Serviceability Response of Rehabilitated Unbonded Post-tensioned Indeterminate I-Beams Consisting UHSSCC

Document Type : Regular Paper


1 Ph.D. Student, Civil Eng. Dept., Shahid Bahonar University of Kerman, Kerman, Iran

2 Professor, Civil Eng. Dept., Shahid Bahonar University of Kerman, Kerman, Iran


The ultra-high strength self-compacting concrete, UHSSCC is the new generation type of concrete with a compressive strength higher than 80MPa. The application of this type of concrete on the serviceability state in CFRP strengthened unbonded post-tensioned indeterminate I-beam is monitored and the results are compared theoretically using different standards. For this aim, full scale I-beam of 9m length was cast, by UHSSCC. During the beam service load test, the stress and strain of materials, and also deflection and crack widths were monitored at different locations using different types of sensors. Based on the experimental measurements and observations, the beam serviceability response was compared theoretically by different methods. As the considerations prepared in the standards do not cover strengthening of such members with unbonded tendons, and also no trace of deflection prediction for such continuous member, one can find in the open literature. It is therefore, this investigation was planned. A comparison between theoretical and monitored results was performed for serviceability response and it was found that although, the stress of materials are well within the standards limitations for crack widths of 0.1 and 0.2 mm of bonded tendon, but the full service load is reached at a higher load, while the flexural crack, experience a width of 0.3 mm. It is also apparent that the loads corresponding to the conventional suggested deflection limits will cause to exceed serviceability state of strengthened unbonded beam, and new limitations are introduced for crack widths of 0.1, 0.2 and 0.3 mm to predict service deflection of beams.


Main Subjects

[1] CEB-FIP Model Code for structures. (1990). “Comite-Euro international du beton/federation internationale de la precomtrainte”.
[2] ACI 209R. (1992). “Prediction of creep, shrinkage and temperature effects in concrete structures”. American Concrete Institute, Farmington Hills, MI, USA.
[3] Rashid, M. A., Mansur, M. A., Paramasivam, P. (2002). “Correlations between Mechanical Properties of High-Strength Concrete”. Journal of Materials in Civil Engineering, Vol. 14, pp. 230-238.
[4] Ghasemi, S., Maghsoudi. A.A., Akbarzadeh.B., H., Ronagh, H.R. (2015). “Sagging and hogging strengthening of continuous unbonded posttensioned HSC beams by NSM and EBR”. Journal of Composite and Construction (ASCE), Vol. 20, pp. 04015056-1-13.
[5] Toutanji, H., Zhao, L., Zhang, Y. (2006). “Flexural behavior of reinforced concrete beams externally strengthened with CFRP sheets bonded with an inorganic matrix”. Engineering Structures, Vol. 28, pp. 557-566.
[6] Xiong, G.J., Jiang, X., Liu, J.W., Chen, L. (2007). “A way for preventing tension delamination of concrete cover in mid-span of FRP strengthened beams”. Construction and Building Materials, Vol. 21, pp. 402–408.
[7] Hashemi, H. (2007). “Study of reinforced high strength concrete strengthened beams by FRP”. PhD. Thesis, Civil Eng. Dept., Shahid Bahonar University of Kerman, Kerman, Iran.
[8] Askari. D.Y., Maghsoudi, A.A. (2014). “Monitoring and theoretical losses of post-tensioned indeterminate I-beams”. Magazine of Concrete Research, Vol. 66, pp. 1-16.
[9] Askari. D.Y., Maghsoudi, A.A., (2014). “Ultimate tendon stress in CFRP strengthened unbonded HSC post-tensioned continuous I-beams”. Journal of Rehabilitation in Civil Engineering, Vol. 2, pp. 35-45.
[10] Maghsoudi, A.A., Askari. D.Y. (2015).  “Ultimate unbonded tendon stress in CFRP strengthened post-tensioned indeterminate I-beams cast with HSCs”. International Journal of Engineering, Transactions C, Vol. 28, pp. 350-359.
[11] PCI. (2003). “Interim guidelines for the use of self-consolidating concrete in precast/prestressed concrete institute member plants”. Chicago, IL, USA.
[12] ACI318R. (2011). “Building code requirements for structural concrete and commentary”. American Concrete Institute, Farmington Hills, MI, USA.
[13] Vu., N.A., Castel., A., François., R. (2010). “Response of post-tensioned concrete beams with unbonded tendons including serviceability and ultimate state”. Engineering Structures, Vol. 32, pp. 556-569.
[14] Fib. (2001). “Externally bonded FRP reinforcement for RC structures”. Technical Report Bulletin 14, Geneva, Switzerland. 
[15] ACI 318R-14. (2014). “Building code requirements for structural concrete and commentary”. American Concrete Institute, Farmington Hills, MI, USA.
[16] ACI 440.2R. (2008). “Guide for the design and construction of externally bonded FRP systems for strengthening concrete structures”. American Concrete Institute, Detroit, MI, USA.
[17] ACI 363R. (2010). “State-of-the-art report on high-strength concrete”. American Concrete Institute, Farmington Hills, MI, USA.
[18] Fib. (2008). “Constitutive modelling of high strength high performance concrete”. Technical Report Bulletin 42, Geneva, Switzerland.
[19] Akbarzadeh B.H., Maghsoudi, A.A. (2009). “Experimental investigations and verification of debonding strain of RHSC continuous beams strengthened in flexure with externally bonded FRPs”. Journal of Materials and Structures, Vol. 43 pp. 815-837.
[20] Pellegrino, C., Modena, C. (2009). “Flexural strengthening of real-scale RC and PRC beams with end-anchored pretensioned FRP laminates”. ACI Structural journal, Vol. 106 pp. 319-328.
[21] BS 8110. (1997). “Structural use of concrete”. Part 1, British Standards Institution, London, UK.