Seismic response trends of SDOF plan irregular structures. Simplified approach

Abstract

Plan irregular structures experience a torsional seismic response even if the seismic input is unidirectional, due to an uneven distribution of mass and stiffness (in the elastic range of behavior) and of mass and strength (in the inelastic range of behavior). The seismic behavior of plan irregular structures is difficult to preview due to coupling between the translational and the rotational movement and to the change of the importance of stiffness and strength when moving from the elastic to the inelastic range of behavior. Past studies have also shown a high sensitivity of the seismic response of plan irregular structures to the characteristics of the ground motion. Therefor establishing trends of behavior for plan irregular structures is a goal very difficult to achieve but still it is a basic requirement for defining simplified approaches useful in current praxis. Dynamic nonlinear analysis and the simplified SESA method (Kober D, Zamfirescu D, Effects of general torsion on structural displacements. In: Proceedings 14 ECEE. ISBN 978-608-65185-1-6, 2010) were used for investigation. Structural displacements, rotations and rotational moments were checked and compared. The aim of the study is to establish behavior trends for plan irregular structures, looking especially at the variation of the rotation around CM, due to mass inertia.