مدل جدید برای تعیین سهم ورقه‌های U-شکل FRP در ظرفیت برشی تیرهای بتنی مقاوم سازی شده

نوع مقاله : علمی - پژوهشی

نویسندگان

1 گروه مهندسی عمران، دانشکده فنی و مهندسی، دانشگاه آیت ا... بروجردی، بروجرد، ایران.

2 گروه مهندسی عمران، دانشکده فنی مهندسی دانشگاه دامغان، دامغان، ایران

چکیده

در سالهای اخیر استفاده از مصالح کامپوزیت FRP به دلیل وزن کم، مقاومت کششی بالا و آسانی اجرا در سطوح مختلف، بعنوان رویکردی مناسب برای تقویت و مقاومسازی اعضای بتن آرمه مطرح و مورد قبول مجامع مهندسی عمران و آئین نامهها بوده است. از سوی دیگر تحقیقات گستردهای بر روی تقویت خمشی و محوری اعضای بتن آرمه با استفاده از ورقه های FRP و میزان بهبود آن انجام شده اما میزان توجه به مطالعات تحلیلی و آزمایشگاهی بر روی مقاومت برشی اعضای مقاوم سازی شده با FRP و بخصوص تعیین دقیق سهم مصالح کامپوزیت نسبت به بحث مقاومت خمشی و محوری محدود بوده است. در این مطالعه با استفاده از روش مدیریت داده به روش گروهی و همچنین شبکه عصبی مصنوعی چند لایه، مدل‌هایی کارآمد برای تعیین سهم برش تحمل شده توسط ورقه‌های U-شکل FRP در تیرهای بتنی مقاومسازی شده بصورت خارجی ارائه شده است. همچنین با انجام آنالیز حساسیت، تغییرپذیری مدل های ایجاد شده نسبت به متغیرهای ورودی ارزیابی گردیده است. برای توسعه مدل‌ها، پارامترهای: کرنش نهایی FRP، ضخامت FRP، مدول الاستیسیته FRP، میزان و نحوه اجرای FRP، ارتفاع موثر FRP، عرض تیر، عمق موثر تیر، نسبت دهانه برشی به عمق موثر و مقاومت فشاری بتن در نظر گرفته شده است. برای کنترل صحت نتایج حاصل از مدل های ارائه شده، نتایج آنها با مقادیر محاسبه شده از ضوابط ACI 440، fib-TG9.3 و JSCE و براساس شاخص های آماری متنوع مقایسه شده است. نتایج نشان داده است که مدل های ایجاد شده عملکرد مطلوبی داشته و می توانند بعنوان رویکردی مطمئن در پیش طراحی برشی تیرهای بتنی تقویت شده با ورقه‌های U-شکل FRP مورد استفاده قرار گیرند.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

A new model for determining the shear contribution of FRP in RC beams strengthened with U-shape FRP sheets

نویسندگان [English]

  • Masoud Ahmadi 1
  • Mehdi Ebadi Jamkhaneh 2
1 Department of Civil Engineering, Ayatollah Boroujerdi University, Boroujerd, Iran
2 Department of Civil Engineering, School of Engineering, Damghan University, Damghan, Iran
چکیده [English]

Due to their lightweight, high tensile strength, and ease to install on irregular surfaces, the use of FRP systems for the repair and strengthening of reinforced concrete structures has become an accepted practice within civil engineering community and codes. Extensive research has been conducted on structural members to identify the improvement in their flexural and axial capacity due to FRP strengthening. However, the analytical and experimental studies on shear strengthening with FRP systems, especially exact determining FRP contribution, are limited. This study provides a multi-layer artificial neural network and group method of data handling approach for predicting the shear contribution of FRP in RC beams strengthened by externally bonded FRP sheets. To achieve the main purpose; ultimate strain of FRP, thickness of FRP, elastic modulus of FRP, width, spacing and angle of FRP sheet, effective depth of FRP, width and of effective depth of beam, compressive strength of concrete, and shear span to depth ratio were considered as input parameters while the shear contribution of the FRP is calculated as the target one. In order to verify the validity of the proposed models, a comparative assessment was conducted between experimental results and predicted values obtained directly from the models and existing guideline equations such as ACI 440, fib-TG9.3, and JSCE. The results indicate that the proposed models could predict the shear contribution of FRP in RC beams strengthened by FRP sheets with a good degree of precision and can be used as a confident approach for pre-design concrete beams strengthened with externally bonded U-shape FRP plates.

کلیدواژه‌ها [English]

  • Shear
  • FRP sheet
  • Strengthening
  • Concrete beam
  • New model
[1]  Cavagnis F, Ruiz MF, Muttoni A. Shear failures in reinforced concrete members without transverse reinforcement: An analysis of the critical shear crack development on the basis of test results. Eng Struct 2015;103:157–73.
[2]  Ahmad SH, Fareed S, Rafeeqi SFA. Shear strength of normal and light weight reinforced concrete slender beams without web reinforcement. Civ Eng Archit 2014;2:33–41.
[3]  Oller E, Pujol M, Marí A. Contribution of externally bonded FRP shear reinforcement to the shear strength of RC beams. Compos Part B Eng 2019;164:235–48.
[4]  Rasheed HA. Strengthening design of reinforced concrete with FRP. CRC Press; 2014.
[5]  Hadhood A, Agamy MH, Abdelsalam MM, Mohamed HM, El-Sayed TA. Shear strengthening of hybrid externally-bonded mechanically-fastened concrete beams using short CFRP strips: Experiments and theoretical evaluation. Eng Struct 2019;201:109795.
[6]  Colotti V. Effectiveness factors for bond strength in FRP shear-strengthened RC beams. Mater Struct 2016;49:5031–49.
[7]  Mitsui Y, Murakami K, Takeda K, Sakai H. A study on shear reinforcement of reinforced concrete beams externally bonded with carbon fiber sheets. Compos Interfaces 1997;5:285–95.
[8]  Triantafillou TC. Shear strengthening of reinforced concrete beams using epoxy-bonded FRP composites. Struct J 1998;95:107–15.
[9]  Swamy RN, Mukhopadhyaya P, Lynsdale CJ. Strengthening for shear of RC beams by external plate bonding. Struct Eng 1999;77.
[10]        Chaallal O, Nollet M-J, Perraton D. Shear strengthening of RC beams by externally bonded side CFRP strips. J Compos Constr 1998;2:111–3.
[11]        Dolan CW, Rider W, Chajes MJ, DeAscanis M. Prestressed concrete beams using non-metallic tendons and external shear reinforcement. Spec Publ 1993;138:475–96.
[12]        Uji K. Improving shear capacity of existing reinforced concrete members by applying carbon fiber sheets. Trans Japan Concr Inst 1992;14.
[13]        Täljsten B. Plate bonding: Strengthening of existing concrete structures with epoxy bonded plates of steel or fibre reinforced plastics 1994.
[14]        Chajes MJ, Januszka TF, Mertz DR, Thomson TA, Finch WW. Shear strengthening of reinforced concrete beams using externally applied composite fabrics. Struct J 1995;92:295–303.
[15]        Vielhaber J, Limberger E. Upgrading of concrete beams with a local lack of shear reinforcement. Fed Inst Mater Res Test (BAM), Unpubl Report, Berlin, Ger 1995.
[16]        Smith ST, Teng JG. Shear-bending interaction in debonding failures of FRP-plated RC beams. Adv Struct Eng 2003;6:183–99.
[17]        Teng JG, Chen JF. Debonding failures of RC beams strengthened with externally bonded FRP reinforcement: behaviour and modelling. Proc. first Asia-Pacific Conf. FRP Struct. (APFIS 2007), The University of Hong Kong, Hong Kong, China; 2007, p. 12–4.
[18]        Khalifa A, Nanni A. Improving shear capacity of existing RC T-section beams using CFRP composites. Cem Concr Compos 2000;22:165–74.
[19]        Gamino AL, Sousa J, Manzoli OL, Bittencourt TN. R/C Structures strengthened with CFRP Part II: Analysis of shear models. Rev IBRACON Estruturas e Mater 2010;3:24–49.
[20]        Khalifa A, Alkhrdaji T, Nanni A, Lansburg S. Anchorage of surface mounted FRP reinforcement. Concr Int 1999;21:49–54.
[21]        El-Mihilmy MT, Tedesco JW. Prediction of anchorage failure for reinforced concrete beams strengthened with fiber-reinforced polymer plates. Struct J 2001;98:301–14.
[22]        Umezu K. Shear Behavior of RC Beams with Aramid Fiber Sheet, Japan Concrete Institute, Non-Metallic (FRP) Reinforcement for Concrete Structures. Proceeding Third Int. Symp., vol. 1, 1997, p. 491–8.
[23]        Barros JAO, Dias SJE, Lima JLT. Efficacy of CFRP-based techniques for the flexural and shear strengthening of concrete beams. Cem Concr Compos 2007;29:203–17.
[24]        Monti G. Tests and design equations for FRP-strengthening in shear. Constr Build Mater 2007;21:799–809.
[25]        Diagana C, Li A, Gedalia B, Delmas Y. Shear strengthening effectiveness with CFF strips. Eng Struct 2003;25:507–16.
[26]        Sakar G. Shear strengthening of RC beams subjected to cyclic load using CFRP strips. Adv Compos Lett 2008;17:096369350801700604.
[27]        Jayaprakash J, Samad AAA, Abbasovich AA, Ali AAA. Shear capacity of precracked and non-precracked reinforced concrete shear beams with externally bonded bi-directional CFRP strips. Constr Build Mater 2008;22:1148–65.
[28]        Khalifa A, Belarbi A, Nanni A. Shear performance of RC members strengthened with externally bonded FRP wraps. Proc. Twelfth World Conf. Earthquake, Auckland, New Zealand, January, Citeseer; 2000.
[29]        Naderpour H, Alavi SA. A proposed model to estimate shear contribution of FRP in strengthened RC beams in terms of Adaptive Neuro-Fuzzy Inference System. Compos Struct 2017;170:215–27. https://doi.org/10.1016/j.compstruct.2017.03.028.
[30]        FIB. (2001). Design and use of externally bonded fibre reinforced polymer reinforcement (FRP EBR) for reinforced concrete structures. fib Bulletin No. 14, Technical report.
[31]        ACI Committee 440. (2002). Guide for the design and construction of externally bonded FRP systems for strengthening concrete structures. Farmingt Hills Am Concr Inst.
[32]        CIDAR. (2006) Design guideline for RC structures retrofitted with FRP and metal plates: Beams and slabs. Standards Australia, Sydney, NSW 2001, Australia.
[33]        DT200 CNR. (2004). Guidelines for design, execution and control of strengthening interventions by means of fibre-reinforced composites–materials, reinforced concrete and prestressed concrete structures, masonry structures. Rome, Italy Natl Res Counc Advis Comm Tech Regul Constr.
[34]        CSA S806. (2002). Design and construction of building components with fibre-reinforced polymers. Canadian Standards Association.
[35]        Beale MH, Hagan MT, Demuth HB. Neural network toolbox. User’s Guid MathWorks 2010;2:77–81.
[36]        Ivakhnenko AG. Polynomial Theory of Complex Systems. IEEE Trans Syst Man Cybern 1971;SMC-1:364–78. https://doi.org/10.1109/TSMC.1971.4308320.
[37]        Naderpour H, Nagai K, Haji M, Mirrashid M. Adaptive neuro‐fuzzy inference modelling and sensitivity analysis for capacity estimation of fiber reinforced polymer‐strengthened circular reinforced concrete columns. Expert Syst 2019:e12410.
[38]        Naderpour H, Mirrashid M, Nagai K. An innovative approach for bond strength modeling in FRP strip-to-concrete joints using adaptive neuro–fuzzy inference system. Eng Comput 2019:1–18.
[39]        Naderpour H, Eidgahee DR, Fakharian P, Rafiean AH, Kalantari SM. A new proposed approach for moment capacity estimation of ferrocement members using Group Method of Data Handling. Eng Sci Technol an Int J 2020;23:382–91.
[40]        Naderpour H, Nagai K, Fakharian P, Haji M. Innovative models for prediction of compressive strength of FRP-confined circular reinforced concrete columns using soft computing methods. Compos Struct 2019;215:69–84.
[41]        Naderpour H, Fakharian P. Predicting the torsional strength of reinforced concrete beams strengthened with FRP sheets in terms of artificial neural networks. J Struct Constr Eng Doi 2017;10.
[42]        Azimi A. GMDH-Network to estimate the punching capacity of FRP-RC slabs. J Soft Comput Civ Eng 2017;1:86–92.
[43]        Farahnaki R, Azimi A. An equation to determine the ultimate flexural load of RC beams strengthened with CFRP laminates. J Soft Comput Civ Eng 2018;2:86–95.
[44]        Engineers) J (Japan S of C. Recommendations for upgrading of concrete structures with use of continuous fiber sheets, JSCE Tokyo, Japan; 2001.
[45]        Chen JF, Teng JG. Shear capacity of FRP-strengthened RC beams: FRP debonding. Constr Build Mater 2003;17:27–41.
[46]        Li W, Li J, Ren X, Leung CKY, Xing F. Coupling effect of concrete strength and bonding length on bond behaviors of fiber reinforced polymer–concrete interface. J Reinf Plast Compos 2015;34:421–32.
[47]        Cao SY, Chen JF, Teng JG, Hao Z, Chen J. Debonding in RC beams shear strengthened with complete FRP wraps. J Compos Constr 2005;9:417–28.
[48]        Bousselham A, Chaallal O. Behavior of reinforced concrete T-beams strengthened in shear with carbon fiber-reinforced polymer-An experimental study. ACI Struct J 2006;103:339.
[49]        Li W, Leung CKY. Shear Span–Depth Ratio Effect on Behavior of RC Beam Shear Strengthened with Full-Wrapping FRP Strip. J Compos Constr 2015;20:4015067.
[50]        Chen GM, Teng JG, Chen JF. Finite-element modeling of intermediate crack debonding in FRP-plated RC beams. J Compos Constr 2010;15:339–53.
[51]        Zhang T, Oehlers DJ, Visintin P. Shear strength of FRP RC beams and one-way slabs without stirrups. J Compos Constr 2014;18:4014007.
[52]        Bentz EC, Massam L, Collins MP. Shear strength of large concrete members with FRP reinforcement. J Compos Constr 2010;14:637–46.
[53]        Alam MS, Hussein A. Size effect on shear strength of FRP reinforced concrete beams without stirrups. J Compos Constr 2012;17:507–16.
[54]        Leung CKY, Chen Z, Lee S, Ng M, Xu M, Tang J. Effect of size on the failure of geometrically similar concrete beams strengthened in shear with FRP strips. J Compos Constr 2007;11:487–96.
[55]        Fazel Zarandi MH, Türksen IB, Sobhani J, Ramezanianpour AA. Fuzzy polynomial neural networks for approximation of the compressive strength of concrete. Appl Soft Comput 2008;8:488–98. https://doi.org/10.1016/j.asoc.2007.02.010.
[56]        Najafzadeh M, Azamathulla HM. Neuro-Fuzzy GMDH to Predict the Scour Pile Groups due to Waves. J Comput Civ Eng 2015;29:04014068. https://doi.org/10.1061/(ASCE)CP.1943-5487.0000376.
[57]        Madandoust R, Ghavidel R, Nariman-zadeh N. Evolutionary design of generalized GMDH-type neural network for prediction of concrete compressive strength using UPV. Comput Mater Sci 2010;49:556–67. https://doi.org/10.1016/j.commatsci.2010.05.050.
[58]        Madandoust R, Bungey JH, Ghavidel R. Prediction of the concrete compressive strength by means of core testing using GMDH-type neural network and ANFIS models. Comput Mater Sci 2012;51:261–72. https://doi.org/10.1016/j.commatsci.2011.07.053.
[59]        Garson GD. Interpreting neural-network connection weights. AI Expert 1991;6:46–51.
[60]        Sato Y, Ueda T, Kakuta Y, Tanaka T. Shear reinforcing effect of carbon fiber sheet attached to side of reinforced concrete beams. Proc. 2ND Int. Conf. Adv. Compos. Mater. Bridg. Struct. ACMBS-II, Montr. 1996, 1996.
[61]        Wu G, An L, Lv Z. The investigation on shear capacity of CFRP strengthened RC beams. Archit Struct 2000;30:16–20.
[62]        Täljsten B, Elfgren L. Strengthening concrete beams for shear using CFRP-materials: evaluation of different application methods. Compos Part B Eng 2000;31:87–96.
[63]        Annaiah RH. Shear performance of RC beams strengthened in situ with composites 2001.
[64]        Park SY, Naaman AE, Lopez MM, Till RD. Shear strengthening effect of RC beams using glued CFRP sheets. FRP Compos. Civ. Eng. Proc. Int. Conf. FRP Compos. Civ. Eng. Kong Inst. Eng. Hong Kong Inst. Steel Constr., 2001.
[65]        Li W, Leung CKY. Effect of shear span-depth ratio on mechanical performance of RC beams strengthened in shear with U-wrapping FRP strips. Compos Struct 2017;177:141–57.
[66]        Khalifa A, Nanni A. Rehabilitation of rectangular simply supported RC beams with shear deficiencies using CFRP composites. Constr Build Mater 2002;16:135–46.
[67]        Tan Z, Ye LP. Experimental research on shear capacity of RC beam strengthened with externally bonded FRP sheets. China Civ Eng J 2003;36:12–8.
[68]        Kuang Z, Liu C, Wang H. Experimental Research on Concrete Beams without Stirrups Streng-thened for Shearing by Using Carbon Fiber Reinforced Plastic. JOURNAL-TONGJI Univ 2004;32:575–9.
[69]        Dias SJE, Barros JAO. Experimental research of a new CFRP-based shear strengthening technique for reinforced concrete beams 2005.
[70]        Dias SJE, Barros JAO. NSM CFRP laminates for the shear strengthening of T section RC beams 2006.
[71]        Qu Z. Analysis and design model of DRP shear-strengthened concrete beams 2008.
[72]        Zhang, Y, Hu, H. (2006). Study on shear behavior of RC beam strengthened with CFRP sheet. Journal of Hunan University of Technology, 21, 31–36.
[73]        Altin S, Anil Ö, Kopraman Y, Mertoğlu Ç, Kara ME. Improving shear capacity and ductility of shear-deficient RC beams using CFRP strips. J Reinf Plast Compos 2010;29:2975–91.
[74]        Koutas L, Triantafillou TC. Use of anchors in shear strengthening of reinforced concrete T-beams with FRP. J Compos Constr 2012;17:101–7.
[75]        Mofidi A, Chaallal O. Shear strengthening of RC beams with externally bonded FRP composites: Effect of strip-width-to-strip-spacing ratio. J Compos Constr 2011;15:732–42.
[76]        Ozden S, Atalay HM, Akpinar E, Erdogan H, Vulaş YZ. Shear strengthening of reinforced concrete T‐beams with fully or partially bonded fibre‐reinforced polymer composites. Struct Concr 2014;15:229–39.
[77]        Mofidi A, Chaallal O. Tests and design provisions for reinforced-concrete beams strengthened in shear using FRP sheets and strips. Int J Concr Struct Mater 2014;8:117–28.