Report No.: CCEER-10-5
Title: Post-Earthquake Evaluation and Emergency Repair of Damaged RC Bridge Columns Using CFRP Materials
Authors: Vosooghi, A., and Saiidi, M.
Date: September 2010
Sponsoring Agency: California Department of Transportation (Caltrans)
Department of Civil Engineering/258
University of Nevada, Reno
Reno, NV 89557
The main objective of the study was to develop a rapid and effective repair method using carbon fiber reinforced polymer (CFRP) materials for earthquake-damaged reinforced concrete bridge columns. This study consisted of three main phases.
In the first phase, a data base of 33 test columns was developed and analyzed and five distinct apparent seismic damage states were defined. The damage states were correlated to measured seismic response parameters in terms of drift, frequency, strains, and yield and ultimate displacements. Fragility curves were developed and applied for two case studies in performance-based design (PBD) and performance-based assessment (PBA) of bridge columns.
Comprehensive experimental and analytical studies were conducted in the second phase of the study. Two standard single columns, one standard two-column bent, and two substandard columns were tested on a shake table, repaired using CFRP fabrics, and retested on the shake table to evaluate the proposed repair procedure. The measured data were extensively analyzed to investigate the performance of the repaired columns compared to the original column responses. It was concluded that the strength and ductility of the standard columns were successfully restored and those of sub-standard columns were upgraded to the current seismic standards after the repair. However, the stiffness was not restored due to material degradation during the original column tests. Even though the repair process was done rapidly and was treated as "emergency" repair with implication that it was a temporary measure, it can be treated as a permanent repair as long as the stiffness of repaired columns is sufficient for non-seismic loading. In the analytical studies, extensive static and dynamic nonlinear analyses were performed on the column models and a simple analytical method was developed for the repaired columns to account for stiffness degradation.
Based on the results from the experimental and analytical studies, repair design recommendations were developed in the third phase to aid bridge engineers in quickly designing the number of layers of CFRP layers based on the apparent damage and basic information about the column fixity, size, and reinforcement.