上フランジを連続拘束されたH形断面梁の崩壊形式と塑性変形性能

The upper flanges of H-shaped beams are often restrained by the floor slab or purlin members. When beams undergo lateral buckling, the stiffening effect of a restraint on the upper flange is significant. When the upper flange is compressed by such a long-term load, lateral buckling rarely occurs. Although lateral buckling may occur, if the lower flange is compressed by seismic or wind loads, the constraint on the upper flange works effectively, which increases the elastic lateral buckling strength. However, the elastic–plastic behavior of H-shaped beams is not completely understood as only a few experimental studies exist that consider the effects of continuously restraining the upper flange of H-shaped beams. In a common experiment, experiment that simulated an H-shaped beam by continuously restraining the upper flange was conducted by constructing a floor slab for the beam. This arrangement may be considered as almost practical; however, the behavior of the H-shaped beam itself is unclear because the influences of the floor slab and the stud bolt cannot be completely removed. In this study, the influences of the floor slab and the stud bolt are removed, and the consecutive restriction jigs of the upper flange are suggested. The large-deformation behavior of the H-shaped beam via a loading experiment is confirmed.As a result, the following conclusions are reached: (1) The continuous, complete restraint on the upper flange significantly increases the maximum strength and plastic deformation capacity of the beam with respect to lateral buckling. The buckling wave are observed close to the fixed end. Although the web tends to be deformed on the side close to the upper flange, the amount of lateral displacement of the lower flange is suppressed. (2) The continuous, complete restraint on the upper flange slightly increases the maximum strength and plastic deformation capacity of the beam in the local buckling of the web. Moreover, the lateral displacement of the lower flange and the deformation of the web do not change considerably. And continuous complete restraint of the upper flange does not affect the maximum buckling strength, plastic deformation capacity and degradation gradient for the beam in the local buckling of the flange. (3) When the upper flange is continuously constrained, the provision of the stiffener may possibly achieve the same effect as restraint lateral buckling. In addition, since the continuous restraint itself of the upper flange itsel