The objectives of this paper are (1) to identify the basic parameters which control the earthquake response of torsionally coupled systems composed of resisting elements providing force interaction during yielding; (2) to clarify differences in response between systems subjected to single-component ground motion and systems subjected to double-component ground motion; (3) to clarify differences in response among an elastic system, an elasto-plastic system without force interaction, and an elasto-plastic system with force interaction, and(4) to evaluate the effects of magnitude of eccentricity and magnitudes of yield shear forces on the response of elasto-plastic systems with force interaction.

A single-story structure with a rectangular deck and four resisting elements was used to examine these objectives. First, dimensionless equations of motion were formulated containing the basic parameters which control earthquake response and, then, parametric studies were carried out to determine the effects of such parameters on elasto-plastic coupled translational-torsional response.