Elastic axis of special classes of buildings under earthquake excitation

• Published in: Engineering structures Vol. 237; p. 112203
• Main Authors: Terzi, Vasiliki G., Athanatopoulou, Asimina
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 15-06-2021; Elsevier BV
• Subjects: Damping; Divergence; Earthquakes; Elastic axis; Equations of motion; Isotropic buildings; Mathematical analysis; Multistory buildings; Seismic activity; Seismic response; Stiffness; Torsional excitation; Translational-torsional coupling; Isotropic buildings; Translational-torsional coupling; Elastic axis; Torsional excitation
• ISSN: 0141-0296; 1873-7323
• DOI: 10.1016/j.engstruct.2021.112203

•Dynamic elastic axis is defined as the axis of twist under torsional base excitation.•Mathematical formulae are developed for the determination of dynamic elastic axis for single-story and isotropic multi-story buildings.•The dynamic elastic axis is independent of the torsional base excitation.•The coincidence with the elastic axis is verified for small frequency excitations.•Inertial and damping effects are observed in the high frequency domain of excitation.
In the present paper the existence of a stable vertical axis of twist in single story and isotropic multistory buildings is investigated. For this purpose, a torsional base excitation is applied at the buildings base and the equation of motion is transformed in the frequency domain. By using the diaphragm constraint equations, analytical formulae are developed which provide the location of the twist axis which is called dynamic elastic axis. It is proved that the coordinates of the dynamic elastic axis depend on stiffness, mass, damping and excitation frequency. Numerical examples are presented. All the results produced by using the developed equations are compared with the coordinates of the elastic axis derived by the application of static forces. The divergence of the two methods is discussed in detail.