Repair Method by Reducing Yield Strength for Damaged Steel Frame and Dominant Plastic Failure Mode and Energy Absorption Capacity of Repaired Frame

Abstract

In Japan, a lot of structural damage occurred due to great earthquakes, so a necessity to establish resilience-oriented restoration design method has been discussed. Some repair methods for damaged steel structures proposed in the Japanese restoration technical guideline, but few studies have investigated the seismic performance of the whole repaired frame. In the restoration design for the damaged structures, it is desirable to ensure the formation of collapse mechanisms that have high energy absorption capacity. Therefore, the previous study has proposed a new restoration concept and a repair method by reducing the yield strength of the steel member to control the portion where plastic hinges form in the steel frame. This research aims to evaluate the relationship between the dominant plastic failure mode and the energy absorption capacity of repaired steel frames, and aims to establish the restoration design method considering these factors. This paper investigates the energy absorption capacity of each plastic failure mode of the steel frame, which repaired using the proposed method in a previous study, in relation to reliability indicators of each plastic failure mode. Based on the results of plastic hinge analysis and the energy absorption capacity of steel members, the energy absorption capacity of the repaired frame was calculated for each failure mode. And the reliability indexes of each failure mode were evaluated by reliability analysis FOSM. Furthermore, by comparing these analysis results, the effectiveness of the evaluation of energy absorption capacity of repaired frame using the proposed method have been confirmed.