In this paper, the effect of out-of-plane deformation between attachment and beam flange on Joint yield moment of Web-clamped type beam-to-column connection was investigated. In this study, simple mechanical model implied following joint behavior; 1) In the case that the shape of attachments is determined, out-of-plane deformation increases when the distance between the beam center and the bolt hole center bf becomes wider or the thickness of beam flange tf becomes thinner; 2)The joint yield moment degrades when the out-of-plane deformation increases. These behaviors of the simple mechanical model were investigated by finite element analysis.
