Keywords: carbon fibres, reinforced concrete, flexure, moment, deflection, flanged.

Although many experimental investigations [1,2,3,4] were conducted on fibre reinforced polymer (FRP) reinforced concrete beams with rectangular section, there has been very little research [4] into the behaviour of concrete flanged beams reinforced with FRP bars which are more widely used in practice than beams with rectangular sections. The ACI guidelines for the design and construction of concrete reinforced with FRP bars [1] stated that the behaviour of reinforced concrete beams with nonrectangular cross-section has yet to be confirmed by experimental results.

This paper presents test results of five concrete beams reinforced with carbon fibre reinforced polymer (CFRP) bars. The test programme included three flanged and two rectangular cross-section beams. In addition, a companion concrete flanged beam reinforced with steel bars is tested for comparison purposes. The amount of CFRP reinforcement used and flange thickness were the main parameters investigated in the test specimens.

It was observed that the crack width in CFRP reinforced concrete flanged beams was greater than that of the companion steel reinforced concrete flanged beam. One CFRP reinforced concrete rectangular beam exhibited concrete crushing failure mode, whereas the other four CFRP reinforced concrete beams failed due to tensile rupture of CFRP bars. The CFRP tensile rupture mode of failure was brittle and accompanied with loud sound, wide cracks and excessive deflections. Flanged beams exhibited higher load capacity than rectangular beams of the same depth and CFRP reinforcement. The amount of CFRP reinforcement had a significant effect on the load capacity of the beams tested. The ACI 440 design guide for FRP reinforced concrete members underestimated the moment capacity of beams failed due to tensile rupture of CFRP bars and reasonably predicted deflections of the beams tested.

A computational analysis for estimating the moment capacity of concrete flanged beams reinforced with FRP bars was developed. The analysis covers the two positions of the neutral axis, i.e. within or below the flange. The experimental moment capacity of the CFRP reinforced concrete beams tested compared favourably with that predicted by the computational analysis.

1

ACI committee 440, "Guide for Design and Construction of Concrete Reinforced with FRP Bars (ACI 440.1R-01)", American Concrete Institute, Farmington Hills, Mich., 41p, 2001.

2

Abdalla, H.A., "Evaluation of Deflection in Concrete Members Reinforced with Fibre Reinforced Polymer (FRP) Bars", Composites Structures, Vol. 56, pp. 63-71, 2002. doi:10.1016/S0263-8223(01)00188-X

3

Engel, R.S., Croyle, M.G. Bakis, C.E. and Nanni, A., "Deflection of Reinforced Concrete Beams Reinforced by Fiber Reinforced Polymer Grid with Various Joint Designs", Fourth International Symposium on Fiber Reinforced polymer Reinforcement for Reinforced Concrete Structures, SP-188, C.W. Dolan, S.H. Rizkall and A. Nanni, ed., American Concrete Institute, Farmington Hills, Mich., pp. 75-85, 1999.

4

Grace, N.F., Soliman, A.K., Abdel-Sayed, G. and Saleh, K.R., "Behavior and Ductility of Simply and Continuous FRP Reinforced Beams", Journal of Composites for Construction, ASCE, Vol. 2, No. 4, pp. 186-194, 1998. doi:10.1061/(ASCE)1090-0268(1998)2:4(186)

purchase the full-text of this paper (price £20)

go to the previous paper
go to the next paper
return to the table of contents
return to the book description
purchase this book (price £135 +P&P)