Punching Shear Resistance of Flat Slabs Strengthened with Near Surface–Mounted CFRP Bars
Publication: Journal of Composites for Construction
Volume 25, Issue 4
Abstract
This paper presents the effectiveness of strengthening slab–column connections against punching shear failure with near surface–mounted (NSM) carbon fiber–reinforced polymer (CFRP) bars. The experimental program consists of preparing and testing eight samples, two control, and six strengthened samples. The main variables of the experiment are the strengthening layout and the cross-sectional area of CFRP bars. The results show that NSM strengthening increases the ultimate load by up to 44%. The strengthening delays the formation of the first crack in concrete, thus maintaining a linear behavior for load–displacement and load–strain curves for a higher level of load. The NSM strengthening increases the flexural stiffness by over 100% and maintains a strong bond with concrete throughout the loading. The flexural strength of the slab increases, which subsequently improves the punching shear capacity. The experimental results are compared with several design codes by modification and implementation of Chen and Li’s method. There is a good agreement between the calculated ultimate capacity of the strengthened samples and the obtained experimental results.
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References
Abdul-Kareem, A. H. 2019. “Punching strengthening of concrete slab–column connections using near surface mounted (NSM) carbon fiber reinforced polymer (CFRP) bars.” J. Eng. Res. Rep. 9 (2): 1–14. https://doi.org/10.9734/jerr/2019/v9i217013.
Abdullah, A., C. G. Bailey, and Z. J. Wu. 2013. “Tests investigating the punching shear of a column–slab connection strengthened with non-prestressed or prestressed FRP plates.” Constr. Build. Mater. 48: 1134–1144. https://doi.org/10.1016/j.conbuildmat.2013.07.012.
Agbossou, A., L. Micheal, M. Lagache, and P. Hamelin. 2008. “Strengthening slabs using externally-bonded strip composites: Analysis of concrete covers on the strengthening.” Composites, Part B 39 (7–8): 1125–1135. https://doi.org/10.1016/j.compositesb.2008.04.002.
Akhundzada, H., T. Donchev, and D. Petkova. 2019. “Strengthening of slab–column connection against punching shear failure with CFRP laminates.” Compos. Struct. 208: 656–664. https://doi.org/10.1016/j.compstruct.2018.09.076.
Akhundzada, H., T. Donchev, D. Petkova, and A. B. Samsoor. 2018. “Influence of the positioning of CFRP laminates for improving punching shear capacity of column-to-slab connections.” ACI Spec. Publ. 327: 18.1–18.8.
Alexander, S. D. B., and S. H. Simmonds. 1992. “Tests of column-flat plate connections.” ACI Struct. J. 89 (5): 495–502.
Azizi, R., and S. Talaeitaba. 2019. “Punching shear strengthening of flat slabs with CFRP on grooves (EBROG) and external rebars sticking in grooves.” Int. J. Adv. Struct. Eng. 11 (1): 79–95. https://doi.org/10.1007/s40091-019-0218-4.
Bilotta, A., F. Ceroni, E. Nigro, and M. Pecce. 2015. “Efficiency of CFRP NSM strips and EBR plates for flexural strengthening of RC beams and loading pattern influence.” Compos. Struct. 124: 163–175. https://doi.org/10.1016/j.compstruct.2014.12.046.
Binici, B., and O. Bayrak. 2005. “Use of fiber-reinforced polymers in slab–column connection upgrades.” ACI Struct. J. 102 (1): 93–102.
BSI (British Standards Institution). 2005. Steel for the reinforcement of concrete—Weldable reinforcing steel—Bar, coil and decoiled product—Specification. BS 4449:2005. London: BSI.
BSI (British Standards Institution). 2013. Testing hardened concrete. Determination of secant modulus of elasticity in compression. BS EN 12390-13. London: BSI.
CEB (Comite European Du Beton). 1996. RC elements under cyclic loading. Lausanne, Switzerland: CEB.
CEB-FIP (Comite European Du Beton-Federation International Du Precontrainte). 1993. Model code 1990. Lausanne, Switzerland: CEB-FIP.
CEN (European Committee for Standardization). 2004. Design of concrete structures—Part 1–1: General rules and rules for buildings. Eurocode 2. Brussels, Belgium: CEN.
Chen, C. C., and C. Y. Li. 2005. “Punching shear strength of reinforced concrete slabs strengthened with glass fiber-reinforced polymer laminates.” ACI Struct. J. 102 (4): 535–542.
De Lorenzis, L., and J. G. Teng. 2007. “Near-surface mounted FRP reinforcement: An emerging technique for strengthening structures.” Composites, Part B 38 (2): 119–143. https://doi.org/10.1016/j.compositesb.2006.08.003.
Elbakry, H. M. F., and S. M. Allam. 2015. “Punching strengthening of two-way slabs using external steel plates.” Alexandria Eng. J. 54 (1): 1207–1218. https://doi.org/10.1016/j.aej.2015.09.005.
El-Salakawy, E. F., M. A. Polak, and K. A. Soudki. 2004. “New shear strengthening technique for concrete slab–column connections.” ACI Struct. J. 100 (3): 297–304.
Erdogan, H., B. Binici, and G. Ozcebe. 2010. “Punching shear strengthening of flat-slabs with CFRP dowels.” Mag. Concr. Res. 62 (7): 465–478. https://doi.org/10.1680/macr.2010.62.7.465.
Esfahani, M. R., M. R. Kianoush, and A. R. Moradi. 2009. “Punching shear strength of interior slab–column connections strengthened with carbon fiber reinforced polymer sheets.” Eng. Struct. 31 (1): 1535–1542. https://doi.org/10.1016/j.engstruct.2009.02.021.
Farghaly, A., and T. Ueda. 2011. “Prediction of punching shear strength of two-way slabs strengthened externally with FRP sheets.” J. Compos. Constr. 15 (2): 181–193. https://doi.org/10.1061/(ASCE)CC.1943-5614.0000177.
FIB (Federation internationale du beton). 2010. FIB model code. Fib model code for concrete structures. Lausanne, Switzerland: FIB.
George, J. P., and R. T. Mohan. 2020. “Punching shear strengthening of flat slabs with external bonded CFRP on grooves (EBROG).” In National Conf. on Structural Engineering and Construction Management, 909–915. Cham, Switzerland: Springer.
Gopinath, S., A. R. Murthy, and H. Patrawala. 2016. “Near surface mounted strengthening of RC beams using basalt fiber reinforced polymer bars.” Constr. Build. Mater. 111 (1): 1–8. https://doi.org/10.1016/j.conbuildmat.2016.02.046.
Harajli, M., and K. A. Soudki. 2003. “Shear strengthening of interior slab–column connections using carbon fiber-reinforced polymer sheets.” J. Compos. Constr. 7 (2): 145–153. https://doi.org/10.1061/(ASCE)1090-0268(2003)7:2(145).
Hassan, T., and S. Rizkalla. 2004. “Bond mechanism of near-surface-mounted fiber-reinforced polymer bars for flexural strengthening of concrete structures.” ACI Struct. J. 101 (6): 830–839.
Kim, Y. J., J. M. Longworth, R. G. Wight, and M. F. Green. 2010. “Punching shear of two-way slabs retrofitted with prestressed or non-prestressed CFRP sheets.” J. Reinf. Plast. Compos. 29 (8): 1206–1223. https://doi.org/10.1177/0731684409103143.
Kinnunen, S., and H. Nylander. 1960. Punching strength of reinforced concrete slabs with shear reinforcement. Transactions No. 158. Stockholm, Sweden: Royal Institute of Technology.
Koppitz, R., A. Kenel, and T. Keller. 2014. “Punching shear strengthening of flat slabs using prestressed carbon fiber-reinforced polymer straps.” Eng. Struct. 76: 283–294. https://doi.org/10.1016/j.engstruct.2014.07.017.
Lawler, N., and M. A. Polak. 2011. “Development of FRP shear bolts for punching shear retrofit of reinforced concrete slabs.” J. Compos. Constr. 15 (4): 591–601. https://doi.org/10.1061/(ASCE)CC.1943-5614.0000188.
Lee, D., and L. Chang. 2013. “Bond of NSM systems in concrete strengthening—Examining design issues of strength, groove detailing and bond-dependent coefficient.” Constr. Build. Mater. 47 (1): 1512–1522. https://doi.org/10.1016/j.conbuildmat.2013.06.069.
Meisami, M. H., D. Mostofinejad, and H. Nakamura. 2013. “Punching shear strengthening of two-way flat slabs using CFRP rods.” Compos. Struct. 99: 112–122. https://doi.org/10.1016/j.compstruct.2012.11.028.
Meisami, M. H., D. Mostofinejad, and H. Nakamura. 2015. “Strengthening of flat slabs with FRP fan for punching shear.” Comp Struct. 119: 305–314. https://doi.org/10.1016/j.compstruct.2014.08.041.
Moe, J. 1961. Shearing strength of reinforced concrete slabs and footings under concentrated loads. Development Dept. Bulletin No. D47. Skokie, IL: Portland Cement Association.
Novidis, D., S. J. Pantazopoulou, and E. Tentolouris. 2007. “Experimental study of bond of NSM-FRP reinforcement.” Constr. Build. Mater. 21 (8): 1760–1770. https://doi.org/10.1016/j.conbuildmat.2006.05.054.
Ruiz, M. F., A. Muttoni, and J. Kunz. 2011. “Strengthening of flat slabs against punching shear using post-installed shear reinforcement.” ACI Struct. J. 107 (4): 434–442.
Seo, S. Y., L. Feo, and D. Hui. 2013. “Bond strength of near surface-mounted FRP plate for retrofit of concrete structures.” Compos. Struct. 95 (1): 719–727. https://doi.org/10.1016/j.compstruct.2012.08.038.
Sissakis, K., and S. A. Sheikh. 2007. “Strengthening concrete slabs for punching shear with carbon fiber-reinforced polymer laminates.” ACI Struct. J. 104 (1): 49–59.
Wahab, N., K. A. Soudki, and T. Topper. 2011. “Mechanism of bond behavior of concrete beams strengthened with near-surface-mounted CFRP rods.” J. Compos. Constr. 15 (1): 85–92. https://doi.org/10.1061/(ASCE)CC.1943-5614.0000146.
WEBER. 2021. “Moisture-tolerant epoxy adhesive for structural bonding application.” Accessed May 20, 2019. https://www.uk.weber/files/gb/202009/02.020A%20webertec%20EP%20structural%20adhesive.pdf.
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Published In
Journal of Composites for Construction
Volume 25 • Issue 4 • August 2021
Copyright
© 2021 American Society of Civil Engineers.
History
Received: Jan 7, 2020
Accepted: Apr 21, 2021
Published online: Jun 9, 2021
Published in print: Aug 1, 2021
Discussion open until: Nov 9, 2021
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