Browsing by Author "Zemp, René"
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- ItemControl 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
- ItemDesign, 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 laA 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.
- ItemPendular Tuned Mass Dampers in Free-Plan Chilean Tall Buildings(2008) Zemp, René; Llera Martin, Juan Carlos de la; Breschi, LeopoldoThe 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