Presented By: Taylor Brodbeck, North Carolina State University
Description: Bridges subjected to extreme damage have usually been considered unrepairable and requiring replacement. However, recent studies have shown that a repair technique, called plastic hinge relocation, is capable of restoring the column to its original force and displacement capacities. In this repair, the original plastic hinge is strengthened so that should another large earthquake occur, damage will form above the repair in a previously undamaged section, ensuring a predictable and ductile response. The aim of this research is to improve the constructability and performance of the plastic hinge relocation repair using a steel jacket. Experimental tests were conducted on RC columns subjected to reverse cyclic loading which were repaired and re-tested. To reduce the construction time of the repair, reinforcing bars and couplers were pre-embedded in the footing allowing for additional reinforcing steel to be coupled in place at the time of the repair. The steel jacket utilized a bolted connection which simplified construction and was shown to be a suitable alternative to welding when designed as a slip-critical connection. Previous research has shown that the repair’s response is weakened when bars which fracture in the original plastic hinge debond from the repair. In these tests, anchorage of the fractured bars was improved by increasing the confining pressures by using a larger jacket thickness and bond conditions were improved by replacing the cracked concrete around the fractured bars. This enhanced the seismic resilience of the repaired column, evident by an increase in dissipation of energy and reduction in strength degradation.
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