In this study, a series of static cyclic loading tests were conducted on serially connected two RC walls to investigate the shear stiffness degradation of the walls under varying axial load. The shear forces carried by the two walls were measured by the load cells independently located at the two bases. The shear resistance at the tensile-side shear walls decreased down to nearly zero in inelastic range, while the compressive-side wall carried nearly all of the total shear force. The shear distribution could not be simulated by the frame analysis using the conventional three vertical line element wall model, where the shear stiffness reduction is assumed to be same with the two walls regardless of the axial load level. A new model, called axial-shear model, was proposed to evaluate the shear stiffness degradation of the central line element including the varying axial load based on the stress-strain constitutive relation of the plane strain element, from which the shear distributions measured in the tests could fairly be simulated.
