INVESTIGATION OF GLASS FIBRE REINFORCED POLYMER  REINFORCING BARS AS INTERNAL REINFORCEMENT FOR  CONCRETE STRUCTURES    by    David Tse Chuen Johnson          A thesis submitted in conformity with the requirements for the degree of Master’s of Applied Science Graduate Department of Civil Engineering University of Toronto

© Copyright by David Tse Chuen Johnson (2009)

Investigation of Glass Fibre Reinforced Polymer Reinforcing Bars as Internal Reinforcement for Concrete Structures Master’s of Applied Science David Johnson Department of Civil Engineering University of Toronto 2009

  ABSTRACT   A study of the existing data shows that two areas of GFRP bar research among others are in need of investigation, the first being behaviour of GFRP bars at cold temperatures and the second being the behaviour of large diameter GFRP rods. Based on the results of experimental work performed, cold temperatures were found to have minimal effect on the mechanical properties of the GFRP bars tested. In addition, through beam testing, large 32mm diameter GFRP bars were found to not fail prematurely due to interlaminar shear failure. By evaluating the mechanical and durability properties of GFRP bars and behaviour of GFRP RC, it can be concluded that GFRP appears to be an adequate alternative reinforcement for concrete structures. Because of high strength, low stiffness and elastic behaviour of GFRP bars, issues of significant importance for reinforced concrete are bond development, influence of shear on member behaviour and member deformability.  

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ACKNOWLEDGEMENTS There are many people involved in this research project that without their help, this project would not be what it is today. First and foremost, I would like to thank Professor Shamim A. Sheikh for his patience and guidance during this research project and the writing of this thesis. I would also like to thank the second reader of this thesis Professor Frank J. Vecchio for his help and constructive comments. The experimental program for the research project required the assistance of two separate labs and numerous laboratory support staff. First and foremost, special thanks are due to the laboratory staff at the University of Toronto Structural Research Labs (Renzo Basset, Joel Babbin, Giovanni Buzzeo, Alan McClenaghan and John MacDonald).

The

assistance also provided by the technical staff of the concrete technology group at Kinectrics Inc. is also greatly appreciated (Ron Cullen, Joe Aloisio). The support from engineers and material provided by Schock Bauteile GmbH and Schock Canada Inc. was critical to the success of the program. I would especially like to thank Christian Witt, Benjamin Jütte for their continued support during the duration of the research program. In addition, special thanks are due to Dr. André Weber of Schock Bauteile GmbH for his support and for providing the research reports used in this thesis. Financial support from the University of Toronto, Government of Ontario, NSERC Canada and the ISIS Research Network was greatly appreciated. Finally, to all of my colleagues and friends in the Department of Civil Engineering, your support and friendship was invaluable. Present and former members of the FRP research group at U of T (Michael Colalillo, Alex Caspary, Jingtao Liu, Sylvio Tam and Ciyan Cui) helped through all stages of the program whether it be the casting of specimens or just being there to bounce ideas off of, for that you were invaluable and I thank you all. The work of undergraduate research students Junghyun Park and Arjang Tavassoli was also greatly appreciated. As well as fellow research students at the University of Toronto who also helped with the casting and testing of the specimens namely Boyan Mihailov and Jimmy Susetyo.

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I would also like to especially thank Karen Woo for not only her help in the lab but also her continued support during the entire degree.

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TABLE OF CONTENTS 1 

OBJECTIVE AND SCOPE ................................................................................................. 1  1.1 

Research Signficance ................................................................................................. 1 

1.2 

Corrosion Case Study (America’s Bridges) ............................................................... 2 

1.2.1 

The extent of corrosion in bridges ...................................................................... 2 

1.2.2 

Recent progress on corrosion mitigation ............................................................ 3 

1.2.3 

Extent of corrosion damage in Canada ............................................................... 4 

1.2.4 

GFRP as a potential solution .............................................................................. 5 

1.3  2 

3 

Scope of the Research Program ................................................................................. 6 

BACKGROUND ON GFRP REINFORCING BARS .................................................... 7  2.1 

Fibre Materials ........................................................................................................... 7 

2.2 

Resin Materials .......................................................................................................... 9 

2.3 

Fabrication Techniques .............................................................................................. 9 

2.4 

ISIS Certification Standard and CSA S807 ............................................................... 9 

2.5 

Mechanical Properties of Glass Reinforcing Bars. .................................................. 11 

2.5.1 

Available Bars .................................................................................................. 12 

2.5.2 

Glass Transition Temperature (Tg) .................................................................. 14 

2.5.3 

Cure Ratio ......................................................................................................... 15 

2.5.4 

Other reinforcement products ........................................................................... 18 

2.5.5 

Summary ........................................................................................................... 18 

LITERATURE REVIEW .................................................................................................... 19  3.1 

Previous Work on the Flexural Behaviour ............................................................... 19 

3.1.1 

Nawy et al 1971, 1977 ...................................................................................... 21 

3.1.2 

Brown and Bartholomew 1993 ......................................................................... 21 

3.1.3 

Benmokrane, Challal and Masmoudi 1996 ...................................................... 22 

3.1.4 

Vijay and Gangarao 2001 ................................................................................. 22 

3.1.5 

Yost, Gross and Dinehart 2003......................................................................... 23 

3.1.6 

General conclusions on the flexural behaviour ................................................ 24 

3.2 

Previous Work on Bond ........................................................................................... 24 

3.2.1 

Malvar 1995 ...................................................................................................... 25  v

4 

3.2.2 

Tastani and Pantazopoulou 2002 ...................................................................... 25 

3.2.3 

Achillides and Pilakoutas 2004 ........................................................................ 26 

3.2.4 

Wambeke and Shield 2006 ............................................................................... 27 

3.2.5 

Mosley, Tureyan and Frosch 2008 ................................................................... 27 

3.2.6 

General conclusions on the bond behaviour ..................................................... 28 

3.2.7 

Summary ........................................................................................................... 28 

DURABILITY OF GFRP REINFORCEMENT .............................................................. 30  4.1 

Alkali Resistance of GFRP Reinforcing Rods ......................................................... 30 

4.1.1 

Alkali resistance and testing ............................................................................. 30 

4.1.2 

Alkali resistance of commercially available bars ............................................. 31 

4.2 

Creep Rupture Strengths .......................................................................................... 33 

4.2.1 

Creep rupture test method (CSA S806-02) ....................................................... 33 

4.2.2 

Creep rupture strength of Available GFRP bars ............................................... 34 

4.3 

Performance in Extreme Temperature Environments .............................................. 37 

4.3.1 

Glass Transition Temperature (Tg) .................................................................. 37 

4.3.2 

Bar mechanical property change under extreme heat ....................................... 38 

4.3.3 

Bond strength degradation under extreme heat ................................................ 40 

4.3.4 

Response of GFRP Reinforcing Bars to Extreme Cold .................................... 42 

4.4 

Fatigue Strength of GFRP Reinforcing Rods .......................................................... 42 

4.4.1 

5 

Test method and results of fatigue testing ........................................................ 42 

4.5 

Do Simulated Lab Tests Reflect the True Conditions?............................................ 45 

4.6 

Summary of Durability ............................................................................................ 45 

EXPERIMENTAL WORK ................................................................................................. 47  5.1 

GFRP Extreme Cold Temperature Tests ................................................................. 47 

5.1.1 

Objective of cold temperature tests .................................................................. 47 

5.1.2 

Specimen preparation ....................................................................................... 47 

5.1.3 

Control sample testing at room temperature ..................................................... 49 

5.1.4 

Cold temperature test setup .............................................................................. 51 

5.1.5 

Specimen mounting .......................................................................................... 52 

5.1.6 

Instrumentation ................................................................................................. 53 

5.1.7 

Testing procedure ............................................................................................. 54  vi

5.2 

6 

5.2.1 

Objective of the test .......................................................................................... 54 

5.2.2 

Specimen design ............................................................................................... 54 

5.2.3 

Construction and casting of the beams ............................................................. 55 

5.2.4 

Instrumentation ................................................................................................. 57 

5.2.5 

Test setup and procedure .................................................................................. 58 

RESULTS AND DISCUSSION ....................................................................................... 61  6.1 

Cold Temperature Test Results ................................................................................ 61 

6.1.1 

Results of the tensile tests on 8mm bars ........................................................... 61 

6.1.2 

Results of the tensile test on 12mm bars .......................................................... 64 

6.1.3 

Results of tensile tests on 16mm ...................................................................... 65 

6.2 

Large Beam Tests..................................................................................................... 68 

6.2.1 

Load deflection response .................................................................................. 68 

6.2.1 

Moment-curvature response ............................................................................. 70 

6.2.2 

Bar stress-strain response ................................................................................. 71 

6.2.3 

Crack width behaviour...................................................................................... 77 

6.2.4 

Bond and stress development behaviour .......................................................... 77 

6.3 

7 

GFRP-Reinforced Large Beams .............................................................................. 54 

Prediction of Large Beam Samples .......................................................................... 84 

6.3.1 

Sectional analysis (Response 2000).................................................................. 84 

6.3.2 

Non linear finite element analysis (VecTor2) .................................................. 86 

6.3.3 

Results of analysis procedures .......................................................................... 87 

DESIGNING WITH GFRP .............................................................................................. 92  7.1 

Canadian Design Codes for GFRP RC .................................................................... 92 

7.2 

International Codes for Design ................................................................................ 93 

7.3 

Proposed Design Methodology for GFRP Bars ....................................................... 94 

7.3.1 

Flexural design ................................................................................................. 95 

7.3.2 

Designing for Shear with GFRP ....................................................................... 99 

7.3.3 

Quantifying ductility......................................................................................... 99 

7.3.4 

Vijay and Gangarao 2001 (DF Factor) ........................................................... 100 

7.3.5 

Yost & Gross 2002 (EFS Design) factor and method .................................... 101 

7.3.6 

CHBDC code J-Factor and design equations ................................................. 102  vii

7.4 

7.4.1 

Brief Summary of Design ............................................................................... 104 

7.4.2 

Analysis and Discussion of Sample Design ................................................... 105 

7.4.3 

Moment-Shear Interaction .............................................................................. 108 

7.5 

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Hybrid Section Design ........................................................................................... 110 

7.5.1 

Principle of hybrid design............................................................................... 110 

7.5.2 

Comparative study of reinforcement types and layouts ................................. 110 

7.6  8 

Design Example of a One-way Slab Reinforced with GFRP Bars ........................ 103 

Summary on the Design of GFRP-Reinforced Concrete Members ....................... 114 

CONCLUSIONS .............................................................................................................. 115  8.1 

General Conclusions on GFRP bars and GFRP Reinforced Concrete................... 115 

8.2 

Future work ............................................................................................................ 116 

REFERENCES ................................................................................................................... 118  Test and Technical Reports .......................................................................................... 118 

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LIST OF TABLES Table 1-1 Summary of Deficiency in the American Bridge Inventory (FHWA, 2006) ..................3  Table 1-2 Structurally Deficient Bridges per state for those bordering Canada..............................4  Table 2-1 Types of Available Structural Glass Fibres.....................................................................8  Table 2-2 Chemical Composition and Properties of Various Glass Types. (Ehrenstein 2007) .....8  Table 2-3 Minimum Modulus of Elasticity requirements for ISIS Compliance ...........................10  Table 2-4 Durability Grades and Requirements for Glass FRPs ...................................................11  Table 2-5 Mechanical Properties of ASLAN 100 Reinforcing Bar ..............................................12  Table 2-6 Mechanical Properties of Pultrall V-Rod Reinforcing Bar ...........................................13  Table 2-7 Mechanical Properties of Pultrall V-ROD HM Reinforcing Bar ..................................13  Table 2-8 Mechanical Properties of Schöck ComBAR Reinforcing Bars ....................................14  Table 2-9 Glass Transition Temperatures for Schöck ComBAR ..................................................15  Table 3-1 Selected Flexural Behaviour Tests on GFRP RC..........................................................20  Table 4-1 Summarized Alkali Resistance of Commercially Available GFRP bars. .....................32  Table 4-2 Summarized Creep Rupture Data for 16mm ComBAR bars ........................................34  Table 4-3 Linear Regression of Creep Rupture Data for 16 mm Bar ............................................35  Table 4-4 Predicted Millionth Hour Creep Strengths for 16mm Bar ............................................36  Table 4-5 Creep Rupture Data for 8mm and 25mm ComBAR bars .............................................36  Table 4-6 Summary of Glass Transition Temperature Results .....................................................38  Table 4-7 Cyclic Bending Tests Results ........................................................................................44  Table 5-1 Samples for Cold Temperature Testing ........................................................................48  Table 6-1 Results of 8mm Cold Temperature Tests ......................................................................62  Table 6-2 Summary of results for 8mm tests ................................................................................62  Table 6-3 Test Results for 12mm ComBAR Samples ...................................................................64  Table 6-4 Summarized Results of 12mm Tests .............................................................................65  Table 6-5 Test Results for 16mm ComBAR Samples ...................................................................66  Table 6-6 Summarized Results of Select 16mm Tests ..................................................................67  Table 6-7 Cracking Load, Moment and Midspan Displacement for all samples ..........................69  Table 6-8 Failure Load, Moment and Midspan Displacement for all samples .............................70  Table 6-9 Peak Bar Stresses for all Large Beam Tests..................................................................72  ix

Table 6-10 Estimates of GFRP Bar Modulus of Elasticity for 5 Large beams .............................75  Table 6-11 Summary of modulus of elasticity estimates...............................................................77  Table 6-12 Summary of Calculated Bond Strengths .....................................................................81  Table 6-13 Pull-Out Bond Strengths for 16mm GFRP Bar...........................................................82  Table 6-14 Summary of parameters in Response 2000 analysis ...................................................85  Table 7-1 Key differences between S806-02 and S6-06 ...............................................................92  Table 7-2 Materials Resistance Factors and Stress Limits from Various Codes for GFRP Design ............................................................................................................................................94  Table 7-3 Key Design Details for Sample Slab ...........................................................................104  Table 7-4 Summary of performance measures for sample slab ..................................................108  Table 7-5 Key for section names .................................................................................................111 

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LIST OF FIGURES Figure 2-1 Pultrall V-Rod, Hughes Bros. Aslan 100 FRP and Schöck ComBAR (Left to Right) ...................................................................................................................................... 11  Figure 2-2 Photograph of V-Rod and V-Rod HM (Courtesy B. Benmokrane)...................... 14  Figure 2-3 Tensile Strength vs. Cure Ratio for configurations of resin and laminates (Hülder, 2008) ....................................................................................................................................... 17  Figure 3-1 Idealized normal stress distribution (Achillides, 2004) ........................................ 26  Figure 4-1 Setup for Creep Rupture Tests on ComBAR bars (Weber, 2005) ........................ 33  Figure 4-2 Plot of Sustained Stress vs Failure Time in Creep Rupture Tests ........................ 35  Figure 4-3 Comparison of ComBAR sizes in creep rupture................................................... 37  Figure 4-4 Tensile Strength vs. Temperature for ComBAR bars (Nause 2005) .................... 39  Figure 4-5 Tensile Strength vs. Temperature for V-Rod bars (Robert et al. 2009)................ 40  Figure 4-6 Pull-out and Push-through bond testing at various temperatures (Weber 2008) .. 41  Figure 4-7 Load Slip Charts for ASLAN 100 FRP under varying temperature conditions. (Katz et al. 1999) .................................................................................................................... 41  Figure 4-8 Specimens and Reinforcing for Dynamic Tests at Karlsruhe (Kreuser 2007)..... 43  Figure 4-9 Test Setups for fatigue strength testing at Karlsruhe (Kreuser 2007)................... 43  Figure 5-1 Schöck ComBAR specimens with attached couplers ........................................... 48  Figure 5-2 Thermotron Unit used for preconditioning ........................................................... 49  Figure 5-3 Overview of Control Sample test setup (16mm sample shown (TCB16-01)) ...... 50  Figure 5-4 Universal Test Machine with Attached Environmental Chamber ........................ 51  Figure 5-5 BEMCO Control Unit and Thermocouple Readout.............................................. 52  Figure 5-6 ComBAR Sample Mounted into Environmental Chamber (TCB16-03 shown) .. 53  Figure 5-7 Geometry of Large Beam Samples ....................................................................... 55  Figure 5-8 Formwork for the large beams .............................................................................. 56  Figure 5-9 GFRP wrapped beams .......................................................................................... 57  Figure 5-10 Test setup for large beam tests ............................................................................ 58  Figure 5-11 MTS Machine used for testing............................................................................ 58  Figure 5-12 Load arrangements for large beam tests ............................................................. 59  Figure 5-13 Picture of TCB 3202 before application of load. ................................................ 60  xi

Figure 5-14 Picture of TCB 3202 during testing. ................................................................... 60  Figure 6-1 Typical debonding failure ..................................................................................... 63  Figure 6-2 Typical rupture failure .......................................................................................... 63  Figure 6-3 Photograph of ruptured coupler in sample TCB12-04.......................................... 65  Figure 6-4 Load Deformation Response of All Large Beam Samples ................................... 68  Figure 6-5 Moment curvature responses for all 5 beams ....................................................... 71  Figure 6-6 GFRP bar stress strain plots for TCB3201 & 3202 .............................................. 73  Figure 6-7 GFRP bar stress strain plots for TCB3203 ........................................................... 74  Figure 6-8 GFRP bar stress strain plots for TCB3204 & 3205 .............................................. 74  Figure 6-9 Bar Stress and Moment Diagram for TCB3201 ................................................... 78  Figure 6-10 Bar Stress and Moment Diagram for TCB3202 ................................................. 79  Figure 6-11 Bar Stress and Moment Diagram for TCB3203 ................................................. 79  Figure 6-12 Bar Stress and Moment Diagram for TCB3204 ................................................. 80  Figure 6-13 Bar Stress and Moment Diagram for TCB3205 ................................................. 80  Figure 6-14 Debonded GFRP bar inside large beam post failure ........................................... 84  Figure 6-15 Response 2000 moment curvature prediction with experimental results ........... 85  Figure 6-16 Mesh for VecTor 2 Analysis ............................................................................... 87  Figure 6-17 Load deflection of TCB3201 & 3202 with software analysis predictions.......... 88  Figure 6-18 Load deflection of TCB3203 with software analysis predictions ....................... 89  Figure 6-19 Load deflection of TCB3204 & 3205 with software analysis predictions.......... 90  Figure 7-1 Flow Chart for Tensile Rupture Controlled Design Flexural Strength Calculation ................................................................................................................................................ 98  Figure 7-2 Geometry and Loading of Sample Slab .............................................................. 104  Figure 7-3 Moment Curvature Response for Sample Slab ................................................... 106  Figure 7-4 Areas for determination of energy dissipation .................................................... 107  Figure 7-5 Moment Shear Interaction for Sample Slab ........................................................ 109  Figure 7-6 Concrete Section used for Hybrid Section Analysis ........................................... 111  Figure 7-7 Moment Curvature Responses for all 4 Sections ................................................ 112  Figure 7-8 Enlarged Low Curvature Region of Moment Curvature Responses .................. 113   

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LIST OF APPENDICIES Appendix A – Stress-Strain plots for Cold Temperature Samples Appendix B – Beam Photos Appendix C – Model Parameters for VecTor 2 Analysis Appendix D – Sample Design of Rupture Controlled GFRP RC Slab

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1

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OBJECTIVE AND SCOPE 1.1 Research Signficance Infrastructure in Canada is aging and deteriorating; the costs of repair and

rehabilitation are a constant strain on the already limited available public funds. The replacement cost of Ontario’s bridges and highways is estimated to be approximately 57 billion (MTO, 2009). Canada spends a significant amount of money annually on its infrastructure but even at that pace cannot clear up the backlog of work that needs to be done on not only its bridges, but infrastructure in general. Even in poor economic times public infrastructure remains a top spending priority, and that money has to be well spent and used as effectively as possible. Aging infrastructure and the inflating costs to maintain them is not only a Canadian problem, it’s a worldwide issue. In a recent study in 2006 from the federation international du beton (fib), their task force 9.3 on reinforced concrete estimated that worldwide infrastructure maintenance and repair exceeds 100 billion euros ($155 billion CDN) annually. Consider the United States of America, the Federal Highway Administration (FHWA) in their recent 2007 bridge inventory check identified 594,806 total bridges in America, of which 79,635 (13.4%) were functionally obsolete and 72,178 (12.05%) were deemed structurally deficient, equating to a staggering total of 151,813 (25.5%) deficient bridges. The American Society of Civil Engineers (ASCE) in their report card on American Infrastructure in 2003 indicated that a total investment of 1.3 trillion US dollars would be required over 5 years to bring infrastructure in America up to an acceptable level (ASCE, 2003). While Canada does not have nearly as accurate an idea of its inventory, the trends and problems are very similar and needs to be fixed. Reinforced concrete since its inception in 1893 has been plagued by the problems associated with the corrosion of the steel reinforcing bars. With advances in polymer technology, Glass Fibre Reinforced Polymer (GFRP) bars are emerging as the viable solution to the problem of steel corrosion in newly built and rehabilitated structures. With all the

2 delays and deferrals of rehabilitation and inspection work, Canada can’t afford to continue building structures that are still vulnerable to corrosion. The 2006 collapse of the Laval overpass and even more recently the Saint-Laurent parking garage in Montreal in 2008 are both sobering reminders of how important it is to inspect and rehabilitate our aging infrastructure effectively both cost and performance wise. Stainless steel reinforcing, while effective at mitigating corrosion, is proving too costly a material for widespread use in all structures. Reinforced concrete has evolved over the past century with such advances as air entrainment in concrete, epoxy coated reinforcing and the most recent use of stainless steel reinforcing. GFRP is the next advancement in that line, with new certification standards available and manufacturers producing bars of consistent quality, it is essential that the engineering community understand this new material as much as possible to facilitate its integration into Canadian and international infrastructure and derive benefits from its durable performance.

1.2 Corrosion Case Study (America’s Bridges) 1.2.1 The extent of corrosion in bridges  While it would be preferable to consider Canadian bridges in the case study, however having no national inventory or national body makes a country wide study impossible. The U.S. Federal Highway Administration (FHWA 2007) has identified in its reports over the past decade that corrosion is one of the largest contributors to structural deficiency among the bridges in the United States national bridge inventory. A structural deficiency as defined by the FHWA is characterized by “deteriorated conditions of significant bridge elements and reduced load carrying capacity” (FHWA 2007). Corrosion can be assumed to affect any and every concrete bridge to some extent, however, in this section only bridges that have deteriorated to a condition that qualifies as structurally deficient will be considered. By analysing the bridge inventory it can be seen that 64% or 380,772 bridges have their primary load carrying components made out of concrete (either pre-stressed or reinforced). Of those 380,772 bridges only 23,542 (6%) are structurally deficient. That

3 number is much better compared to the overall 12.05% of all bridges that are structurally deficient. Structural deficiency of a key component like a concrete deck slab on a steel bridge can also qualify the bridge to be structurally deficient. Steel bridges comprise 139,445 (23.27%) of the total inventory of which a very high 34,057 (23.5%) are structurally deficient.

1.2.2 Recent progress on corrosion mitigation     The large number of deficient bridges is one major issue; more importantly however, is the annual backlog of bridges that need maintenance. The FHWA over the past 20 years has been annually keeping track of how many deficient bridges exist in their system. Shown in the Table 1-1 is a snapshot of them over the past few years taken from the 2006 FHWA report to congress showing the rates of deficiency by bridge class during a recent 10 year period. Table 1-1 Summary of Deficiency in the American Bridge Inventory (FHWA, 2007) Year 1994 1996 1998 2000 SD 6.0 6.0 5.4 5.2 Interstate Roads FO 18.2 18.7 16.2 16.4 SD 10.9 10.2 9.3 8.3 Arterial Roads FO 10.7 10.9 10.8 11.0 SD 16.1 14.9 14.0 13.2 Collector Roads FO 11.7 11.4 11.8 11.7 SD 27.9 25.9 23.5 21.9 Local Roads FO 12.4 12.1 12.5 12.5 SD – Structurally Deficient, FO – Functionally Obsolete, *All numbers are percentages

2002 5.1 16.0 8.0 11.0 12.5 11.9 20 12.7

2004 5.1 16.1 7.7 10.7 12.0 11.6 19 12.3

What is clear in the above table is that there is a backlog of bridge work that needs to be done. While progress is being made in some areas, most notably local and collector roads, the rates of deficiency are still quite high. One alarming trend that can be quickly found by scanning through the bridge inventory is that many structurally deficient bridges were built between 1993 and 1997. Bridges as little as 10 years old are already becoming structurally deficient. In the case of two states:

4 Mississippi and Oklahoma, there are 178 and 106 currently deficient bridges built in that 4 year span, respectively. The backlog of deficient bridges cannot be completely dealt with if structures are deteriorating significantly in 10 years time after construction.

1.2.3 Extent of corrosion damage in Canada  Canada is well known for its significantly colder winters and liberal use of deicing salts, whose detrimental effects on reinforced concrete structures are well researched and documented. It is unclear at this time just how many bridges are being affected because of a lack of book keeping at the government level and a lack of a central co-ordinating and governing body. Comparing the states that border Canada in the FHWA inventory can provide some insight into the effects de-icing salts and colder climates have on their bridges. Listed in Table 1-2 are the percent of structurally deficient bridges in cold climate states that border Canada as of December 2007. Table 1-2 Structurally Deficient Bridges per state for those bordering Canada State Michigan

# of Bridges and % of State Inventory that is Structurally Deficient 1, 569 (14.39 %)

Minnesota

1,149 (8.8 %)

Montana

472 (9.48 %)

New Hampshire

380 (16.12 %)

New York

2,118 (12.23 %)

North Dakota

741 (16.64 %)

Illinois

2,482 (9.56 %)

Ohio

2,842 (10.17 %)

Pennsylvania

5,757(25.9 %)

Vermont

500 (18.5 %)

5 With the exception of 4 states, all of the states in the above list are above the national average. With consistent standards and rating according to the National Bridge Inspection Standards, it can be concluded that the presence of de-icing salts and extreme conditions do indeed increase the rates of structural deficiency in bridges to some extent depending on the quality of the maintainers. One can expect that in Canada the rates would be similar if not higher because of a longer winter.

1.2.4 GFRP as a potential solution  Stainless steel bars are being introduced into newly constructed reinforced concrete bridges to help stop the corrosion of newly built structures. Stainless steel is significantly more expensive than regular steel and it is not currently feasible to use it in all the bridges that need to be built annually. The cost of stainless steel reinforcing bars can be estimated to be 5 to 6 times greater than a traditional carbon steel bar (Russell, 2004) which can roughly translate into an additional 10-15% of the initial capital costs of the bridge. The costs of GFRP on the other hand, are competitive depending on the manufacturer. Research conducted by the National Composites Network in Europe (Halliwell, 2002) has shown that GFRP reinforcing bars cost about half of what stainless steel costs. The cost of GFRP bars in recent years has been coming down primarily due to a larger market and competition. The integration of GFRP into infrastructure has generally been delayed because of a lack of any set standards for manufacturing or design. That problem will change with the new Canadian Standard CSA S807 which complements the current RILEM and ACI standards in Europe and America. With a competitive marketplace, standards in place, pilot project bridges, and significant research and development: GFRP is emerging as a legitimate alternative to steel reinforcing. It is important then to fully evaluate GFRP in the context of a primary reinforcing product, by looking at the short and long-term structural and durability performance to determine its adequacy as internal reinforcement for concrete structures.

6

1.3 Scope of the Research Program The overall goal of the study herein is to evaluate the latest generation of GFRP reinforcing products, as well as identify and evaluate the overall adequacy of using these products as not only secondary but primary load carrying tensile reinforcement in reinforced concrete. Only GFRP in typical reinforced concrete applications will be considered, prestressed as well as complex disturbed region design will not be discussed in this study. The research program is focused around three primary goals: i) an evaluation of current generation GFRP products and the current certification guidelines, ii) the testing and analysing of the structural behaviour of large scale GFRP reinforced members, iii) the analysis of the current design provisions and design methodologies for GFRP reinforced members. In addition, the code provisions in Canada, the United States and Europe for designing with GFRP will be evaluated. Based on an evaluation of previous research and experimental results, modifications and refinements to Canadian code provisions will be proposed. Sound design methodologies for the design of both GFRP and GFRP-steel hybrid sections will also be introduced. Finally at the conclusion of the study, the overall suitability of GFRP as concrete reinforcement will be discussed.

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2

BACKGROUND ON GFRP REINFORCING BARS FRP’s of various types and configurations have existed since the post world war II

era (Tang, 1997). Their high strength to weight ratio have made them an attractive building and structural rehabilitation material. With recent advances in polymer technology, FRP reinforcing bars can now allow engineers to utilize the benefits of using FRP as internal reinforcing for concrete structures. Currently there are three major manufacturers of GFRP reinforcing bars, two North American and one European.

2.1 Fibre Materials Both FRP wrap systems and FRP reinforcing bars can be made from one of three typical materials. The most commonly known fibre material of the three is carbon fibre, famous for its use in other industries including most notably aircraft, formula race car construction and sporting goods. The other two materials are aramid (Kevlar) and glass. Each of the three materials has different mechanical and structural properties, which should be taken into consideration when choosing which material would best suit the application. Some studies have indicated that the type of material can also influence the resistance to environmental exposure and in turn the durability. Tam and Sheikh (2007) tested the durability of various FRP materials to determine their resistance to environmental exposures. Aramid and carbon FRP reinforcing bars are seldom considered for use in reinforced concrete because of their significantly higher costs than standard glass. FRP reinforcing bars made of carbon or aramid will not be dealt with in any detail in this study. As well, it should be noted that bars made of basalt fibres are also beginning to emerge onto the marketplace. Within the glass category there are further subdivisions. Shown in Table 2-1 are the types of glass currently available which are usable in FRPs. The type of glass commonly used for reinforcing rods is the E-glass type, the exact same type that is used in FRP wrap systems. E-glass is the material of choice because of its low cost relative to the other

8 available types. A comparison of the chemical compositions and mechanical properties for all the types of glass are shown below in Table 2-2 (Ehrenstein 2007). Table 2-1 Types of Available Structural Glass Fibres Glass Designation E-Glass S-Glass C-Glass ECR Glass AR-Glass

Type Standard conventional glass type High strength glass Chemical resistant glass Chemically resistant conventional glass Alkali resistant glass

Table 2-2 Chemical Composition and Properties of Various Glass Types. (Ehrenstein 2007)

Component % SiO2 Al2O3 CaO MgO B2O3 K2O Na2O ZrO2 Properties Density (g/cm3) Tensile Strength (MPa) Modulus of Elasticity (MPa) Ultimate Strain (%) Thermal Coefficient (x10-6/oC) Softening Temperature (oC)

E-Glass

S-Glass

C-Glass

ECR-Glass

AR-Glass

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