Pendular Tuned Mass Dampers in Free-Plan Chilean Tall Buildings

Abstract

The first low-cost tuned mass damper system in Chilean building construction was recently designed and included on a 21-story plus 6-basement building. The structure is an example of the so-called Chilean free-plan building concept, which is characterized by shear-wall elevator and staircase core plus a perimeter frame with shallow beams and post-tensioned reinforced-concrete slabs. This article focuses on the most relevant results of the design, construction, testing and implementation of a 150 kN magnetorheological (MR) damper developed to seismically control this structure equipped with 2 tuned masses (TMs) at the roof of 160 tons each. First, the governing non-linear equations of motion of the TM-MR damper assembly are presented. Building displacements and accelerations are computed and analyzed for a suite of subduction-type and near field ground motions. It is observed that the RMS response modification factors obtained for earthquake excitation are strongly dependent on the frequency content of the excitation and may range in the average from 9% to 37% relative to the bare structure. A complete testing program was performed on the constructed damper and a physical controller proposed for the MR damper. A pull-back test on one of the TMs in the building was carried out to validate this controller. Its performance is essentially equivalent to that of an LQR controller, but the information required to implement it is considerably less. The MR damper designed was capable of controlling the TM displacements very effectively