Strengthening methods for reinforced concrete sections with Fiber reinforced polymers

Transcription

1 IOSR Jurnal f Mechanical and Civil Engineering (IOSR-JMCE) e-issn: ,p-ISSN: X, Vlume 14, Issue 6 Ver. I (Nv. - Dec. 2017), PP Strengthening methds fr reinfrced cncrete sectins with Fiber reinfrced plymers Gultekin Aktas *,1, Sultan Erdemli Gunaslan 1 1 (Civil Engineering Department, Dicle University Engineering Faculty, Diyarbakir, Turkey) * (Crrspnding Authr: Gultekin Aktas) Abstract: FRP materials in strengthening f Reinfrced Cncrete (RC) elements tends t be mre ppular depends n develpment f civil engineer applicatin areas in the recent years. Damaged buildings and strengthening buildings with lw standards became ne f the fast develping subjects all ver the Wrld. Buildings that purpse f use has been changed, ld buildings nt in cmpliance with earthquake regulatin and damaged buildings need t be strengthened. In this study, the advantages f carbn fiber reinfrced plymers (CFRP) as ne f the strengthening technique with the ther classical methds discussed due t their prperties f being thin and light as shirt fabric with high strength capacity. Keywrds -Cncrete, fiber reinfrced plymers, strengthening methds Date f Submissin: Date f acceptance: I. Intrductin The Carbn Fiber Reinfrced Plymers (CFRP) cmpsites are preferable material due t their light weight and easy implementatin with high tensile strength and crrsin resistance fr strengthening cncrete structures. The fiber reinfrced plymer (FRP) cmpsite wrap has been established as an effective methd, alternative t traditinal strengthening techniques, such as steel plate bnding, sectin enlargement, and external pst-tensining applicatins fr strengthening and rehabilitatin f cncrete structures. High stiffness-t-weight and strength-t-weight ratis f these materials cmbined with their superir envirnmental durability have made them a cmpeting alternative t the cnventinal strengthening and repair materials. In many civil engineering applicatins such as rehabilitatin f RC buildings, strengthening f bridge piers, etc. usage f FRP as a cmpsite material is ne f the best ptin t be used as external reinfrcing because f their high tensile strength, light weight, resistance t crrsin, high durability, and ease f installatin [1-5]. Cnfinement f cncrete with externally bnded FRP is an imprtant applicatin f FRP cmpsites. Several methds have been researched and prven effective in increasing the axial lad capacity f reinfrced cncrete clumns. These methds include cncrete, steel, and fiber reinfrced plymer (FRP) jackets. Lateral cnfinement using FRP r spiral reinfrcement has been demnstrated t increase cmpressin strength, defrmability, and energy absrptin capacity f cncrete. Numerus experimental studies have been cnducted t examine the perfrmance f FRP cmpsites in retrfitting existing cncrete clumns [6 13]. Recently the retrfit with FRP materials with desirable prperties prvides replacement fr traditinal materials, such as steel jacket, t strengthen the reinfrced cncrete structural members. II. Strengthening Methds Externally bnded steel plates, cncrete jackets, steel jacketing, External Pst-Tensining and wrapping FRP are knwn as cmmn strengthening methds. The mst imprtant step in retrfitting is the selectin f an suitable interference technique based n the structural type and its vacancy. On the ther hand type and lcatin f prblem, availability f time and skill, appearance and cst are imprtant factrs in case f strengthening methd selectin. Accrding t JSCE, 1999[14]; Retrfitting f structures shall flwed as fllws : Identify the perfrmance requirements fr the existing structure t be retrfitted and draft an verall plan frm inspectin thrugh selectin f retrfitting methd, design f retrfitting structure and implementatin f retrfitting wrk. Inspect the existing structure t be retrfitted. Based n the results f the inspectin, evaluate the perfrmance f the structure and verify that it fulfills perfrmance requirements. If the structure des nt fulfill perfrmance requirements, and if cntinued use f the structure thrugh retrfitting is desired, prceed with design f the retrfitting structure. DOI: / Page

2 Strengthening methds fr reinfrced cncrete sectins with Fiber reinfrced plymers Select an apprpriate retrfitting methd and establish the materials t be used, structural specificatins and cnstructin methd. Evaluate the perfrmance f the structure after retrfitting and verify that it will fulfill perfrmance requirements. If it is determined that the retrfitting structure will be capable f fulfilling perfrmance requirements with the selected retrfitting and cnstructin methds, implement the retrfitting wrk. Cncrete Jacketing: Cncrete jacketing is typically applied methds f repair and strengthening f cncrete members. Jacketing is ne f the mst generally used techniques t strengthen reinfrced cncrete (RC) clumns. The size f the jacket, the number and diameter f the steel bars used in the jacketing prcess depend n the structural analysis that was made t the clumn., If it is required, beams, slabs, and walls can be enlarged t add stiffness r lad-carrying capacity. Extensive lngitudinal and transverse reinfrcement is added in the new layer f cncrete, enhancing the shear and flexural strength and ductility. It is necessary t prvide a gd bnd between new and ld cncrete in reinfrced cncrete jacketing. Reinfrced cncrete jacketing can be applied ne, tw, three r fur side f the clumn,depending n the state f the implementatin and space arund the clumn. In rder t made jacketing t a required level; Strength f the new material must be greater than existing ne Min 10 cm thickness f the jacket fr cast- in situ cncrete New reinfrcement and cncrete must be cllabrated with existing cncrete and reinfrcement This methd applicatin is difficult t cnstruct in sme active buildings such as hspitals, schls, industry etc. because f the implementatin is taken time, made nise and many ther limitatins. In mst cases Size f the clumns r reinfrced cncrete members increased by cncrete jacketing. Reinfrced cncrete jackets are build by enlarging the existing crss sectin with a new layer f cncrete and reinfrcement Fig 1 shw that the enlargement f cncrete and reinfrcement [15]. Fig.1. Typical cncrete jacketting f reinfrce cncrete clumns DOI: / Page

3 Strengthening methds fr reinfrced cncrete sectins with Fiber reinfrced plymers Steel Jacketing and Externally Bnded Steel: Strengthening methd with steel plate bnd r steel welding in reinfrced cncrete is cncerned are fast and effective.the steel jacket retrfit has been used as a methd t enhance the shear strength and ductility f reinfrced cncrete (RC) clumns in buildings Cnfining reinfrced cncrete clumn in steel jackets is ne f the remarkable methds t imprve the axial lad carrying capacity. As cmpared with cnventinal hps r spirals, steel jacket has an effective utility f easily prvide a large amunt f transverse steel, hence strng cnfinement t the cmpressed cncrete and t prevent spalling f the shell cncrete The jacketting f the clumn with thin steel plates placed at a small distance frm the clumn surface, with the ccurring space being filled with nn-shrinking gruts shwn in Fig 2. A steel jacket usually cnsists f tw half shells f steel placed arund the clumn, and welded tgether after placing. The space between the jacket and clumn is filled with pure cement grut. A space between the jacket and the jining member, t avid the prbability f direct lad carrying actin f the jacket, it culd cause lcal buckling in the jacket. The jacket prvides a passive cnfinement effect. The jacket can be cnsidered as similar t cntinuus hpreinfrcement. The simplicity and speed f the jacketting applicatin prvide a slutin fr critical interventin time immediately after a strng earthquake, particularly fr special buildings such as hspitals and schls [16]. Fig 2. Strengthening f RC clumn with Steel jacketing External Pst-Tensining Methd: Pst-tensining is a methd f strengthening cncrete r structural member with high-strength (prestressing) steel, strands, cables r bars, typically referred t as tendns. Psttensining tendns are regarded active strengthening as prestressed cncrete members. The steel is influential as reinfrcement even thugh the cncrete may nt be cracked. It can be applied t reinfrced and prestressed cncrete members. Pst-tensining is a technique used t prestress reinfrced cncrete after cncrete is placed The tensining prvides the structural member with an immediate and active lad-carrying capacity Pst-tensined structures can be designed t have minimum deflectin and cracking, even under whle lad. Pst tensining methd fr strengthening generally used t beam fr enhanced the flexural capacity, imprves the cracking perfrmance and als have a beneficial effect n shear capacity when the applicatin f an axial lad cmbined with a hgging bending mment. Strengthening f a beam with external tendns with equal number f tendns are typically used n each side f the beam. Tendn frce and eccentricity are adjusted until an ptimum slutin fr the required uplift frce is btained [17]. External Wrapping by FRP: Fibers are the effective reinfrcements material, as they satisfy the required cnditins and transfer strength t the matrix cnstituent influencing and enhancing their prperties as required. The perfrmance f a fiber cmpsite is evaluated by its length, shape, rientatin, cmpsitin f the fibers and the mechanical prperties f the matrix.(pandey,2004). The main fibre types used in civil engineering are Carbn fibers (CFRP),Glass (GFRP) and Aramid (AFRP) illustrated in Fig.3. Carbn fibers are anistrpic in nature Carbn fiber is prduced at 1300ºC. High strength, excellent creep level, resistance t chemical effects,lw cnductivity, lw density and high elastic mdulus are the advantages f carbn fibers.carbn fibers are expensive and anistrpic materials and ıt has a lw cmpressin strength these are the weak sides f carbn fibers. Glass Fibers (GFRP) : Glass fibers are istrpic in nature and mst widely used filament. Cmmn types f glass fibers are E-Glass, S-Glass and C - Glass. The characteristic prperties f DOI: / Page

4 Strengthening methds fr reinfrced cncrete sectins with Fiber reinfrced plymers glass fibers are : high strength, lw cst, gd water resistance and resistance t chemicals. Aramid Fibers (AFRP) : Aramid fibers widespread knwn as a kevlar fiber in the markets.the structure f aramid fiber is anistrpic in nature and usually are yellw in clurs. Aramid fibers mre expensive than glass, mderate stiffness, gd in tensin applicatins (Cables and tendns) but lwer strength in cmpressin, Aramids have high tensile strength, high stiffness. high mdulus and lw weigh and density.impact-resistant structures can be prduced frm aramids. Fig 3. a) Typical Carbn fibers(cfrp) b) Typical Glass fibers (GFRP) c) Typical Aramid fibers (AFRP) FRP material are used as external reinfrcement in the cnstructin industry since 1970[18]. Tday, these FRP prducts take the frm f bars, cables, 2-D and 3-D grids, sheet materials, plates, etc. FRP prducts may succeed in the same r better reinfrcement bjective f cmmnly used metallic prducts such as steel reinfrcing bars, prestressing tendns, and bnded plates as indicated by ACI 440 [19]. A typical FRP applicatin shwn in Fig.4 as strengthening materials fr a cncrete sectin t determine the cnfining effect f carbn fiber reinfrced plymer n strength and energy dissipatin capacity [20]. DOI: / Page

5 Strengthening methds fr reinfrced cncrete sectins with Fiber reinfrced plymers Fig.4. Applicatin f FRP n cncrete sectin fr seismic retrfitting Epxy resins are used fr small injectin, surface cating r filling larger cracks r hles. If ıt is suitably applied, these materials culd be bnded easily t cncrete and are able t restring the riginal structural strength t cracked cncrete. The epxy mixture strength is depend n the temperature f curing, lwer strength fr higher temperature and methd f applicatin. Viscsity must be suitable t the thickness f the crack t be injected. Cracks t be injected with epxy resins shuld be between ~ 0.1 mm and ~ 6 mm in width. It is very difficult t retain injected epxy resin in cracks greater than ~ 0.6 mm in width, althugh high viscsity epxies have been used with sme success. Epxy resins cure t frm relatively brittle materials with bnd strengths exceeding the shear r tensile strength f the cncrete. III. Cnclusin The recent studies shw that FRP strengthening r retrfitted techniques can enhance stress-strain perfrmance f existing reinfrced cncrete structures. Reinfrced cncrete structures may need strengthening r retrfitted due t incrrect calculatins and applicatins f prject the use f unsuitable materials fr standards r guidelines, the lw quality f cncrete, inadequate lateral reinfrcement, change f usage, additinal strey, envirnmental factrs and pr wrkmanship etc. The usage f FRP cmpsites in strengthening applicatins has superirities due t the lightweight, high strength, resistance t crrsin, speed and ease f applicatin and frmed n site. References [1] A. Karasin, S. Erdemli, M.E. Oncu, Mdels fr Cnfined Cncrete Clumns with Fiber Cmpsites, Internatinal Jurnal f Advanced Research in Engineering and Technlgy, 2014, vl. 5(12), [2] P. Gülkan, "Quantificatin f Seismic Damage and Structural Interventin, Secnd Japn-Turkey Wrkshp n Earthquake Engineering, İstanbul, [3] M. E. Oncu, A. Karasin, S. Yılmaz, Behavir Of Strengthen Cncrete Sectins with CFRP Under Axial Lading. Jurnal f New Wrld Sciences Academy Engineering Sciences, 2010, vl.5(3), p [4] ACI440.2R-08, Guide fr the design and cnstructin f externally bnded FRP systems fr strengthening cncrete structures, ACI 2008 [5] Task Grup 9.3FRP (Fiber Reinfrced Plymer) reinfrcement fr cncrete structures, July Design and use f externally bnded fibre reinfrced plymer reinfrcement (FRP EBR) fr reinfrced cncrete structures, fib CEB-FIP Bulletin 14,Swithzerland, [6] H. Saadatmanesh, M. R. Ehsani, and L. Jin,. Strength and Ductility f Cncrete Clumns Externally Reinfrced with Fiber Cmpsite Straps, ACI Structural Jurnal, 1994,V. 91, N. 4, p [7] J.P. Mehle, State f Research n Seismic Retrfit f Cncrete Building Structures in the US, US-Japan Sympsium and Wrkshp n Seismic Retrfit f Cncrete Structures, [8] E. Canbay, G. Ozcebe, and U. Ersy, High-strength cncrete clumns under eccentric lad, Jurnal f Structural Engineering, vl.132(7), p , [9] H. Saadatmanesh, M. R. Ehsani, and L. Jin, Repair f Earthquake-Damaged RC Clumns with FRP Wraps, ACI Structural Jurnal Title. n. 94-S20, p , [10] A. Ilki, O. Peker, E. Karamuk, C. Demir, N. Kumbasar, Frp Retrfit f Lw and Medium Strength Circular And Rectangular Reinfrced Cncrete Clumns, Jurnal f Materials in Civil Engineering, vl.20(2), p , [11] G. Campine, N. Miraglia, M. Papia, Strength and strain enhancements f cncrete clumns cnfined with FRP sheets, Structural Engineering and Mechanics, Vl. 18, N. 6, [12] Guide t Cncrete Repair United States Department f the Interir Bureau f Reclamatin, Technical Service Center, [13] D. Rylance, Intrductin t Cmpsite Materials, Department f Materials Science and Engineering, Massachusetts Institute f Technlgy Cambridge, MA 02139, March DOI: / Page

6 Strengthening methds fr reinfrced cncrete sectins with Fiber reinfrced plymers [14] "Guıdelınes Fr Retrfıt Of Cncrete Structures (Draft)", JSCE Wrking Grup n Retrfit Design f Cncrete Structures in Specificatin Revisin Cmmittee, Translatin frm the CONCRETE LIBRARY N.95 published by JSCE, September [15] U. Ersy, A.T. Tankut and R. Suleiman, Behavir f jacketed clumns, ACI Structural Jurnal, vl.90(3), p , [16] Girgi, M Seismic Upgrade f Reinfrced Cncrete Clumns with FRP, Universita La Sapienza di Rma, Italy [17] Krauser,L Repaırs, Mdıfıcatıns, And Strengthenıng Wıth Pst-Tensınıng Ptı Jurnal,July 2006, Page [18] ISIS Canada Educatinal Mdule N. 4. February An Intrductin t FRP-Strengthening f Cncrete Structures, Principal Cntributr: L.A. Bisby, Ph.D., P.Eng.Department f Civil Engineering, Queen s University Cntributr: B.K. Williams, [19] ACI 440.3R Guide Test Methds fr Fiber-Reinfrced Plymers (FRPs) fr Reinfrcing r Strengthening Cncrete Structures. ACI, [20] K.V Celik, and A. Karasin "Karbn elyaf ile betnun güçlendirilmesi", Dicle üniversitesi mühendislik fakultesi dergisi, Vl.(5), p.1-11, Gultekin Aktas Strengthening methds fr reinfrced cncrete sectins with Fiber reinfrced plymers. IOSR Jurnal f Mechanical and Civil Engineering (IOSR-JMCE), vl. 14, n. 6, 2017, pp DOI: / Page