An optimum design methodology of active tuned mass damper for asymmetric structures

Abstract The application of active tuned mass damper (ATMD) for the reduction of both the translational and torsional responses is discussed in the present paper to a two-degree-of-freedom (2DOF) torsionally coupled system (structure), able to represent the dynamic characteristics of the idealized one-storey asymmetric building consisting of a diaphragm (slab) supported by structural elements, such as frames or walls, in each of the two orthogonal directions, i.e. general asymmetric structures. Depending on the ratio of the torsional to the translational eigenfrequency, i.e. the torsional to translational frequency ratio (TTFR), of asymmetric structures, the following three scenarios can be distinguished: (1) torsionally flexible structures (TTFR 1.0). Taking into account the optimum position of the ATMD within the width of the asymmetric structure, a careful examination of the effects of the normalized eccentricity ratio (NER) on the performance of the ATMD is carried out by resorting to both the translational and the torsional displacement variances of the asymmetric structure. Extensive numerical simulations have been performed to accurately estimate the dynamic characteristics of the ATMD for asymmetric structures subject to ground acceleration. In the numerical simulations, the optimum parameter criterion of the ATMD is defined as the minimization of the minimum translational and torsional displacement variances of the asymmetric structure with the ATMD. Evaluation criterion on the effectiveness of the ATMD is selected as the ratio of the minimization of the minimum translational and torsional displacement variances of the asymmetric structure with the ATMD to the translational and torsional displacement variances of the asymmetric structure without the ATMD. Based on the four criteria above defined, the influences of both the NER and the TTFR of asymmetric structures are investigated on the optimum parameters and effectiveness of the ATMD.