Title:
Drift Capacity of Reinforced-Concrete Columns Strengthened with Post-Tensioned External Clamps (Prepublished)
Author(s):
Julian D. Rincon, Santiago Pujol, Yu-Mei Chen, Aishwarya Y. Puranam, Shyh-Jiann Hwang, and Yo Hibino
Publication:
Structural Journal
Volume:
Issue:
Appears on pages(s):
Keywords:
drift capacity; external post-tensioned clamps; lateral prestress; RC columns; retrofit
DOI:
10.14359/51751796
Date:
6/17/2026
Abstract:
This article presents results from ten tests on reinforced concrete (RC) columns strengthened with post-tensioned clamps. The test columns were subjected to displacement reversals at increasing drift ratios and approximately constant axial loads. The transverse reinforcement consisted of post-tensioned clamps made of steel angles and high-strength steel rods. A key feature of the proposed clamps is their capacity to provide active confinement by exerting lateral pressure, which can delay concrete cover spalling, crushing, and the formation of inclined shear cracks. The test results showed the effectiveness of the clamps in enhancing both shear strength and drift capacity. This paper focuses on measured drift capacities, which are compared with drift capacities listed in a database of conventional RC columns compiled by ACI Committee 369, Seismic Repair and Rehabilitation. The comparison is made using existing empirical equations and a machine-learning algorithm calibrated to estimate the drift capacity of conventional RC columns without lateral prestress. Consistently, the results suggested that columns with post-tensioned clamps had drift capacities exceeding estimates obtained for similar columns reinforced with conventional ties. The proposed clamps offer a practical alternative for mitigating the seismic vulnerability of older RC columns with insufficient transverse reinforcement. Their ease of design and implementation makes them a feasible retrofit and repair solution, especially for mass retrofitting efforts and emergency repairs after strong ground motion.