Experimental investigation on flexural behavior of concrete beams strengthened under constant load by CFRP sheets

Document Type : Research Article


Faculty of Civil Engineering, Yazd University, Yazd, Iran


Today, strengthening of reinforced concrete structures and especially flexural strengthening by fiber reinforced polymers (FRP) is used worldwide as an efficient way. In this study, the existing of a constant load during FRP flexural strengthening versus load removal before strengthening were experimentally investigated and compared. A preload with two different predetermined amounts, one to make the beam cracked elastically and the other to make beam deflected to plastic region, was applied before the strengthening of beam samples. All Externally Bonded Reinforcement In Groove (EBRIG) installed FRP sheets were ruptured during test and no de-bonding was observed. Pre-cracking of beams in unloaded strengthened beams caused a minor decrease in ultimate load capacity of strengthened beams. Also ductility and ultimate deformation was decreased. Flexural strengthened beams under constant load showed better ultimate strength (up to 8%) and also better ductility and energy dissipation ability.It can be concluded that FRP flexural strengthening of beams under constant load is more appropriate than load removal of beams during strengthening. The appropriate amount of load during strengthening must be studied in detail but excessive loading to plastic extents is not appropriate.


Main Subjects

[1] D. Mostofnejad, , Reinforce Concrete Structure, Esfahan, Arkan Publishers, 1 (2015).
[2] M.Eftekhar, Structural PhD Thesis, Investigation on influence of flexural strengthening on behavior of beams retroftted by CFRP sheets, civil engineering department, IUT, (2010).
[3] M.Esfahani and M.Bani jamli, Investigation of flexural strengthening techniques on FRP strengthened Beams, civil engineering and Sustainable Development, Mashhad, Iran , (2013).
[4] D.Mostofnejad and E.Mahmoudabadi, Grooving as Alternative Method of Surface Preparation to Postpone Debonding of FRP Laminates in Concrete Beams, Journal of Composites for Construction,14(6) (2010)804-811.
[5] D.Mostofnejad and M. J. Hajrasouliha, Performance Of Grooving Method To Postpone Debonding Of FRP Sheets In Strengthened Concrete Beams, IJST, Transactions of Civil Engineering, 37(2013) 219-232.
[6] D.Mostofnejad, Shameli, M. ,Performance of EBROG Method under Multilayer FRP Sheets for Flexural Strengthening of Concrete Beams,” Procedia Engineering, 14 (2011) 3176-3182 .
[7] D.Mostofnejad and A.Moghaddasi, Bond effciency of EBR and EBROG methods in different flexural failure mechanisms of FRP strengthened RC beams, Construction and Building Materials, Volume 54,(2014) 605-614.
[8] A. Hosseini and D. Mostofnejad, Experimental Investigations into bond behavior of CFRP sheets attached to concrete using EBR and EBROG techniques, Composites Part:B, V. 51(2013) 130-139.
[9] D.Mostofnejad and K.Khazaei, Effect of GM patterns on ductility and debonding control of FRP sheets in RC strengthened beams, Construction and Building Materials, 93(2015) 110-120.
[10] A. M. Morsey, E. M. El-Tony and M. El-Naggar, Flexural Strengthening of Pre-Damaged Beams Using Embedded CFRP Rods, Alexandria Eng. Journal, Elsevier, 54(2015) 1175-1179.
[11] ASTM E2126-09 , Standard Test Methods for Cyclic Load Test for Shear Resistance of Vertical Elements of the Lateral Force Resisting Systems for Buildings, ASTM International, 11(2018).