フラッシュ形エンドプレート接合形式を有するH形断面梁の崩壊挙動と横座屈耐力推定法

The flush end plates connections have been researched in several countries. For example, in Japan, Kato, Sakuma and Mukai have presented the prediction method of ultimate moment strength of the connection, and in Europe, ECCS(2016) has presented the moment resistant and stiffness evaluation, and classification criteria for the rotational ductility. In addition there are numerous studies of the lateral buckling of H-shaped beams. For example, Ikarashi, Tomo and Wang(2011) have presented the effects of boundary condition and moment ratio on elastic lateral buckling strength of H-shaped beams.This paper presents a method to predict the ultimate strength of the H-shaped beams connected by flush end plates which fall into the lateral buckling or the connection failures. The method is based on the determination of the two boundary conditions due to yielding of flush end plates.The study is conducted by the following procedure: First, the behavior of the connection is researched by the no buckling experiment under the cyclic loading. As a result, it is found that the moment strength which cause the plastic deformations of the endplates and which contacts the deformed endplates on the surface of column can be predicted. In addition the non-linear FEM analysis is conducted to compare the moment-rotation relationship of the beams connected by flush endplates with those of the beams connected rigidly. As a result, they are similar. It means that lateral buckling strength can be predicted by the method based on the study of rigid connections. Next, the behaviors of the lateral buckling of the beams are researched by the buckling experiments under the cyclic loading, and then the boundary conditions of the beams are estimated by strain gauges put on the flanges. In addition the FEM analysis is conducted to estimate the boundary conditions of the beams from the lateral moment in flanges. As a result, it is found that the lateral moment is small in tension flange near the connection, so that the connection is not restraining warping of the end of the beam. We recommend that the boundary conditions of the beams connected by flush end plates are simple support or lateral bending support. The lateral buckling strengths under the two boundary conditions determine that which strength must be applied. Final, the several effects of factors are researched.Findings of this study can be summarized as follows:(1)The ultimate moment strength of the flush end plate connection is pred