Abstract
Recently, it has been reported that severe disasters cause serious, such as The 1995 Southern Hyogo Prefecture Earthquake and The 2011 off the Pacific coast of Tohoku Earthquake, damage to a lot of building structures. Based on these experiences, there are many discussions about RESILIENCE, REPAIRABILITY and RECOVERY for damaged building structures.
When building structures are designed considering these design concepts, it is necessary to prepare effective repair methods for structural damage which generated by seismic loads, and to establish methods to set objectives of the structural performance of repaired frames.
A lot of past research reported the methods related to seismic retrofitting and reinforcement before suffering from great earthquake disaster, and technical manuals has been published. However, although a technical guideline and design procedure to repair damaged building structures has been published, few studies has reported on investigating the relationship and the recovery of the structural performance after repair. Furthermore, planning method for repairing strategies to actualize objectives of the structural performance after repair has not been reported. When repairing strategies for damaged building structures are planned, it is necessary to verify the influence of repaired members on whole system of the repaired building structure. Although the technical guideline provides repair methods for damaged structural members and general evaluation of the performance recovery of repaired members, No methods to set the objective of the structural performance of the whole system after repair has not been established, and also no effective methods to estimate ultimate behavior and likely collapse modes of repaired building structures subjected to seismic loads are provided
This research focuses on the ultimate limit state of steel frames subjected to seismic loads, and try to investigate ultimate behavior and likely collapse modes of repaired frames. This study models a limit state function of repaired frames that have experienced severe earthquake, and try to investigate likely collapse modes of repaired frames based on first order reliability method. This limit state function is formulated using probability distribution of strength and load effect considering the influence of the repair.
In order to investigate structural performance parameters which affect ultimate state and collapse modes of repaired frames, simple analytical studies using the formulated limit state function and first order reliability method are conducted. From the result of analytical study, the influences of beam column strength ratio, strength increasing ratio by repair and load distribution are described.
Based on previous experimental studies which have investigated the recovery of structural performance of steel members repaired by actual repair methods, analytical model of multi-story steel moment resisting frame are constructed. And in order to verify the validity of proposed estimation method, analytical studies using this frame model are conducted. From the results of analytical studies, it is confirmed that the proposed method can evaluate likely collapse modes of repaired steel frame.
