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1st International Structural Specialty Conference 1ère Conférence internationale sur le spécialisée sur le génie des structures

Calgary, Alberta, Canada May 23-26, 2006 / 23-26 Mai 2006

Experimental Investigation on the Fatigue Behaviour of GFRP Experimental Investigation on the Fatigue Behaviour of GFRP Reinforced Concrete Bridge Deck Slabs A. El Ragaby, E. El Salakawy, and B. Benmokrane ISIS Canada, NSERC Research Chair in FRP Reinforcement for Concrete Structures Department of Civil Engineering, Université de Sherbrooke, Sherbrooke, Québec, Canada

Abstract: Fatigue performance is an important limit state that must be considered by bridge engineers. Since bridge deck slabs directly sustain repeated moving wheel loads, they are most susceptible to fatigue failure than other bridge elements. Recently, glass FRP composites have been widely used as internal reinforcement for concrete bridge deck slabs subjected to harsh environmental and loading conditions as it is less expensive than other kinds of FRP (Carbon and Aramid). Many researchers have investigated the fundamental mechanical properties of FRP products; however, there is a lack of information on the performance of FRP-reinforced concrete elements subjected to cyclic fatigue loading. This research is designed to investigate the fatigue behaviour and fatigue life of concrete bridge deck slabs entirely reinforced with Glass FRP bars. A total of four full-scale deck slabs (3000 mm x 2500 mm x 200 mm) were cast and tested under concentrated cyclic loading till failure. The slab edges were restrained against rotations and lateral displacement. Different reinforcement types (steel and Glass FRP), ratios, and configurations for top reinforcement in both directions were used. Different schemes of cyclic loading (accelerated fatigue loading) representing all vehicles with different load magnitudes and repetitions that the bridge deck slab may undergo during its lifetime were used. Results are presented in terms of deflections, strains in concrete and FRP bars, and crack widths at different levels of cyclic load. The results showed the superior fatigue performance and fatigue life of concrete bridge deck slabs reinforced with GFRP composite bars. 1. Introduction Fatigue performance is an important limit state that must be considered by designers of bridge decks, parking garages, and other structures subjected to cyclic loading resulting from moving vehicles which may exceed 100 million load cycles over the service life of a bridge. The most susceptible element of bridges to fatigue loading is the deck slabs since they directly sustain repeated moving wheel loads. An un-cracked bridge deck resists traffic loads primarily through one-way (transverse) flexural response. After the deck slab cracking, it resists traffic loads through arching action, behaving like a flat dome. The increase in flexural capacity due to arching action can be so significant that punching shear capacity will control the design of a bridge deck slab. Research on punching shear in bridge decks, however, has been limited, especially experimental studies regarding fatigue. The reasons for this seem to stem from the understanding that the ultimate load carrying capacities of deck slabs are very large and a conventional design code based on an allowable stress method is too conservative to require consideration of fatigue effect (Hassan et al. 2000, Matsui and Tei 2001, Yost and Schmeckpeper 2001). To overcome corrosion related problems in many concrete structures in Canada and the northern United States, FRP, as non-corrosive materials, have being investigated by researchers as a


potential substitute for steel reinforcement in concrete structures. FRP materials possess the necessary property of high tensile strength that makes them attractive as structural reinforcement for concrete. Due to the relatively low modulus of elasticity of FRP bars, concrete members reinforced with FRP will develop wider and deeper cracks than members reinforced with steel. Eventually, the overall shear capacity of concrete members reinforced with FRP bars as flexural reinforcement is lower than that of concrete members reinforced with steel bars. In bridge deck slabs, due to the lack of shear reinforcement, the shear strength is provided only by the concrete (Saadatmanesh and Ehsani 1996, Humar and Razaqpur 2000, Benmokrane and El-Salakawy 2002). Several codes and design guidelines for concrete structures reinforced with FRP bars have been published recently. In particular, the Canadian Highway Bridge Design Code, CHBDC, (CAN/CSA-S6-00 2000) includes a new section (Chapter 16) about using FRP composites as reinforcement for concrete bridges (CAN/CSA-S6-00 2000). Since it is less expensive than other kinds of FRP (Carbon and Aramid), Glass FRP is more attractive to the infrastructure applications and the construction industry. In fact, several concrete bridge decks have been recently built in North America using GFRP composite bars as main reinforcement for their deck slabs (ElSalakawy et al. 2005, Benmokrane et al. 2006). Although there is a substantial amount of information about the flexural performance of FRP reinforced concrete elements, long-term behaviour and durability issues are still lacking. Concrete bridge deck slabs are governed by long-term fatigue endurance and durability of constituent materials. Hence, it is necessary to understand the fatigue behaviour of such structures especially when using new materials such as GFRP bars. This research is designed to study the fatigue behaviour of restraint concrete bridge deck slabs reinforced with different configuration of GFRP bars under fatigue loads. Some design recommendations to improve the current design provisions are introduced. 2. Literature Review Fatigue properties of reinforced concrete are related to its constituent materials, concrete and reinforcement (steel or FRP). In particular, under fatigue loading, a reinforced concrete deck slab can be affected by both strengths of materials and bond strengths between dissimilar materials. The bond between the constituent materials can be the critical factor for the fatigue life of the structure. During fatigue loading, the structure undergoes local and overall deformations which lead to continuous redistribution of stresses [18]. From experimental investigations, some knowledge is now available on fatigue life and behaviour of plain concrete, and both steel and FRP reinforcement. These results are the basic information for systematic investigation of the combined response of the reinforced concrete structural member subjected to fatigue loading. (Mallet 1991, Hwan 1986, Tilly and Moss 1982, Demers 1998, Adimi et al. 2000, Katz 2000) Several researches have been carried on manly on steel RC deck slabs specimens or prototypes while a few researches were carried on FRP RC and also steel-free concrete deck slabs under pulsating or moving loading to simulate the effect of passing vehicles on a bridge deck. Different reinforcement configuration including isotropic reinforcement pattern (equal reinforcement ratios, minimum of 0.3%, top and bottom in all directions) and orthotropic reinforcement pattern (transverse reinforcement ratio higher than that in the longitudinal direction) were used. (Okada et al 1974, Sonoda and Horikawa 1982, Pardikaris and Beim 1988, Youn and Chang 1998, Graddy et al. 2002, Kumar and GangaRao 1998, Rahman et al. 2000, Bakht and Selvadurai 1996, Matsui et al. 2001, Memom et al. 2003). Test results can be summarized as following:  The damage caused by moving wheel-load was much more severe than the damage caused by stationary pulsating load. The fatigue life of the isotropic reinforced bridge decks under moving wheel-load was about 20 times the fatigue life of the orthotropic reinforced ones;


 A radial cracking pattern was observed under both static and stationary pulsating loading conditions while a grid-like cracking pattern was observed under moving wheel-loads;  The fatigue life of the deck panels with the same static strength and reinforcement ratio increases as the effective depth increases while the fatigue life of the deck panels with compressive reinforcement was shorter than the ones without it;  The rate of fatigue degradation in decks reinforced with FRP bars compared well with decks reinforced with steel bars;  The decks reinforced with FRP bars had a linear variation in stiffness degradation even after 2,000,000 fatigue cycles; thus 2,000,000 fatigue cycles could be conservatively assumed as 80% of the fatigue life of these decks;  Even under several concentrated loads simulating the running wheel load, the steel-free and FRP reinforced deck slabs had a high load carrying capacity;  Using of a grid of minimum reinforcement near the bottom face of the steel-free deck slab was recommended (second generation). 3. Details of the Experimental Program 3.1. Test Prototypes The experimental program includes four full size bridge deck prototypes (2500 mm width, 3000 mm length, and 200 mm thick). Three deck slabs prototypes were reinforced with different reinforcement ratios and configurations of GFRP bars and one slab prototype was reinforced with conventional steel bars as a control one. Bottom and top concrete cover of 38 mm were used for all slabs prototypes. The main bottom transverse GFRP reinforcement for the three GFRP reinforced decks, S1, S3, and S4 was calculated based on the empirical design method recommended by the updated version of Section 16 (2006) of the Canadian Highway Bridge Design Code (CHBDC) [11] (Clause 16.8.7.1), for internally restrained cast in place deck slabs. According to this clause, a minimum FRP reinforcement area in the transverse bottom direction is set to 500ds/Efrp where ds is the distance from top of the slab to the centroid of the bottom transverse reinforcement. This approach results in using 1#19 GFRP @150 mm in the bottom transverse direction with reinforcement ration of 1.2%. The longitudinal bottom reinforcement for the three slabs consists of 1#16 GFRP @ 200 mm with a reinforcement ratio of 0.6%. Different configuration and reinforcement ratio for the top reinforcement layer were used. For slab S1, 1#16 GFRP @ 200 was used for the top layer in both directions with a reinforcement ratio of 0.6%. For S3, a minimum reinforcement ratio of 0.3% was used for the top layer in both directions which results in using 1#13 GFRP @ 300 mm in each direction. Slab S4 had no top reinforcement at all in any direction. The control slab S0, reinforced with steel bars, was designed according to the empirical method according to CHBDC-2000 (CAN/CSA-S6-00-Section 8– clause 8.18.4.2) which recommended the use of 0.3% isotropic steel reinforcement ratio in all direction for the bottom and top layers which results in using 1#10M @ 210 mm. Table 1 summarizes all the reinforcement details of the four test prototypes. It also includes the capacities of identical slab prototypes that were tested using the same set-up under monotonic (static) loading conditions only (El-Gamal et al. 2005). 3.2. Materials Properties 3.2.1 Concrete All test specimens were constructed using normal weight, ready-mixed concrete (Type V, MTQ) with a targeted 28-day concrete compressive strength of 37 MPa. All test slab prototypes were cast and kept in the laboratory, for at least 14 days, wrapped with plastic sheets in humid environment for curing. The previous researches indicated that the cracking status significantly


affect the fatigue response of concrete deck slabs [19, 21]. One of the significances of this research is that all test prototypes, after the curing period in controlled environment, were stored out-doors in real environmental conditions for at least one year. This was done to simulate the environment that a real bridge will undergo to allow for the formation of concrete cracking that arise mainly from environmental conditions. Also, this storage period helped to stabilize the concrete properties (compressive strength and modulus of elasticity). These properties can be varied during fatigue testing if the slabs were tested within a short time of casting which leads to a scatter in the results. During this period, the deck slab prototypes were exposed to more than 25 freeze-thaw cycles (-35 to +35°C) and about 20 wet-dry cycles. The actual concrete compressive and tensile strengths were determined based on the average value of compressive and tensile splitting tests carried out on standard cylinder specimens of (150x300 mm) on the day of testing of the slabs. The standard cylinder specimens were subjected to the same environmental conditions as their reference slabs. The obtained average concrete compressive strength was about 41 MPa. Table 1. Reinforcement details of test prototypes Sl ab S 1 S 3 S 4 S 0

Transverse Direction

Longitudinal Direction

Bottom

Bottom

No.19 @150 mm No.19 @150 mm No.19 @150 mm No.10M@210 mm

Top No.16 @ 200 mm No.13 @ 300 mm No Reinforcement No.10M @ 210 mm

Static Capacity

Top

No.16 @ 200 mm No.16 @ 200 mm No.16 @ 200 mm No.10M@210 mm

(kN)

No.16 @ 200 mm No.13 @ 300 mm No Reinforcement No.10M@210m m

732 N/A 707 691

3.2.2. Reinforcement TM

Two types of reinforcing bars were used in this study; sand-coated GFRP V-ROD (Pultrall Inc. 2004) and CSA grade 400 deformed steel bars. The mechanical properties of these reinforcing bars were obtained from standard tests that were carried out according to CAN/CSA-S806-02 or ASTM A370-05, where appropriate. Table 2 summarizes all the mechanical properties of the reinforcing bars used in this research.

Table 2. Mechanical properties of reinforcing bars Bar Type GFRP No.13 GFRP No. 16 GFRP No. 19 Steel No 10M

71

Modulus of Elasticity (GPa) 45 ± 2

Tensile Strength (MPa) 756 ± 11

1.7 ± 0.03

15.9

198

44 ± 1

727 ± 9

1.65 ± 0.03

19.0

283

44 ± 1.3

637 ± 15

1.37 ± 0.03

11.3

100

200

fy=453

εy=0.2

Bar Diameter (mm)

Bar Area 2 (mm )

9.5

Ultimate Strain %


4. Test Set-up All slabs were tested under a single concentrated load at the centre of a clear span of 2000 mm. This load was applied through a 75-mm thick steel plate that measures 250 x 600 mm, which is equivalent to the footprint of a wheel as specified by the CHBDC (CAN/CSA-S6-00). A 20-mm thick neoprene sheet was used between the plate and the concrete surface. All test prototypes were tested with the two longitudinal edges restrained against both displacements and rotations. To apply the end restraint, the slab was tied to two steel I-beams spaced at 2000 mm (centre-tocentre) using steel bolts that were fitted into holes through the thickness of the slab. To ensure the same degree of restraint for both sides and for all deck slab prototypes, all bolts were tied using a constant torque, which was maintained during the entire fatigue test. A load actuator, 500 kN capacity with +/- 250 mm stroke, was used to apply fatigue loads. It was mounted vertically in stiff steel frame that was tightly bolted to a rigid floor. Figure 1 shows a photo for the test set-up. 4.1. Repeated Fatigue loading Moving vehicular loads was simulated by stationary concentrated load varying cyclically in magnitude. During this research, an accelerated fatigue loading scheme was used. It consists of variable amplitude fatigue loading where all the slabs were subjected to sinusoidal waveform fatigue load cycles between a minimum load level and variable maximum load levels (Fig. 2). The minimum load level was fixed at 15 kN for all slabs to prevent any impact effect during cyclic loading and also represent the effect of permanent dead loads on bridges (pavement, insulation, etc). Different peak loads of 183.8, 245.0, 367.5, and 490.0 kN which were equivalent to the multipliers of load level for fatigue limit state, 1.5Pfls, 2Pfls, 3Pfls, and 4Pfls, respectively (Pfls = 87.5*1.4*1.0 = 122.5 according to CAN/CSA-S6-00, Clause 3.5.1). Each of the different fatigue loading schemes (for example, 15 kN minimum and 183.75 kN peak load) was applied for 100,000 cycles at frequency of 2 Hz (duration of about 14 Hours for each peak load). If failure occurred during cycling, the test was stopped immediately. If the test prototype completed the last 100,000 at the largest peak load (490 kN) without failure, the test continued at the same load level till failure. For slab S3, an extra 300,000 cycles at lower peak loads (100,000 at each of Pfls, 1.25 Pfls, 1.75 Pfls), 122.5, 153.1, 214.4 kN, respectively, were applied to the deck slab to asses the effect of cycling at lower peak load level. 4.2. Test Procedure Prior to the initiation of the fatigue loading, the slab prototypes were pre-cracked by performing two monotonic static load cycles. Each cycle included loading till 183.8 kN (1.5 Pfls) and unloading to zero. This was conducted to determine the cracking loads, to initiate cracks from mechanical loads to simulate real bridges, and to assess the pre-cracking and post-cracking stiffness and behaviour of the test prototypes. At the end of each load step (100,000 cycles at certain peak load) another monotonic load cycle includes loading till 183.8 kN (1.5 Pfls) and unloading to zero was performed to asses the degradation that may occur in the deck slab due to fatigue loading. The previous procedure was repeated till failure. Note that due to equipment limitation, it was necessary to increase the minimum load level from 15 kN to 50 KN for all load steps utilizing peak load levels higher than 400 kN.


500

100,000 Cycles

450

100,000 Cycles

400

Load (kN)

350 300

Till Failure

100,000 Cycles

100,000 Cycles

250 200 150 100 50 0 0

10

20

Figure 1. Test set-up

30

40

50

Figure 2. Cyclic load Pattern

4.3. Instrumentations For each slab, a total of twenty six electrical resistance strain gauges were used to measure the strains in reinforcing bars and the concrete top surface. Six LVDTs were used to measure the slab deflection at different locations around the loaded area and at supports. Also, a high accuracy (0.001 mm) LVDT was installed at the position of first crack to measure crack width. A data acquisition system, monitored by a computer is programmed to record the readings of all strain gauges, LVDTs, and the load cell. 5. Test Results and Analysis The test results are presented in terms of deflections, strains in reinforcing bars and concrete, crack propagations, and crack patterns which were all measured during the monotonic loading steps that were carried out at the end of each fatigue loading step. Figure (3) summarizes the number of cycles that each slab sustained under each fatigue load step till failure. It can be noticed that the steel reinforced slab, S0, has the shortest fatigue life among all the tested slabs as it sustained only 300,000 cycles at the first three fatigue loading steps and failed after only 120 cycles at 450 kN peak load. Slabs S3, S1, and S4 have consistence results although they have different top reinforcement ratios. Note that slab S3 was subjected to 300,000 cycles at lower peak loads (100,000 at each of Pfls, 1.25 Pfls, and 1.75 Pfls) which did not affect its performance as it sustained almost the same fatigue loading steps compared to the other two slabs (S1 and S4). So it can be stated that applying repeated loads with amplitude equals or up to 1.75 times the fatigue limit state has insignificant effect on the restraint GFRP-reinforced concrete deck slabs.


Slab S0 Slab S1 100000

Slab S3

No. of Cycle

80000

Slab S4

60000 40000

Slab S4 Slab S3 Slab S1 Slab S0

Sl ab

20000 0 122.5

183.75

245

425

490

Peak Load (kN)

Figure 3. Number of cycles for all slabs to failure 5.1. Deflection Characteristics Any progressive deterioration of the deck slab would be evident from increasing deflections and stresses with the increase of the number of cycles. Typical deflection behaviour and results are obtained for the four test prototypes. Figure (4) shows the static load-deflection behaviour for slab S1 recorded at the end of each fatigue loading step. Note that St-00 and St-01 refer to the two static loading and unloading loops that were carried out before applying the fatigue load cycles. Also, St-183, for example refers to the loading and unloading loop after completing 100,000 cycles at 183 kN peak load, and so on. From this figure, one can notice that the progressive loss of flexural stiffness and the increasing of both the elastic deflection and the residual deflection with the increase of the number and peak load of the cycles. The load-deflection respond of the concrete deck was linear even after cycling at higher peak load level till 367 kN peak load level after total of 300,000 load cycles. After that the load-deflection respond was bilinear as shown in St-450 curve. Figure (5) shows a comparison between the static response of the five tested slabs after two different fatigue load steps, 245 kN and 367 kN. After 245 kN fatigue loading step, Fig. (5-a), it is clear that the damage accumulate to slab S1 and S4 (they have the same residual deflection and stiffness) was the same although slab S4 had no top reinforcement at all. Slab S3 which was subjected to more load cycles than S1 and S4 (an extra 300,000 load cycles at smaller peak load) had much more accumulated fatigue damage. For the steel reinforced slab S0, although it was subjected to the same fatigue loading as S1 and S4, it had much more damage. This was mainly due to the big difference between the modulus of elasticity of steel and concrete and the mechanical bond mechanism (depending on ribs at the surface of the steel bars) which cause much damage to concrete during cyclic loading. After 367 kN fatigue load step, all the GFRP reinforced slab had almost the same fatigue damage although they all have different reinforcement ratios in the top and bottom layers (Fig. 5-b). It can be also noted that the magnitude of damage that was accumulated to the slab reinforced with steel was 2.5 times greater than that of the GFRP reinforced ones.


250

Load (kN)

200

St-00 St-01

St-183

St-245

St-367

St-450

150

100

50

0 0

1

2

3

4

5

6

7

8

Deflection (mm)

Figure 4. Static response of slab S1 after different fatigue loading steps 250

Load (kN)

200 150

S3 S1

100

S4

50

S0 0 0

1

2

3

4

5

6

Deflection (mm) 250

Load (kN)

200

S3

S0

S1

150

S4

100 50 0 0

5

10

15

20

Deflection (mm)

a- after 245 kN fatigue loading step

b- after 367 kN fatigue loading

step Figure 5. Comparison between static responses after different fatigue loading steps 5.2. Strain Measurements Similar behaviour and changes were observed in the maximum measured strains in reinforcing bars. Figure (6) shows comparisons between the maximum measured strains in the reinforcing bars in the transverse direction for different slab prototypes. Although slab S3 has completed 300,000 cycles at lower peak load levels more than slab S1, the difference in the measured strains in the FRP bars does not exceed 10%. For the FRP bars, the maximum recorded strain which was about 2400 micro-strain is still less than 20% of the ultimate strain. For steel, this value was about 85% of the yield strain. Figure (7) shows comparisons between the maximum measured concrete compressive strains measured on the top surface of slabs at different locations around the loaded area. It presents the maximum measured concrete strain in the transverse direction after 367 kN fatigue loading step.


The largest strain of about 1250 micro-strain was measured for the steel reinforced slab, S0. While the GFRP reinforced slab without top reinforcement recorded the lowest value of about 400 micro-strain. Just before failure, slab S4 had the largest concrete compressive strain of about 1300 micro-strain compared to 1100 and 800 micro-strain for S1 and S3, respectively. These compressive strain values were well below the ultimate compressive strain of concrete (2500 micro-strain), which indicate the deterioration of concrete strength as a result of fatigue loading due to extensive cracking. 5.3. Crack Patterns and Failure Mode Whenever the tensile stresses in the extreme fibre exceeded the modulus of rupture of concrete, the external load induced cracks in the concrete deck. These cracks tend to occur well in advance under fatigue loading when compared to static loads. Before applying any loads, either static or dynamic, a mesh of hair cracks resulting from shrinkage and environmental effects during the one year storage, was observed at the bottom face of all deck slabs. At the end of each fatigue loading step, all the cracks were well marked on the faces of the deck slab. The cracks propagated and got widened as the number of load cycles and the peak load increased. At earlier stages of fatigue loading, cracks were observed on the bottom face of the deck where some major fatigue cracks propagated in the longitudinal direction parallel to the supports similar to flexural cracks of simply supported one-way slabs. A few cracks were observed at the midspan in the transverse direction beneath the loaded area. With the increase of load cycles, more cracks were developed in the transverse and radial direction forming a grid-like pattern. No cracks were observed around the periphery of the loading plate until failure occurs. 250

Load (kN)

200

S0

S1 S3

150 100 50 0 0

500

1000 1500 2000 Strain (Microstrain)

2500

250 200 Load (kN)

S4

S0

150 S1 S3

100 50 0

-1500

-1000 -500 Strain (Microstrain)

Figure 6. Comparison between transverse strains bars strains after 183 kN fatigue load step load step

0

Figure 7. Comparison between compressive at top face of concrete after 367 kN fatigue


When a relatively stable condition was reached, approximately after the 245 kN fatigue loading step, the crack growth (propagation) reduced considerably. However, crack width and crack growth in the vertical direction continued to increase. This cracking mechanism is in good agreement with the observations of other researches (Kumar and GangaRao 1998, Rahman et al. 2000). During cycling, crack faces clapped together and rubbed against each other and as a result fine sand was observed falling from cracks and with the increased number of cycles, small pieces of concrete or aggregate occasionally dropped as well. Figure (8) shows a typical crack pattern at different fatigue loading steps on the bottom face of the slabs prototypes.

a- Slab S3 after 245 kN fatigue load step

b- Slab S1 before failure

Figure 8. Crack pattern on bottom face at different fatigue loading steps All the four slabs failed in punching shear after different number of load cycles at the maximum final peak load. The top surface of the failure zone had an elliptical shape around the corners of the loading plate while the bottom surface has approximately a circular shape with a diameter equal to the spacing between the two supporting girders. Figure (9) shows both the top and bottom faces of slabs S1 after failure. 6. Conclusions A total of four full-size concrete deck slabs were constructed and tested to failure under variable amplitude of fatigue loading. One deck slab was reinforced with conventional steel bars and the other three slabs were reinforced with different configurations and ratios of Glass FRP composite bars. The deck slabs were subjected to different combinations of fatigue loading with different peak load levels while their edges were restraint against later movement and rotations. Based on the experimental results, the following conclusions can be drawn:

a- Bottom face

b- Top face

Figure 9. Bottom and top face of tested slabs at failure (Punching shear failure mode)


1- The punching shear is the mode of failure of restraint concrete bridge deck slabs reinforced with steel or Glass FRP composite bars under fatigue loads; 2- The Glass FRP reinforced concrete bridge decks has a better fatigue performance and longer fatigue life , about 2.5 times, more than the steel reinforced ones, as there is no much big difference in the modulus of elasticity between GFRP composite bars and concrete as the case in steel bars; 3- Deterioration of concrete deck slabs subjected to fatigue loads can be noticed through the cumulative damage to the deck slab observed from the increase in both residual and elastic deflection and strains in both reinforcing bars, and concrete; 4- Fatigue loading at peak load level up to 1.75 times the fatigue limit state load does not cause any significant damage to concrete bridge deck slabs with span to depth ratio less than 15, 5- The top reinforcement has a little effect on the fatigue performance of concrete bridge deck slab at lower peak load levels (less than twice fatigue limit state load); this effect becomes insignificant at higher peak load levels; 6- The proposed FRP reinforcement ratio adopted by the updated version of section 16 of CAN/CSA-S6-00 is adequate to meet the fatigue strength and fatigue life requirements of concrete bridge decks. 7. References Adimi, M.R., Rahman, A.H., and Benmokrane, B. New Method for Testing Fibre-Reinforced Polymer Rods under Fatigue. Journal of Composites for Construction, 2000; 4(4): 206- 213. Bakht, B. and Selvadurai, A.P.S. Performance of Steel-Free Deck Slabs under Simulated Rolling Wheel Loads. Proceedings of the Second International Conference on Advance Composite Materials in Bridges and Structures (ACMBS-II), 1996,CSCE, Montreal, QuÊbec: 767-776. Benmokrane, B. and El-Salakawy, E.F., Editors. Durability of fibre reinforced polymer (FRP) composites for construction. Proceeding of the Second International Conference, 2002; Montreal, Quebec, Canada, 715 p. Benmokrane, B., El-Salakawy, E.F. El-Ragaby, A., and Lackey, T. Designing and Testing of Concrete Bridge Decks Reinforced with Glass FRP Bars. ASCE Journal of Bridge Engineering, 2006; Vol. 11, No. 2, March/April, pp. 169-182. Canadian Standards Association (CSA). Canadian Highway Bridge Design Code. CAN/CSA-S600, 2000; Rexdale, Toronto, Ontario, Canada, 734 p. Canadian Standards Association (CSA). Design and Construction of Building Components with Fibre Reinforced Polymers.� CAN/CSA-S806-02, 2002; Rexdale, Toronto, Ontario, Canada, 177 p. Demers, C.E. Fatigue Strength Degradation of E-glass FRP Composites and Carbon FRP Composites. Journal of Construction and Building Materials, 1998; (12): 311-318. El-Gamal, S., El-Salakawy, E.F., and Benmokrane, B. Behaviour of Restrained FRP-Reinforced Bridge Decks under Wheel Loads." ACI Structural Journal; 2005;102(5): 727-735. El-Salakawy, E.F., Benmokrane, B., El-Ragaby, A., and Nadeau, D. Field Investigation on the First Bridge Deck Slab Reinforced with Glass FRP Bars Constructed in Canada. ASCE Journal of Composites for Construction, 2005; 9(6) : 470-479. Graddy, J.C, Kim, J., Whitt, J.H., burns, N.H., and Klingner, R.E. Punching-Shear Behaviour of Bridge Decks under Fatigue Loading. ACI Structural Journal, 2002; 90(3): 257-266. Hassan, T., Abdelrahman, A., Tadros, G., and Rizkalla, S. Fibre Reinforced Polymer Reinforcing Bars for Bridge Decks. Canadian Journal of Civil Engineering, 2000; 27: 839-849. Humar, J. and Razaqpur, G., editors. Advanced Composite Materials in Bridges and Structures. Proceeding of the Third International Conference, 2000; Ottawa, Ontario, Canada, 876p. Hwan, B. Fatigue Analysis of Plain Concrete in Flexure. Journal of Structural Engineering, ASCE, 1986; 112, (2): 273-288 Katz, A. (2000), "Bond to Concrete of FRP Rebars after Cyclic Loading.", Journal of Composites for Construction, ASCE, Vol. 4, No. 3, Aug. 2000, pp 137-144. Kumar, S. and GangaRao, H.V.S. Fatigue Response of Concrete Decks Reinforced with FRP Rebars. Journal of Structural Engineering, ASCE, 1998; 124(1): pp 11-16.


Mallet.G. Fatigue of Reinforced Concrete, State of the Art Review. Transportation and Road Research, 1991; Laboratory, Department of Transport, London. Matsui, S., and Tei, K. Researches and Japanese Development on Highway Bridge Slabs and Contribution of Wheel Runing Machines. Proceedings of the Third International Conference on Concrete under Sever Conditions, 2001; University of British Columbia, Vancouver, PP. 9921008. Matsui, S., Tokai, D., Higashiyama, H., and Mizukoshi, M. Fatigue Durability of Fibre Reinforced Concrete Decks Under Running Wheel Load. Proceedings of the Third International Conference on Concrete under Sever Conditions, 2001; University of British Columbia, Vancouver, Canada: 982-991. Memon, A.H., Mufti, A.A., and Bakht, B. Fatigue Investigation of Concrete Bridge Deck Slab Reinforced with GFRP and Steel Straps. Proceedings of the Sixth International Symposium on FRP Reinforcement for Concrete Structures, 2003; Singapore: 9235-932. Okada, K., Okamura, H. and Sonoda, K. Fatigue Failure Mechanism of Reinforced Concrete Bridge Deck Slabs. Transportation Research Record, Bridge Engineering, 1978; 1(664): 136144. Pardikaris, P.C., and Beim, S. RC Bridges Under Pulsating and Moving Load. Journal of Structural Engineering, ASCE, 1988; 114(3): 591-607. TM – Technical Data Sheet.” ADS Composites Group Inc. Pultrall Inc. (2004). “V-ROD http://www.pultrall.com, Thetford Mines, Quebec, Canada. Rahman, A.H., Kingsly, C.Y., and Kobayashi, K. Service and Ultimate Load Behaviour of Bridge Deck Reinforced with Carbon FRP Grid. Journal of Composites for Construction, ASCE, 2000; 4(1): 16-23. Saadatmanesh, H., and Ehsani, M.R., Editors, International Conference on Composites for Infrastructure. Proceeding ICCI, 1996; Tucson, Arizona, USA. Sonoda, K. and Horikawa, T. Fatigue Strength of Reinforced Concrete Slabs under Moving Loads. IABSE Colloquium, “Fatigue of steel and concrete structures, Proceedings, IABSE Reports, 1982; 37, Zurich: 455-462. Tilly, G.P. and Moss, D.S. Long Endurance Fatigue of Steel Reinforcement. IABSE Colloquium, Fatigue of steel and concrete structures, Proceedings, IABSE Reports, 1982; Zurich: 229-238. Yost, J. R. and Schmeckpeper, E. R. Strength and Serviceability of FRP Grid Reinforced Bridge Decks. ASCE Journal of Bridge Engineering, 2001; 6(6): 605-612. Youn, S.G., and Chang, S.P. (1998), "Behaviour of Composite Bridge Decks Subjected to Static and Fatigue Loading." ACI Journal Structural Journal, Vol. 95, No. 3, pp. 249-258.


Superior Fatigue Life