Title:
Evaluating Seismic Provisions for FRP-Reinforced Circular Columns (Prepublished)
Author(s):
Jahanzaib and Shamim A. Sheikh
Publication:
Structural Journal
Volume:
Issue:
Appears on pages(s):
Keywords:
code provisions; drift capacity; ductility; FRP; moment capacity; seismic performance; steel
DOI:
10.14359/51750572
Date:
2/27/2026
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 CODE-318-19, CSA A23.3-24, CSA S806-12, 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 (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 about 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 a substantial increase in moment capacity (Mmax) compared to 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 probable moment to calculate the shear demand still remains questionable and requires more analytical investigations.