DAMPING OF TORSIONAL VIBRATIONS OF HIGH-RISE BUILDINGS UNDER SEISMIC EFFECTS USING DAMPERS GENERATING REACTIVE FORCE COUPLES

Abstract

Introduction. To ensure the safety of buildings and structures in seismically active regions, special protection measures against destruction are applied. One of the most universal, effective, and economical methods of active vibration suppression is the method of reactive damping. An important form of natural vibrations of buildings is torsional motion. Certain segments of seismic accelerograms can provoke the development of such vibrations. There is a relationship between torsional and bending modes of vibration: bending vibrations can cause torsional deformations, and vice versa. This occurs because the centres of mass and the centres of stiffness of structural sections do not generally coincide, which leads to the occurrence of coupled bending-torsional vibrations. The aim of this work is to investigate the response of finite element (FE) models of high-rise buildings to seismic effects represented as harmonic functions with variable frequencies, varying the direction of the effect and the position of the centre of mass, as well as a comprehensive study of the results of experiments on damping torsional vibrations of high-rise buildings using a pair of reactive dampers capable of generating variable moments counteracting torsional vibrations. Methods. To evaluate the behaviour of high-rise buildings with reactive dampers under harmonic loads, an appropriate mathematical model was investigated. The calculations were performed using a software package based on the finite element method (FEM), and the dynamic response of the structure was determined numerically using the Newmark method. Results. The developed software tool allowed for frequency-vector analysis considering the displacement of the centre of mass from the centre of stiffness, and provided data on the torsional angles of the building at various positions of its centre of mass and variations in the parameters of the harmonic effect (frequency and direction) considering internal friction. A comprehensive study of the results of experiments on damping torsional vibrations of highrise buildings using a pair of reactive dampers capable of generating variable moments counteracting torsional vibrations was conducted. It is shown that the use of reactive dampers with optimally selected parameters reduces the amplitude range of torsional vibrations by 50–80 %.