EFFECT OF STIFFENERS ON THE ANGLE OF INCLINATION IN STEEL PLATE SHEAR WALLS

Steel plate shear walls (SPSW) are an efficient but largely underused building lateral force resisting system. The system comprises of a moment frame (the boundary frame) with slender steel web plates that are welded or bolted inside the boundary frame. The resulting structure is similar to a vertical plate girder. The system resists lateral load primarily through tension field action of the post-buckled web plate. The magnitude and orientation of this tension field is governed by the relative stiffness of the web plate and boundary frame. The 2010 Seismic Provisions currently require that the tension field inclination angle be either 40° or computed using a formula derived from elastic analysis. This paper presents a new relationship for the diagonal tension angle considering effect of stiffeners. It is demonstrated that the tension field inclination may move, from an initially low angle under an elastic post-buckled state, toward 45° as the plate is loaded plastically.