تاثیر آرایش نوارهایFRP، ابعاد تیر و مقدار آرماتور کششی در ظرفیت برشی تیر بتن مسلح

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه مهندسی عمران، واحد نجف آباد، دانشگاه آزاد اسلامی، نجف آباد، ایران

2 گروه مهندسی عمران، واحد نجف آباد، دانشگاه آزاد اسلامی، نجف آباد

چکیده

در ایـن مقالـه، بـه بررسـی اثـر فواصـل قـرار گیـری نوارهـای FRP ،تعداد الیه و سـطح مقطـع آن، میزان آرماتـور طولی، ابعـاد تیـر و مقاومـت فشـاری بتـن در ظرفیـت برشـی تیرهـای بتنـی بـا مقطـع مسـتطیلی شـکل تحـت بـار متمرکـز متقـارن، مقـاوم شـده بـا نوارهـای FRP بـه روش اجـزاء محـدود پرداختـه شـده اسـت. بدیـن منظـور تحلیـل غیـر خطـی 101 نمونـه، جهـت ارزیابـی تاثیـر متغیرهـای فـوق بـر ظرفیـت باربـری و تغییرمـکان وسـط دهانـه تیرهـای مختلـف بـا و بـدون نـوار تقویـت انجـام شـده اسـت. نتایـج حا کـی از آن اسـت کـه بـه ازای مقاومـت فشـاری ثابـت بـرای بتـن، افزایـش عـرض نـوار تقویتـی و افزایـش تعـداد الیـه هـای آن افزایـش ظرفیـت باربـری نسـبت بـه نمونـه هـای کنتـرل دسـته خـود را بـه همـراه دارد،. بـا تغییـر در چیدمـان نوارهـای تقویتـی بـا فواصـل نامنظـم در طـول تیـر، افزایـش ظرفیـت باربـری در حـدود 6 %الـی 35 %حاصـل مـی شـود. همچنیـن افزایـش در میـزان آرماتـور طولـی از مقـدار 10ϕ بـه 14ϕ ،افزایـش مقاومـت فشـاری بتـن از مقـدار 30MPa بـه 50MPa ،و افزایـش سـطح مقطـع تیـر از مقـدار 300mm×150 بـه 400mm×150 در نمونـه هـای تقویـت نشـده سـبب افزایـش ظرفیـت باربـری بـه ترتیـب در حـدود 31 ،%23 ،%55 %و کاهـش تغییرمـکان وسـط دهانـه مـی گـردد.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Effect of FRP Strips Configuration, Beam Dimensions and Amount of Tensile Rebars on Shear Capacity of Reinforced Concrete Beams

نویسندگان [English]

  • Mehrdad Hejazi 1
  • Mitra Mohammad 2
1 Department of Civil Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran
2 Dept of Civil Engineering/Islamic Azad University, Najafabad Branch
چکیده [English]

In this paper, the effect of the distance, number of layers and cross-sectional area of FRP strips, the amount of longitudinal rebars, dimensions of beam and compressive strength of concrete on shear capacity of reinforced concrete beams with rectangular crosssection stiffened by FRP strips under symmetrical concentrated loads using the finite element method has been studied. For this reason, the non-linear analysis of 101 reinforced beams has been performed for evaluation of the effect of the parameters on load capacity and mid-span deflection of the beams with and without strengthening. Obtained results indicate that for a constant concrete compressive strength, increasing the width and the number of layers of FRP strips increases the load capacity compared to the control beam. By changing the layout of reinforcing strips with irregular intervals along the beam, the load capacity increase is about 6% to 35%. Also, the increase of the amount of longitudinal rebars from Φ10 to Φ14 creasing the compressive strength of the concrete from 30 MPa to 50 MPa, and increasing the cross-sectional area of the beam from 150 × 300 mm to 150 × 400 mm in unstiffened beams, increase the load capacity by 31%, 23% and 55%, respectively.

کلیدواژه‌ها [English]

  • Reinforced Concrete Beam
  • FRP Strips
  • Tensile Rebar
  • Shear Capacity
  • Ductility

مراجع

[1]  H.A. Raghu, J.J. Myers, A. Nanni, Shear performance of RC beams strengthened in situ with composites, Report, University of Missouri, Rolla, (2001).
A. Khalifa, G. Tumialan, A. Nanni, A. Belarbi, Shear strength- ening of continuous RC beams using externally bonded CFRP sheets, in: American Concrete Institute, Proc., 4th International Symposium on FRP for Reinforcement of Concrete Structures (FRPRCS4), Baltimore, MD, 1999, pp. 995-1008.
[3] J.A. Barros, S.J. Dias, Near surface mounted CFRP laminates for shear strengthening of concrete beams, Cement and Concrete Composites, 28(3) (2006) 276-292.
[4]  M. Chajes, T. Thomson, B. Tarantino, Reinforcement of con- crete structures using externally bonded composite  materials, in: RILEM PROCEEDINGS, CHAPMAN & HALL, 1995, pp. 501-501.
[5] A.S. Mosallam, S. Banerjee, Shear enhancement of reinforced concrete beams strengthened with FRP composite laminates, Composites Part B: Engineering, 38(5-6) (2007) 781-793.
[6] H.-T. Hu, F.-M. Lin, Y.-Y. Jan, Nonlinear finite element analy- sis of reinforced concrete beams strengthened by fiber-reinforced plastics, Composite Structures, 63(3-4) (2004) 271-281.
[7]  Y.-S. Shin, C. Lee, Flexural behavior of reinforced concrete beams strengthened with carbon fiber-reinforced polymer lami- nates at different levels of sustaining load, Structural Journal, 100(2) (2003) 231-239.
[8]  O. Buyukozturk, O. Gunes, E. Karaca, Characterization and modeling of debonding in RC beams strengthened with FRP composites, in: 15th ASCE Engineering Mechanics Conference, Columbia University, New York, 2002, pp. 1-8.
[9]   R.S. Wong, F.J. Vecchio, Towards modeling of reinforced concrete members with externally bonded fiber-reinforced poly- mer composites, ACI Structural Journal, 100(1) (2003) 47-55.
[10]  N.F. Grace, G. Sayed, A. Soliman, K. Saleh, Strengthening reinforced concrete beams using fiber reinforced polymer (FRP) laminates, ACI Structural Journal-American Concrete Institute, 96(5) (1999) 865-874.
[11] A. Sharif, G. Al-Sulaimani, I. Basunbul, M. Baluch, B. Gha- leb, Strengthening of initially loaded reinforced concrete beams using FRP plates, Structural Journal, 91(2) (1994) 160-168.
[12]   J. Dong, Q. Wang, Z. Guan, Structural behaviour of RC beams with external flexural and flexural–shear strengthening by FRP sheets, Composites Part B: Engineering, 44(1) (2013) 604-612.
[13]  A.K. El-Sayed, Effect of longitudinal CFRP strengthening on the shear resistance of reinforced concrete beams, Composites Part B: Engineering, 58 (2014) 422-429.
[14]   D. Baggio, K. Soudki, M. Noel, Strengthening of shear critical RC beams with various FRP systems, Construction and Building Materials, 66 (2014) 634-644.
[15]  W. Li, C.K. Leung, Shear span–depth ratio effect on behav- ior of RC beam shear strengthened with full-wrapping FRP strip, Journal of Composites for Construction, 20(3) (2015) 04015067.
[16]  R.Z. Al-Rousan, M.A. Issa, The effect of beam depth on the shear behavior of reinforced concrete beams externally strength- ened with carbon fiber–reinforced polymer composites, Advanc- es in Structural Engineering, 19(11) (2016) 1769-1779.
[17]  K. ŞENGÜN, G. ARSLAN, INFLUENCE OF CFRP ON THE STRENGTH OF RETROFITTED RC BEAMS WITH- OUT STIRRUPS, Sigma, 35(1) (2017) 77-85.
[18]  H. Naderpour, S. Alavi, A proposed model to estimate shear contribution of FRP in strengthened RC beams in terms of Adap- tive Neuro-Fuzzy Inference System, Composite Structures, 170 (2017) 215-227.
[19]  W.-F. Chen, D.-J. Han, Plasticity for structural engineers, J. Ross Publishing, 2007.
[20]  E.A. Sumner, Unified design of extended end-plate moment connections subject to cyclic loading, Virginia Tech, 2003.
[21]  T. Jankowiak, T. Lodygowski, Identification of parameters of concrete damage plasticity constitutive model, Foundations of civil and environmental engineering, 6(1) (2005) 53-69.
[22]  W. Van Paepegem, J. Degrieck, Calculation of damage-de- pendent directional failure indices from the Tsai–Wu static failure criterion, Composites science and technology, 63(2) (2003) 305- 310.
نشریه مهندسی عمران امیرکبیر
دوره 51، شماره 3
مرداد و شهریور 1398
صفحه 465-478

فایل ها

هم رسانی

ارجاع به این مقاله

آمار