Bulletin of Earthquake Science and Engineering

Bulletin of Earthquake Science and Engineering

Experimental Evaluation of the Performance of Temporary Strengthening Systems for Earthquake-Damaged Reinforced Concrete Columns

Document Type : Research Article

Authors
Mohamad Reza Shokrzadeh 1
Fariborz Nateghi-Alahi 2
1 Postdoctoral Fellow, International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran
2 rofessor, Structural Engineering Research, International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran
10.48303/bese.2026.2080755.1254
Abstract
Following an earthquake, damaged reinforced concrete (RC) columns, as primary vertical load-bearing components, can influence the residual stability of buildings and the safety of post-earthquake operations. In damaged structures, access is often required for emergency response, preliminary inspection, damage assessment, and initial stabilization measures. Under such conditions, conventional permanent repair or strengthening techniques may not be suitable because they can require preparation time, wet construction processes, adhesive materials, or on-site welding. Therefore, temporary strengthening systems that can be rapidly installed through dry mechanical connections and subsequently removed after the emergency, inspection, and initial stabilization stages can provide a practical alternative for restoring a level of structural safety.
This study experimentally evaluates the cyclic performance of three temporary strengthening systems based on mechanically assembled bolted steel jackets for severely earthquake-damaged RC columns. For this purpose, one-third-scale RC column specimens were first subjected to quasi-static cyclic loading until a severe level of damage was developed. The damaged specimens were then temporarily strengthened using three different steel-jacket configurations.
The first system consisted of a bolted steel jacket equipped with energy-dissipating plates intended to enhance hysteretic energy dissipation while limiting further damage concentration. The second configuration incorporated a corrugated steel sheet within the jacket system, whereas the third configuration employed a steel jacket combined with a lateral knee brace. All strengthening systems were designed to be installed without concrete casting, bonding agents, or on-site welding, thereby facilitating rapid assembly and potential removal after completion of the temporary intervention.
Following installation, the strengthened specimens were re-tested under cyclic lateral loading in combination with a constant axial load to assess their post-damage structural response. The experimental results indicate that all three temporary strengthening systems improved the behavior of the damaged RC columns under repeated cyclic loading. In particular, the jackets reduced the concentration of damage within the plastic hinge region, restrained buckling of the longitudinal reinforcement, and enhanced the cyclic stability of the previously damaged specimens. The results further showed that the three configurations did not provide identical structural benefits. Among the investigated systems, the steel jacket equipped with energy-dissipating plates demonstrated the most favorable performance in maintaining effective stiffness and increasing energy dissipation capacity during cyclic loading. By contrast, the corrugated-sheet and knee-brace configurations showed comparatively greater effectiveness in improving confinement of the core concrete and maintaining stability at large displacement demands. These differences indicate that the response of temporarily strengthened columns depends on the mechanical characteristics and load-transfer mechanism of the selected jacket configuration.
The findings demonstrate the feasibility of using mechanically connected steel-jacket systems as temporary post-earthquake strengthening solutions for severely damaged RC columns. Their rapid installation, dry assembly, avoidance of field welding and adhesive materials, and removability after the emergency stage make them particularly relevant where immediate structural stabilization is required before detailed assessment or permanent rehabilitation. The study, therefore, supports the use of temporary steel strengthening as a practical strategy for improving the short-term safety, cyclic stability, and residual functionality of earthquake-damaged RC columns during emergency response and early recovery operations.
Keywords
Temporary Strengthening
Earthquake-Damaged RC Columns
Mechanical Steel Jacket
Cyclic Behavior
Energy Dissipation
Subjects
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  • Receive Date 13 December 2025
  • Revise Date 15 May 2026
  • Accept Date 24 May 2026