Seismic Repair of Circular Reinforced Concrete Bridge Columns by Plastic Hinge Relocation with Grouted Annular Ring

Abstract

ABSTRACT Modern seismic design practice for bridge structures involves the implementation of capacity design principles which localize plastic hinges in columns, while protecting against other modes of failure. The resulting structures are capable of reliably sustaining far greater deformations than their predecessors; however, despite their initial resilience, the formation of plastic hinges can result in buckling and rupture of longitudinal steel, typically leading to the structure’s demolition and reconstruction. Replacement is deemed necessary since the inelastic strain capacity of reinforcing bars severely diminishes once buckling occurs, rendering the structure vulnerable to collapse in future earthquakes. Recent research demonstrates the feasibility of a repair technique in which the previously damaged region is strengthened such that future inelastic action occurs at a new location, although there are presently a limited number of tests on which to base reliable design recommendations. Results of an experimental program are presented in this paper, in which six extensively damaged columns are repaired using the plastic hinge relocation technique and retested. The proposed repair strategy consists of a grouted annular ring composed of conventional materials (i.e. steel rebar, a steel sleeve, and concrete or grout). The results substantiate plastic hinge relocation as a viable repair option for columns with buckled and fractured longitudinal bars and serve to expand the existing data set considerably. A novel analytical model which accurately predicts the behavior of the repaired column is also presented.