This paper presents a study on cyclic flexural behavior of thickness-reduced steel pipe repaired by welded patch plates. In this study, cyclic flexural tests of repaired pipes are performed, and the experimental results are compared with finite element (FE) analyses. In FE analyses, several combinations of patch plate thickness and reduced pipe thickness are modeled. From numerical results, the buckling behavior of thickness-reduced steel pipe repaired by patch plate is explained. It is shown that a required thickness of patch plate is larger than the thickness reduction to achieve the same level of ductility performance in the repaired pipe.

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Low yield point strength steel 100 (LYP100) was widely applied to the metallic shear panel damper. To develop function separate damper with LYP100, panel shapes, stiffeners and vertical ribs which affect the deformation capacity of the damper were investigated by static cyclic loading tests. The test results show that the deformation capacity can be improved greatly by alleviating the stress concentration locating at the panel corners. The largest mean shear strain 70% was achieved by optimizing the parameters.

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This experimental study is a part of the investigation on the seismic design method for Double Tubes Hybrid System (DTHS) for buildings. This structural system consists of RC core walls as the interior tube, and the exterior frames composed of RC short columns and RC spandrel walls as the exterior tube. The RC core walls are designed as the Energy Dissipation Structural Walls (EDSW), which are composed of RC coupled shear walls linked by short steel H-shaped beams as the energy dissipation devices. The hysteretic behavior of EDSW as the core tube has been experimentally investigated and reported elsewhere. It is clarified that EDSW behave in a very ductile manner under cyclic lateral loading, and have an ample energy dissipation capacity.
The exterior frame is made of RC spandrel walls and RC short columns. We call such a new constructional system frame as the Spandrel Wall Frame (SWF). We focus on the behavior of SWF in this paper, so that an experimental study is carried out on the SWF specimens. With respect to the RC short columns, we introduce steel Tube jacketing Reinforced Concrete (TRC) columns instead of the ordinary RC columns. The study was programmed to investigate the elasto-plastic behavior of SWF specimens under horizontal cyclic loads. The elasto-plastic behavior of the SWF showed sufficient deformability and horizontal force carrying capacity as the exterior tube of DTHS buildings.

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It is clear from the former researches on reinforced concrete filled steel tubular (RCFT) structures that RCFT structures have higher strength and deformation capacity than concrete filled steel tubular (CFT) structures. However, in the case of actual applications to large-scaled structures, the thin-walled steel tube and high strength concrete must be used from the view point of economic condition. Therefore, in this study, compression tests of RCFT columns which were made by thin-walled steel tube in cooperation with high strength concrete were carried out, meanwhile corresponding tests of CFT, reinforced concrete (RC), pure concrete and steel tube columns were conducted to compare with RCFT. By a series of comparison and analysis, characteristics of RCFT columns were clarified, and following conclusions were drawn: RCFT columns have better shear-resistibility than CFT columns; with RCFT columns, excellent bearing capacity can be achieved in plastic zone by combining the thin-walled steel tube with high strength concrete. This has economical meaning while RCFT was applied to actual construction.

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This paper addresses the loading tests of beam-to-column connection with exterior diaphragm and circular tube column. These tests were conducted to verify the validity of the derived collapse load that was based on plastic analysis. Major findings obtained from tests are summarized as follows: (1) the test specimens of exterior diaphragm type moment connection exhibited sufficient deformation capasity until 0.1 rad drift angle, (2) the derived collapse load formula correlated well with the specimen which were connected beam flanges to diaphragms by weld.

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