Case Study on the Restoration of Flexural Capacity of Continuous One-Way RC Slabs with Cutouts
Publication: Journal of Composites for Construction
Volume 15, Issue 6
Abstract
Introducing openings in existing reinforced concrete (RC) slabs can severely weaken the slabs because of the cut out of the concrete and reinforcing steel. This paper reports field tests on the use of carbon fiber-reinforced polymer (CFRP) composite strengthening techniques to restore the flexural capacity of RC slabs after having openings cut out in the positive moment region. The uniqueness of this study is that the tests were performed on an existing multistory RC building that was scheduled for demolition. Five tests on five different slabs were conducted using three different strengthening techniques—namely, externally bonded (EB) CFRP plates, EB CFRP plates with CFRP anchors, and near-surface mounted (NSM) CFRP strips—to determine the most effective system for strengthening. Test results showed that the three strengthening techniques increased the load-carrying capacity of the slabs with openings, with the NSM technique being more effective than the EB technique. However, the use of CFRP anchors to mechanically anchor the EB plates prevented complete detachment, and hence enabled the restoration of the slab to its full flexural capacity.
Get full access to this article
View all available purchase options and get full access to this article.
Acknowledgments
The writers gratefully acknowledge the contribution of the following people of the Constructed Facilities Laboratory at North Carolina State University, without whom this work would not have been possible: Jerry Atkinson, Joshua Griffin, Gregory Lucier, Chemin Lim, Lee Nelson, Diego Vasquez, and Catrina Walter. The writers also would like to thank Rusty Griffin of D. H. Griffin Companies for providing the opportunity to conduct these tests and the help provided on site, and Fyfe Company LLC for providing the FRP anchors.
References
ACI Committee 437 (2003). “Strength evaluation of existing concrete buildings.” ACI 437.1R-03, American Concrete Institute, Farmington Hills, MI, 28.
ACI Committee 440 (2008). “Guide for the design and construction of externally bonded FRP systems for strengthening concrete structures.” ACI 440.2R-08, American Concrete Institute, Farmington Hills, MI, 76.
ASTM. (2007). “Standard test methods and definitions for mechanical testing of steel products.” A 370-07, ASTM International, West Conshohocken, PA, 47.
ASTM. (2004). “Standard test method for obtaining and testing drilled cores and sawed beams of concrete.” C 42/C 42M-04, ASTM International, West Conshohocken, PA, 6.
Casadei, P., Ibell, T., and Nanni, A. (2003). “Experimental Results of One-Way Slabs with Openings Strengthened with CFRP Laminates.” Proc., Fiber-Reinforced Polymer Reinforcement for Concrete Structures, FRPRCS-6, World Scientific, Singapore, 1097–1106.
Chen, J. F., and Teng, J. H. (2001). “Anchorage strength models for FRP and steel plates bonded to concrete.” J. Struct. Eng., 127(7), 784–791.
Ebead, U., and Marzouk, H. (2004). “Fiber reinforced polymer strengthening of two-way slabs.” ACI Struct. J., 101(5), 650–659.
Enochsson, O., Lundqvist, J., Täljsten, B., Rusinowski, P., and Olofsson, T. (2007). “CFRP-strengthened openings in two-way concrete slabs—an experimental and numerical study.” Constr. Build. Mater., 21(4), 810–826.
Lam, L., and Teng, J. (2001). “Strength of RC cantilever slabs bonded with GFRP strips.” J. Compos. Constr., 5(4), 221–227.
Oehlers, D. J., and Seracino, R. (2004). Design of FRP and steel plated RC structures: Retrofitting beams and slabs for strength, stiffness and ductility, Elsevier, Oxford, UK.
Orton, S. L., Jirsa, J. O., and Bayrak, O. (2008). “Design considerations of carbon fiber anchors.” J. Compos. Constr., 12(6), 608–616.
Seracino, R., Raizal Saifulnaz, M. R., and Oehlers, D. J. (2007). “Generic debonding resistance of EB and NSM plate-to-concrete joints.” J. Compos. Constr., 11(1), 62–70.
Smith, S. T., Hu, S., Kim, S. J., and Seracino, R. (2011). “FRP-strengthened RC slabs anchored with FRP anchors.” Eng. Struct. 33(4), 1075–1087.
Smith, S. T., and Kim, S. J. (2009). “Strengthening of one-way spanning RC slabs with cutouts using FRP composites.” Constr. Build. Mater., 23(4), 1578–1590.
Tan, K., and Zhao, H. (2004). “Strengthening of openings in one-way reinforced concrete slabs using carbon fiber-reinforced polymer systems.” J. Compos. Constr., 8(5), 393–402.
Teng, J. G., Chen, J. F., Smith, S. T., and Lam, L. (2002). FRP-strengthened RC structures, Wiley, Chichester, West Sussex, UK.
Vasquez, A., and Karbhari, V. M. (2003). “Fiber-reinforced polymer composite strengthening of concrete slabs with cutouts.” ACI Struct. J., 100(5), 665–673.
Zhang, H. W., and Smith, S. T. (2012). “FRP-to-concrete joint assemblages anchored with multiple FRP anchors.” Compos. Struct., 94(2), 403–413.
Information & Authors
Information
Published In
Copyright
© 2011 American Society of Civil Engineers.
History
Received: Feb 26, 2010
Accepted: May 23, 2011
Published online: Nov 15, 2011
Published in print: Dec 1, 2011
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.