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.