LOAD-CARRYING CAPACITY OF REINFORCED CONCRETE BEAMS WITH ADHESIVELY BONDED STEEL PLATES. Yoshiki Tanaka 1 Jun Murakoshi 1 Eiji Yoshida 1

Transcription

1 LOAD-CARRYING CAPACITY OF REINFORCED CONCRETE BEAMS WITH ADHESIVELY BONDED STEEL PLATES Yoshiki Tnk 1 Jun Murkoshi 1 Eiji Yoshid 1 Abstrct To evlute the lod-crrying cpcity of reinforced concrete bems with externlly bonded steel plte, the influence of the bonded steel pltes to the soffit on the sher strength of the bems, nd the effect of sher strengthening using wing-type side steel pltes for stocky concrete bems (brod nd low web) hve been exmined. From the results, it ws found tht the sher strength is properly evluted by sher cpcity equtions for non-plted reinforced concrete bems unless crck develops t the edge of the steel plte, nd tht the side plte bonding is likely to hve potentil to be effective in strengthening for the stocky bems without stirrup. Additionlly, loding tests using two 75-yer-old deteriorted reinforced concrete bems with dhesively bonded steel pltes to the soffit were crried out. The bonded steel pltes no longer contributed to the lod crrying cpcity fter the joints between the steel pltes filed due to debonding. Introduction In Jpn, number of the concrete girders nd decks of existing highwy bridges were strengthened with dhesively bonded steel pltes or fiber reinforced polymer (FRP) sheets when design lods were chnged or when the members deteriorted (Figs. 1 nd 2). For the efficient mngement of existing bridges, the lod-crrying cpcity of not only conventionl concrete bems but lso concrete bems with the bonded steel pltes should be properly evluted. The lte 196s, severl reserchers delt with the strengthening method tht steel pltes were dhesively bonded with two-prt epoxy resin dhesive on the soffit of reinforced concrete bems. In those dys, becuse the ftigue deteriortion of concrete decks ws frequently found on the Jpnese highwy bridges, experimentl studies on the steel plte bonding technique pplying to the bridge decks were crried out. 1-4 Then the FRP sheets were not mjor mterils for construction. The steel plte bonding immeditely becme mjor tool to improve the durbility of bridge decks, hving the dvntge of pplicbility in service, nd the efficient strengthening with the minimum chnge in 1 Public Works Reserch Institute, Jpn

2 ppernce. The strengthening method using FRP sheets for reinforced concrete ws developed in erly 199s. Currently, the mterils becme used commonly to improve the durbility of bridge decks fter revision of the legl mximum weight for trucks from 2 tons to 25 tons in 1993, nd the ductility of existing bridge piers fter the gret Hnshin erthquke in Extensive reserch works were crried out not only in Jpn, but lso in the world. Bsed on the results, severl design guidelines for strengthening reinforced concrete members using FRP hve been estblished. 5-8 On the other hnd, the effects of the steel plte bonding technique hs not been so sufficiently identified s guideline could be estblished. In reserch progrm from FY28 to 21, the effect of sher strengthening using the steel plte bonding on reinforced concrete bems ws exmined. This summry report provides the outlines of three series of experimentl studies focusing on; Series I: the influence of the steel plte bonded to the soffit on the sher cpcity of reinforced concrete bems (further for the evlution of plted concrete decks), Series II: the effect of side steel plte bonding on the sher cpcity of stocky reinforced concrete bems, 9 nd Series III: the lod-crrying cpcity of two 75-yer-old deteriorted concrete girders with the steel plte bonded to the soffit. 1 Series I: Influence of Steel Plte Bonded to the Soffit on Sher Cpcity of Reinforced Concrete Bems Test Progrm: A test scheme nd detils of specimens re shown in Fig. 3 nd Tble 1. The height of the specimens, except Specimens A-7 nd A-8, ws set s 19 mm, referring to the thickness of the typicl bridge decks built in 196s. No stirrup ws rrnged except tht on the support points for rrnging min reinforcing brs. Specimens A-1 to A-8 hd two longitudinl reinforcing brs. For Specimens A-4 to A-8, the steel plte with thickness of 4.5 mm ws dhesively bonded on the soffit of concrete bems. The steel plte nd n dhesive lyer for every bem were s wide s the bem with width of 15 mm. The thickness of the dhesive lyer ws 5 mm. The distnce from the center of ech the support point to the end of the steel plte x ws 8 mm, nd tht from the edge of steel plte for the support ws 3 mm. The test prmeter of Specimens A-4 to A-6 is the rtio of sher spn to effective depth d s, which excludes the dimension of the steel plte. The effective depth nd sher spn of Specimens A-7 nd A-8 wre lrger thn those of Specimen A-5 with the sme /d s rtio. Control specimens A-1 to A-3 with no steel plte hd different reinforcement rtios, respectively. Specimens B-4 to B-6, nd B-8 hd min reinforcing br nd doubly reinforcing br, the steel plte being bonded to the soffit. The thickness of the steel plte of Specimens B-4, B-5, nd B-6 ws 4.5, 6, nd 12 mm, respectively. Specimens B-4 to B-6 were simply supported on the bonded steel plte, s the sher spn ws 4 mm. Then the bonded steel plte hd no curtilment ner the supports. For Specimen B-8, the steel plte ws bonded fter the concrete bem hd been precrcked under cyclic loding with sher spn of 5

3 mm. Specimen B-8 ws monotoniclly loded with sher spn of 1 mm, hving the curtilment of the steel plte with distnce to the center of the support x of 8 mm. Plte bonding ws crried out t three weeks or more fter csting. Anchor holes were drilled nd mechnicl steel nchors were instlled on the soffit of concrete bems, which ws roughened with hnd grinder. The steel plte ws supported with the nchors s the gp to the surfce of concrete ws held with 5 mm spcers. Side openings wre cpped with epoxy resin putty. The epoxy resin dhesive ws filled into the gp by grouting. In Specimens A-4 to A-8, inorgnic zinc-rich primer for protecting the steel plte up to bonding remined similrly to prctice. The steel pltes for Specimens B-4 to B-6, nd B-8 were not coted. Loding tests were conducted t week or lter fter the grouting. The putty on the sides ws ground; tht t the ends of the steel pltes remined. The tensile-sher bond strengths of the epoxy resin dhesives were 12.3 MP to 18.4 MP. Results: All test results re lso shown in Tble 1. Specimens A-4 to A-6 filed due to crcking t the end of steel plte (Fig. 4).The sher force t crcking t the end of the steel plte V p2 my be clculted bsed on model provided by Tumiln et l. 11 In the model, the mximum (tensile) principl stress cting on the concrete ner the end of the bonded steel plte is estimted bsed on the pproximte solution by Roberts 12, being compred with the tensile strength of concrete. Although Tumiln et l. 11 pplied the modulus of rupture f r to the threshold tensile strength, the splitting tensile strength f t is pplied in this report, becuse it is more understndble for the model. Figure 5 shows the reltionship between the clculted sher force t the crcking V p2 nd the experimentl results V ex including the results of Specimens A-4 to A-6 nd the other experimentl results obtined from previous reserch except the results of specimens with rtio x / of more thn.25. The clculted vlues V p2 re somewht lrger thn the experimentl vlues when the vlue is lrger. However, considering tht the previous dt contin the severl unknown prmeters, it ppers tht the sher force t the crcking cn be properly estimted. Incidentlly, the dtbse bsed on the previous reserch shows tht the results of specimens with rtio x / of more thn.25 showing debonding filure do not depend on the vlue of V p2, rther they minly depend on the ultimte flexurl strength of non-plted reinforced concrete bems. In Fig. 6, the results of specimens exhibiting flexure-sher filure in concrete re shown in reltion to the clculted sher strength V sh bsed on the conventionl empiricl eqution 25 for estimting sher force t flexure-sher filure. The influence of the bonded steel pltes is estimted by substituting the dimensions contining the steel plte for the clcultion of the reinforcement rtio nd the effective depth in the eqution. The other tringle symbols indicte the results of control specimens contining Specimens A-1 to A-3 nd the previous reserch relted. For the results of specimens with rtio /d of 1.7 to 1.75, the other empiricl eqution for deep bems 26 is pplied. From the results, it ws

4 found tht the sher cpcity of the plted bems cn be estimted by the conventionl equtions. For reference, the clculted sher strength bsed on n eqution in ACI318 (Eq. 11-5) 27 with fctor of 1.3 is lso compred with the test results except the deep bem in Fig. 6b. Series II: Effect of Side Steel Plte Bonding on Sher Cpcity of Stocky Reinforced Concrete Bems 9 Test Progrm: Configurtions of specimens nd test setup re shown in Figs. 7 to 8. Of the sme dimension of two reinforced concrete bems, Specimen S, of which wing-type steel pltes ws dhesively bonded on the sides of web t both sher spns. The other bem with no steel plte ws nmed Specimen N. The concrete bems were designed s simply supported T-shped bem with stocky cross section consisting of web width of 6 mm nd height of bem of 85 mm, contining ten No.11 longitudinl reinforcing brs with yield point of 534 MP. For both specimens, four 9 mm di. stirrups with spcing of 25 mm were rrnged t sher spn (right side in Fig. 8), no stirrup being t the other sher spn. Similrly to the old reinforced concrete bridges, ll the stirrups were round steel brs with yield point of 292 MP. The compressive cylinder strength of concrete ws 33 MP. Four steel pltes with size of 24 mm x 52 mm x 4.5 mm nd yield point of 36 MP, coted by inorgnic zinc-rich primer, were prepred. The procedure for bonding ws the sme s Series I. The tensile-sher bond strength of the epoxy resin dhesive ws 16.1 MP. Twelve steel nchors with size of M1 nd n embedded length of 7 mm for supporting ech the steel plte t grouting were preinstlled before csting. The thickness of dhesive of 5 mm ws kept. Two point loding were monotoniclly pplied to the bems with sher spn of 2 m. Crcking inside the web concrete covered by the steel pltes were monitored using molded guges nd guges on the stirrups. After sher filure occurred t the sher spn with no stirrup, once unloded. Then verticl restriner consisting of four tendon brs with 13 mm di. were instlled t 1/3 of the sher spn with no stirrup from the ner loding point. Reloding beyond the yielding of stirrups becme vilble by using the restriner, lthough finlly the flnge yielded t the sher spn with no stirrup. Results: Reltionships between lod nd deflection t midspn for both specimens re shown in Fig. 9. Crcks observed on the web t the first pek due to sher filure t the sher spn with no stirrup re shown in Fig. 1. The lod t ech event in the loding tests is summrized in Fig. 11. The lod t digonl crcking (detected with the molded guges in Specimen S) ws ttributed to neither the stirrup nor the bonded steel plte. For the web without stirrup, the bonded steel pltes showed n pprecible effect of improving the sher cpcity, which ws pproximtely 1.5 times s high s tht of the non-plted specimen.

5 The side steel pltes of both sher spns were debonded t similr lods regrdless of stirrups, while the debonding of the steel pltes on the web with stirrups did not immeditely expnd compred with tht on the web without stirrup. At the sher spn with stirrups, even fter debonding, the steel pltes were to some extent likely to contribute to the dely in filure. The stirrups, however, showed ductile behvior compred with n estimted level bsed on the modified truss theory despite the bonded steel pltes. Series III: Loding Tests of Old Concrete Bems with Steel Plte Bonding 1 Outline of test bems: To exmine the lod-crrying cpcity of old reinforced concrete bems with externlly bonded steel pltes to the soffit, six bems with spn length of 1 m were tken from the first nd seventh spns of concrete highwy bridge built in 1935 (Fig. 1). In bout 1981, steel pltes were bonded to the soffit of most decks nd bems in the bridge. Becuse the significnt deteriortion of the decks nd bems ws found when the dministrtor ws considering the delivery of the bridge to the other smll dministrtor, eight deteriorted spns of the bridge were replced in 21. According to the results of the investigtion nd observtion before the removl, the degree of the deteriortion of eight spns differed widely from ech other. On the bems t the first spn, corrosion of steel pltes, wter lekge nd crcks in concrete were widely observed. The bems t the seventh spn less deteriorted thn tht t the first spn. Of six bems obtined, bem from the seventh spn nd nother bem from the first spn, nmed Specimen S1 nd S2, respectively, were tested. Observtions nd survey of mterils: Crcks observed on the test bems before the loding test nd ech cross section cut fter the test re shown in Fig. 12. Coting prtilly covering web concrete ws removed for the observtions. The crcks were widely observed on the web of Bem S2. The crck depth, however, ws found to be shllower thn tht concerned. Innumerble horizontl crcks were found in the flnges of both bems. Hmmer soundings detected the debonding re of the steel pltes s shown in Fig. 12. From prtil dissection survey conducted fter the loding tests, two 8 mm di. stirrups with spcing of pproximtely 2 mm were found. The mechnicl properties of concrete cores t uncrcked prts, reinforcing brs nd the steel plte tken from the tested bems re shown in Tbles 2 to 3. It should be noted tht the modulus of elsticity of the concrete cores tken from Bem S2 ws considerbly lower thn tht of Bem S1. Test progrm: Two point loding were crried on the bems with spn length of 1 meters s the originl spn. Two strin guges were mounted on the min reinforcing brs t loding point section, fter the web concrete ws dug s smll s possible. Asphlt surfcing remined t loding, becuse the removl would ffect the crcked flnge, nd n dditionl preprtion for the surfce would be required. The tests were crried out in winter. For Bem 2, verticl restriners were instlled t the joints between the bonded steel pltes in order to temporrily ttempt to mitigte the debonding of the splice plte, lthough no effect ws found from the result.

6 Results: Reltionships between lod nd deflection t midspn of both the old bems re shown in Fig. 13. In Tble 4, the mximum lods re compred with clculted ultimte lods, which were obtined using the mesured dimensions nd the properties of mterils, except the sphlt surfcing. The sign of debonding of splice pltes in Bem S1 ws detected t 4 kn by using LVDTs (Fig. 14), nd in Bem S2 t 32 kn. After the sign of debonding in Bem S1, the lod further incresed up to the ultimte flexurl cpcity of the conventionl reinforced concrete bem with no deteriortion, while the rigidity significntly decresed. The flexurl cpcity of the deteriorted bem S2 ws 8% lower thn tht of Bem S1, being 5% lower thn the estimted vlue. After the pek, yielding of the min reinforcing brs ws recognized by strin redings, nd the flnge ws modertely crushed (Fig. 14b). Conclusions 1 - From the test results nd the previous reserch, it ws found tht the sher cpcity of reinforced concrete bems with steel plte bonded to the soffit is properly evluted by substituting the dimension contining the steel plte for the clcultion of the reinforcement rtio nd the effective depth in the sher cpcity equtions for non-plted reinforced concrete bems, unless crck develops t the edge of the steel plte. 2 - The side plte bonding is likely to hve potentil to be effective in strengthening for the stocky reinforce concrete bems without stirrup. The effect of the side steel pltes, however, my be limited depending on the web reinforcement rtio in existing bems. 3 - In the results of loding tests using old reinforced concrete bems, the bonded steel pltes no longer contributed to the lod crrying cpcity fter the steel splice pltes filed due to debonding. Acknowledgments The uthors thnk Ngno prefecture nd engineers who ssisted with the survey of the old bridge. References 1. Oht, M., Aizw, I., Momot, K., nd Nkmur, T., Experimentl Study on Strengthening Using Steel Plte Bonding for Reinforced Concrete Decks, Tech. Note of PWRI, No. 681, April (in Jpnese) 2. Ishitni, T., Higi, T., nd Hosod, K., Experimentl Study on Strengthening Methods for Reinforced Concrete Decks, -Steel Plte Bonding Technique-, Report of Jpn Highwy Corportion Lbortory, pp , Dec (in Jpnese) 3. Iiok, Y., nd Higi, T., Experimentl Study on Strengthening Methods for Reinforced Concrete Decks, -Steel Plte Bonding Technique (Prt 2)-, Report of Jpn Highwy Corportion Lbortory, pp , Nov (in Jpnese) 4. Iiok, Y., Higi, T., nd Hosod, K., Experimentl Study on Strengthening Methods for Reinforced Concrete Decks, -Steel Plte Bonding Technique (Prt 3)-, Report of Jpn Highwy Corportion Lbortory, pp , Dec (in Jpnese)

7 5. Recommendtions for Upgrding of Concrete Structures with Use of Continuous Fiber Sheets, Concrete Librry 11, Jpn Society of Civil Engineers, July, 2. (in Jpnese) 6. Mufti, A.A., et l., New Cndin Highwy Bridge Design Code design provisions for fibre-reinforced structures, Cn, J, Civ. Eng., 34, pp , ACI 44 Committee, Guide for the design nd construction of externlly bonded FRP systems for strengthening concrete structures, ACI, July Zureick, A., Ellingwood, B. R., Nowk, A. S., Mertz, D. R., nd Trintfillou, T. C., Recommended Guide Specifiction for the Design of externlly Bonded FRP Systems for Repir nd Strengthening of Concrete Bridge Elements, NCHRP Report 655, TRB, Yoshid, E., Murkoshi, J. nd Tnk, Y, Effect of Adhesively Bonded Steel Pltes on Web Reinforcement for Reinforced Concrete Bems, Proceedings of JCI, pp.73-78, 21. (in Jpnese) 1. Yoshid, E., Murkoshi, J. nd Tnk, Y, Structurl Testing of Deteriorted Reinforced Concrete Girders Strengthened by Externlly Bonded Steel Pltes, Proc. JSCE Annul meeting, V, pp , 21. (in Jpnese) 11. Tumiln, J. G., Belrbi, A., nd Nnni, A., Reinforced Concrete Bems Strengthened with CFRP Composites: Filure due to Concrete Cover Delmintion, Center for Infrstructure Engineering Studies, 99-1, Deprtment of Civil Engineering, Univ. of Missouri - Roll, Mrch Roberts, T. M., Approximte nlysis of sher nd norml stress concentrtions in the dhesive lyer of plted RC bems, Structurl Engineer, 67(12), pp , Jones, R., Swmy, R. N., Bloxhm, J., nd Bouderblh, A., Composite behviour of concrete bems with epoxy bonded externl reinforcement, Int J Cem Compos, 2(2), pp.91-17, Mcdonld, M. D., The flexurl performnce of 3.5m concrete bems with vrious bonded externl reinforcements, TRRL Supplementry Report 728, Jones, R., Swmy, R. N., nd Ang, T. H., Under- nd over-reinforced concrete bems with glued steel pltes, Int J Cem Compos Lightweight Concr, 4(1), pp.19-32, Swmy, R. N., Jones, R., nd Bloxhm, J. W., Structurl behviour of reinforced concrete bems strengthened by epoxy-bonded steel pltes, Structurl Engineer, 65A(2), pp.59-68, Feb Jones, R., Swmy, R. N., nd Chrif, A., Plte seprtion nd nchorge of reinforced concrete bems strengthened by epoxy-bonded steel pltes, Structurl Engineer, 66(5), pp.85-94, Correspondence from Roberts, 67(12), pp , Oehlers, D. J., nd Morn, J. P., Premture filure of externlly plted reinforced concrete bems, J. of Structurl Engineering, ASCE, 116(4), pp , April Bsunbul, I. A., Gubti, A. A., Al-Sulimni, G. J., nd Bluch, M. H., Repired reinforced concrete bems, ACI Mterils J., 87(4), pp , July-Aug Oehlers, D. J., Reinforced concrete bems with pltes glued to their soffits, J. Structurl Engineering, ASCE, 118(8), pp , Hussin, M. et l., Flexurl behvior of precrcked reinforced concrete bems strengthened externlly by steel pltes, ACI Structurl J., 92(1), pp.14-22, Jn.-Feb Bluch, M. H., Zirb, Y. N., Azd, A. K., Shrif, A. M., Al-Sulimni, G. J. nd Bsunbul, I. A., Sher strength of plted RC bems, Mg. of Concrete Res., 47, No. 173, pp , Swmy, R. N., Jones, R., nd Chrif, A., Contribution of externlly bonded steel plte reinforcement to the sher resistnce of reinforced concrete bems, Repir nd Strengthening of Concrete Members with Adhesive Bonded Pltes, SP-165, ACI, pp.1-24, (The session ws held in 1992) 24. Sno, M., nd Miur, T., A study on design method for strengthening concrete members by steel-plte-bonding, Proc. of JSCE, 55, pp , Nov (in Jpnese) 25. Okmur, H., nd Higi, T., Proposed design eqution for sher strength of reinforced concrete bems without web reinforcement, Proc. of JSCE, 3, pp , Aug Niw, J., Eqution for sher strength of reinforced concrete deep bems bsed on FEM nlysis, Proc. of JCI 2nd Colloquium on Sher Anlysis of RC Structures, pp , Oct (in Jpnese) 27. ACI 318 Building Code Requirements for Structurl Concrete nd Commentry, ACI, 25.

8 Fig. 1 Steel pltes bonded to the soffit of decks nd girders in concrete bridge Fig. 2 Steel pltes bonded on the webs of concrete girders 25 L 3 25 A 3 L -16 A 3 Anchors M1, depth 6 mm s s s 5 5 Specimens A-4 to A-8 s : spcing of nchor L 5 B Supports for B-8 B 3 Anchors M1, depth 4 mm Specimens B-4 to B-6, nd B h Adhesive Steel plte A-A Steel nchor t sp B-B Fig. 3 Configurtions of specimens in Series I

9 Tble 1 Detils nd test results of specimens in Series I Specimen A-1 A-2 A-3 A-4 A-5 A-6 A-7 A-8 B-4 B-5 B-6 B-8 Steel plte strengthening No No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Continuity of steel plte t support No No No No No Yes Yes Yes No Height of bem h, mm Sher spn, mm Effective depth d, mm (fter strengthening) /d Longitudinl reinforcing brs 2-#7 2-#5 2-#6 2-#5 2-#5 2-#5 2-#7 2-#8 1-#5 1-#5 1-#5 1-#5 Rtio of reinforcement before strengthening, % Rtio of reinforcement fter strengthening, % Doubly reinforcing brs #5 1-#5 1-#5 1-#5 Thickness of steel plte t sp, mm Comp. cylinder strength of concrete, MP Splitting tensile strength of concrete, MP Yield point of reinforcing brs, MP Yield point of steel plte, MP Digonl crcking lod P cr,ex, kn Mximum lod P mx,ex, kn Type of filure S S S D D D S S ** ** ** S Note: 1) Width of bems nd pltes : 15 mm, Thickness of dhesive lyer : 5 mm 2) **: Loding ws stopped t digonl crck lod. 3) A steel plte ws instlled on the soffit of Specimen B-8, fter initil crcks developed due to cyclic loding when the sher spn ws set s 5 mm. 4) S : sher filure, D : filure due to crcking t the edge of steel plte, : Sher filure hppened fter the yielding of steel plte. Fig. 4 Filure due to crcking t the edge of the bonded steel plte in Specimen A-6

10 2 V ex (kn) V p2 (kn) Fig. 5 Comprison between the mesured sher forces t crcking t the edge of steel plte nd the clculted sher force t debonding of steel plte Note: Pinted symbols indicte the results obtined from this study. 2 2 V ex (kn) 1 /d = 1.7~1.75 V ex (kn) V sh (kn) () V sh Plted Non-plted Plted Non-plted V u,aci (kn) (b) 1.3 V u,aci (except the deep bem) Fig. 6 Comprisons between the mesured sher force of the plted bems t digonl crcking nd the clculted sher cpcity for flexure-sher crcking. Note: Pinted symbols indicte the results obtined from this study.

11 A 面 52 * A B * * D E B 面 Fig. 7 Wing-type steel pltes bonded to the sides of web in Series II 3 Steel 鋼 板 t=4.5mm plte 主 鉄 筋 ゲージ(SO) Guges 6 モールドゲージ(MO) Molded guges ( 断 面 4は*のみ) スターラップゲージ(ST) Guges Sher スターラップ spn without 無 し stirrup 側 2 上 筋 ( No. 段 取 2筋 )D6 断 面 1 断 面 2 断 面 3 Sher スターラップ spn with 有 stirrups り 側 1 2 Anchors アンカー P/2 P/2 4-φ9@25mm 4-Φ9 断 面 4 断 面 D35 5 スターラップゲージ(ST) Guges 1 No モールドゲージ(MO) Molded guges Verticl PC 鋼 棒 restriner 設 置 位 置 鋼 Steel 板 t=4.5mm plte 主 鉄 筋 Guges ゲージ(SO) t = 4.5 Fig. 8 Detils nd test setup of side-plted bems in Series II Note: Steel pltes were bonded on the web in Specimen S. 2 Lod (kn) Sher filure t sher spn without stirrup Filure t flnge t sher spn without stirrup First yielding of stirrup Lod (kn) Sher filure with debonding t sher spn without stirrup Filure t flnge t sher spn without stirrup Debonding First yielding of stirrup Crcking in web Flexurl crck Deflection t midspn (mm) Specimen N Crcking in web Flexurl crck Deflection t midspn (mm) Specimen S () Specimen N (no plte) (b) Specimen S (plted) Fig. 9 Reltionship between lod nd deflection of side-plted reinforced concrete bems

12 Without stirrup P/2 P/2 With stirrups () Specimen N (no plte) Without stirrup P/2 P/2 With stirrups (b) Specimen S (plted) Fig. 1 Crcks observed t sher filure t the sher spn without stirrup Note: Htching indictes the re of debonding of the steel pltes. Lod (kn) t digonl crcks t sher filure t yielding of stirrup * The sher spn with stirrups ws not completely filed due to the yield of the other sher spn. t debonding of steel plte t filure of upper flnge t sher spn without stirrup * * No plte Plted No plte Plted At sher spn without stirrup At sher spn with stirrups Fig. 11 Comprisons of the lod t digonl crcking, the lod t debonding, nd the mximum lod in Series II

13 4 Asphlt lyer P/2 P/2 2 4 Asphlt lyer St. pl., t = Debonding re 65 Sprice plte, t =9 65 : Core smpling 44 2 () Bem S1 45 Resin, t = St. pl., t = Epoxy resin 4 P/2 2 P/2 4 Asphlt lyer Ver. restriner b b Sprice plte, t = 9 65 Debonding re Unit: mm 45 (b) Bem S2 Asphlt lyer St. pl., t = Resin, t = St. pl., t =9 b-b Fig. 12 Deteriortion of old reinforced concrete bems with bonded steel pltes Note: Crcks in decks ner cross bems re not drwn. Crcks observed in cross sections were investigted fter loding tests. Tble 2 Test results of concrete cores tken from the old bems Bem Core Cylinder strength, Modulus of elsticity, Density, No. MP GP kg/m S1 2 * * S *) The vlues of the cores were used for the clcultion of the ultimte lods shown in Tble 4. Tble 3 The results of tensile tests of reinforcing brs nd steel pltes Types nd sizes Yield point Tensile strength Modulus of elsticity (MP) (MP) (GP) Stirrups 8 mm di Doubly reinforcing brs 22 mm di Min reinforcing brs 24 mm di Steel pltes 9 mm thick Note: All dt were obtined from tensile tests, being the verges of three test pieces.

14 8 6 Debonding t right joint 45 kn Mx. lod 519 kn Yielding of reinforcing brs S1 8 6 Debonding t left joint 396 kn S2 Mx. lod 478 kn Yielding of reinforcing br Lod (kn) 4 2 Debonding t left joint 398 kn Lod (kn) 4 2 Debonding t right joint 321 kn Deflection t midspn (mm) Deflection t midspn (mm) () Bem S1 (b) Bem S2 Fig. 13 Reltionship between lod nd deflection t midspn of the old bems () At sign of debonding of splice plte (b) Flexurl filure Fig. 14 Filure observed in Bem S1 Tble 4 Comprisons of ultimte lods of the old bems Bem Mesured ultimte lod, Clculted ultimte lod, P u,ex (kn) P u,cl (kn) P u,ex / P u,cl S (52).46 (1.3) S (51).43 (.95) Note: Prentheses indicte the clculted ultimte lods of reinforced concrete bems without steel pltes.