Kenjiro Mori

Study on Ultimate Seismic Behavior and Repair Method of Damaged SteelFrames

Recently, there are many discussions about repairability and recovery on damaged buildings. It is desirable to establish the design manuals for recovery considering continuous use of structures. In our previous researches, the damaged steel members of H-shaped and square tube section were reproduced by loading test. From the loading test results, the inelastic behavior and restoring force characteristics were clarified, and also the analytical model were proposed which can chase test results well. It means that we have already conducted the member based research on repairability. So, in this study, to investigate the inelastic behavior and restoring force characteristics of repaired steel frames, the loading test is performed on half size scaled - partial frame model as parameters with strength ratio of column-beam and panel-beam. It is assumed that the various type of failure mode is generated on original state and repaired state. During loading test on original state, local buckling is observed on H-shaped steel beam. Therefore, the damaged area is repaired by welding cover plates method which is recommended by Japanese restoration manual for damaged building structure by severe seismic disasters. And also, the loading tests on repaired state is performed, and it is confirmed that the strength is restored at the same or high level compared with original state. However, in case of beam failure mode on original state, different failure mode is observed on repaired state. Furthermore, a finite element analysis is performed, and the resistant mechanism during ultimate state is investigated analytically in detail.

The Repair Method of Damaged H-shaped Steel Members and Experimental Study on Recovery after Repair

Recently, there have been many discussions about repairability for damaged building structures after severe disasters. In japan, a technical manual for repairing damaged buildings has been established; however, its repair abilities have not been reported sufficiently. In this study, the Box-Shaped Repair Method which has been suggested on Japanese technical guideline is adopted for the damaged steel members, and its applicability and feasibility are investigated experimentally. Herein, the damaged portion on steel member such as plastic hinge or local buckling occurrence is covered with steel plate by welding. So the loading test is performed as parameters with section size of steel members, thickness of cover plate and welding size during repair process, and loading path. The procedure of this study is as follows; the first, the damaged test specimens of H-shaped steel member with local buckling are reproduced by initial loading test. Next, the damaged specimens with plastic residual deformation are returned to the original position. Finally, the loading test is done after repair. From test results, it is confirmed that the fundamental structural performance such as the rigidity, maximum strength, and absorbed energy after repair are improved by comparison of original state. And also, this performance can be controlled by adjusting the thickness of cover plate and welding condition. Furthermore, from the observation of test results, the analytical model of repaired steel member is suggested. From the comparison of test results, it can be said that the proposed model shows good agreements both test results and theoretical figure.

Repair Method of Damaged Steel Framed Structures and Ultimate SeismicState of Repaired Steel Frames

Recently, a lot of building structures have been experienced severe natural disasters, and it was reported that various types of terrible collapse mode were occurred. And also, there are many discussions about repairability and recovery on damaged buildings over the world. In particular, there has been focused on new keyword a²¯ Resilience a²° in any field including structural engineering. In Japan, a technical guideline for repairing damaged buildings has been established. However, the applicability and feasibility of repair method and recovery has not been well reported. Herein, to investigate the recovery and ultimate seismic state of repaired steel framed structures, experimental and analytical studies are conducted. Herein, the actual repairing technique for steel framed structure is suggested. During experimental study, the damaged steel member is reproduced by loading tests with consideration of past reports of mega-earthquake disasters. The next, the damaged portion is repaired by proposed method by use of steel-cover plate technique. After this repair process, the loading test is done again. And the recovery of structural performance is estimated by comparison of original and repaired state. From the test results, it is confirmed that the strength and ductility are improved after repair. Furthermore, the analytical model and restoring force characteristics of repaired steel member are suggested by observation of ultimate behavior during loading test. Here, the purpose on seismic design is to guarantee the overall failure mode formation on frames. So, the structural demand of strength and rigidity and column-to-beam strength ratio on repaired state are discussing analytically.

AN EXPERIMENTAL STUDY ON REPAIR METHOD AND RECOVERY OF STRUCTURAL PERFORMANCE FOR DAMAGED RHS STEEL MEMBERS

There are many discussions about repairability and recovery on damaged building structures. In considering sustainable use of damaged building structures, it is required to apply suitable repair methods for each damaged component members. Several repair methods for damaged RHS steel members have been proposed in technical guideline. However, the specific work procedure and the relationship between repair method and recovery have not been well reported in past researches. This study focuses on a repair method for RHS steel members. The detailed repair procedure is validated based on actual examples. Furthermore, the recovery of structural performance after repair is clarified.

Ductility and Damage Evaluation Method of Steel Columns Subjected to Inelastic Cyclic Loading Under Constant Axial Force

In order to evaluate the performance of steel structures under cyclic loading of earthquake, it is necessary to simulate accurately the behavior of the structure until the ultimate states such as the buckling or the fracture of the steel members. In this paper, the database is structured, which stores the test results of the past study of H-shaped steel columns subjected to inelastic cyclic loading under constant axial force. It provides reference to strength, ductility and energy absorbing capacity until the ultimate states of the H-shaped steel columns under various experiment conditions. The next, the prediction method considering cumulative damage is necessary to predict the capacity of H-shaped steel columns until the ultimate states under cyclic loading. Herein, they are analyzed statistically with a large number of past references from the database. The key parameters related to performance and damage evaluation are investigated and estimated by this enormous analysis. Also, the evaluation equations are established from the analysis results, which is formulated and obtained from regression analysis considering the key parameters. From the comparison of results, the proposed method for damage evaluation show good agreements with the test results of the database.