IJE TRANSACTIONS C: Aspects Vol. 28, No. 3 (March 2015) 350-359   

downloaded Downloaded: 104   viewed Viewed: 2008

A. A. Maghsudi and Y. Askari D.
( Received: August 31, 2014 – Accepted: January 30, 2015 )

Abstract    Based on the bending experiment for two-span continuous post-tension beams with unbounded tendons and externally applied CFRP sheets, the analysis of the stress increment of unbonded tendons is monitored in the loading process. Since self-compacting concrete (SCC) is a suitable innovation,, understanding the implementation of this type of concrete on the ultimate unbonded tendon stress is critical. For these aims, results of four continuous un-bonded post-tensioned I-beams in two groups were cast and monitored by electrical strain gauges andare presented here. In the first group, the beams (UPN1-12, SUPN1-12) consisted of high strength normal concrete (HSNC), while in the second group (UPS1-12, SUPS1-12) high strength self-compacting concrete (HSSCC) were tested. The beams are made which are compared with the theory proposed by different codes, and a preliminary modification is given for each code equation. The results of standard error of estimate Sy/x , indicates that for two types of HSCs (strengthened and non-strengthened beams), the ACI 318-2011 provides better estimates than AASHTO-2010 model, whereas this model provides better estimates as compared toBS 8110-97.Comparison of increase in experimental ultimate tendon stress of beams indicates that the increase in tendon stress at ultimate state in strengthened beams is lower than that in non-strengthened beams cast with HSCs.


Keywords    Strengthened, CFRP Sheet, Unbonded Tendons, Stress Increases, High Strength Normal and Self-Compacting Concrete, Continuous Beams



اساس آزمایش خمشی صورت گرفته برای تیرهای پس­کشیده سراسری دو دهانه، با کابل بدون پیوستگی و مقاومسازی شده و نشده با الیاف کربن، افزایش تنش در کابل­ها در مراحل مختلف بارگذاری پایش گردیده است. از آنجاکه بتن خودمتراکم، اختراعی مطلوب در صنعت بتن به شمار می­آید، لذا آشنائی با تاثیر این نوع بتن بر افزایش تنش در چنین کابل­هائی امری ضروری است. در مقاله حاضر، آزمایشبارگذاری چهار تیر یپیوسته پس کشیده با مقطع I شکل که در دو گروه مجزا ساختهو با نصب انواع کرنش سنج­های الکتریکیدر حین بارگذاری پایش، و نتایج مربوطهارائهشدهاست. گروه اول، شاملتیرهای (UPN1-12, SUPN1-12) ساخته شده با بتن معمولی مقاومت بالا و گروه دوم شامل تیرهای (UPS1-12, SUPS1-12) ساخته شده با بتن خودمتراکم مقاومت بالا می باشد. همچنین، مقایسه نتایج آزمایشگاهی تیرها با آیین­نامه­های مختلف ارزیابی شده و اصلاح مقدماتی در روابط هر یک از آئین نامه­ها پیشنهاد شده است. نتایج حاصل از تخمین خطای استاندارد (sy/x) نشان داد که آیین­نامهACI318-2011نسبت به آیین­نامه AASHTO-2010 و آیین­نامه AASHTO-2010 نسبت به آیین نامه BS 8110-97 تخمین بهتری از تنش در کابل­های فاقد پیوستگی در حالت نهایی دارد. به علاوه، میزان افزایش تنش در حالت نهایی در تیرهای مقاومسازی شده کمتر از تیرهای مقاومسازی نشده (ساخته شده با بتن مقاومت بالا) می­باشد


1.          Harajli, M.H., Kanj, M., ‘‘Ultimate flexural strength of concrete members prestressed with unbounded tendons”, ACI Structural Journal, Proceedings, Vol. 88, No.5, (1991), 663-671.

2.          Lim, j.H., Moon, J.H., Lee L.H., ‘‘Ultimate stress of unbonded tendon in continuous members”, Magazine of Concrete Research, Vol. 55, No.5, (2003), 461-470.

3.          Ozkul, O., Nassif, H., Tanchan, P. and Harajli, M., “Rational approach for predicting stress in beams with unbonded tendons”, ACI Structural Journal, Vol. 105, No.3, (2008), 338–347.

4.          Yang, K.H., Mun, J.H. , “Flexural capacity and stress in unbonded tendons of post-tensioned lightweight concrete beams”, Journal of Advances in Structural Engineering, Vol. 16, No.7, (2013), 1297-1310.

5.          He,  Z., Liu, Z., “Stresses in external and internal unbonded tendons: unified methodology and design equations”, ASCE Journal of the Structural Division, Vol. 136 , (2010), 1055–1065.

6.          Zhou, W. and Zheng W., ‘‘Unbonded Tendon Stresses in Continuous PostTensioned Beams”., ACI Structural Journal,Vol., 111, No.3,  (2014), 525536.

7.          Maghsoudi, A.A., Arabpour, D.F., ‘‘Application of nanotechnology in self-compacting concrete design”, International Journal of Engineering, Vol. 22, No.3, (2009), 229-244.

8.          PCI Self-Consolidating Concrete FAST Team, ‘‘Interim guidelines for the use of self-consolidating concrete in PCI member plants”, PCI Committee Summary Report, PCI Journal, (2003), 14-18.

9.          Walraven, J., ‘‘Structural aspects of self-compacting concrete. in 3rd international symposium on self-compacting concrete”, Reykjavik, Iceland, (2003), 15-22.

10.       Hashemi, S.H., Rahgozar R., Maghsoudi, A.A., ‘‘Flexural testing of high sttrength reinforced concrete beams strengthened with CFRP sheets”, International Journal of Engineering, Vol. 22, No.2,  (2009), 131-146.

11.       Dehghani, H., Fadaee, M.j., ‘‘Reliabilty-based torsional design of reinforced concrete beams strengthened with CFRP laminate”, International Journal of Engineering, Vol. 26, No.10, (2013), 1103-1110.

12.       Akbarzadeh, h., Maghsoudi, A.A., ‘‘Experimental and analytical investigation of reinforced high strength concrete continuous beams strengthened with fiber reinforced polymer”, Journal of Materials and Design, Vol. 31, (2010), 1130-1147.

13.       ACI 318. ‘‘Building code requirements for structural concrete and commentary”, Michigan (USA), American Concrete Institute, (2011).

14.       Okamura, H. and Ozawa, K., ‘‘Mix-design for self-compacting concrete”, Concrete Library of JSCE, Vol. 25, No.6,  (1995), 107-120.

15.       Domone, PL., ‘‘Self-compacting concrete: an analysis of 11 years of case studies”, Cement and Concrete Composites, Vol. 28, No.2, (2006), 197-208.

16.       Askari, D.Y., Maghsoudi, A.A., ‘‘Monitoring and theoretical losses of post-tensioned indeterminate I-beams”, Magazine of Concrete Research, Vol. 66, No.22, (2014), 1129-1144.

17.       Precast/Prestressed Concrete Institute (PCI), “Interim guidelines for the use of self-consolidating concrete in  precast/prestressed concrete institute member plants”, TR-6-03. PCI, Chicago, Illinois, (2003).

18.       AASHTO, “LRFD bridge design specifications”, American Association of State Highway and Transportation Officials, 16. Washington, D.C., (2010).

19.       BS 8110, ‘‘Structural use of concrete”, Part 1, British Standards Institution, London, UK, (1997).

20.       Mattock, A.H., Yamazaki. J., Kattula, B.T., ‘‘Comparative study of prestressed concrete beams, with and without bond", ACI Journal, Proceedings Vol. 68, (1971), 116-125.

21.       Mojtahedi, S., Gamble, W.L., ‘‘Ultimate steel stresses in unbonded prestressed concrete”, Journal of Structural Division, ASCE, Vol. 104, (1978), 1159-1165.

22.       MacGregor, R.J.G., “Strength and ductility of externally post-tensioned segmental box girders”, PhD dissertation, The University of Texas at Austin, (1989).

23.       MacGregor, R.J.G., Kreger, M.E., Breen J.E., “Strength and ductility of a three-span externally post-tensioned segmental box girder bridge model”, Research report no. 365-3F, Center for Transportation Research, The University of Texas at Austin, Austin, (1989).

24.       Pannell, F.N., “Ultimate moment resistance of unbounded prestressed concrete beams”, Magazine of Concrete Research, Vol. 21, (1969), 43-54.

25.       Tam, A., Pannell, F., “The ultimate moment of resistance of unbounded partially prestressed reinforced concrete        beams”, Magazine of Concrete Research, V. 28, (1976), 203-208.

26.       Chapra, Steven, C. and Canale, Raymond, P., ‘‘Numerical methods for engineers”, Second Edition, McGraw-Hill, New York, (1988).

oman";h �bd�g`w� mily: "Times New Roman";mso-bidi-font-weight:bold;mso-no-proof:no'>16.     Baykasoglu,  C.,   Kirca,   M.   and   Mugan,    A.,   “Nonlinear 








failureanalysis of carbon nanotubes by using molecular­mechanics based models” Composites Part B: Engineering, Vol. 50, (2013), 150–157.

17.     Tserpes, K.I. and Papanikos, P., “The effect of Stone–Wales defect on the tensile behavior and fracture of single-walled carbon nanotubes” Composite Structures, Vol. 79, (2007), 581–589.

18.     HosseiniKordkheili, S.A. and Moshrefzadeh-Sani, H., “Mechanical properties of double-layered graphene sheets” Computational Materials Science, Vol. 69, (2013), 335–343.

19.     Nardelli M B, Yakobson B I and Bernholc J,  “Brittle and ductile behavior in carbon nanotubes” Phys. Rev. Lett. 81, (1998), 4656-4659.

20.     Nardelli, M B, Yakobson, B I and Bernholc, J, “Mechanism of strain release in carbon nanotube” Phys. Rev. B, Vol. 57, (1998), 4277-4280.

21.     Banhart, F, “Irradiation effects in carbon nanostructures” Reports on Progress in Physics, Vol. 62, (1999), 1181–221

22.     Zhang, P., Jiang, H., Huang, Y., Geubelle P.H. and Hwang K.C., “An atomistic-based continuum theory for carbon nanotubes: analysis of fracture nucleation” Journal of the Mechanics and Physics of Solids, Vol. 52, (2004), 977–998.

23.     Jiang, H., Feng, X. Q., Huang, Y., Hwang, K.C.and Wu, P.D., “Defect nucleation in carbon nanotubes under tension and torsion: Stone–Wales transformation” Comput. Methods Appl. Mech. Engrg. , Vol.193, (2004), 3419–3429.

24.     Tserpes, K.I., Papanikos, P. and Tsirkas, S.A., “A progressive fracture model for carbon nanotubes” Composites: Part B, Vol. 37, (2006), 662–669.

25.     Xiao, J.R., Staniszewski, J. and Gillespie Jr, J.W., “Fracture and progressive failure of defective graphene sheets and carbon nanotubes” Composite Structures, Vol. 88, (2009), 602–609

26.     Xiao, J.R., Staniszewski, J. and Gillespie, Jr. J.W., “Tensile behaviors of graphene sheets and carbon nanotubes with multiple Stone–Wales defects” Materials Science and Engineering A, Vol. 527, (2010), 715–723.

27.     Broek, D., “Elementary engineering fracture mechanics” Springer, 1982.

28.     Irwin, G. R., “Onset of fast crack propagation in high strength steel and aluminum alloys” Sagamore Research Conference Proceedings, (1956) 289-305.

29.     Stone, AJ. and Wales, D., “Theoretical studies of icosahedral C60 and some related species” ChemPhys Lett, Vol.128, (1986), 501-503.

30.     Chkhartishvili, L. and Berberashvili, T., “Geometrical Model Based Refinements in Nanotube Chiral Indices” World Journal of Nano Science and Engineering, Vol. 1, (2011), 45-50.

31.     Tada, H., Paris, P. C. and  Irwin G. R., “The stress analysis of cracks” handbook 3rd ed, 1973.

32.     Chow, C.L. and  Wang, J., “An anisotropic theory of elasticity for continuum damage mechanics” International Journal of Fracture, Vol. 33, (1987), 3-16.

33.     Li, C. and Chou, T.W., “A structural mechanics approach for the analysis of carbon nanotubes” International Journal of Solids and Structures, Vol. 40, (2003), 2487–2499.

International Journal of Engineering
E-mail: office@ije.ir
Web Site: http://www.ije.ir