Title:
Flexural Stiffness of GFRP- and CFRP-RC Circular Members under Eccentric Loads Based on Experimental and Curvature Analysis
Author(s):
Abdeldayem Hadhood, Hamdy M. Mohamed, and Brahim Benmokrane
Publication:
Structural Journal
Volume:
115
Issue:
4
Appears on pages(s):
1185-1198
Keywords:
circular; columns; curvature; design; fiber-reinforced polymer bars; model; moment; stiffness
DOI:
10.14359/51702235
Date:
7/1/2018
Abstract:
Current North American codes and fiber-reinforced polymer (FRP) design guidelines do not yet have design provisions for columns for reasons such as the lack of research and experimental results on such elements. One of the most required yet still missing parts of ACI 440 related to fiber-reinforced polymer-reinforced concrete (FRP-RC) design is the determination of relative flexural stiffness of members under combined flexural and axial loads. The analysis and design of RC structures pertain to the relative stiffness of their members (columns and beams), as well as the assumed effective flexural stiffness values (EIe). This study integrated the results of full-scale experiments into a developed analytical model to originally establish moment-curvature responses and estimate the relative stiffness at different load levels. The analytical modeling adopted the layer-by-layer approach to integrate stresses over the cross-sectional areas. The model accounts for the second-order effect and FRP properties. The experimental program included results of full-scale circular members reinforced with glass and carbon FRP (GFRP and CFRP) bars tested at different levels of eccentricity. Five eccentricity-to-diameter ratios were applied (0%, 8.2%, 16.4%, 32.8%, and 65.6%). Moment-curvature relationships were analytically constructed and compared to the experimental results. This study predominantly worked on several expressions to estimate the relative stiffness and compared them to experimental results. The ACI 318 code provisions on the stiffness are reviewed, discussed, and considered as a reference for a rapid, streamlined adoption in future FRP codes. Modified ACI 318 equations to determine the relative flexural stiffness at ultimate load levels for GFRP- and CFRP-RC members are proposed.
Related References:
ACI Committee 318, 2014, “Building Code Requirements for Structural Concrete (ACI 318-14) and Commentary (ACI 318R-14),” American Concrete Institute, Farmington Hills, MI, 520 pp.
ACI Committee 440, 2015, “Guide for the Design and Construction of Concrete Reinforced with FRP Bars (ACI 440.1R-15),” American Concrete Institute, Farmington Hills, MI, 88 pp.
Ali, A. H.; Mohamed, H. M.; and Benmokrane, B., 2017, “Shear Strength of Circular Concrete Beams Reinforced with Glass Fiber-Reinforced Polymer Bars and Spirals,” ACI Structural Journal, V. 114, No. 1, Jan.-Feb., pp. 39-49.
ASTM D7205/D7205M-06(2011), 2011, “Standard Test Method for Tensile Properties of Fiber Reinforced Polymer Matrix Composite Bars,” ASTM International, West Conshohocken, PA, 13 pp.
Afifi, M. Z.; Mohamed, H. M.; Chaallal, O.; and Benmokrane, B., 2014, “Confinement Model for Concrete Columns Internally Confined with Carbon FRP Spirals and Hoops,” Journal of Structural Engineering, ASCE, V. 141, No. 9, Sept., pp. 1-10.
Afifi, M. Z.; Mohamed, H. M.; and Benmokrane, B., 2015, “Theoretical Stress-Strain Model for Circular Concrete Columns Confined by GFRP Spirals and Hoops,” Journal of Engineering Structures, V. 102, Aug., pp. 202-213. doi: 10.1016/j.engstruct.2015.08.020
CAN/CSA S806-12, 2012, “Design and Construction of Building Components with Fiber Reinforced Polymers,” Canadian Standards Association, Mississauga, ON, Canada, 208 pp.
Chen, W. F., and Atsuta, T., 1976, Theory of Beam-Columns, Volume 1: In-Plane Behavior and Design, J. Ross Publishing.
Hadhood, A.; Mohamed, H. M.; and Benmokrane, B., 2017a, “Failure Envelope of Circular Concrete Columns Reinforced with Glass Fiber-Reinforced Polymer Bars and Spirals,” ACI Structural Journal, V. 114, No. 6, Nov.-Dec., pp. 1417-1428. doi: 10.14359/51689498
Hadhood, A.; Mohamed, H. M.; and Benmokrane, B., 2017b, “Experimental Study of Circular High-Strength Concrete Columns Reinforced with GFRP Bars and Spirals under Concentric and Eccentric Loading,” Journal of Composites for Construction, V. 21, No. 2, Apr., pp. 1-10.
Hadhood, A.; Mohamed, H. M.; Ghrib, F.; and Benmokrane, B., 2017c, “Efficiency of Glass-Fiber Reinforced-Polymer (GFRP) Discrete Hoops and Bars in Concrete Columns under Combined Axial and Flexural Loads,” Journal of Composites: Part B, V. 114, pp. 223-236. doi: 10.1016/j.compositesb.2017.01.063
Hadhood, A.; Mohamed, H. M.; and Benmokrane, B., 2017d, “Axial Load-Moment Interaction Diagram of Circular Concrete Columns Reinforced with CFRP Bars and Spirals: Experimental and Theoretical Investigations,” Journal of Composites for Construction, V. 21, No. 2, Apr., pp. 1-10.
Hadhood, A.; Mohamed, H. M.; and Benmokrane, B., 2017e, “Strength of Circular HSC Columns Reinforced Internally with Carbon-Fiber-Reinforced Polymer Bars under Axial and Eccentric Loads,” Construction and Building Materials, V. 141, pp. 366-378. doi: 10.1016/j.conbuildmat.2017.02.117
Harik, I. E., and Gesund, H., 1986, “Reinforced Concrete Columns in Biaxial Bending,” Concrete Framed Structures—Stability and Strength, Elsevier Science Publishers, pp. 111-132.
Hognestad, E., 1952, “A Study of Combined Bending and Axial Force in Reinforced Concrete Specimens,” PhD dissertation, University of Illinois Urbana-Champaign, Champaign, IL.
Kent, D. C., and Park, R., 1971, “Flexural Members with Confined Concrete,” Journal of the Structural Division, ASCE, V. 7, pp. 1969-1990.
Khuntia, M., and Ghosh, S. K., 2004a, “Flexural Stiffness of Reinforced Concrete Columns and Beams: Analytical Approach,” ACI Structural Journal, V. 101, No. 3, May-June, pp. 351-363.
Khuntia, M., and Ghosh, S. K., 2004b, “Flexural Stiffness of Reinforced Concrete Columns and Beams: Experimental Verification,” ACI Structural Journal, V. 101, No. 3, May-June, pp. 364-374.
Lloyd, N. A., and Rangan, B. V., 1996, “Studies on High-Strength Concrete Columns under Eccentric Compression,” ACI Structural Journal, V. 93, No. 6, Nov.-Dec., pp. 631-638.
Mander, J. B.; Priestley, J. N.; and Park, R., 1988, “Theoretical Stress-Strain Model for Confined Concrete,” Journal of Structural Engineering, ASCE, V. 114, No. 8, pp. 1804-1826. doi: 10.1061/(ASCE)0733-9445(1988)114:8(1804)
Mehanny, S. S. F.; Kuramoto, H.; and Deierlein, G. G., 2001, “Stiffness Modeling of RC Beam-Columns for Frame Analysis,” ACI Structural Journal, V. 98, No. 2, Mar.-Apr., pp. 215-225.
Mirza, S. A., 1990, “Flexural Stiffness of Rectangular RC Columns,” ACI Structural Journal, V. 87, No. 4, July-Aug., pp. 425-435.
Mohamed, H. M., and Benmokrane, B., 2015, “Torsion Behavior of Concrete Beams Reinforced with Glass Fiber-Reinforced Polymer Bars and Stirrups,” ACI Structural Journal, V. 112, No. 5, Sept.-Oct., pp. 543-552. doi: 10.14359/51687824
Popovics, S., 1973, “A Numerical Approach to the Complete Stress-Strain Curve of Concrete,” Cement and Concrete Research, V. 3, No. 5, pp. 583-599. doi: 10.1016/0008-8846(73)90096-3
Quast, U., 1970, “Suitable Simplifications for the Solution of the Load-Bearing Problem of the Prismatic Reinforced Concrete Support with Rectangular Cross-Section,” Dr.-Ing. dissertation, Faculty of Civil Engineering, Technical University of Carolo-Wilhelmina, Braunschweig, 123 pp.
Zadeh, H. J., and Nanni, A., 2013, “Design of RC Columns using Glass FRP Reinforcement,” Journal of Composites for Construction, ASCE, V. 17, No. 3, pp. 294-304. doi: 10.1061/(ASCE)CC.1943-5614.0000354
Zadeh, H. J., and Nanni, A., 2017, “Flexural Stiffness and Second-Order Effects in Fiber-Reinforced Polymer-Reinforced Concrete Frames,” ACI Structural Journal, V. 114, No. 2, Mar.-Apr., pp. 533-544. doi: 10.14359/51689257