on the rate of cure and also on the properties of epoxy resin adhesives has been determined. When epoxy adhesives are used to bond composite sheets to concrete, they are applied in the field. As such, water exists on the surface of concrete. This water may come from rain or in the moist air. The presence of water may interfere with the bonding of the composite sheets to concrete. Work has been done on the effect of different amounts of water on the curing rate of the epoxy adhesives and also on their resulting properties. Two types of epoxies were investigated. One is a generic epoxy (Shell Epon 828) and the other is a commercially available epoxy (Sikar Dur 30). This knowledge would be useful for the people that apply the composite sheet to the concrete. It also provides assurance to the people that use the system (the customer of the technology).
2. The effect of amount of hardener on the curing of the epoxy adhesives and the resulting properties have been determined. Epoxy adhesives consist of two parts: the epoxy resin itself and the hardener (or curing agent). The amount of hardener has influence on the curing rate and also on the resulting properties. Since the application of the adhesive is in the field, variation from the exact amount may occur. Investigation has been made of the effect of this variation. This knowledge is useful for the people that apply the adhesives and also for the people that use the system.

Internal reinforcement using composite:

A new reinforcement rod of wavy shape was developed before the start of the ISIS project and it was patented. This rod provides three features that are more advantageous compared to current rods. First the rod has wavy shape which improves the mechanical interlock between the rod and concrete, thus improving shear transfer. Second the rod is made of thermoplastic composite, which enables bending. Third the rod consists of a shell of composite and a relatively cheap core, thus enables to reduce the cost of the material. A Master thesis student has worked on the stress analysis of the rod/concrete system for the optimization of the shape of the wavy rod. The achievements of this work are as follows:

1. An optimized shape for the rod has been determined. This gives the ratio between diameter of the lobe and the diameter of the rod so that maximum reinforcement effect can be obtained. Both spherical shape and ellipsoidal shape lobes were studied.
2. Optimal distance between rods was determined.

2003-04

Effect of presence of water during the curing of the epoxy adhesive has been studied and documented. During the application of composite sheets to reinforce concrete in the field, water is invariably present. The presence of water may affect the curing of the epoxy adhesive and as such may affect the performance of these adhesives. The effectiveness of the composite reinforcement depends to a great extent the bonding to the concrete through the epoxy adhesives. The report in the form of a journal publication has shown that small amount of water (less than 3%) can enhance the performance of the epoxy adhesive whereas a large amount of water can be detrimental to the performance of the adhesive. The job is therefore how to control this amount of water.

Water absorption of water into the epoxy adhesive was greatly reduced by the incorporation of nanoclay particles into the epoxy resin. During the normal operation of the composite reinforcement to concrete, or the normal operation of the optical fibers in the concrete, water can absorb into the epoxy adhesives. Again this absorption can degrade the bonding effectiveness of the adhesive. Incorporation of nanoclay particles into the epoxy decreases the rate and amount of water absorption into epoxy by more than 30%. This can significantly prolong the durability of the interface between the composite reinforcement or optical fiber with the concrete.

Flammability resistance of epoxy adhesive has been greatly enhanced with the incorporation of nanoclay particles. For the use of polymeric resins such as epoxy or polyester in concrete, either in the form of polymeric composites for reinforcement or for bonding optical fibers to the concrete, flammability is a great concern. Incorporation of nanoclay particles into epoxy have been shown to greatly improve the flammability resistance of the epoxy resin. It was shown that epoxy with nanoclay particles can become self extinguishing after being burnt with a fire. This improvement can significantly improved the confidence of the users.

2004-05

Epoxy resins have been worked to improve flammability resistance. Nanoclay particles have been used. Significant improvement of flammability resistance of these epoxy resins has been obtained. It has been demonstrated that while unmodified epoxies keep on burning after the fire source is extinguished, the epoxies modified with the nanoclay are self extinguishing. This exciting improvement has attracted attention from a few companies to improve their resins. These are ADS Marquez Composites, GyF Plastiques Inc., Epoxy Tech and Forintek Inc. in Quebec. One important thing to note is that while many epoxies now possess good flammability resistance, however these epoxies contain halogens such as chlorine and bromine which are toxic. While these materials are still allowed in North America, they have been banned in Europe. If North America also follows the lead in Europe, then the existing epoxies with flammability resistance will not be allowed to be used. The epoxies developed here will be a good replacement. The cost of the modified epoxies is not much more than the cost of the current epoxies.

Properties and behavior of the effect of the amount of curing agent on the properties of epoxies have been determined. This is useful to understand the effect of variation in curing agents, as may occur in the field applications, on the properties of the composite/adhesive/concrete assembly.

2005-06

• Dr. Hoa was invited to give a plenary lecture on Polymer Nanocomposites at the annual meeting of the American Society for Composites, held at Drexel University in September 2005.
• Dr. Hoa was invited to give a seminar at the Department of Chemical Engineering, West Virginia University on Polymer Nanocomposites, October 2005.
• Four companies in Quebec have agreed to participate into the exploitation of the Polymer Nanocomposites technology developed at Concordia. These are Marquez Transtech (on flammability resistance of epoxy adhesives), Forintek  Ltd  and Epoxy Tech Ltd. (On durability of adhesive used in bonding woods), and GyF Plastiques Ltd. (On strength and flammability resistance of adhesives).
• Dr. Hoa became the Concordia representative of the network Nanoquebec.

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Monograph on Durability of FRPs in Civil Infrastructure (2.1.3)
Project Leader: Dr. Nemkumar Banthia, University of British Columbia

2003-04

• Significant part of literature search has been completed.

2004-05

• Chapters are being edited/assembled.

2005-06

• Chapters are being edited/assembled.

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Mechanics and Durability of FRP/Concrete Interfaces (2.1.4)
Project Leader: Dr. Kenneth Neale, Université de Sherbrooke

2002-03

Fundamental models are being developed to characterize interfaces (FRP-to-concrete) for FRPs externally bonded to concrete. Finite element codes incorporating micro-mechanical constitutive laws are under development. These will be validated against appropriate experimental data.

2003-04

• Fundamental material (micro-mechanical) models for describing the behaviour of FRP/concrete interfaces for FRPs externally bonded to concrete have been developed. These are being incorporated into in-house computer codes for investigating the performance of FRP-strengthened beams and slabs.
• In the past year, 3 Ph.D. students and 1 M.A.Sc. student have been recruited for this research.

2004-05

• Various computer codes have been developed for simulating the bond behaviour of FRP-strengthened structures.
• Codes are being validated against experimental data.
• Applications to beams and slabs are in progress.

2005-06

• Computer codes have been developed to model bond behaviour of FRP-strengthened concrete structures.
• Numerical predictions are in excellent agreement with test data.

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Fire Resistance of FRP Systems (2.1.5)
Project Leader: Dr. Mark Green, Queen’s University

2002-03

The work has initially considered the fire resistance of three applications of FRP in buildings:

1. Columns wrapped with FRP
2. Beams strengthened with FRP in flexure and shear
3. Slabs with internal FRP reinforcement

Combined structural and heat transfer numerical models have been developed for all three of these applications. The numerical models can also incorporate insulation applied to the outside of the beams or columns when they are wrapped with FRP. The column model is the most advanced and has been successfully compared against fire tests on reinforced concrete columns and recently against the full-scale FRP wrapped column tests conducted in November and December 2002. The beam model is still under development but some success in comparing the model to published fire test results has been encouraging. The heat transfer numerical models for slabs with internal FRP have been successfully validated against test results published in the literature. Full-scale fire endurance tests were conducted on two circular columns that were wrapped with carbon FRP and insulated with a proprietary coating. These tests showed that such columns can achieve a fire endurance rating (under applied load) in excess of 4 hours according to CAN/ULC-S101. Thus, FRP-wrapped circular columns, with appropriate fire protection, can provide the fire resistance ratings required for building applications.

2003-04

The work has initially considered the fire resistance of three applications of FRP in buildings:

• Columns wrapped with FRP
• Beams strengthened with FRP in flexure and shear
• Slabs with internal FRP reinforcement

Combined structural and heat transfer numerical models have been developed for all three of these applications. The numerical models can also incorporate insulation applied to the outside of the beams or columns when they are wrapped with FRP. The column and beams models have been successfully compared against fire tests on reinforced concrete columns and beams, and recently against the full-scale FRP wrapped column and beam tests conducted in this test program.
Four intermediate scale fire tests were conducted on slabs strengthened with FRP and insulated with different insulation schemes. These tests were conducted to evaluate the effectiveness of the insulation and to provide validation for the numerical thermal models.

Full-scale fire endurance tests under load were conducted on two beam-slab specimens that were strengthened with carbon FRP and insulated with a proprietary coating. Also, a square column wrapped with glass FRP was fire tested under load. These tests showed that such beams and columns can achieve fire endurance ratings (under applied load) in excess of 4 hours according to CAN/ULC-S101. Thus, FRP wrapped columns and beams, with appropriate fire protection, can provide the fire resistance ratings required for building applications.

2004-05

• Numerical modelling – The numerical models for the thermal behaviour of beams were modified based on tests conducted in January 2004. Preliminary validation of the numerical models was conducted. Numerical models were also developed to predict the flexural strength of the beams at room temperature.
• Full-scale tests – Two fire tests on beams were conducted in November 2004. These beams were strengthened with CFRP sheets and protected with sprayed insulation. The beams were exposed to 4 hours of the ULC standard fire and each beam achieved a 4-hour fire rating. Residual strength tests were conducted on these beams (and two other beams from previous fire tests) to determine the remaining strength of the beams after exposure to fire. The beams were tested to failure in flexure and the residual strength of the beams was found to exceed the expected unstrengthened flexural capacity of the beams. Two circular columns were wrapped with FRP sheets and one of these wrapped columns was insulated. Both of these columns will be tested in May 2005.
• Parametric studies – The numerical models for beams were used to evaluate several different parameters such as the type of section, insulation properties, FRP thermal properties and concrete properties.
• Design guidelines – Some preliminary design recommendations have been made for circular columns wrapped with FRP and for beam-slabs strengthened with FRP. These guidelines recommend that the strengthened service load on a strengthened member should not exceed the ultimate design strength of the unstrengthened member. This provides a maximum allowable strength increase in the range from 25% to 70%. Further, the nominal strength at high temperature should at all times be greater than the strengthened service load on the member. It should be noted that these guidelines do not require that the temperature in the FRP remain below the glass transition temperature.

2005-06

1. Numerical modelling – The numerical models for the thermal behaviour of beams have been updated as more tests have been conducted. A thermal model that simulates the moisture movement in reinforced concrete slabs is under development. This model should be more effective at predicting temperatures close to the glass transition temperature of the FRP.

2. Full-scale tests –Two fire tests on columns were conducted in May 2005. These beams were strengthened with CFRP sheets. One was protected with sprayed insulation and the other had no protection. The columns were exposed to up to 5 hours of the ULC standard fire. The insulated column achieved a 4 hour fire rating, and had much reserve strength after 5 hours of fire exposure.  The column without fire protection failed after approximately 3.5 hours of fire exposure. Additionally, two full-scale (300´300´3800 mm) square reinforced concrete columns were constructed for future fire tests.

3. Parametric studies – The numerical models for beams were used to evaluate several different parameters such as the type of section, insulation properties, FRP thermal properties, and concrete properties.

4. Design guidelines – Some preliminary design recommendations have been made for circular columns wrapped with FRP and for beam-slabs strengthened with FRP. These guidelines recommend that the strengthened service load on a strengthened member should not exceed the ultimate design strength of the unstrengthened member. This provides a maximum allowable strength increase in the range from 25% to 70%. Further, the nominal strength at high temperature should at all times be greater than the strengthened service load on the member. It should be noted that these guidelines do not require that the temperature in the FRP remain below the glass transition temperature. Nevertheless, if the strength of the FRP is to be used in fire, then the temperature of the FRP should be kept below the glass transition temperature. This work is being conducted in consultation with American Concrete Institute (ACI) Committee 440 on FRP Reinforcement.

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Service Life Prediction of RC Structures (2.1.6)
Project Leader: Dr. Moh Boulfiza, University of Saskatchewan

2005-06

A general framework for allowing an accurate prediction of the service performance/life of GFRP reinforced concrete structures has been developed. The proposed approach explicitly models the different mechanisms controlling the long-term performance of GFRP composites inside the concrete environment and, hence, provides a natural framework for predicting the performance of the system GFRP+Concrete.

The proposed models should be able to predict the response of traditional accelerated tests as well as more realistic field conditions. Hence, predicting the response of accelerated tests could serve as a means for validation of the models. The following section summarizes the procedure and the progress to date.

Concrete Performance:

At the current stage of the project, we have a fairly complete set of robust models for characterizing the performance concrete under various environments and loadings, including:

• Concrete degradation under external loading;
• Moisture flow and transport of chemical species within concrete;
• Reaction of aqueous species with each other and with solid phases in concrete.

GFRP Performance:

Theoretical work: Models for predicting the performance of GFRP composites are being developed in compliance with the current state of scientific and thermo-dynamical knowledge. In this context it is very important to note that we are far beyond Fick's laws of diffusion. Although numerous diffusion models have been proposed over the years for modeling hygrothermal effects in polymers and polymer matrix composites, the one dimensional Fickian model remains the most frequently used model mainly due to its simplicity. Understanding the mechanisms of water sorption and diffusion in polymers is of particular importance in relation to our ability to interpret related transport phenomena in FRPs and predicting their service life. It has been shown that a polymer below its glass transition temperature (Tg) must possess history-dependent diffusion coefficients and experience time-dependent changes in surface concentrations in order to maintain sorption-equilibrium at its boundaries. These time-dependencies are intrinsically related to the relaxation times for molecular rearrangement in the polymer. Additional structural parameters influencing the transport mechanism include the molecular weight, degree of crosslinking and degree of branching of the polymer, and its thermal and solvent expansion coefficients.

Improved modeling capabilities will be achieved by using Maxwell Stefan equations for setting up the appropriate mass balances, thermodynamical simulations for solubility calculations and the Free Volume Theory for (Multi Component) diffusion. Together with knowledge of chemical degradation, this should allow us to predict the service life behavior.

Experimental work: An intensive effort is underway for creating a database for the transport properties and thermodynamic data relevant to GFRP materials. Experiments required to obtain material properties or for validation purposes, will be carried out in compliance with ASTM D-570 for diffusion and ASTM C-581-03 for chemical resistance. It has been determined that experiments for assessing / validating the osmotic fibre/environment effects should also be carried out. Subjecting a GFRP composite to a combined continuous chemical and mechanical loading is expected to give a different ageing behaviour than in unloaded state, for example caused by strain and creep. Hence, combined tests should be carried out to validate the mathematical models used.

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Focus Area 2.2: Evaluation of FRP Materials for Infrastructure

Durability of FRPs for New Construction (2.2.1)
Project Leader: Dr. Brahim Benmokrane, Université de Sherbrooke

2002-03

The on-going research program includes specimens cut from GFRP rods of different sizes (10, 12, 16, and 19-mm diameter) and CFRP bar size No. 10 (10-mm diameter). The bar specimens are subjected to the individual or the combined effect of alkaline solution (pH 13, concrete environment and simulated pore water solution), sustained tensile load (varying between 10 to 30% of ultimate tensile strength), and four levels of temperatures (ambient, 40, 50 and 60 C). During the last decade, there has been an important increase in the use of Fibre Reinforced Polymer (FRP) Composites bars as concrete reinforcement in the construction industry because of their inherent advantages in terms of light weight, high specific strength and stiffness ratios and their non-corrosive properties. However, the existing design guidelines and codes (ACI 440.1R-01, CAN/CSA-S06-00, CAN/CSA- S806-02, JSCE, ISIS-M03-01) indicate that the prescribed safety factors and environmental reduction coefficients are very conservative and therefore, limiting the large scale use of FRP reinforcements for concrete structures. This conservative design philosophy is based on the lack of validated experimental data related to long term durability of FRP bars. The main objective of the present research program is to investigate the durability of FRP reinforcing bars for different loading and environmental conditions and to predict the service life of FRP reinforcing bars for concrete structures. A new experimental setup for accelerated ageing tests was designed and fabricated (heating tunnel combined with creep steel frames) to include the combination of environmental exposure, temperature, sustained stress levels and exposure times. The FRP specimens used in this study were cut to a length of 1300 mm and grouted with a resin-mortar matrix inside 410-mm long steel tubes at both ends, according ACI 440 K design guideline. Each specimen was instrumented with electrical strain gages to monitor the longitudinal strains and after exposure period, the specimens that did not failed are tested for residual properties, which are compared to the reference properties. To date, eight series, with a total of eighty specimens 10, 12, and 16 mm-diameter GFRP bars, were investigated under two different environmental conditions (de-ionized water and alkaline solution); different loading (20, 30 and 40% UTS), and subjected to temperature varying from 20oC to 75oC during two months and three months. The experimental residual tensile strengths are presented and compared to the sort-term ultimate, guaranteed and design tensile strengths according to the existing design guidelines and codes. Preliminary experimental observations indicate that the used environmental conditions have no significant effect on the physical and mechanical properties of the GFRP bars. Further statistical analysis taking into account the standard deviation of the experimental test results are in progress and a model of service life prediction will be proposed.

2003-04

The effect of the sustained loading and environmental parameters on the modulus of elasticity is of particular importance since the design of concrete structures reinforced with GFRP bars is predominantly controlled by serviceability criterion, rather than strength. Since the current GFRP products have high strength beyond the strength design requirements, the modulus of elasticity becomes the greater concern. Any decrease in the modulus of elasticity will affect crack width, deflections, and other serviceability parameters. This research provides a much needed data on the creep strain in the GFRP bars in ambient temperature, the change in the modulus of elasticity with time under load, and the residual tensile strength of the bars. The main objective of this research is to evaluate the creep behaviour of GFRP reinforcing bars under alkaline and water environment and to measure the change in the tensile properties including strength, modulus and ultimate elongation. Sustained tensile loading combined with these environments were applied to the bars during the entire duration of the test to investigate whether creep rupture would occur and to obtain creep strain versus time up to 10,000 hours. The GFRP bars (E-glass and vinyl ester) were subjected to two levels of sustained tensile stress at 25 to 38% of guaranteed tensile strength while being surrounded by either alkaline solution (pH 12.8) or de-ionized water (pH 7.0). The initial strain applied to the bars varied between 4000 to 6000 micro-strain, which is 2.9-4.3 times the maximum allowable strain for sustained loads (creep) given by the ACI 440.1R-03. Axial strain in the central conditioned part of the bars was monitored with time to evaluate the creep behaviour. Following the extended creep test, the GFRP bars were tested in axial tension till failure for residual tensile strength, elastic modulus, and axial strain. The obtained experimental results shown that the tested Glass FRP bar performed very well under these extreme loading and environmental conditions. The average residual tensile strength was found to be 139 and 144% of the allowable design stress for bars conditioned in de-ionized water at 25 and 38% stress level, respectively. In alkaline solution this range was 126 and 97%. More importantly, no significant change in the elastic modulus was observed under the stress levels and environmental conditions used. The entire group of bars had a residual modulus ranging from 38.5 to 42.9 Gpa, which is almost in the range of the original elastic modulus.

2004-05

There is an urgent demand for durability data in the field of FRP composites for civil infrastructures. This research focuses on evaluating the residual tensile properties of traditional E-glass/Vinylester FRP reinforcing bars under loading in common media of alkaline and water solution. Large-scale laboratory equipment was designed and built specifically for this purpose.
The following specific objectives were targeted:

• Assess the residual tensile properties of GFRP reinforcing bars in alkaline or water media, at elevated or ambient temperature, combined with sustained loading.
• Investigate the effect of bar size on long-term behaviour.
• Compare the residual tensile strength to the design limits given by codes and design guidelines (CAN/CSA-S6, CAN/CSA-S806, ISIS Manual No. 3, ACI 440).

The study included the combined effects of high temperature and alkaline or water environments on GFRP bars under axial tension. The elevated temperatures were used to accelerate GFRP bar absorption of the medium solution. The residual mechanical properties of GFRP bars were investigated with respect to the combined effects of temperature and alkaline or water medium, in addition to constant sustained tension. Three different bar sizes (16, 12.7 and 9.5 mm) were tested at elevated temperature and ambient temperature for different lengths of time. The elevated temperature used for 2 and 4 months is believed to simulate field conditions of 40 and 80 years, respectively. The alkaline and water media are representative of the most commonly encountered field conditions.

The following conclusions were drawn from the research:

• A maximum of 11% reduction in tensile strength (compared to the guaranteed strength) was observed in the 9.5-mm GFRP bars after exposure to the combined effect of 60 degree C temperature and alkaline solution under sustained stress equal to 29%.
• The residual tensile strength for the conditioned specimens was higher (a minimum of 130%) than the specified design strength recommended in ACI 440.1R-03 design guidelines.
• The reduction in the ultimate strain after conditioning falls within the acceptable limits. The lowest residual strain was still 43% higher than the specified design strain recommended by ACI 440.1R-03.
• The research proves that almost no change in the elastic modulus of the GFRP bars will take place; an acceptable drop in the ultimate strength and failure strain were observed.
• The environmental reduction factors recommended by many codes for the allowable strength of FRP bars are thought to be very conservative. The research proves that almost no change in the elastic modulus of the GFRP bars will take place; an acceptable drop in the ultimate strength and failure strain were observed.

The microstructural analysis (SEM, DSC and FTIR) show that the different conditionings mainly induce a delamination/debonding mechanism, which weakens the glass fibre/resin matrix interface and partly hinders the stress transfer between adjacent fibres. A moderate chemical.

2005-06

There is an urgent demand for durability data in the field of FRP composites. This project focuses on evaluating certain durability characteristic of FRP reinforcing bars in terms of strength and elastic modulus reduction at different loading and environmental conditions. Specially, this project is to identify the degradation mechanisms of FRP rods under harsh environments, sustained stress and thermal conditions; to develop strength and stiffness reduction factors using accelerated test for the evaluation of alkaline effects on durability of GFRP rods; to develop a model from accelerated laboratory tests for prediction of service life of FRP bars in concrete corresponding to observed experimental behaviour. Additionally, various micro-structural analysis tests are being conducted to identify the degradation mechanisms of the GFRP bars. The test program consists of experimental tests and theoretical analyses. The test specimens will be tested under the combination conditions of environmental exposure, temperature and application of a constant load for different exposed periods. The following parameters were used in this research, which are:

1. Sustained tensile stress. Axial tension was applied on all bars during the entire duration of the test to mimic field conditions. The sustained stress is a major factor in this durability study as it gives way to the external media to migrate through the micro-cracks on the matrix around the fibres, increasing the attack level. The stress level was kept at 20-40% of the guaranteed tensile stress, corresponding to strains of 2400- 4000µe. These levels of strains are about 1-2 times the values recommended by current codes, this was done to explore the potentials of the material and evaluate how conservative the current codes are.
2. Surrounding media: Two different media were used to simulate the most common state of the bars in the field; de-ionized water and alkaline solution. The alkaline solution (pH = 12.7-13.1) simulates the cement paste and was kept constant throughout the test.
3. Temperature: Both ambient and elevated temperatures were used. The elevated temperatures were used to expedite the absorption of the medium solution by the GFRP bars. Ambient temperature is defined by 20oC and elevated temperature was 45 to 75oC.
4. Diameters of GFRP ISOROD bars. Three types of more used diameters (9, 12.7 and 15.9 mm) are used to evaluate the scale effect.
5. Types of testing. An accelerated exposure in high temperature for 1, 2 and 3 months. For verification, some tests have been done for long-term duration (8 and 14 months).

Main Findings: The residual mechanical properties of GFRP bars are investigated under combined effects of temperature and alkaline or water medium, in addition to constant sustained tension. The data obtained are focused on the residual strength and stiffness as affected by these parameters. The research proves the almost no change in the elastic modulus of the GFRP bars will take place, an acceptable drop in the ultimate strength and failure strain were observed. The environmental reduction factors recommended by many codes for the allowable strength of FRP bars are thought to be very conservative. The findings suggest the need to adopt less conservative design limits than currently used. The elevated temperature used is believed to simulate the site conditions over 75 years. The findings suggest the need to adopt less conservative design limits than currently used.

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Durability of FRPs for Rehabilitation (2.2.2)
Project Leader: Dr. Pierre Labossière, Université de Sherbrooke

2002-03

FRPs for Repair of Structural Damages Caused by Alkali-Aggregate Reactions:

This project was initiated as a follow-up to an innovative Masters Thesis dealing on the use of FRPs to repair AAR-damaged reinforced concrete beams (Lacasse, 2001). The current research project involves the measurement of longitudinal and transverse strains on concrete cylinders made of AAR-inducing concrete, and wrapped with various FRPs (approximately 100 specimens are included in the research program). Measurements must continue until the effects of AARs reach a plateau. At regular intervals, some specimens are removed and tested to failure in compression. Although it was difficult to predict the duration of the measurement program at the onset of the test, it was originally expected to exceed two years. In 2002/03, extensive strain measurements were taken on the specimens every three months, according to the original schedule. The series of measurements planned for May 2003 will determine whether or not it is necessary to continue the ageing process; it is currently anticipated that the final compressive testing of specimens will take place during the Fall 2003.

Long-Term Behaviour of FRPs and FRP-Repaired Structures:

This project was initiated in 1996 in collaboration with the Public Works Research Institute of Japan. Identical plates of FRPs and epoxy, as well as FRP-wrapped concrete cylinders, are exposed to the actual climatic conditions of Sherbrooke, Tsukuba and Okinawa since 1997. At the three locations, specimens were removed from the exposure sites in 2002 after reaching five years of exposure. In 2002/03, the first complete data analysis of the specimens removed after one and three years of exposure was completed; a first conference paper has now been submitted and a journal paper that will incorporate the results of the five years of exposure is now in the planning stages. However, a more sophisticated statistical analysis will have to be undertaken to explain the complex inter-relations between the various conditions observed at the three exposure sites. In Sherbrooke, special conditions occurred in 2002 due to the necessity to move the exposure site to a new location to accommodate construction on the university campus. Also, discussions were undertaken with another international research partner to operate another exposure site; the matter is still under discussion.

Durability of FOSs Integrated to External FRP Reinforcement of Concrete Structures:

2003-04

FRPs for Repair of Structural Damages Caused by Alkali-Aggregate Reactions: This project was initiated as a follow-up to an innovative Masters Thesis dealing on the use of FRP’s to repair AAR-damaged reinforced concrete beams (Lacasse, 2001). The current research project involves the measurement of longitudinal and transverse strains on concrete cylinders made of AAR-inducing concrete, and wrapped with various FRPs (approximately 100 specimens are included in the research program). Measurements must continue until the effects of AARs reach a plateau. At regular intervals, some specimens are removed and tested to failure in compression. Although it was difficult to predict the duration of the measurement program at the onset of the test, it was originally expected to exceed two years. In 2002/03, extensive strain measurements were taken on the specimens every three months, according to the original schedule. A series of measurements done in May 2003 indicated that it would be appropriate to continue the ageing process; it is currently anticipated that the final compressive testing of specimens will take place in Spring/Summer 2004.

Long-Term Bahaviour of FRPs and FRP-Repaired Structures: This project was initiated in 1996 in collaboration with the Public Works Research Institute of Japan. Identical plates of FRPs and epoxy, as well as FRP-wrapped concrete cylinders, are exposed to the actual climatic conditions of Sherbrooke, Tsukuba and Okinawa since 1997. At the three locations, specimens were removed from the exposure sites in 2002 after reaching five years of exposure. In 2003, the first complete data analysis of the specimens removed after one, three and five years of exposure were completed: a first conference paper was presented (FRPRCS, Singapore). A journal paper that will incorporate more extensive data of the five years of exposure is now in the planning stages. However, a more sophisticated statistical analysis will have to be undertaken to explain the complex inter-relations between the various conditions observed at the three exposure sites. In Sherbrooke, special conditions occurred in 2002 due to the necessity to move the exposure site to a new location to accommodate construction on the university campus. The new exposure site was completed in May 2003. Discussions with potential international research partners to operate other exposure sites have not materialized yet; the matter remains still under discussion.

Durability of FOSs Integrated to External FRP Reinforcement of Concrete Structures:  This project was initiated a few years ago, when FRP-reinforced beams were submitted to wet-dry and free-thaw ageing conditions (Raîche, 2000). Some of the beams were then instrumental with FOSs, in order to estimate whether or not the ageing process would influence their accuracy. However, it was not possible to complete this component of the project at the time, and the results were saved for future use. More recent beam specimens, submitted to cyclic loads (in project 3.2.1), were also instrumental with FOSs. An analysis of all the data obtained in the two projects was presented in the Ph.D. Thesis of C. Gheorghiu, completed in July 2003.

2004-05

Project Summary – See details of the three inter-related sub-projects; all sub-projects involve frequent manipulation of a variety of specimens submitted to specific predetermined ageing conditions, and the systematic acquisition of data over extended periods.

FRPs for Repair of Structural Damages Caused by Alkali-Aggregate Reactions:

• Measurement of longitudinal and transverse strains on concrete cylinders made of AAR-inducing concrete, and wrapped with various FRPs (total of approximately 160 specimens). Measurements continued until all AARs reached a plateau. At regular intervals, some specimens removed and tested to failure in compression. Also, acoustic emission/IRM measurements for some specimens.
• Final testing of the specimens took place during fall 2004.
• Current investigations: correlation between acoustic/IRM measurements, degradation of the specimens due to the AARs, compressive strength, effect of the confinement on AARs.
• April to August 2005 – analyse database from test results with advanced statistical methods.
• Fall 2005 – develop methods to apply FRPs in practical AAR strengthening cases.
• Data analysis to be completed in December 2005.
• Masters thesis by Hugo Pelletier to be completed by December 2005.

Long-Term Behaviour of FRPs and FRP-Repaired Structures:

• Initiated in 1996 in collaboration with the Public Works Research Institute of Japan.
• Identical plates of FRPs and epoxy, as well as FRP-wrapped concrete cylinders, are exposed to the actual climatic conditions of Sherbrooke, Tsukuba and Okinawa since 1997.
• At the three locations, specimens were removed from the exposure sites in the summer of 2004 after reaching seven years of exposure. (Results obtained for 0, 1, 3, 5 and 7 years of exposure.)
• Dr. Itaru Nishizaki from PWRI, Japan, visited Sherbrooke in November 2004; plans for 10-year extension of research project are investigated.
  A sophisticated statistical analysis is underway to explain the complex inter-relations between the various conditions observed at the three exposure sites.
  Now to August 2005 – compare results from 7-year exposure at three locations using advanced statistical analyses.
• September 2005 to December 2005 – design and plan series of accelerated ageing tests, using models developed from real exposure data.
• January 2006 to April 2006 – Fabricate first series of specimens for accelerated ageing tests and calibrate the ageing process from models and real data.
• Masters thesis by Bogdan Sarsaniuc to be completed by March 2006.

Durability of FOSs Integrated to External FRP Reinforcement of Concrete Structures:

• The results presented in the Ph.D. Thesis of C. Gheorghiu (completed in July 2003).
• Significant events in 2004-2005: presentations at international conferences in 2004 (ACIC London 2004, CICE Adelaide 2004), papers published in journals.
• Sub-project completed.

2005-06

FRPs for Repair of Structural Damages Caused by Alkali-Aggregate Reactions:

1. Measurement of longitudinal and transverse strains on concrete cylinders made of AAR-inducing concrete, and wrapped with various FRPs (total of approximately 160 specimens). Measurements continued until all AARs reached a plateau. At regular intervals, some specimens removed and tested to failure in compression. Also, acoustic emission/IRM measurements for some specimens.
2. April to December 2005 – Final testing. Correlation between acoustic/IRM measurements, degradation of the specimens due to the AARs, compressive strength, effect of the confinement on AARs was investigated. The data base was analysed from test results with advanced statistical methods. Data analysis was completed in April 2006.
3. Sub-project to be completed in Summer 2006.

Long-term Behaviours of FRPs and FRP-Repaired Structures:

1. Initiated in 1996 in collaboration with the Public Works Research Institute of Japan.
2. Identical plates of FRPs and epoxy, as well as FRP-wrapped concrete cylinders, are exposed to the actual climatic conditions of Sherbrooke, Tsukuba and Okinawa since 1997. At the three locations, specimens were removed from the exposure sites in the summer of 2004 after reaching seven years of exposure. (Results obtained for 0, 1, 3, 5 and 7 years of exposure.) Remaining specimens to be removed in 2007.
3. Continued collaboration. Dr. Itaru Nishizaki from PWRI, Japan, visited Sherbrooke in November 2004; P. Labossière visited PWRI in March 2006. Plans for 10-year extension of research project are investigated. There is a possibility of investigating new types of CFRP plates. A sophisticated statistical analysis was achieved to explain the complex inter-relations between the various conditions observed at the three exposure sites.
4. RC-Beams externally reinforced with FRP were also tested after 6 years exposure to climate. No significant deterioration was measured.
5. Current sub-project to continue until recovery of last remaining specimens in 2007 and continuation beyond this date with new specimens is investigated.

Durability of FOSs Integrated to External FRP Reinforcement of Concrete Structures

• Sub-project completed.

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Focus Area 2.3:  Innovative Structures

Hybrid FRP/Concrete Structural Systems (2.3.1)
Project Leader: Dr. Aftab Mufti, University of Manitoba

2002-03

The purpose of this project is to integrate the steel-free deck slab with FRP/concrete hybrid columns and beams to develop a total corrosion free-structural system. Completed work 02/03: Investigation of fatigue behaviour of steel free concrete bridge decks under cyclic loading is underway. Initially, tests were conducted on concrete cylinders to understand the fatigue behaviour. From the test results, S-N Curve was developed to estimate the fatigue strength of the steel-free concrete ArchPanels and bridge deck slabs. A non-composite full-scale model of a steel-free ArchPanel was tested under cyclic loading to investigate its fatigue behaviour. In a steel-free concrete deck slab, when loads are applied, cracking of concrete has to occur to initiate arching action. In demonstration projects, it was found that the longitudinal crack widths are higher than serviceability. Therefore to reduce the crack width hybrid system internally with either GFRP grid or CFRP grid and externally steel strap was used and tested under cyclic loading to investigate the fatigue behaviour. Test results showed that, hybrid system could reduce the crack widths significantly and also eliminate corrosion completely from the deck slab. The model deck slab with hybrid system satisfied the serviceability criterion and lifetime number of axles, that a concrete bridge deck slabs would experience.

Investigation of fatigue behaviour of steel free concrete bridge decks laterally confined by prestressed concrete straps under cyclic loading is also underway. In all applications of the FLC steel free deck slab, the straps have typically been made of steel. Realizing that the substantial modulus of elasticity of concrete in a component in tension can be mobilized prior to cracking, the axial stiffness of reinforced concrete straps as well as Prestressed concrete straps with GFRP tendons was investigated experimentally as well as analytically. Based on the axial stiffness of the prestressed concrete straps, a full-scale partial model of a steel-free deck slab with prestressed concrete straps as transverse confinement was constructed and tested by subjecting it to 500,000 cycles of a pulsating load which peaked at 208 kN. This loading is equivalent in its effect to damage induced by all wheel loads expected in 75 years on a bridge deck. The tests have confirmed that within the expected range of tensile forces in straps of typical FRC deck slabs, the 150x100 mm prestressed concrete straps have about twice the stiffness as that of 50x25 mm steel straps. Because of the early failure of pretensioned concrete straps, the ultimate failure loads of FRC slabs with these straps is substantially smaller than that of slabs with steel straps. It was, nevertheless, determined that the fatigue resistance of the proposed slabs is not inferior to that of the conventional slabs. A M.Sc. student defended these concepts in his thesis in 2003.

In the project on the effect of driving stresses on concrete filled FRP tubes, five 355 mm tubes were driven into the ground, extracted and cut into 6.0 m and 0.30 m segments. Previously the 6 m segments were tested to investigate the effect of the driving on the overall behaviour of the system. In this year push out tests were conducted on the 0.3 m to investigate the effect of the driving on the bond between the concrete core and the shell. In addition coupons were cut from the shell and tested in tension, also concrete core were drilled and tested in compression. The preliminary results and analysis indicate that the driving does not have a significant effect on the strength of the tubes.

Investigation of the fatigue behaviour of GFRP decks under static and cyclic loading was undertaken to study the behaviour of the FRP bridge deck. A bridge deck consisting of a number of triangular filament-wound tubes bonded with epoxy resin was developed. GFRP plates were adhered to the top and bottom of the tubes to create one modular unit. The first phase of the R&D project examined four generations of the bridge deck. In the first generation, three prototype specimens were tested to failure, and their performance was analyzed. Based on the behaviour observed, second and third generations of bridge decks were fabricated and tested. The fourth generation deck was produced with the optimum amount of fibres, resulting in the most cost-effective deck among all the four generations. For the second and fourth generation decks, prototype specimens were tested to failure, while two million cycles were applied to the third generation specimen with a load varying between 10% and 135% of the service load level. The performance was evaluated based on load capacity, mode of failure, deflection at service load level, strain behaviour, and stiffness degradation under cyclic loading. All decks tested exceeded the requirements to support the HS30 design truck load specified by AASHTO with a margin of safety. Analytical models, based on Finite Element Analysis (FEA) and Laminated Plate Theory (LPT), to optimize and to design the section of the FRP deck were conducted parallel to the experimental investigation. The second phase of the R&D project was completed in the summer of 2002 to examine the transverse joint between the FRP deck modules. A full-scale specimen was fabricated incorporating the deck joint and tested under static and cyclic loading. Wardrop Engineering is currently working with the Manitoba Highways Department to transfer the FRP deck technology into a demonstration bridge in northern Manitoba. The bridge is designed to be portable, lightweight and modular for use on winter roads. ISIS Canada has been asked to provide assistance in establishing remote structural health monitoring of the bridge to assess the performance of the FRP deck under the severe environmental conditions in the north.

Another project involved the research on FRP dowel alternatives evaluated concrete filled FRP tubes and pultruded FRP dowels as a replacement to epoxy coated steel dowels. The premise of the research is to reduce concrete bearing stress around dowels in order to extend the service life of the pavement structure. The laboratory testing included repeated loading of up to 2M axle loads on full-scale pavement slab samples fitted with one of four dowel types. The results of the experiment and of associated finite element analysis indicated that FRP tubes are a viable corrosion free alternative to steel dowels under highway loads.

Projected milestones for next fiscal year 2003/04: Continue the analysis of the experimental data from the fatigue tests of the model deck slab with hybrid system and development of a rational model for the fatigue behaviour of steel free concrete bridge decks under cyclic loading. The expected start date for cyclic testing of concrete filled FRP tubes is September, 2003. Analysis of connections between concrete filled FRP tubes used as columns and girders. Knowledge exchange, technology transfer and networking: ISIS Canada continues to collaborate with the industrial and government partners (noted above) on the concrete filled FRP tubes project.

2003-04

• Design and construction of the second generation steel-free bridge deck was completed in March of 2004
• Installation of civionics and SHM instrumentation will be completed in June of 2004
• Vigorous testing will be conducted beginning in June 2004
• Initially, tests were conducted on a non-composite steel-free concrete ArchPanel under cyclic loading to investigate its fatigue behaviour
• In a steel-free concrete deck slab, when loads are applied, cracking of concrete has to occur to initiate arching action
• In demonstration projects, it was found that the longitudinal crack width is higher than serviceability limits
• To reduce crack width, a hybrid internal system of either GFRP crack control grid or CFRP crack control grid with external steel straps were used and tested under cyclic loading to investigate the fatigue behaviour
• Test results showed that the hybrid system could reduce the crack widths significantly and also eliminate corrosion completely from the deck slab
• The model deck slab with the hybrid system satisfied the serviceability criteria and lifetime number of axles that concrete bridge deck slabs would experience
• Mr. Amjad Memon has developed the P-N Curve, to investigate the fatigue strength of concrete bridge deck slabs
• Tests indicate that GFRP reinforcement compared to CFRP and steel has much better fatigue life

2004-05

• Design of a cantilever steel free bridge deck supporting a traffic barrier to study fatigue and durability of steel free cantilever bridge decks will be completed by June 2005.
• The steel free bridge deck will be constructed and fitted with civionics and SHM instrumentation by September 2005.
• Testing of the steel free bridge deck will commence in October 2005.
• Destructive static tests have been completed on the internal panel of the second generation steel free bridge deck and a cantilever reinforced with CFRP negative moment reinforcement.
• A detailed instructional video was filmed and documented detailing the civionics incorporated in the second generation steel free bridge deck and accompanies the Civionics Specification 2004 developed by ISIS Canada Research Network.
• Further destructive static and fatigue testing is currently being conducted on the internal panel and cantilevers of the innovative bridge deck.
• Design of 5 circular concrete panels was completed in November 2004.
• Casting of concrete started in February 2005 and was completed in March 2005. Five samples were cast: 1 Concrete panel without steel straps; 2 Concrete panels with 8 radial steel straps; 2 Concrete panels with 6 radial steel straps.
• Testing will be conducted in immediate future.

2005-06

• The design of the steel-free bridge deck with cantilevers supporting traffic barriers to study fatigue and durability of steel-free cantilever bridge decks has been completed.  Two large specimens consisting of 3 girder lines each is yet to be tested: one under static load conditions, one under fatigue load conditions.
• The steel-free bridge deck will be constructed and fitted with civionics and SHM instrumentation prior to testing.
• Literature review on the state-of-the-art of steel-free decks has been completed.
• The design of two steel-free bridge decks has been completed.  One of the bridge decks was designed using the full-depth, cast-in-place deck slab method and the other bridge deck was designed using the cast-in-place deck slab on stay-in-place formwork method.

• Completion of static and fatigue testing of the internal panel of a second generation steel-free bridge deck

• Completion of static and fatigue testing of the cantilevers sections of the second generation steel free bridge deck
• Five circular steel-free concrete panels with a supporting ring beam were cast and tested by end of 2005. 
• New four circular steel-free concrete panels without a ring beam were cast in September and October 2005.  Two samples out of four were tested by end of March 2006, with the other two samples to be tested before end of April 2006.

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FRP Reinforced Concrete Structures (2.3.2)
Project Leader: Dr. Bruno Massicotte, École Polytechnique de Montréal

2002-03

The first ISIS project at Ecole Polytechnique, this project is attracting new students and research personnel. Two topics are under investigation.

1. Modelling of FRP Reinforced Concrete Members:

The main objective of this research project is to improve existing numerical models for predicting the behaviour of concrete structures reinforced or strengthened by FRPs. The emphasis in this first year has been on experimental activities. Two test series related to FRPs have been carried out in the last 18 months while the aspects related to implementing FRPs interaction with concrete in an existing FE constitutive model started at the beginning of 2003. The model, initially developed in an in-house software, is being integrated in a commercial nonlinear finite element software. In order to further develop the model mentioned above, experimental data are needed. A limited test series on FRPs that was carried out before ISIS project began provided valuable data on the stress distribution in FRP laminates on strengthened Prestressed girders. These data will be used for validating the FE constitutive model.

2. Development of innovative precast components for bridges:

This project is sponsored by the Quebec Ministry of Transportation and will begin in the fall of 2003. It consists in developing design criteria for using FRP stirrups for the new series of precast Prestressed concrete bridge girders adopted by the QMT. An experimental and analytical project will be carried out in collaboration with Professor Benmokrane from Sherbrooke University. This project is closely related to the first topic described in a) above since refined finite element modelling will be needed for broadening the scope applications beyond that covered by the tests.

2003-04

The research project progressed slowly in the first 8 months of the grant period because of the unavailability of the laboratory (from May 2003 to April 2004) related to the construction of a new laboratory obtained from a CFI grant. Moreover, new highly qualified research personnel joined the research team in January 2004. The research activities are now progressing at an accelerated pace and experimental activities have resumed in May 2004. The current project includes the following distinct but closely related topics: the modeling of FRP reinforced concrete members; the development of innovative precast components for bridges. Most of the research activities carried out in the last year were related to the first topic.

Modelling of FRP Reinforced Concrete Members:

Objective: To improve existing numerical models for predicting the behaviour of concrete structures reinforced or strengthened by FRPs

Methodology: Development of two families of models: sophisticated 3D finite element constitutive models, and design oriented software

Validation of model with tests on members strengthened with FRPs
Activities:

• FE 3D constitutive model developed at EPM was integrated into FE software ANSYS
• Model validation completed and users manual completed at 50% at the end of March (activity expected to be complete by the end of June)
• Completion of Mrs. Nathalie Chagnon thesis on the use of FRP for strengthening deficient rectangular bridge piers: results indicated a very promising avenue. Experimental activities expected to resume in the Fall of 2004
• Completion of a report on a test series on the strengthening prestressed concrete girders carried out prior to the beginning of this ISIS project (project sponsored by the Quebec Ministry of Transportation). Conclusion led to writing and acceptance of second phase (see next point). Design oriented software AIS was validated and improved.
• Research project on the strengthening of damaged prestressed girders was proposed in 2004 to the QMT. The project include the testing of full scale PC girder in 2005. Sika will collaborate.

2004-05

The research project is progressing normally as experimental activities resumed in the summer of 2004. The project has contributed to initiate collaborative research activities with research groups and industrial partners: Sherbrooke University, Minho University (Portugal), LCPC (France), Quebec Ministry of Transportation (QMT), Sika and Pultrall. The project has attracted highly qualified personnel. A visit to Professor Urs Meier at EMPA Laboratory in September 2004 was extremely instructive. This will certainly have a direct impact on current projects and potential collaborative research work and technological transfer are being discussed. The current project includes the following distinct but closely related topics: the modelling of FRP reinforced concrete members; the development of innovative precast components for bridges. Most of the research activities carried out in the last year were related to the first topic.

Modelling of FRP Reinforced Concrete Members:

Objective: To improve existing numerical models for predicting the behaviour of concrete structures reinforced or strengthened by FRPs.
Methodology:

• Development of two families of models: sophisticated 3D finite element constitutive models, and design oriented software.
• Validation of model with tests on members strengthened with FRPs.

Activities:

• FE 3D constitutive model developed at EPM was integrated into FE software ABAQUS.
• Model validation completed and users manual completed at 95% at the end of March (activity expected to be complete by the end of June).
• The model will be freely available to ISIS researchers in June 2005.
• Follow up on Mrs Nathalie Chagnon thesis on the use of FRP for strengthening deficient rectangular bridge piers is expected to resume in 2004.

Project on the strengthening prestressed concrete girders carried out prior to the beginning of this ISIS project (project sponsored by the Quebec Ministry of Transportation) has resumed. Tests on large scale specimens are planned for 2005-06. Possible collaboration with EMPA is being considered.

2005/06

The main three activities planned for fiscal year 2005/2006 have been carried out satisfactorily.

Development of a nonlinear finite element constitutive model for FRP reinforced concrete members:

• Numerical modelling of splitting forces / slip mechanism has been completed.  The model allows studying the slip mechanism of internal reinforcement (steel or FRP) along with the associated concrete splitting.  This complex failure mechanism can now be studied numerically to better understand the effects of FRP on strengthening deficient lap splice regions of rectangular columns, as observed in project 3.2.5.
• Writing of the documents for the freely available constitutive model has progressed. Documents are updated as the model is improved.
• Three refereed journal papers have been submitted (CJCE and ASCE Jour. of Structural Eng.).
• One conference paper was presented at CONMAT05 in Vancouver.
• A tests series aimed at measuring the bar force–bar slip–splitting forces interaction for eventually improving the model robustness has been planned and will be carried out in 2006.

Development of innovative precast components for bridges:

• This project partially sponsored by QMT uses the model in A above to study the behaviour of concrete girders with internal CFRP stirrups.
• This project is carried out in collaboration with Professor Benmokrane from Sherbrooke University.
• A test series has just been completed at Sherbrooke.  The finite element model described in A is currently used to study the behaviour of internal FRP reinforcement and establish the model validity.
• A parametric study will be carried out to further understand the behaviour of prestressed concrete girders with CRFP and GFRP stirrups.
• An experimental program on full scale prestressed concrete bridge girders will be proposed to QMT.

Development of an innovative surface anchorage system for FRP laminates:

• This project on the strengthening of damaged prestressed concrete girders is partially sponsored by QMT.
• Results of a previous test series on external CFRP laminates applied on damaged large scale girders showed a premature failure.  Various techniques have been investigated.  A simple and practical method has been developed and satisfactorily tested.
• Numerical modelling of the proposed strengthening technique using the finite element model described in A above is being carried out.
• A full scale test of the technique is planned for the fall of 2006.
• Consideration of prestressing FRP as developed at EMPA using the anchorage technique developed at École Polytechnique de Montréal will be addressed in 2006.  Contacts with EMPA will be made.

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Prestressed Girders with FRP Webs (2.3.3)
Project Leader: Dr. John Newhook, Dalhousie University

2002-03

• Obtained new Ph.D. student to work on project.
• Completed literature review of beams with corrugated steel webs.
• Completed review of existing field projects with corrugated steel webs
• Established experimental program to be conducted in 2003-2004.

2003-04

• Fabricated quasi-isotropic GFRP corrugated sheets for testing
• Established empirical shear connection design between web and concrete flange
• Demonstrated adaptation of isotropic shear buckling equations for corrugated steel webs to quasi-isotropic FRP webs
• Designed shear buckling test setup for use in optimization of fibre orientation
• Constructed and tested first small scale (5 m span) beam with corrugated FRP web and prestressed concrete tension flange
• FRP web girder proved to have higher capacity than similar steel web girder
• Shear buckling equations were able to accurately predict experimental shear buckling failure

2004-05

• Tested GFRP web beams: established theoretical equations for predicting shear capacity; established flexural behaviour characteristics; demonstrated feasibility of girder design.
• Completed experimental and theoretical investigation of shear connection design between web and concrete flange.

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FRP Products for Masonry Structures (2.3.4)
Project Leader: Dr. Nigel Shrive, University of Calgary

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FRPs for Glulam Structural Members (2.3.5)
Project Leader: Dr. Farid Taheri, Dalhousie University

2002-03

• We have generated a complete spreadsheet that includes all design steps outlined in ICBO for FRP-reinforced Glulam beams.
• We have created a GUI, windows design module for FRP-reinforced Tutor arches. The program is extremely slick, and has several menus, just like any up-to-date GUI program. - We have developed two unique solutions for the design of FRP-Glulam beams.
• We have explored the vibration and impact characteristics of FRP-reinforced Glulam beams. Several publications have been prepared and submitted to some of the most reputed international journals.
• We have been negotiating with the Department of Transportation, through JSCL Canada Inc. to design a 70’ FRP-reinforced Glulam bridge

• Establishing a frame work for collaborating with Twaron Teijin, one of the world largest fiber producers.
• Success in resurrecting TenLam
• Having published in one of the world’s most reputed journals

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Hog Waste Storage Facilities Using FRPs (2.3.6)
Project Leader: Dr. Aftab Mufti, University of Manitoba

2002-03

This project has been successfully completed. The project investigated the suitability of innovative design procedures for reinforced concrete manure storage tanks using advanced composite materials (FRP) as internal or external reinforcing element. This study introduced and developed the use of glass fibre reinforced polymers (GFRP) for new concrete technology in manure storage facilities. This investigation provided the foundation for the selection of an optimum composite material to be used to design and build more economical and environmentally benign manure storage facilities. The experimental test results for the structural specimens in contact with manure for 4, 8, 12, 18 and 24 months suggested that GFRP reinforcement bars exhibit a high resistance to degradation in a manure environment. Experimental data generated in this project suggested that in the high stress areas, where cracks are formed in the concrete tank wall, the steel reinforcement degrade (corrode) at a very high rate compared with the degradation of GFRP rods. The cracks that will form in GFRP reinforced concrete beams are expected to have little effect on the behaviour of reinforcement, since the experimental results suggest a very low rate of GFRP degradation in manure environment. Consequently the use of GFRP in high stress area of the storage tanks merits further development. The results and the findings of the research carried out in this project were documented in seven Technical Reports that have been written and distributed to Agri-Food Research and Development Initiative (ARDI), Manitoba Triple S Hog Manure Management Initiative and Manitoba Livestock Manure Management (MLMMI), the co-founders of the project. In addition to the Technical Reports, the work performed in this study has been documented and the results and finding presented at several meetings and conferences (i.e., ISIS annual and conference meetings, and CSCE conference).

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Innovative FRP-Reinforced Precast Concrete Deck Panels (2.3.7)
Project Leader: Dr. Kenneth Neale, Université de Sherbrooke

2002-03

• Design and testing of innovative “all FRP” precast panels for bridge decks.

2003-04

• The experimental work on full-scale specimens has been completed.
• The numerical modelling of the deck panels is underway.
• This constitutes the M.A.Sc. research of an M.A.Sc. student (D. Tardif).

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Innovative Corrosion-Free Bridge System (2.3.8)
Project Leader: Dr. Mamdouh El-Badry, University of Calgary

2003-04

• Examined the behaviour in compression of different types of concrete-filled FRP tubes. Such members represent verticals in the proposed bridge truss girder. Both pultruded and filament wound GFRP tubes were used.
• Examined the bond behaviour between concrete and GFRP tubes using epoxy adhesive or mechanical anchors. This serves to examine the behaviour of diagonal tension members in the proposed bridge truss girder.
• Investigated the performance of different types of connections were tested.
  Established the optimum dimensions.

2004-05

• Investigated the performance of different types of connections of concrete-filled filament-wound FRP tubes as truss members to the top and bottom flanges of precast, prestressed bridge truss girders. Eight large-scale connections were tested: four under static loading and four under fatigue loading.
  Fabricated four 2.5-m long truss girders for testing under static and fatigue loading.
• Six 8-m long truss girders with portions of the deck slab are currently being fabricated for testing under static, fatigue and time-dependent effects.

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Reinforced and Prestressed Concrete-Filled FRP Tubes (2.3.9)
Project Leader: Dr. Amir Fam, Queen’s University

2003-04

• Established fundamental understanding of behavior of concrete-filled FRP tubes (CFFT) with internal reinforcement or prestressing. This subject has never been studied prior to ISIS project 2.3.9
• 6 large scale CFFT (325 mm diameter & 4.2 m long), pre-tensioned and post-tensioned with steel strands, have been tested.
• 7 medium size CFFT (220 mm diameter & 2.4 m long) with internal GFRP, CFRP and steel reinforcement, have been tested.
• A general numerical model has been developed to predict the behavior of internally reinforced or prestressed CFFT subjected to a general state of axial and bending loads.
• The use of light-weight concrete to fill the tubes and the freeze-thaw durability of CFFT is currently being studied
• Three master’s students (Mandal, Cole and Kong) are being trained by the project leader. Cole has received the best presentation award in ISIS Conference 2004.
• Through Project 2.3.9, I was able to collaborate with Dr. Mufti and Mr. Helmi at U of M to study the fatigue behavior of CFFT, splicing techniques and effect of driving stresses in pile applications.

2004-05

• Established fundamental understanding of behaviour of concrete-filled FRP tubes (CFFT) with internal reinforcement or prestressing. This subject has never been studied prior to ISIS project 2.3.9.
  • 6 large scale CFFT (325 mm diameter & 4.2 m long), pre-tensioned and post-tensioned with steel strands, have been tested in flexure.
  • 7 medium size CFFT (220 mm diameter & 2.4 m long) with internal GFRP, CFRP and steel reinforcement, have been tested in flexure.
  • 14 medium size CFFT (220 mm diameter & 0.7-1.4 m long) with internal GFRP, CFRP and steel reinforcement, have been tested in shear.
  • 15 CFFT (175 mm diameter & 350 mm long) were used in a durability study to test CFFTs under 300 freeze-thaw cycles as well as under sustained axial loading, including the interaction between the two conditions.
  • A general numerical model has been developed to predict the behaviour of internally reinforced or prestressed CFFT subjected to a general state of axial and bending loads.
• The use of light-weight concrete to fill the tubes and the freeze-thaw durability of CFFT is currently being studied.
• The project has been extended to include a phase on spun-cast CFFT with hollow core to reduce deadweight. A new student (Qasrawi) has started on January 2005.
• One Master’s student has finished and graduated and three Master’s students (Cole, Qasrawi and Kong) are being trained by the project leader. Cole has received the best presentation award in ISIS Conference 2004.
• Through Project 2.3.9, I was able to collaborate with Dr. Mufti and Mr. Helmi at U of M to study the fatigue behaviour of CFFT, splicing techniques and effect of driving stresses in pile applications. I’m currently cosupervising Doctoral student (Helmi) with Dr. Mufti.

2005/06

• Shear behavior and strength of concrete-filled FRP tubes with internal FRP and steel reinforcement has been studied and understood. Fourteen specimens were tested with various shear span to diameter ratios to find the critical shear span. A paper has been submitted for possible publication in the ISIS Special Issue of the CJCE.
• Flexural behavior of concrete-filled FRP tubes with internal steel and FRP longitudinal reinforcement is studied and a model is developed. Results of this study has been published in the ASCE J of Composites for Construction
• Flexural behavior of prestressed concrete-filled FRP tubes has been studied through six large scale specimens with different levels of prestressing , including pretensioned and posttensioned specimens. Analytical model has also been developed.  A journal paper has been published on the analytical model in ASCE J of structural Engineering (See Table 5b). The experimental results to be published in the PCI Journal this summer.
• Developed a novel spun-cast concrete-filled FRP tubular system for mono pole and highway overhead sign structures.  The system has been successfully fabricated for the first time. Some specimens include internal reinforcement for improved ductility.  Nine large scale specimens have been fabricated and currently being tested at Queen’s University.
• The performance of concrete-filled FRP tubes under freeze-thaw cycles combined with sustained axial loads has been studied.  A paper is currently under review in Concrete International.

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Durability of FRP Pins and Reinforcement in Heritage Concrete Structures (2.3.10)
Project Leader: Dr. Aftab Mufti, University of Manitoba

2003-04

• The design of the concrete mixes to be used in the construction of the laboratory test specimens that will resist imposed loads and degradation under the service exposure conditions (i.e. freeze and thawing, moisture) was completed
• The design and fabrication of the test specimens (i.e., large-scale marker anchor assemblies, full size reinforced concrete beams, and cylinders) required in the experimental program was completed
• A total of 100 specimens were cast and the laboratory tests program was initiated
• A testing arrangement for the pullout test to measure the bond strength was established
• The freeze and thaw cycle that closely simulate the real-life conditions at Brookside Cemetery in Winnipeg has been established based on a series of trial tests in order to secure the temperatures at the surface of the reinforced support beam recommended by the ASTM E1512.
• 16 large-scale marker anchor assemblies have been exposed to 50 freeze-thaw cycles and the preparation of the specimens to be tested to determine the effects of accelerated environmental conditions (the resistance to freezing and thawing and moisture) on the mechanical properties and microstructure of marker anchor assemblies started
• The activities that were carried out during the reporting period were documented in the Technical Progress #1 that was written and distributed to the Veteran Affair Canada; Public Works and Government Services Canada-Heritage Conservation Services

2004-05

• All 56 pullout tests have been completed.
• The design of the lateral test apparatus has been completed and all 44 lateral tests have been performed.
• The apparatus for applying sustained stress on the GFRP reinforced concrete support beam specimens inside the environmental chamber has been designed for the shear tests specimens.
• The apparatus for applying sustained stress on the GFRP reinforced concrete support beam specimens inside the environmental chamber has been designed for the bending tests specimens.
• The final technical report has been submitted to Veteran Affairs Canada; Public Works and Government Services Canada-Heritage Conservation Services.

2005-06

• The design of the shear and bending test apparatus has been completed and all bending and shear tests have been performed.

• A 24 ft (7.32 m) field trial beam was designed, constructed, instrumented and installed at Brookside Cemetery in August 2004.  The 24 ft (7.32 m) GFRP reinforced beam was monitored during and after installation.  The measurements taken include:
  • temperature of the concrete beam,
  • clear span distance and on center distance between the supports of the beam,
  • frequency response of the beam to a 68 kg mass excitation at the mid-span,
  • deflection of the beam; and
  • crack width
• Periodic monitoring of the GFRP reinforced concrete beam is being taken on an ongoing basis to provide insight into the performance and state of the reinforced concrete beam.

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Innovative Designs for Piles, Columns, Concrete Filled FRP Tubes (2.3.11)
Project Leader: Dr. Aftab Mufti, University of Manitoba

2003-04

• Completed testing of coupons cut from FRP tubes in tension-tension fatigue to obtain the S-N curve and establish the fatigue properties of the tubes
• Completed cyclic testing of a full scale specimen under reversed bending, more tests to follow

2004-05

• Completed testing a full scale specimen under reversed cyclic bending.
• Testing of another full scale specimen under reversed cyclic bending is in progress and is expected to finish one million cycles in June.
• Investigated the use of several coupon types.
• Tested coupons in tension-tension fatigue.

2005-06

• Completed testing full-scale specimen under fully reversed bending for 1.1 million cycles under a load equal to 25% of the ultimate bending moment and then under a load equal to 37.5% of the ultimate load until failure after 406,000 cycles.
• Completed fatigue testing 69 coupon specimens under different loading conditions to study their effect on the fatigue life of coupons, and to study the stiffness degradation behaviour of the specimens.
• An analysis was conducted on the coupon test results and mathematical models were developed for fatigue life predictions and stiffness degradation.
• An analytical study is underway to develop a model for the behaviour of concrete filled FRP tubes under reversed bending loading.

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FRP Wraps for Eccentrically-Loaded and/or Slender Reinforced Concrete Columns (2.3.12)
Project Leader: Dr. Luke Bisby, Queen’s University

2004-05

• The literature survey phase of the project has been completed.
• ISIS Student researcher Jason Fitzwilliam has designed and fabricated test specimens for his experimental program to study the effects of load eccentricity and slenderness on FRP-strengthened reinforced concrete columns. The bulk of Fitzwilliam’s testing is expected to be completed during the summer of 2005.
• Numerical models have been developed to describe the axial load – moment interaction diagrams for FRP-wrapped reinforced concrete columns. Models are currently being extended to include slenderness and load eccentricity effects in predicting the load-deformation response of the columns.

2005-06

• ISIS Student researcher Jason Fitzwilliam has designed, fabricated, and tested test specimens for his M.Sc. thesis experimental program to study the effects of slenderness on FRP-strengthened (wrapped) reinforced concrete columns. Fitzwilliam is currently performing data analysis and writing up his findings in preparation for his defense.
• Fitzwilliam has been invited to present his research findings at the ISIS Canada Annual Conference in Calgary in May of 2006, and has also submitted a refereed conference paper to the CICE’06 conference in Miami in December of 2006.
• ISIS Student researcher Michael Ranger has designed, fabricated, and begun testing test specimens for his M.Sc. thesis experimental program to study the effects of load eccentricities on the behaviour of FRP-strengthened (wrapped) reinforced concrete columns. Ranger is currently in the testing phase of his research and has submitted a conference paper abstract to the FRPRCS-8 conference in Greece in the summer of 2008.
• Numerical models have been developed to describe the axial load – moment interaction diagrams for FRP-wrapped reinforced concrete columns. Models are currently being extended to include slenderness and load eccentricity effects in predicting the load-deformation response of the columns. Once validated by the test data of both Fitzwilliam and Ranger, the models will be used (by Ranger and an NSERC Summer Research Assistant during the summer of 2006) to develop slenderness limits and design recommendations for these types of members.

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Focus Area 2.4:  Integrated Fibre Optic FRP Products

FRP Structural Towers (2.4.1)
Project Leader: Dr. Dimos Polyzois, University of Manitoba

2002-03

During this year the research team:

• Designed and fabricated a filament winder
• Began the fabrication of scaled tower components
• Conducted extensive materials testing
• Developed a finite element model for the analysis of composite turbine towers
• Designed a full scaled turbine tower
• Developed a proposal for the construction of a full scale tower top to be submitted to Manitoba Hydro
• Conducted several meetings with a consortium of private companies interested in the composite towers. These include: a) Sequoia Energy Inc., Victoria, B.C. b) GREP (Global Renewable Energy Partners), California c) Wind Kraft-Kontor, Germany d) NEG-Micon, Chicago

2003-04

• Conducted a finite element analysis of various types of towers, such as single cell steel towers and multiple cell composite towers
• Designed a steel tower using German Codes for evaluating the finite element program
• Carried out experimental work to determine properties of the GFRP material and the strength of the adhesive to be used in the interconnection of the cells
• Fabricated and tested 2.5m long cells
• Built a new mandrel to allow the fabrication of 5m long specimens

2004-05

• Conducted a finite element analysis of various types of towers, such as single cell steel towers and multiple cell composite towers.
• Designed a steel tower using German Codes for evaluating the finite element program.
• Carried out experimental work to determine properties of the GFRP material and the strength of the adhesive to be used in the interconnection of the cells.
• Fabricated and tested 2.5-m long cells.
• Fabricated and tested to failure two 5-m towers each consisting of 16 cells.
• Test results were in excellent agreement with theoretical predictions.

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Smart FRP Tendons (2.4.2)
Project Leader: Dr. Alex Kalamkarov, Dalhousie University

2002-03

• Pultrusion machine has been renovated for integration of sensor/actuator fibres and wires, with respect to pulling wheels and temperature controllers. Innovative cut-off mechanism and resin bath were developed.
• New generation of pultruded FRP tendons with embedded Fabry-Perot FOS produced and tested.
• Smart Concrete Beam project with embedded GFRP rebars with integrated Fabry-Perot FOS was successfully performed in collaboration with Dr. John Newhook, Civil Engineering Department, Dalhousie University. Four smart concrete beams were manufactured and tested.
• Experiments on the environmental and variable temperature exposure of the smart concrete beams have been conducted. The smart concrete beams were instrumented with the embedded GFRP rebars with embedded Fabry-Perot FOS.
• Refined Pultrusion processing technologies and equipment developed for integration of Shape Memory Alloy wires and Piezoceramic fibre sensors/actuators and FOS sensors into the FRP reinforcements during Pultrusion.
• Smart FRP tendons were produced and tested with NiTi-based Shape Memory Alloy wires integrated during Pultrusion.

• New generation of pultruded FRP tendons with embedded Fabry-Perot FOS produced and used in the Smart Concrete Beam project.
• Phase 2 of the Smart Concrete Beam project with embedded GFRP rebars with integrated Fabry-Perot FOS has been performed.
• Development of innovative sensor detection and cut-off mechanism is order to cut the smart pultruded FRP rods with the embedded actuator/sensors fibers, without cutting the embedded fibers or wires.
  • Experiments on the static and dynamic loading, comparison with the conventional gauges and extensometers is being conducted in the Phase 2 of the Smart Concrete Beam project with embedded GFRP rebars instrumented with Fabry-Perot FOS. Within this framework, two separate beam configurations are chosen: with and without shear reinforcements. All three beams are characterized by loading conditions: cyclic (stepwise) and long-term creep loadings. They also differ from the objective of measuring strain simultaneously from tension and compression layers of the beams. The design of the concrete beams is carried out following the ACI specifications (ACI – 318 (440)) and the ISIS (CSA A23.) guidelines. The dimensions of the beams are: for beams with shear reinforcements (200 mm wide by 385 mm deep by 3,000 mm long) and for beam without shear reinforcements (150 mm wide by 355 mm deep by 3,000 mm long). In addition to shear reinforcement requirement, all three beams have flexural reinforcement consisting of two M25 steel bars of 3,000 mm long. The GFRP tendon of 9.5 mm diameter, placed in the middle of steel reinforcements, carries the smart feature with embedded mono Fabry-Perot fiber-optic sensor. The beams are cast on February 09, 2004.
  • The comprehensive testing program of the beams includes: (a) monitoring of strain due to two-point cyclic (stepwise) loading; (b) monitoring of strain due to long-term creep loading; (c) temperature-induced strain monitoring; and (d) beam deflection monitoring. For the validation purposes of the acquired data from our customized Fabry-Perot fibre-optic sensor, the beams are strain gauged on the outer surface of the smart tendons in the vicinity of the sensor location. In addition, for mechanical load testing, an LVDT system is mounted on the bottom surface of the beams (SM211 & SM221) and two deflection dial gages (one at the midspan and the other at the position of sensor) are set for the beam SM231. The results of the experiments are being analyzed. Based on the available data, efforts are being made to investigate the use of Fabry-Perot sensors in other forms of structural members.

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