Research Article Shear Behavior of Concrete Beams Reinforced with GFRP Shear Reinforcement

Transcription

1 International olymer Science Volume 215, Article ID , 8 page Reearch Article Shear Behavior of Concrete Beam Reinforced with GFR Shear Reinforcement Heecheul Kim, Min Sook Kim, Myung Joon Ko, and Young Hak Lee Department of Architectural Engineering, Kyung Hee Univerity, 1732 Deogyeong-daero, Giheung-gu, Yongin-i, Gyeonggi-do , Republic of Korea Correpondence hould be addreed to Young Hak Lee; leeyh@khu.ac.kr Received 5 Augut 215; Revied 23 September 215; Accepted 27 September 215 Academic Editor: Gonzalo Martínez-Barrera Copyright 215 Heecheul Kim et al. Thi i an open acce article ditributed under the Creative Common Attribution Licene, which permit unretricted ue, ditribution, and reproduction in any medium, provided the original work i properly cited. Thi paper preent the hear capacitie of concrete beam reinforced with gla fiber reinforced polymer (GFR) plate a hear reinforcement. To examine the hear performance, we manufactured and teted a total of eight pecimen. Tet variable included the GFR trip-width-to-pacing ratio and type of opening array. The pecimen with a GFR plate with a 3 2opening array howed the highet hear trength. From the tet reult, the hear trength increaed a the trip-width-to-trip-pacing ratio increaed. Alo, we ued the experimental reult to evaluate whether the hear trength equation of ACI and ACI 4.1R can be applied to the deign of GFR hear reinforcement. In the reult, the ACI 4 equation underetimated the experimental reult more than that of ACI Introduction Several tudie have been carried out on the flexural behavior of concrete beam with fiber reinforced polymer (FR) tenile reinforcement becaue FR material have advantage uch a corroion reitance, light weight, machinability, workability, and high trength [1 5]. Mot FR hear reinforcement for concrete member ha been tudied a a mean of retrofitting. Hawileh et al. [6] and Al-Tamimi et al. [7] uggeted technique that involved externally bonding carbon fiber reinforced polymer (CFR) laminate or heet to reinforced concrete member. Haan and Rizkalla [8] reearched the bonding trength of FR plate that were either embedded or attached to the exterior of concrete member. However, typical hear reinforcement (tirrup) for concrete member i difficult to fabricate with FR material becaue of their brittle nature and unidirectional characteritic. Therefore, FR hear reinforcement ha not yet been ufficiently invetigated. The trength of the bent portion i ignificantly le than that of the traight part of FR rod; hence everal code and deign guideline have pecified the reduced capacity of FR tirrup caued by bending the bar [9 12]. Recent tudie invetigated the hear capacitie of FR tirrup and propoed an equation of hear trength [12 15]. Kim et al. propoed a new type of FR hear reinforcement a a ubtitute for teel tirrup [16]. late-type FR hear reinforcement ha better contructability and eaier fabrication than FR tirrup. Alo, plate hear reinforcement doe not reduce the trength by concentrating tre in the bent portion. In an earlier paper, the type of FR and hape of reinforcement did not ignificantly affect the hear trength. In thi paper, conidering economic and eae of fabrication, we ue a lattice haped GFR material for hear reinforcement. To evaluate the applicability of FR plate for hear reinforcement, hear tet were conducted uing concrete beam embedded with GFR plate with opening, conidering the array of the opening and the GFR trip-widthto-pacing ratio a the main variable. We alo analyzed the failure mode and train ditribution. 2. Experimental Invetigation 2.1. Experimental Material. Following ASTM C39 [17], we teted even cylindrical pecimen of 15 mm diameter and 3 mm height. The average compreive trength of the 28- day concrete wa 44.6 Ma. Ten deformed teel bar with diameter of mm and yield trength of 5 Ma were ued

2 2 International olymer Science Table 1: Detail of the experimental variation of the GFR plate deign. GFR plate Specimen f Type fu Width (w f ) Thickne (t) Center-to-center pacing of vertical trip () (Ma) (mm) (mm) (mm) A-1 A A-2 A A-3 A A-4 A A-5 A A-6 A B-3 B C-3 C Figure 1: Schematic view of a concrete beam reinforced with GFR plate. a longitudinal reinforcement. We ued GFR plate with opening embedded in the concrete a hear reinforcement. The tenile tet of the FR wa conducted baed on CSA S86-2 [1]. The tenile tre wa 48 Ma. Figure 1 how a chematic view of a pecimen Specimen Detail. We conidered the array of opening, GFR trip-width-to-pacing ratio, and the amount of reinforcement a variable. The GFR plate were manufactured in three hape a hown in Figure 2 and 3. Each plate had the ame total area (b f h f ); the A-Type had a 2 2 opening array, B-Type a 3 2opening array, and C-Type a 3 3 opening array. All the interection of the horizontal ( )and vertical (9 ) component made right angle. The difference in the width of the horizontal and vertical component of each plate provided variant within each type of opening array. Detail of the three plate deign and the variation within each type are given in Table 1. We teted a total of eight concrete beam embedded with GFR plate with opening. Figure 4 illutrate how we placed GFR plate in the pecimen depending on their hape. The anchorage length (l d ) wa 3 mm, far from the point of upport. The total pan (L) andclearpan(l n ) were mm and 21 mm, repectively. The thickne of the concrete cover wa mm, and the hear pan-to-depth ratio wa 2.4. All the pecimen were reinforced uing ten deformed teel bar with a diameter of mm in two layer to enure hear failure prior to flexural failure in the beam tet Tet Setup. Load wa applied to each pecimen at a rate of 5 kn/min uing a hydraulic jack with a maximum capacity of 5 kn, a hown in Figure 5. The force generated by the hydraulic jack wa tranmitted to the center of a teel preader beam intalled to apply two-point loading to the beam pecimen. A load cell attached to the bottom of the jack meaured the magnitude of the loading. A linear variabledifferential tranducer (LVDT) intalled at the bottom center ofthepecimenmeauredtheverticaldiplacement.aillutrated in Figure 5, we intalled four train gauge at the center of the horizontal and vertical component of each FR plate. A data logger collected load, diplacement, and train data. 3. Shear Strength Equation Figure 6 define the width of the GFR trip (w f ), effective depth (d), and pacing (). Several mechanim contribute to the hear capacitie of reinforced concrete beam, uch a the concrete, hear reinforcement, mechanical aggregate interlocking, and dowel action of the tenile reinforcement. Shear reinforcement ha a mechanim for reitance to hear, a hown in Figure 7. For thi paper, we replaced the tirrup with a vertical trip of the FR hear reinforcement. The function of the horizontal trip i to anchor the vertical trip. The horizontal projection of the crack i taken a d. ThenumberofFRverticaltrip croing the crack i d/. Auming that all FR vertical trip reach their failure, the hear trength of the hear reinforcement can be obtained from V = A ff fu d. (1) We aume the crack angle to be 45 when calculating the hear trength of the hear reinforcement. The tenile behavior of the FR i characterized by a linearly elatic tre-train relationhip up to failure. Hence, hear failure i aumed to occur after fracture of the hear reinforcement Shear Strength Equation in ACI A hown in (2), the hear trength equation in ACI [15] provide the umoftheheartrengthoftheconcreteandthehear reinforcement. The hear trength of concrete can be obtained from (3), which include the longitudinal teel ratio (ρ w )and hear pan-to-depth ratio (a/d). Equation (4) calculate the heartrengthofthehearreinforcementmaterialbaedon the concept of the hear trength of a teel tirrup in ACI Calculating the hear trength of FR plate require the area of the vertical component (A f ), the number of vertical

3 International olymer Science 3 (a) A-Type (b) B-Type (c) C-Type Figure 2: Deign of the three experimental GFR plate. b f A f =2t f w f, (5) n= d (1+cot α). (6) y x w f Figure 3: Notation of geometry for a GFR plate. h f 3.2. Shear Strength Equation in ACI 4.1R-6. ACI 4.1R provide a hear trength equation for concrete with FR rebar flexural reinforcement. However, in thi paper, we adopted the hear trength equation for concrete in ACI 318 becaue we ued teel flexural reinforcement. The hear trength of the hear reinforcement can be calculated with (7). Equation (8) give the tre level in the FR hear reinforcement at it utmot for ue in deign. ACI 4.1R addree the reduced hear trength of tirrup caued by bending the FR bar, a hown in (9). Becaue our GFR hear reinforcement iaplatetype,wedidnotconiderthebendportion.conider V f,4 =na f f fvd in α, (7) component (n), and the tenile trength in the critical hear pan,ain(4).theareaoftheplate(a f )canbeobtainedfrom (5), and the number of vertical component in the critical hear pan can be obtained from (6): V n =V c +V f, (2) V c = (.16 fc + 17ρ wd ) b a w d, (3) V f,318 =na f f fu in α, (4) f fvd =.4E f f fb, (8) f fb =(.5r b d 4. Experimental Tet Reult +.3) f fuv. (9) 4.1. Failure Mode. A hown in Figure 8, flexural crack occurredatthetenionurfaceinthemiddleofthepan, followed by the formation of inclined crack. A the inclined

4 4 International olymer Science (a) A-1 (b) A (c) A-3 (d) A (e) A-5 (f) A (g) B (h) C-3 Figure4:ArrangementofGFRplateinpecimen. Vertical component w f Steel train gauge FR train gauge Figure 5: Tet etup of typical pecimen. crack propagated toward the loading point, concrete cruhing occurred in the upper end region of the inclined crack at the final tage of failure. In other word, hear-compreion failure (hear failure from the diagonal crack) occurred. The initial crack appeared at a load of approximately 15 kn in the middle of the beam. It appeared to be a flexural crack caued by tenile tre due to bending. At approximately 2 kn, a flexural hear crack appeared at effective depth, far from Figure 6: Definition of w f, d,and. the point of upport. At approximately 45 kn, the diagonal crack appeared, and then a flexural hear crack followed. The reinforcement of the GFR plate increaed reitance to the hearforceathediagonalcrackoccurredandelongated. d

5 International olymer Science 5 A B Table 2: Maximum loading and hear trength tet reult. V c C A f f fu T d Figure 7: Shear reitance by FR hear reinforcement. Specimen max V max (kn) (kn) Failure mode A Shear A Shear A Shear A Shear A Shear A Shear B Shear C Shear Table 3: Size and opening dimenion of FR reinforcement. (a) A-2 Specimen b f h f x y Opening/FR plate (%) A A A A A A B C (b) A-3 coverage condition are met, the plate will demontrate maximum hear trength, and the pecimen will provide effective hear performance. The tet reult for maximum loading and maximum hear trength are ummarized in Table 2. (c) B-3 (d) C-3 Figure 8: Shear-compreion failure in pecimen. When the GFR plate reached the limit of it tenile trength, it fractured, and pecimen failure occurred. We oberved two typical failure mode in repone to the amount of reinforcement provided. Firt, all the pecimen except A-5 and A-6 fractured, and the plate ruptured after they had demontrated their maximum hear trength. The concrete cover of pecimen A-5 and A-6, on the other hand,fracturedbeforetheplatereacheditmaximumhear trength. The pecimen howed two different failure mode becaue the ize of the opening in the plate and the ratio of the area of the opening varied. Thi reult could alo be caued by a lack of concrete coverage. Therefore if the opening ize, ratio of the area of opening, and ufficient concrete 4.2. Array of Opening and Ratio of Opening. Figure 9 how the meaurement ued for each plate type and the variation ofthoetype.thetotalwidthandheightoftheplateare marked a b f and h f, repectively; the width and height of each opening are marked a x and y, repectively.the opening ize and ratio of the area of opening are lited in Table 3. Ratio of the area of opening i the area of all opening divided by the total area of the plate. We deigned the plate to meet the following condition: both the width (x) and depth (y) of the GFR plate opening decribed in Table 3 hould be at leat 1 mm, and ratio of the area of opening hould be higher than 5%. In pecimen A-5 and A-6, which did not meet thoe condition, the concrete exhibited brittle failure before the plate reached the limit of it maximum trength. Specimen C-3, which met the ratio condition but not the ize condition, howed lower maximum hear trength than Specimen B- 3 did, which met both condition. Therefore, if the opening ize i larger than 1 mm and ratio of the area of opening i higher than 5%, ufficient integration between the FR hear reinforcement and the concrete can be expected. Figure 1 how the load-deflection relation for three pecimen (A-3, B-3, and C-3) with the ame ratio of the area ofopening.allthreepecimenexhibitedtheamebehavior before hear failure. Thi tet reult indicate that Specimen

6 6 International olymer Science Load (kn) x b f Figure 9: Dimenion of a GFR plate and it opening A-3 B-3 C-3 y h f Deflection (mm) Figure 1: Load-deflection curve for three different array of opening in GFR hear reinforcement. B-3 had more effective integration than A-3 becaue of a larger bonded area between the concrete and the B-3 plate. Although C-3 had the larget bonded area among the three, it depth (y) wa le than 1 mm. Specimen B-3 howed the larget hear trength. Therefore, to increae hear capacity, the bonded area between the FR plate and the concretehouldbemaximizedwhilemeetingtheconditionof opening ize and ratio of the area of opening Amount of Shear Reinforcement. To examine the influence of the amount of hear reinforcement on hear trength, we deigned each pecimen with different amount of reinforcement. The amount of hear reinforcement wa the product of the number of vertical component in the critical hear pan (n), the width of the vertical component (w f ), and the thickne of the vertical component (t f ), that i, (n w f t f ). Figure 11 how the load-deflection relation for pecimen with variou hear reinforcement area. The amount of hear reinforcement for the experimental variant Load (kn) A-1 A-2 A Deflection (mm) A-4 A-5 A-6 Figure 11: Load-deflection curve for amount of hear reinforcement. V exp /V n A-1 A-2 A-3 A-4 A-5 A-6 Specimen ACI 318 ACI 4.1R Figure 12: Ratio of tet reult to theoretical prediction of hear trength (V exp /V n ). A-1toA-4wacontrolledbythedifferentwidthofthe vertical trip; for A-5 and A-6, it wa controlled by different pacing of the vertical trip. Figure 12 how the ratio of hear trength for ix pecimen (A-1, A-2, A-3, A-4, A-5, and A-6) according to the amount of hear reinforcement. V exp wa obtained from the experiment that meaured hear trength, and V n wa obtained from the equation by which hear trength wa calculated. All of the pecimen, except A-5 and A-6, howed imilar ratio of hear trength. In contrat, pecimen A-5 and A- 6 howed only 8 9% of the calculated value. Becaue the plate had inufficient opening ize and ratio of the area of opening, brittle failure occurred in pecimen A-5 and A-6 before the hear reinforcement reached the limit of it maximum trength.

7 International olymer Science 7 Table 4: Experimental reult and ratio of hear trength. V Specimen c V f,318 V f,4 V exp (kn) (kn) (kn) (kn) Vexp /V n,318 V exp /V n,4 A A A A A A B C V exp (kn) GFR trip-width-to-trip-pacing ratio (w f /) Figure 13: Effect of the GFR trip-width-to-pacing ratio on hear trength. Figure 13 how hear trength according to the width-topacing ratio of the trip for all of the pecimen except the two that did not meet the opening ize and ratio condition (A-5 and A-6). The reult indicate that the hear trength increae a the pacing-width ratio of a trip increae. A expected, effective hear-crack control i etablihed by providing a larger bonded area to reit hear crack. Thi bonded area increae a the width-to-pacing ratio increae. 5. Comparion of Experimental Reult and Shear Strength Equation Table 4 how the hear trength of the concrete (V c ), hear trength of the plate (V f ), and maximum hear trength (V n ), whichitheumoftheheartrengthoftheconcreteandof the plate, of the beam deigned uing the hear trength equation of ACI 318 and ACI 4-1R. The ratio of hear trength (V exp /V n ), which compare the maximum calculated hear trength (V n ) and the experimental hear trength (V exp ), i alo included in Table 4. The hear trength equation in ACI calculate the hear trength of concrete a a contant. A hown in Table 4, the mean value of the hear trength ratio (V exp /V n ) i 1.46 with a tandard deviation of.1 uing ACI 318, and the hear trength ratio (V exp /V n )oftwovalue wa between 1.33 and On the other hand, ACI 4.1R give a mean value 1.83 with a tandard deviation of.21, with aheartrengthratiooftwovaluebetween1.57and2.9. Thi verifie that the hear trength equation in ACI 318 can be ued to predict the hear trength of concrete beam with embedded GFR plate with opening, a long a the plate meet the minimum condition for opening ize and ratio of the area of opening. On the other hand, when uing ACI 4.1R, only % of the deign trength wa applied a tenile trength; therefore, the tet reult were underetimated. 6. Concluion In thi tudy, to analyze the hear performance of concrete beam with embedded GFR plate with opening, we elected the array of opening, ratio of the area of opening, amount of hear reinforcement, and GFR trip-width-totrip-pacing ratio a variable. We ued the hear trength equation in ACI and ACI 4.1R to compare the experimental and theoretical hear trength. We draw the following concluion: (1)Thewidthandheightoftheopeninghouldbelarger than 1 mm, and the ratio of the area of opening hould be greater than 5% to obtain effective hear performance. (2) Three different reult from three different hape of reinforcing plate how that increaing the bonded area between the GFR plate and the concrete increae the performance of the hear reinforcement, provided the baic condition are met. (3) Analyi of the GFR trip-width-to-pacing ratio howed that a the ratio increaed, the bonded area increaed, which improved reitance to hear crack. (4)TheequationinACI318andACI4.1Ryielded generally conervative hear trength reult. The ACI 318 code give a mean value of 1.46 with a tandard deviation of.1. The ACI 4.1R code give a mean value of 1.83 with a tandard deviation of.2. Therefore, the hear trength equation in ACI 318 wa more applicable than that in ACI 4.1R to the GFR platereinforced concrete beam. Notation a/d: Shear pan-to-depth ratio A f : Sectional area of a vertical trip of FR plate (mm 2 ) b w : Web width (mm) d: Ditance from extreme compreion fiber to centroid of longitudinal tenion reinforcement (mm) f c : Specified compreive trength of concrete (Ma) f fu : Specified tenile trength of FR plate (Ma) n: NumberofverticalcomponentoftheFRplate within the critical hear pan : Center-to-center pacing of longitudinal hear reinforcement (mm) t f : Thickne of FR plate (mm) V c : Nominal hear trength provided by concrete (kn) V exp : Shear trength provided by experiment (kn) V f : Nominal hear trength provided by FR plate (kn)

8 8 International olymer Science V n : Nominal hear trength (kn) w f : Width of FR plate (mm) α: Angle between hear reinforcement and longitudinal axi of the member ( ) ρ w : RatioofA to b w d. Conflict of Interet The author declare that there i no conflict of interet regarding the publication of thi paper. Acknowledgment Thi work wa upported by a National Reearch Foundation of Korea (NRF) grant funded by the Korea government (MSI) (NRF ). Reference [1] C. Higgin, G. T. William, M. M. Mitchell, M. R. Dawon, and D. Howell, Shear trength of reinforced concrete girder with carbon fiber-reinforced polymer: experimental reult, ACI Structural Journal,vol.19,no.6,pp ,212. [2] F.-Y. Yeh and K.-C. Chang, Size and hape effect on trength and ultimate train in FR confined rectangular concrete column, Mechanic,vol.28, no.4,pp , 212. [3] A. Mofidi and O. Chaallal, Shear trengthening of RC beam with externally bonded FR compoite: effect of trip-widthto-trip-pacing ratio, Compoite for Contruction, vol. 15, no. 5, pp , 211. [4]M.M.R.Taha,M.J.Maia,K.-K.Choi,.L.Shrive,andN. G.Shrive, Creepeffectinplainandfiber-reinforcedpolymertrengthened reinforced concrete beam, ACI Structural Journal,vol.17,no.6,pp ,21. [5] C. Mazzotti, M. Savoia, and B. Ferracuti, An experimental tudy on delamination of FR plate bonded to concrete, Contruction and Building Material, vol.22,no.7,pp , 28. [6]R.A.Hawileh,H.A.Raheed,J.A.Abdalla,andA.K.Al- Tamimi, Behavior of reinforced concrete beam trengthened with externally bonded hybrid fiber reinforced polymer ytem, Material and Deign, vol. 53, pp , 214. [7] A. K. Al-Tamimi, R. Hawileh, J. Abdalla, and H. A. Raheed, Effect of ratio of CFR plate length to hear pan and end anchorage on flexural behavior of SCC RC beam, Compoite for Contruction,vol.15,no.6,pp ,211. [8]T.HaanandS.Rizkalla, Invetigationofbondinconcrete tructure trengthened with near urface mounted carbon fiber reinforced polymer trip, Compoite for Contruction,vol.7,no.3,pp.248 7,23. [9] ACI Committee 4.1R, Guide for the Deign and Contruction of Concrete Reinforced with FR Bar (ACI 4.1R-6), American Concrete Intitute, Farmington Hill, Mich, USA, 26. [1] Canadian Standard Aociation (CSA), Deign and Contruction of Building Component with Fiber Reinforced olymer (CSA S86-2), Canadian Standard Aociation (CSA), Miiauga, Canada, 22. [11] Intelligent Sening for Innovative Structure (ISIS), Canada Reinforcing Concrete Structure with Fibre Reinforced olymer (ISIS-M3-1), ISIS Canada Reource Centre, Winnipeg, Canada, 21. [12] M. R. Ehani, H. Saadatmaneh, and S. Tao, Bond of hooked gla fiber reinforced platic (GFR) reinforcing bar to concrete, ACI Material Journal,vol.92,no.4,pp.391, [13] K. Ihihara, T. Obara, Y. Satao, T. Ueda, and Y. Kakuta, Evaluation of ultimate trength of FR rod at bent up portion, in roceeding of the 3rd International Sympoium on Non- Metallic (FR) Reinforcement for Concrete Structure,pp.27 34, Sapporo, Japan, [14] E. Shehata, R. Morphy, and S. Rizkalla, Fibre reinforced polymer hear reinforcement for concrete member: behaviour and deign guideline, Canadian Civil Engineering, vol. 27,no.5,pp ,2. [15] A. K. El-Sayed, E. El-Salakawy, and B. Benmokrane, Mechanical and tructural characterization of new carbon FR tirrup for concrete member, Compoite for Contruction, vol. 11, no. 4, pp , 27. [16] D.-J. Kim, M. S. Kim, J. Choi, H. Kim, A. Scanlon, and Y. H. Lee, Concrete beam with fiber-reinforced polymer hear reinforcement, ACI Structural Journal, vol. 111, no. 4, pp , 214. [17] ASTM International, Standard tet method for compreive trength of cylindrical concrete pecimen, ASTM C 39, ASTM International, Wet Conhohocken, a, USA, 21.

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