Abstract
In this paper, the influence of some important parameters affecting flexural behaviour of reinforced concrete beams strengthened with one layer of CFRP laminate has been studied. For this purpose, six reinforced concrete beams were cast and tested in the laboratory. Based on the obtained data, when CFRP laminate is applied to the tension face, too close to the steel rebar, the flexural strength of the strengthened beam is reduced. In general, the performance of the beam strengthened with one wide CFRP strip is better than that strengthened with two equivalent narrow strips. Ultimate load capacity of each strengthened beam was calculated based on the method given by the ACI 440.2R and compared with the test one. It is concluded that to avoid the steel rebar-CFRP laminate interaction effect, the CFRP laminate depth to the effective depth ratio (df / d) should not be smaller than about 1.17.
References
Täljsten, B., “ CFRP – Strengthening - Concrete Structures Strengthened with Near Surface Mounted CFRP Laminates,†Proceeding of 3rd International Conference on Composites in Infrastructure, San Francisco, California, June 10-12, 2002.
Ganga Rao, H. V. S., and Vijay, P. V., "Bending Behavior of Concrete Beams Wrapped with Carbon Fabric" , J. Struct. Eng., Vol. 124, No. 1, 1993, 3-10.
Duthinh, D. and Starnes, M., "Strengthening of Reinforced Concrete Beams with Carbon FRP", Composites in Constructions, edited by Figueiras et. al., 2001, 493-498.
Ramana, V. P. V., Kant, T., Morton, S. E., Dutta, P. K., Mukherjee, A. and Desai, Y. M., "Behavior of CFRPC Strengthened Reinforced Concrete Beams with Varying Degrees of Strengthening", Composites, Part B 31, 2000, 461-470.
Alagusundaramoorthy , P , Harik , I.E. , and Choo ,C.C , " Flexural Behavior of R/C Beams Strengthened with CFRP Sheets or Fabric ," Research Report KTC -02- 13/SPR 200-99-1F , 2002.
Al-Musallam, T. , " Flexural Strength of Concrete Beams Externally Reinforced with GFRP Sheets ," Proceedings of the Fifth Saudi Engineering Conference, 1999, 117-127.
Mukhopadhyaya, P. , Swamy , N. , and Lynsdale , C. , " Optimizing Structural Response of Beams Strengthened with GFRP Plates ," J. of Composites for Construction , Vol.2 , No. 2 , 1998, 87- 95.
Spandea, G. , Bencardino , F. , and Swamy , R.N. , " Structural Behavior Composite RC Beams with Externally Bonded CFRP ," J. of Composites for Construction , Vol.2 , No. 3 , 1998, 132-137
ASTM Designation C33, Standard Specification for Concrete Aggregates, Annual Book of ASTM Standards, Vol. 04, October 2013.
ASTM Designation C39, Standard Specification for compressive strength of cylindrical concrete specimens, Annual Book of ASTM Standard, Vol. 04, October 2013.
ACI 440.2R, “Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structuresâ€, ACI Committee Report 440.2R-08, 2008.
ACI Committee 318, Building code requirements for structural concrete, American Concrete Institute, Farmington Hills, First Printing, 2015.