Browsing by Author "Zemp, René"

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    A long-stroke semi-active MR damper for building control using tuned masses
    (National Information Centre of Earthquake Engineering, 2017) Zemp, René; Llera Martin, Juan Carlos de la; Almazán Campillay, José Luis; Weber, F.
    In this research the comprehensive development of a long-stroke MR-damper designed to control the earthquake performance of an existing 21-story reinforced concrete building in Santiago (Chile) by reacting on one of its tuned masses is presented. The ±1 m stroke MR-damper design is quite unique and considered the nominal response of the building equipped with two pendular masses of weight 160 tons each, and tuned to the fundamental mode of the structure. The realscale long-stroke MR-damper was designed by our research team and manufactured in Chile. The MR-damper was tested using a special testing rig designed to study devices with long stroke at large deformation velocities. The rig was implemented in the dynamics and vibration control laboratory at Universidad Catolica de Chile. Both, the long-stroke MRdamper and the control algorithm were experimentally validated using a suite of periodic and seismic signals. For the building numerical simulations, the nominal MR-damper force-displacement constitutive relationship was replaced by the measured force-displacement response of the damper in order to validate the theoretical MR-damper model used. Such model was used in simulations to predict the performance of the TM-MR damper assembly in the design phase of the damper. Furthermore, a new real-time structural displacement sensor was developed with this application since conventional technology and methods to measure building displacement are inaccurate for a real-time displacement control as proposed with this application. The real-time building displacement sensor was validated using a scaled-down building prototype subjected to shaking table tests before an actual size sensor was implemented within a test building. All electronic components of the tuned-mass MR-damper assembly were tested with a shaking table and subjected to strong motion accelerations while the MR-damper was working in its active mode. It is concluded that the proposed tuned-mass MRdamper solution is technically feasible and may be advantageous in some real-life situations. The stage of development of the technology reached a point that enables commercial implementation in a real structure.
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    Control of tuned masses using MR dampers and a new real time feedback signal and physical controller
    (2012) Zemp, René; Llera Martin, Juan Carlos de la; Weber, F.
    A scaled prototype of an MR damper was active in passive mode on a 160 ton tuned mass in a 21-story building in Santiago, Chile, during the February 27, 2010 earthquake. More recently, a full scale ±100 cm stroke MR damper was designed, manufactured, and is being tested for the same building. The implementation considers a new real time structural measurement system developed to acquire building displacements as feedback for the physical controller of the TM-MR damper assembly. The new measurement system was successfully tested on a shaking table model at Empa. Moreover, results from a number of nonlinear simulations on the building with the full scale semi-active damper shows that the mean displacement reduction for the setup considered is 22% more effective than the building with the bare tuned masses. Finally, the solution was identified to be fairly cost-effective as compared with a passive solution or the bare case
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    Design, testing and implementation of TADAS devices in three RC buildings with shear walls and coupling beams
    (2017) Zemp, René; Urrutia, R.C.; Rendel, Michael; Cavalla, G.; Llera Martin, Juan Carlos de la
    A Triangular Added Damping and Stiffness (TADAS) device is an economic energy dissipation solution to improve the earthquake performance of flexible buildings. TADAS devices have a very stable force displacement constitutive relationship and a high capability of energy dissipation. This research proposes the use of TADAS dampers in coupling beams or lintels between reinforced concrete (RC) shear walls. Coupling beams are typical of RC shear wall buildings with flat slabs and staircase and elevator shear wall cores. The proposed solution integrates into the structure without a relevant impact on the architecture, a significant advantage over other energy dissipation solutions. In this article, three different building applications with TADAS devices are presented. Numerical simulations for these buildings show that drift, displacement, and base shear reductions typically range between 10% and 30%. An effective TADAS design balances stiffness, energy dissipation, and fatigue life of the device under cyclic plastic deformations. Fatigue life for mild steel was determined experimentally and the TADAS devices were designed with a simple model validated by testing of single triangular plates. As expected for rate independent plasticity, tests at different frequencies showed negligible performance variations with deformation velocity. Several TADAS prototypes were cyclically tested and their results are reported in this article. In an effort to analyze the performance and stiffness of the connection between the damper and RC beam, the prototype tests include a section of the capacity-designed concrete beam with the device under simulated as-built conditions. The final design also allows replacing the damper, if needed, after a strong earthquake, and considers an installation procedure that minimizes slip in the connection to the concrete beam.
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    Pendular Tuned Mass Dampers in Free-Plan Chilean Tall Buildings
    (2008) Zemp, René; Llera Martin, Juan Carlos de la; Breschi, Leopoldo
    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
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    Tall building vibration control using a TM-MR damper assembly
    (WILEY, 2011) Zemp, René; Llera Martin, Juan Carlos de la; Almazán Campillay, José Luis
    This research investigates the seismic and harmonic response of a true free-plan tall building equipped with two tuned pendular inertial masses (TMs) and magnetorheological (MR) dampers. Construction of this proof-of-concept building was completed in 2007, and it is the first of its class in Chile. This article provides research results associated with this specific implementation; however, in order to make the results applicable to other building cases a parametric study was considered. A brief description of the structure and TM implementation together with the nonlinear 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. Besides, a new physical controller for the MR dampers is proposed and analyzed. The performance of this controller is compared with that of benchmark LQR controllers. In general, the TM-MR damper assembly improves the lateral performance of this structure for lateral harmonic excitations. However, the expected peak and RMS response modification factors and efficacy of the solution for earthquake excitations are strongly dependent on the frequency content of the excitation. Copyright (C) 2010 John Wiley & Sons, Ltd.