Title:
Evaluating Seismic Provisions for Fiber-Reinforced Polymer-Reinforced Circular Columns
Author(s):
Jahanzaib and Shamim A. Sheikh
Publication:
Structural Journal
Volume:
123
Issue:
4
Appears on pages(s):
261-277
Keywords:
code provisions; drift capacity; ductility; fiber-reinforced polymer (FRP); moment capacity; seismic performance; steel
DOI:
10.14359/51750572
Date:
7/1/2026
Abstract:
This study evaluates the seismic performance of circular columns reinforced with fiber-reinforced polymer (FRP) bars, focusing on the efficacy of existing code provisions (ACI 318-19, CSA A23.3-24, CSA S806-12, and CSA S6-25) in predicting drift and moment capacities. A database of 38 full-scale columns tested under lateral cyclic loading with varying axial load levels, spiral pitches, and reinforcement types (glass fiber-reinforced polymer [GFRP]/steel longitudinal bars) was analyzed to assess code provisions, confinement effectiveness, and strength enhancements. Results demonstrate that CSA S6-25, which incorporates updated FRP compressive strain limits (0.008Ef for spirals), outperformed other codes, aligning with approximately 85% of experimental data in ideal performance quadrants. Close spiral pitch (≤75 mm [2.95 in.]) and low axial loads were critical to achieving drift ratios ≥3% and moment capacity ratios (Mmax/Mo) exceeding 2.0. Replacing steel spirals with GFRP spirals did not result in substantial variation in the seismic performance of columns. Columns with GFRP longitudinal bars exhibited comparable ductility and observed substantial increase in moment capacity (Mmax) compared to the unconfined nominal moment capacity (Mo) due to delayed bar buckling under effective confinement. However, columns with GFRP longitudinal bars observed a softer response, and the determination of the probable moment to calculate the shear demand remains questionable and requires more analytical investigations.
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