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Behavior of RC beams strengthened with NSM CFRP strips under flexural repeated loading

  • 투고 : 2018.06.17
  • 심사 : 2019.02.08
  • 발행 : 2019.04.10

초록

Strengthening with near surface mounted carbon fibre reinforced polymers (NSM-CFRP) is a strengthening technique that have been used for several decades to increase the load carrying capacity of reinforced concrete members. In Iraq, many concrete buildings and bridges were subjected to a wide range of damage as a result of the last war and many other events. Accordingly, there is a progressive increase in the strengthening of concrete structures, bridges in particular, by using CFRP strengthening techniques. Near-surface mounted carbon fibre polymer has been recently proved as a powerful strengthening technique in which the CFRP strips are sufficiently protected against external environmental conditions especially the high-temperature rates in Iraq. However, this technique has not been examined yet under repeated loading conditions such as traffic loads on bridge girders. The main objective of this research was to investigate the effectiveness of NSM-CFRP strips in reinforced concrete beams under repeated loads. Different parameters such as the number of strips, groove size, and two types of bonding materials (epoxy resin and cement-based adhesive) were considered. Fifteen NSM-CFRP strengthened beams were tested under concentrated monotonic and repeated loadings. Three beams were non-strengthened as reference specimens while the remaining were strengthened with NSM-CFRP strips and divided into three groups. Each group comprises two beams tested under monotonic loads and used as control for those tested under repeated loads in the same group. The experimental results are discussed in terms of load-deflection behavior up to failure, ductility factor, cumulative energy absorption, number of cycles to failure, and the mode of failure. The test results proved that strengthening with NSM-CFRP strips increased both the flexural strength and stiffness of the tested beams. An increase in load carrying capacity was obtained in a range of (1.47 to 4.49) times that for the non-strengthened specimens. Also, the increase in total area of CFRPs showed a slight increase in flexural capacity of (1.02) times the value of the control strengthened one tested under repeated loading. Increasing the total area of CFRP strips resulted in a reduction in ductility factor reached to (0.71) while the cumulative energy absorption increased by (1.22) times the values of the strengthened reference specimens tested under repeated loading. Moreover, the replacement of epoxy resin with cement-based adhesive as a bonding material exhibited higher ductility than specimen with epoxy resin tested under monotonic and repeated loading.

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참고문헌

  1. ACI Committee 318 (2014), Building Code Requirements for Structural Concrete, (ACI 318M-14) and Commentary (318R14), Farmington Hills, Michigan, U.S.A.
  2. ACI Committee 440 (2008), Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures, American Concrete Institute, Farmington Hills, Michigan, U.S.A.
  3. Aidoo, J., Harries, K.A. and Petrou, M.F. (2004), "Fatigue behavior of carbon fibre reinforced polymer-strengthened reinforced concrete bridge girders", J. Compos. Constr., 8(6), 501-509. https://doi.org/10.1061/(ASCE)1090-0268(2004)8:6(501)
  4. Al-Abdwais, A. and Al-Mahaidi, R. (2016), "Bond behavior between NSM CFRP laminate and concrete using modified cement-based adhesive", Constr. Build. Mater., 127(1), 284-292. https://doi.org/10.1016/j.conbuildmat.2016.09.142
  5. Al-Abdwais, A.H. and Al-Mahaidi, R.S. (2017), "Bond properties between carbon fibre reinforced polymer (CFRP) textile and concrete using modified cement-based adhesive", Constr. Build. Mater., 154, 983-992. https://doi.org/10.1016/j.conbuildmat.2017.08.027
  6. Al-Mahmoud, F., Castel, A., Francois, R. and Tourneur, C. (2009), "Strengthening of RC members with near surface mounted CFRP rods", Compos. Struct., 91(2), 138-147. https://doi.org/10.1016/j.compstruct.2009.04.040
  7. ASTM C 39/C 39M (2005), Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens, Annual Book of ASTM Standard.
  8. ASTM C 78 (2002), Standard Test Method for Flexural Strength of Concrete (Using Simple Beam with Third-Point Loading).
  9. ASTM C109-02 (2002), Standard Test Method for Compressive Strength of Hydraulic Cement Mortar, Annual Book of ASTM Standard.
  10. ASTM C496/C496M (2011), Standard Test Method for Splitting Tensile Strength of Cylindrical Concrete Specimens, ASTM International, West Conshohocken, Pennsylvania, U.S.A.
  11. Balaguru, P., Nanni, A. and Giancaspro, J. (2008), FRP Composites for Reinforced and Prestressed Concrete Structures: A Guide to Fundamentals and Design for Repair and Retrofit, CRC Press.
  12. British Standards Institution Part 2-Concrete (1997), Methods for Specifying Concrete Mixes, BS1881: Part 116 (1989), Method for Determination of Compressive Strength of Concrete Cubes, British Standards Institution.
  13. Carolin, A., Nordin, H. and Taljste, B. (2001), "Concrete beams strengthened with near surface mounted reinforcement of CFRP", Proceedings of the International Conference on FRP Composites in Civil Engineering.
  14. De Lorenzis, L., Nanni, A. and La Tegola, A. (2000), "Strengthening of reinforced concrete structures with near surface mounted FRP rod", International Meeting on Composite Materials, Proceedings, Advancing with Composites, Milan, Italy, May.
  15. Dezhangah, M. and Sepehrinia, M. (2018), "The effects of different Frp/concrete bond-slip laws on the 3D nonlinear FE modeling of retrofitted RC beams-a sensitivity analysis", Steel Compos. Struct., 26(3), 347-360. https://doi.org/10.12989/SCS.2018.26.3.347
  16. Ghafoori, N. (2009), Challenges, Opportunities and Solutions in Structural Engineering and Construction, CRC Press.
  17. Hadi, A., Raheem, A. and Al-Abdwais, A. (2014), "Strengthening of concrete structure with near surface mounted carbon fibre reinforced polymer and cement based adhesive", Ph.D. Dissertation, Swinburne University of Technology, Australia.
  18. Hashemi, S. and Al-Mahaidi, R. (2008), "Cement based bonding material for FRP strengthening of concrete structures", Proceedings of the 11th Conference on International Inorganicbonded Fibre Composites.
  19. Hong, S.N. and Park, S.K. (2016), "Energy dissipation capacity of reinforced concrete beams strengthened with CFRP strips", Mech. Compos. Mater., 52(2), 231-242. https://doi.org/10.1007/s11029-016-9576-1
  20. Liang, J.F., Yu, D., Xie, S. and Li, J. (2017), "Flexural behaviour of reinforced concrete beams strengthened with NSM CFRP prestressed prisms", Struct. Eng. Mech., 62(3), 291-295. https://doi.org/10.12989/sem.2017.62.3.291
  21. Maalej, M. and Leong, K.S. (2005), "Engineered cementitious composites for effective FRP-strengthening of RC beams", Compos. Sci. Technol., 65(7), 1120-1128. https://doi.org/10.1016/j.compscitech.2004.11.007
  22. Panjehpour, M., Abang, A., Abang, A. and Aznieta, F.N. (2014), "Energy absorption of reinforced concrete deep beams strengthened with CFRP sheet", Steel Compos. Struct., 16(5), 481-489. https://doi.org/10.12989/scs.2014.16.5.481
  23. Rakhshanimehr, M., Esfahani, M.R., Kianoush, M.R., Mohammadzadeh, B.A. and Mousavi, S.R. (2014), "Flexural ductility of reinforced concrete beams with lap-spliced bars", Can. J. Civil Eng., 41(7), 594-604. https://doi.org/10.1139/cjce-2013-0074
  24. Sena-Cruz, J.M., Barros, J.A., Coelho, M.R. and Silva, L.F. (2012), "Efficiency of different techniques in flexural strengthening of RC beams under monotonic and fatigue loading", Constr. Build. Mater., 29, 175-182. https://doi.org/10.1016/j.conbuildmat.2011.10.044
  25. Sharaky, I.A., Torres, L., Comas, J. and Barris, C. (2014), "Flexural response of reinforced concrete (RC) beams strengthened with near surface mounted (NSM) fibre reinforced polymer (FRP) bars", Compos. Struct., 109, 8-22. https://doi.org/10.1016/j.compstruct.2013.10.051
  26. Soliman, S.M., El-Salakawy, E. and Benmokrane, B. (2010), "Bond performance of near-surface-mounted FRP bars", J. Compos. Constr., 15(1), 103-111. https://doi.org/10.1061/(ASCE)CC.1943-5614.0000150