Plastic Hinge Length of RC Shear Walls: A Mechanical Approach Considering Plane Bending and Tension Shift

ABSTRACT Shear walls are often used to stabilize buildings or bridges against horizontal loads like wind or earthquakes. In earthquake design, ductile behavior is usually targeted so that the energy from earthquake excitation can be dissipated. An approach employing a plastic hinge on the wall base is widely used. The length of the plastic hinge is decisive for the rotational capacity, and thus for the ductility of a wall. Due to the complicated behavior of reinforced concrete under cyclic loading, one finds almost only empirical approaches in literature and design regulations to determine the plastic hinge length. The plastic hinge length is influenced by the moment gradient and the shift of tensile forces along the tensile chord. This phenomenon, known as the “tension shift,” is due to the interaction between bending and shear, resulting in inclined cracking. This article separates the tension shift and plane section bending contributions to the plastic hinge length, which are not clearly separated or sufficiently accounted for in empirical approaches. The aim is to allow calculation of displacements resulting from the tension shift in addition to known flexural displacements derived from the moment–curvature relationship under the assumption of plane section bending. Therefore, the tension shift length was measured on several existing shear wall experiments and in a parametric study performed with a nonlinear finite element analysis. Finally, a design approach is proposed with an estimation of the shift angle, which is used to calculate the part of the plastic hinge length due to tension shift. The approach is applicable to both existing walls with small reinforcement amounts and new ductile earthquake walls.