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The Bond Behaviour of Timber Reinforced with GFRP Bars

Orant Horeczy*, Dagmar Svecova**. and SamiRizkalla***

*Graduate Student, Department of Civil Engineering, University of Manitoba, Winnipeg, MB, R3T 5V6, Canada ** Assistant Professor, Department of Civil Engineering, University of Manitoba, Winnipeg, MB, R3T 5V6, Canada ***Distinguished Professor of Civil Engineering and Construction. Director, Constructed Facilities Laboratory NC State University, Centennial Campus, 2410 South Capability Drive, Campus Box 7533, Raleigh. NC 27695-7533

Abstract

The majority of timber bridges require flexural strengthening to increase their load carryjng capacity. Metals have been used for this purpose in the past, however corrosion and heavy weight became the two major factors that prompted research into the application of fiber­reinforced polymers (FRP). In recent years, the increased ava\lability of FRP materi.als has stimulated research into strengthening timber using this material, taking advantage of its high strength to weight ratio.

The short-tenD bond behaviour of timber beams reinforced with glass fiber-reinforced polymer (GFRP) bars was investigated. Wood samples were cut from creosote-treated Douglas Fir stringers to make pullout specimens. Grooves were cut into the creosote-treated surface and GFRP bars were installed using a commercially-available epoxy.

This paper discusses of results of pullout tests with bond length varying between 20 and 50-times bar diameter. Three types of bars were investigated, with fiber-volume ratios ranging from 70 to 80 percent. Additional tests were conducted to investigate the effect of notch size and notch surface quality.

Test results indicated that capacity of the member increased with increases in embeddment length and notch size. but was not dependant on the type of FRP since failure occurred at the interface or adjacent wood. Improved notch preparation did not necessarily increase the capacity in the case of a short embeddment length since the wood failure occurred adjacent to the notch.

IntroductioD

The recent increases in the allowable weight of highway 1rucks require the flexural strengthening of many timber bridges. Recently, the development of high-strength composites have accelerated research into using FRP for strengthening timber bridges to relieve the costs of replacing these bridges. These composites are well-suited for timber strengthening because they are light weight, non-corrosive, and do not require heavy equipment to handle.

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Research has been conducted into the fabrication of glulam beams with different forms of metal reinforcement. Steel reinforcement bars have been inserted into lower laminates during fabrication and were found to increase the strength and stiffness (Lantos, 1970; Bulleit et ai. 1989). Similarly, glulam beams have been reinforced with metal plates of steel (Borgin et aI, 1968) and alumillum (Mark, 1961; Sliker, 1962). Recently, glulam has been produced with plates of FRP to take advantage of the high strength to weight ratio of this material (Gardner et al. 1992; Dagher et al, 1998).

Concurrently. the strengthening of existing timber members with near-surface mounted FRP bars and externally bonded FRP sheets has been investigated. Thin sheets of FRP adhered with epoxy to the tensile surface of wood beams have been found to increase the strength, stiffuess, and ductility of the beams (plevris and Triantafillou, 1991). Similar results were found with prestressed FRP sheets and a procedure for material optim.ization was developed (Triantafillou and Deskovic, 1992). When compared to simple models, FRP enhanced the capacity of reinforced wood beyond the predicted values using transformed sections by bridging weak regions to prevent tensile failure (Johns and .Lacroix, 2000).

One option to strengthen timber beams is to embed longitudinal FRP bars into the section using epoxy, as shown in Figure 1. PreliminaI)' testing of embedded FRP was conducted for sawn timber beam.s, including full scale members (Gentile et al, 2000). Depending on the reinforcement ratio, strength was increased 25 to 50 percent with improvements in the ductility and failure mode. In this paper, the bond behaviour of the embedded technique was investigated to determine the effects of FRP type, notch size, and notch preparation, and to form a basis for future durability testing.

Experimental Program

The experimental program consisted of pullout specimens tested to investigate the bond capacity of FRP embedded into creosote-treated wood. The various parameters considered were type of FRP, notch size, and embeddment length.. The length of the notch was varied from 20 to 50-times bar diameter, while the notch size ranged from 1.2 to 2.O-times bar diameter. After notching, creosote residue was discovered on the groove surfaces and an effective method of removing this residue was developed. The impact of notch preparation on capacity was investigated using clear wood samples as control specimens.

Materials

FRP Reinforcing BtUs. FRP is a two-part composite material consisting of unidirectional fibers embedded in a matrix. The fibers have a high tensile strength while the matrix protects the fibers from abrasion or chemical reaction and transfers the force resisted by the fibers. Tensile tests were conducted on the three FRP bars used in the investigation to determine material properties. The tensile testing was conducted according to CSA 8806-00 (CSA, 2000).

a) ~ TM bars are glass fiber products manufactured by Hughes Brothers, Seward NB. The AsIan bar consisted of unidirectional glass fibers with a minimum. fiber volume ratio of 70

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percent. Pullout tests were conducted using # 10 Alsan bar, with a diameter of 9.5 mm. The stress-strain behaviour of AsIan was linear, with an average ultimate tensile strength and modulus of elasticity of 698 MPa and 42 GPa, respectively. The surface of AsIan is wound with a granular coating as shown in Figure 2(a).

b) c..:BAt™ reinforcing bars are glass fiber products manufactured by Marshall Industries, Lima OH. The C-Bar product consisted of unidirectional glass fibers and an epoxy matrix, with a minimum. fiber volume ratio of 70 percent. Pullout tests were conducted using C-Bar # 10 bar, with a diameter of 9.5 rom. The stress-strain behaviour of C-Bar was linear, witb an average ultimate tensile strength and modulus of elasticity of 712 MPa and 42 GPa, respectively. The surface ofC-BaT is ribbed to provide mechanical interlock as shown in Figure 2(b).

c) Rotaflex™ bars are glass fiber products manufactured by (Northern) Rotafix Ltd., Abercrai, UK. The Rotaflex bar consisted of unidirectional glass fibers and an epoxy matrix, with a fiber volume ratio of approximately 80 percent. Pullout tests were conducted using the Rotaflex # 10 bar, with a diameter of 9.8 mm. The stress-strain behaviour of Rotaflex was linear, with an average ultimate tensile strength and modulus of elasticity of 1088 MPa and 49 GPa, respectively. The higher strength and stiffiless of Rotaflex is due to a higher fiber volume ratio, for use in specifically non-alkaline environments such as timber applications. The surface of Rotaflex is deformed with a minor ribbing as shown in Figure 2(c).

Epoxy. Rotafix CB lOT SlowSet is a two part thixotropic epoxy with a long open time and high viscosity. The ultimate physical properties occur at a minimum set of seven days (at l8°e) with a compressive strength of over 55 MPa after five days set (at 200C). Earlier research had shown CB 1 OT SlowSet epoxy was suitable for bonding GFRP sheets to creosote-treated wood (Mufti et aI.2001)

Wood. The wood for the pullout specimens was selected from a single Douglas-Fir timber beam, provided by the Manitoba Department of Transportation and Government Services. The timber beam was creosote-treated, taken from a dismantled bridge in Southern Manitoba. The original beam was Structural Select grade, having sparsely-located knots and no noticeable longitudinal cracks or warping. The timber beam had a nominal cross-section of 495 mm x 145 tnm, with its original creosote-treatment at the perimeter.

Pullout Bond Tests

Dual-prong specimens were tested to evaluate the bond behaviour of FRP bars embedded in creosote-treated timber. The FRP bars were embedded near the surface of the specimen, with the bars positioned inside notches and secured in place using epoxy. The specimen and test set-up are described in the following.

All pullout specimens had uniditeCtional FRP bars installed into the creosote-treated perimeter using one type of epoxy adherent. The variables tested are shown in Table 1, and are separated ;nto the following two categories:

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The first category of pullout tests (Group-I) were constructed to examine the effects ofFRP type and embeddment length. The three types of glass-fiber reinforcement used were Alsan, Rotaflex, and C-Bar. Each reinforcement was tested with embeddment lengths of 200, 350, and 500 mm. The pullout specimeI1S had a uniform square notch sizc of 15.8-mm. x 15.8-mm{5/8" x 5/8").

The second category of pullout tests (Group-2) investigated the effect of notch size on the pullout capacity. AsIan bar was installed into square notches with dimensions of 12.7-mm x 12.7-mm (1/2" x 112") and 19.O-mmx 19.0-mm (3/4" x 3/4"). Lengths of 200, 350, and 500 mm embeddment were tested.

Fabricotion of Test Specimens. All pullout specimens were cut to have two opposing surfaces of creosote-treated wood and the FRP bars were installed in the longitudinal direction of tbe original timber beam. .After cutting, surfaces with exposed end grains were treated with copper naphthalene preservative to restrain moisture loss and shrinkage. A.lthough defects were allowed in the pullout specimens, the wood was cut in. a manner to prevent large knots from occurring at the beari.J1g surface, especially at the location of the notches.

Using a hand-held router, the notches were cut into each of the two opposing creosote-treated sides for the full length of the specimen, as shown in Figure 3. After grooving, notches were cleaned to remove residue shavings.

The reinforcement bars were bonded to the sides of the specimen with CB-J OT Rotafix Slow Set epoxy, supplied by Concrete Restorations Ltd., Winnipeg. The installation procedure is shown in Figure 4. Slow Set epoxy was applied from. above into the groove by adding an initia1layer of epoxy. The reinforcing FRP bar was placed inside the notch and clamped into position. After filling the notch volume with epoxy, the epoxy was leveled to complete the installation. To improve handling of the specimens, both bars were installed separately. The first bar was installed and allowed to set for 4 days before turning the specimen over and installing the second reinforcement. The specimen was allowed to set until the latter installation had set for a minimum of seven days as recommended.

To anchor the FRP to the testing frame, steel sleeves were bonded to the FRP bar using an epoxy resin. After the steel sleeves were attached and cured, the specimen was tested.

Test Setup and Procedure. The components of the test set-up are shown in Figure 5. The main action of the set-up was to push the block of wood upwards while the FRP bars were anchored to the bottom of the test frame. The load was applied to the specimen using a hydraulic jack with the pistons positioned below the bearing plate. The bearing plate was used to distribute the force over the full area of the cross-section and to prevent shear along the grain. While preventing a cleavage failure in. shear, the bearing plate had a clear distance from the notch perimeter to allow for failure in the wood adjacent to the epoxy-wood interface. A neoprene pad 4 nun thick was used with the bearing plate to ensure the force was evenly distributed A rotating support was used to traD.sfer the load from the cylinders. Additional rollers were placed at the middle of the specimen to prevent tilting during the test.

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Specimens were placed into the test frame with the FRP passing through two drilled holes. A 222 leN capacity (50 kip) hollow load cell was used for each of the FRP extensions to record the load at the anchor. Anchorage was provided by fitting common post-tensiomng chucks unto the steel sleeves. To complete the assembly, a hollow threaded nut and bolt were tightened at each anchor to balance the specimen and create uniform distribution of the applied load. A specimen prior to testing is shown in Figure 6.

Air-cleaning was used to clean the surface of the notch to simulate actual conditions in a field application. However, subsequently effective cleaning of tbe contact surface was used in the second series of pullout tests. The differences in notch preparation are reviewed in detail with clear-wood pullout specimens.

The load was applied using two different schemes. In the first set of pullout tests, Group-I, a ball-support was used to appJy the load to the bearing plate. However, if displacement occurred at one side of the test the specimen was subjected to prying action. Therefore, the second set of pullout tests, Group-2, was modified to allow independent application of the load to each bar. As a result, large cracking could OCCllr at one side without disturbing the loading of the other side or the ability of the cracked side to regain loading. For this reason the pullout groups are discussed. separately in the results.

Effect of Surface Treatment

Since the epoxy-wood iDterface was the locatioD of failure for many pullout specimens, the impact of notch preparation on pullout behaviour was investigated.

Clear wood specimens were used as control specimens to detennine the effect of notch preparation on the bond capacity of a short embedded length. The following levels of Dotch preparation were tested: 1) specimens which were not cleaned, 2) specimens cleaned by pressurized-air (air-cleaning), and 3) specimens cleaned by scraping the surface (contact­cleaning). In addition, specimens which were notched in untreated regions were tested.

A total of 42 clear wood specimens constructed from. the identical Douglas·Fjr timber beam were used for the pullout tests. A typical specimen is shown in Figure 7. All specimens have a bonded length of 150 mm. and an approximate cross-section of 75 nun x 214 mm. Each specimen had one square notch of 19.0 rom (3/4") depth which was made perpendicular to the bearing face. The majority of specimens were notched in the 150 mm face treated with creosote. Nine specimens which had flush untreated faces were notched in the untreated 150 mm face opposite from the creosote.

The treated. specimens were sorted with respect to notch quality based on the presence of creosote residue. The specimens were divided into the following three groups: a) nine specimens with very little residue, b) 15 specimens with medium levels of residue, and c) nine specimens with dense concentrations of residue. Each level of notch quality was randomly assigned to the cleaning procedures to create three similar ranges of cleanliness. In addition, three of the nine untreated specjmens were assigned to each cleaning procedure.

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Surface Preparation Air-cleaning comprised of two steady passes of pressurized-air with the noule pointed towards the bottom surface of the notch. The air-cleaning technique was selected to simulate a basic option for cleaning in a field situation. In contact-Cleaning, a piece of 12.7 mm 012") steel was glided along each surface of the notch depth twice, followed by two passes of pressurized-air as perfonned in the air-cleaning technique. The contact-cleaning method was used to remove the full amount of creosote residue efficiently and quickly. The uncleaned specimens were not cleaned to observe the worst-case scenario for bonding.

Prior to installation, the presence and location of residue on the side surfaces were recorded fOT

each notch. The interior of each notch was observed with residue given a rating of Light (L). Medium (M), or Heavy (H). A Light-rating was given to areas with residue which was visible as powder on the surface when viewed. A Heavy-rating of residue was assigned to areas with a dark, caked. layer of residue, readily visible at a distance. Heavy residue had an oily and sticky texture which fell out as a steady flow of clumps when contact-cleaned. The Medium-rating was between the preceding levels, commonly found as a visibly darker and oilier material than Light, but best descnbed as densely-concentrated powder rather than a caked layer of residue.

The residue of the uncleaned specimens ranged in quantity as determined by the selection process described earlier. Compared to the uncleaned set, air-cleaning was efficient in eitheT removing or reducing the quantity of heavy residue, but amounts of light residue in the form. of visible powder were still present. In the contact-cleaned set, almost every heavy and m.edium concentration of residue was removed, with over 50 percent of the sides having no residue observed after cleaning. The untreated specimens had no change in appearance following cleaning.

Reinforcem.em. Steel reinforcement was selected to simplify fabrication and testing. The steel reinforcement consisted of 12.7 mm (1/2") diameter plain bar with a measured yield strength of 384 MPa. To improve friction in the embedded length, the steel bar was ragged with a mounted grinder to produce six shallow indents at approximately 20 rom on-center. The deformations bad characteristic dimensions of 0.5 mm depth for a width of 4 mm.. CBIOT SlowSet epoxy was used for installation and allowed to set for seven days before testing. The installation procedure was identical to the method used for the pullout specimens.

Testing. Clear-wood pullout specimens were tested using a 133 kN (30 kip) Baldwin testing machine. A specimen prior to testing is shown in Figure 8. A steel plate was attached to the bottom of the specimen to prevent rotation of the specim.en during the test. At the sides of the specime~ an additional steel frame was attached to inhibit cracking of the specimen in the thinnest dimension. Both sets of restraints were tightened only to fit the specimen firmly and not to apply compressive force. The specimen reacted against a 12 mm thick steel bearing plate with a 31.8 mm (1-114") diameter drilled hole. Failure in the wood adjacent to the notch was allowed by providing clear distance from the notch to the hole circumference. A 4 mm. neoprene rubber pad was placed between the specimen and the bearing plate to distribute the force evenly to the specimen. The test was conducted. by stroke-control at a rate of 2.0 mmlmin.

Test Results

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Clear-wood PuHOllt Specimens. The bond capacity for each of the cleaning techniques used is shown in Figure 9. In general, the specimens that were contact-cleaned or untreated exhibited higher capacity than the air-cleaned and uncleaned specimens. However, specimens which had better notch quality did not necessarily have higher capacity than other tests in the same preparation group. Figure 10 shows the capacity of the uncleaned specimens, grouped into the following classes of notch quality at the time of installation: notches with a high-concentration of heavy residue (A), notches with medium levels of residue (B), and notches with clean surfaces (C). The Class-C specimens did not have higher capacity than Class-A specimen.s, irrespective of the difference in residue present. When the interface bond was improved by cleaning, capacity remained limited. by the strength of the wood directly adjacent to the notch.

Failure Modes. The majority of treated pullout specimens failed at the wood adjacent to the notch, or at the epoxy-wood interface. For the strongest specimens. the load applied was limited by the yield strength of the steel reinforcement. The failure modes are categorized into the following three groups: 1) wood failure, 2) interface failure, and 3) yield failure. The modes of failure were identical for both treated and untreated specimens.

Wood failure OCCUlTed when the failure surface was within the wood swrounding the notch. Typical failure of wood is shown in Figure 1l(a). The location of the failure plane varied with specimens, although it regularly occurred within the closest wood at tbe top of the notch and along the grain at the bottom of the notch. The failure was instantaneous, with cracking of the wood prior to failure.

Interface failure occurred when the failure surface coincided with at least one surface of the notch, as shown in Figure 1 1 (b). For some specimens th.e failure plane was at the notch surface and had extended to the exterior of the wood at the bottom of the notch. The failure was instantaneous, with cracking of the wood prior to failure.

Yield failure accounts fot' all specimens whjch had yielding of the steel reinforcement at the grips. M yielding progressed from the grips, the embedded length withstood sustained load until instantaneous failure occurred. The majority of failure was at the interface or the adjoining wood, with three specimens out of 42 baving bar pullout If the interface specimens were reinforced with FRP, yielding of the reinforcement would not occur allowing the specimen to attain bigher loads before pullout or rupture.

Figure 12 shows the pullout capacity of treated specimens with respect to failure mode. The specimens with wood failure had the highest range of capacity, corresponding to variations in the adjacent wood strength. With interface failure, the capacity is more uniform, with high capacity observed with specimens which had clean notch surfaces. As expected. the capaL"ity was most uniform when governed by yielding.

Group-J Bond Pullout Tests. The puxpose of the pullout tests was to determine the bond strength for different types of GFRP bars. Pullout specimens had similar fdilure modes as the interface specimens, however the capacity was not rcstticted by yielding, since FRP mal.erials do not yield Table 2 sbows the failure modes for the Group-l specimens. The specimens reinforced with Asian and Rotaflex failed at the epoxy-wood interface or in the adjacent wood.

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The C-Bar tests failed with bar pullout from the epoxy, having no damage to the bar. Because the bond of C-Bar depends on mechanical interlock instead of adhesion, the surface dcfoImations cracked the epoxy and allowed bar pullout to occur.

Figure 13 shows the capacity of Group-! specimens with respect to embeddment length. The capacity increased with embeddm.ent length for each type of bar tested. The capacity of the Rotaflcx tests were similar to the others, even though the reinforcement had greater tensile modulus and ultimate strength. In this case, the Rotaflex tests were limited by the capacity of the interface andlor the adjacent wood. For larger embeddment lengths, there was greater variability in the pullout capacity which can be attributed to larger probability of intercepting weaker regions of wood at the interface, promoting early wood failure.

The uniform bond stresg was calculated for all pullout tests. The uniform bond stress assumed unifOl1ll distnDution of the ultimate pullout capacity over the three sides surface of the notch, for the length of the specimen. The uniform bond strengths of Group-l specimens are shown in Figure 14. The uniform bond strength decreased linearly with an increase in embeddmcnt length, with a minimum value of 2.00 MPa for the 200 mm length to 1.25 MPa for the 500 mID

length. Based on the limited number of samples, there was no relationship between type of FRP and minimum. unifonn bond stress at ultimate. However, future durability testing will be required to study the long-term perfonnance of these bars.

Group-2 PrJ[out Bond Tests. The second set of pullout tests was constructed with Asian and used to investigate the effect of notch size. Table 3 shows the failure modes for the Group-2 specimens. Small notch specimens had failure at the notch interface or in. the adjacent wood, with the exception of one 500 IIlJl1 specimen which failed by rupture. All of the large-notch specimens failed by rupture of the AsIan bar, without damage to the epoxy.

Figure 15 shows the capacity of Group-2 specimens with respect to embeddment length. The capacity increased with an increase of the embeddment length and was limited by the tensile capacity of the bar. Relatively weak strength occurred in two small-notch specimens which was attributed to the poor condition of the creosote-treated wood adjacent to the notch. The larger notches were less dependant on the capacity of creosote-treated wood and did not have interface or wood failures.

The uniform bond strengths of Group-2 specimens are shown in Figure 16. The uniform bond stress decreased asymptotically with an increase in embeddment length, with a minimum value of 3.50 MPa for the 200 mm length to 1.50 MFa for the 500 mm length. Specimens with smaller notches had similar levels of bond stress, even though the larger notch had 50 percent more surface area than the smaller notch.

Conclusions and ReeommendatioDs

Pullout tests were developed to investigate the bond of FRP installed in creosote-treated timber. The following conclusions and recommendations can be drawn:

1) Pullout capacity increases with increases in embeddment len.gth and notch size.

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2) Contact-cleaning methods to remove the residue is more effective than pressurized-air.

3) Better cleaning techniques will generally increase the pullout capacity.

4) The type of FRP does not control the capacity which is mainly related to the interface bond or the wood strength.

5) A minimum uniform bond strength of 1.5 MPa can be used for the 500 mm specimens. Within the range tested, the minimum uniform bond strength is independent of the notch size and FRP type.

Acknowledgments

The authors would like to express their gratitude to the Manitoba Department of Highways and Government Services and to the ISIS Canada Network for their support of this project. In addition, the material contributions of Hughes Brothers and Concrete Restorations are gratefully acknowledged. Special thanks are extended to Mr. Kenneth Au and Mr. Grant Whiteside for their assistance and to Mr. Walter Saltzberg for his valuable expertise.

References

Borgin, K. B., Loedolff, B. F., and Saunders, G. R. (1968). ''Laminated Wood Beams Reinforced with Steel Strips." J. Struct. Engrg., ASCE, 94{STl), 1681-1705.

Bulleit, W. M., Sandberg, L. B., and Woods, G. J. (1989). "Steel-Reinforced Glued Laminated Timber." J. Struct. Engrg., ASCE, V.1l5(2), 433-444.

CSA. (2000) "CSA-S806-OO - Design and Construction of Building Components with Fibre Reinforced Polymers", Canadian Standards Association.

Dagher, H.I., Poulin, J., Abdel-Magid, B., Shaler. S.M .• Tjoelker, W., and Yeh, B. (1998). "FRP Reinforcement of Douglas Fit and Western Hemlock Glulam. Beams." Proceedings: ICE'98, Nashville, 1N, 17-21 January 1998, 1-3.

Gardner, D. J., Wolcott, M. P., and MWlipahle, U. (1992) "Wood Refuforced with Pultnlded Fibre Reinforced Composites." Proceedings: Pacific Rim Bio-Based Composites Symposium, Rotorua, New Zealand, 9-13 November 1992, 263-269.

Gentile, C., Svecova, D., Saltzberg, W., and Rizkalla, S. H. (2000) "Flexural Strengthening of Timber Beams Using GFRP." Proceedings: Advanced Composite Materials in Bridges and Structw"es, 3rdInt Conference, Ottawa, Canada, 15-18 August 2000. 637-644.

Johns, K. C., and Lacroix, S. (2000) "Composite Reinforcement of Timber in Bending." Can. J. Civ. Eng., V.27, 899 - 906.

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.,

Lantos, G. (1970). ''The Flexural Behavior of Steel Reinforced Laminated Timber Beams." Wood Sci., V.2(3), 136-143.

Mark, R. (1961). "Wood-Aluminum Beams Within and Beyond the Elastic Range." Forest Prod. J.. V.l1(lO), 477-484.

Mufti. A. A., Bakht, B., Svecova, D., and Adams) T. (2001) "Evaluation of a Glue for Bonding FRP Laminates on Timber Beams Treated with Creosotes." 29th Annual Meeting. Canadian Society of Civil Engineers, Victoria, Canada, 30 May - 2 June 2001.

Plevris, N., and Trianta.fi.Ilou, T. C. (1992) <'FRP-Reinforced. Wood as Structural Material." J. Mater. In Civil Engrg., ASCE, V.4(3), 300-317.

Sliker. A. (1962) "Reinforced Wood Laminated Beams." Forest Prod. J., V.12(12), 91~96.

Triantafillou, T. C., and Deskovic. N. (1992) "Prcstressed FRP Sheets as External Reinforcement of Wood Members." J. Struc. Engrg .• V.U8(S), 1270-1284.

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Figure ] Strengthenjm~ of Timber Beams with GFRP BaTS

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figure 2 - Surfaces of Gill Bars

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Figure 3 - NOtch;ns of Specimens Fi~re 4 -ln$Ilation ofReinforcemept

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LOADING

Bearing Pl::IIf'P.

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Figure 5 -Test Setgp for Pullout Bond Specimens

Figure 7 Clear-wood Pulloyt Specimen

12

Fi~re 6 - Pullout Bond Specimen In Test Setup

Figure 8 Clear-wood Pullout Specimen In Test Setup

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FiguTe 9 - Capacity of SpecimenS by lEparation Technigye

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fipe 10 - Capacity ofUncJeaned Specimens Grouped by Notch Quality

Figure 1] - Failure Modes of Clear-wood Pullout Specimens

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Figure 13 - Effect ofEmbeddment LCIDi1h on Pullout Capacity !('rroup-l; FRP IY.Pel

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0.0 0 100 200 300 400 500 600

Length of Embeddment (mm)

Figure 16 - Effect of Embeddment Length on Uniform Bond Strength (Group-2: Notch Sizru

Table 1 - variables of Pullout Bond Tests

Specimen Number FRP Notch Notch NotCh Designation of Tests Type Length (mm) Dia. (mm) Preparation

20/1.6-A 4 Aslan 200 15.8 Air

20/1.6-R 3 Rotaflex 200 15.8 Air

20/1.6-C 3 C-Bar 200 15.8 Air

35/1.6-A 3 Asian 350 15.8 Air

3511.6-R 3 Rotaflex 350 15.8 Ai.r

3S/1.6-C 3 C-Bar 350 15.8 Air

50/1.6-R 3 Rotaflex 500 15.8 Air

50/1.&-C 3 C-Bar 500 15.8 Air

2011.2-A 3 AsIan 200 12.7 Contact

3511.2-A 3 Aslan 350 12.7 Contact

SO/1.2-A 3 Asian 500 12.7 Contact

20/1.9-A 3 AsIan 200 19.0 Contact

3511.9-A J Aslan 350 19.0 Contact

50/1.9-A 3 Aslan 500 19.0 Contact

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Table 2 Failure Modes of Group-1 Pullout BODg Tests

FRP Number Notch FRP Bar Type of Te$ts Pullout Rupture Pullout

Asian 10 10 0 0

Rotaflex 9 9 0 0

C-Bar 9 0 1* 8

Total 28 19 1 8

* R,uoture in one 50/1,6-C test.

Table 3 Failure Modes ofGroup-2 Pullout Bond Tests

Notch Number Notch FRP Bar Size of Tests Pullout Rupture Pullout

12.7mm 9 8 1* 0

19.0mm 9 0 9 0

Total 18 8 10 0

* RuPture in one 50/1.2-A test.

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