Browsing by Author "De La Llera Martin Juan Carlos"

Now showing 1 - 11 of 11
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    A Semi-active piezoelectric friction damper
    (2015) Pardo Varela Javier Ignacio; De La Llera Martin Juan Carlos; Pontificia Universidad Católica de Chile. National Research Center for Integrated Natural Disaster Management
    This research investigates the development of a semi-active piezoelectric friction damper for controlling the seismic response of large-scale structures. The proposed device is made of Duplex steel and leads to high friction capacity, which can be developed either in passive or semi-active modes. For the later, piezoelectric actuators react against a stiff clamping system and apply a variable normal force on the multiple contact surfaces. To validate the design, a prototype, which contact surfaces were made of stainless steel and brake pad material, was built and tested in both friction modes. Moreover, an analytical model of the damper was developed to estimate the performance of the piezoelectric actuators within the clamping system. Experimental results showed that the proposed device achieves a force range factor of 1.9. These experimental results also compare well with those obtained from the analytical model of the damper. Copyright (c) 2014 John Wiley & Sons, Ltd.
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    An empirical model for preliminary seismic response estimation of free-plan nominally symmetric buildings using ANFIS
    (ELSEVIER SCI LTD, 2012) Sepulveda Ovalle Cesar Raul; De La Llera Martin Juan Carlos; Jacobsen Pohlenz Andres
    The good seismic performance of free-plan buildings during the last M-w = 8.8, February 27, 2010 Chile earthquake, deserves special attention in order to understand the clues for such behavior. Also, and because of economic reasons, the development of these building projects are always subjected to a fast track development, which makes difficult to iterate much on the structural configuration of the building unless quick and reliable responses can be provided to architects and owners. Motivated by these facts, this work proposes a new simplified methodology capable of predicting a reasonably accurate response of free-plan nominally symmetric buildings. Because it is well known that the flexural effect of the slab has a strong influence in the response of these buildings, the methodology is based on the decomposition of the building behavior in two simple extreme cases, zero and infinite flexural stiffness between vertical elements, and horizontal ones. The final building behavior lies in between these cases, and is predicted by producing a linear combination of the models through a single model-parameter a that has been calibrated by using a large training database and an adaptive neural network with a fuzzy inference system, ANFIS. Predicted errors for the displacement and forces of new building configurations are usually less than 10% and 15%, respectively, and in many cases are better than that. Besides its accuracy, the numerical efficiency of this model is usually one to two orders of magnitude larger than that of conventional finite element model of the building. (C) 2011 Elsevier Ltd. All rights reserved.
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    Analysis and interpretation of the seismic response of RC buildings in Concepcin during the February 27, 2010, Chile earthquake
    (2013) Westenenk Orrego Benjamin; De La Llera Martin Juan Carlos; Junemann Ureta Rosita; Hube Ginestar Matias Andres; Besa Vial Juan Jose; Luders Schwarzenberg Carl; Inaudi Bonadero Jose Antonio; Riddell Carvajal, Rafael; Jordan Sainte-marie Rodrigo
    Observed trends in the seismic performance of eight severely damaged reinforced concrete (RC) structures after the February 27, 2010, Chile earthquake are presented in this article. After a reconnaissance and surveying process conducted immediately after the earthquake, several aspects not conventionally considered in building design were observed in the field. Most of the considered structures showed extensive localized damage in walls of lower stories and first basements. Several factors indicate that damage was brittle, and occurred mainly in recent RC structures supported on soft soils with some degree of vertical and/or horizontal irregularity. Non-ductile behavior has been inferred due to the lack of evidence of spread damage in the structure, and the fact that very similar structural configurations existed nearby without apparent damage. Some key aspects in understanding the observed damage are: geographical orientation of the building, presence of vertical and horizontal irregularities, wall thickness and reinforcement detailing, and lack of sources for energy dissipation. Additionally, results of a building-code type analysis are presented for the 4 most critical buildings, and Demand/Capacity ratios are calculated and compared with the observed behavior. It is concluded that the design codes must be revised relative to wall design provisions.
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    Characteristics and displacement capacity of reinforced concrete walls in damaged buildings during 2010 Chile earthquake
    (2015) Alarcon Olivari Cristobal Nicolas; Hube Ginestar Matias Andres; Junemann Ureta Rosita; De La Llera Martin Juan Carlos
    About 2 % of reinforced concrete (RC) buildings taller than nine stories suffered important structural damage during 2010 Chile earthquake. The typical structural configuration of residential buildings is characterized by a large number of RC structural walls which provides high lateral stiffness and strength. The first objective of this paper is to obtain global geometric and design parameters of RC structural walls in damaged buildings and correlate their values with the observed damage. The second objective is to compare the roof displacement capacity with the roof displacement demand in critical walls, and hence, try to explain the observed damage. The wall parameters were obtained from five representative damaged structural wall buildings; these are: wall thickness, aspect ratio, axial load, reinforcement ratios, and the ratio between horizontal reinforcement spacing and the vertical bar diameter. The roof displacement capacity is obtained using a plastic hinge approach, and the ACI 318-08 approach, since both methods are proposed in the current Chilean seismic code. The displacement demand is estimated from ground motions recorded in the vicinity of the buildings. It is found that values of wall parameters correlate well with the observed damage. The structural walls were subjected to relatively high axial loads, and some walls included a large amount of vertical reinforcement to provide the required strength, but had inadequate transverse reinforcement thus compromising ductility. Findings from this research suggest that the plastic hinge approach is inadequate to estimate the roof displacement capacity and lacks correlation with the observed damage. Moreover, the use of the ACI 318-08 approach to estimate the roof displacement capacity is also inadequate, but leads to better predictions of wall displacement capacity. As shown by the results of response history analysis, the failure of walls was triggered by high axial loads rather than flexural deformation.
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    Coseismic slip and afterslip of the 2015 Mw 8.3 Illapel (Chile) earthquake determined from continuous GPS data
    (John Wiley & Sons Ltd., 2016) Shrivastava, Mahesh N.; González, Gabriel; Moreno, Marcos; Chlieh, Mohamed; Salazar, Pablo; Reddy, C.D.; Báez, Juan Carlos; Yanez Carrizo Gonzalo Alejandro; González, Juan; De La Llera Martin Juan Carlos; Pontificia Universidad Católica de Chile. National Research Center for Integrated Natural Disaster Management
    We analyzed the coseismic and early postseismic deformation of the 2015, M-w 8.3 Illapel earthquake by inverting 13 continuous GPS time series. The seismic rupture concentrated in a shallow (<20km depth) and 100km long asperity, which slipped up to 8m, releasing a seismic moment of 3.6x10(21)Nm (M-w=8.3). After 43days, postseismic afterslip encompassed the coseismic rupture. Afterslip concentrated in two main patches of 0.50m between 20 and 40km depth along the northern and southern ends of the rupture, partially overlapping the coseismic slip. Afterslip and aftershocks confined to region of positive Coulomb stress change, promoted by the coseismic slip. The early postseismic afterslip was accommodated similar to 53% aseismically and similar to 47% seismically by aftershocks. The Illapel earthquake rupture is confined by two low interseismic coupling zones, which coincide with two major features of the subducting Nazca Plate, the Challenger Fault Zone and Juan Fernandez Ridge.
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    Development of a long-stroke MR damper for a building with tuned masses
    (2016) Zemp Rene; De La Llera Martin Juan Carlos; Saldias Molina Hernaldo Enrique; Weber, Félix; Pontificia Universidad Católica de Chile. Escuela de Ingeniería; Pontificia Universidad Católica de Chile. National Research Center for Integrated Natural Disaster Management
    This article deals with the development of a long-stroke MR-damper aimed to control, by reacting on a tuned mass (TM), the earthquake performance of an existing 21-story office building located in Santiago, Chile. The +/- 1 m stroke MR-damper was designed using the nominal response of the building equipped with two 160 ton pendular masses tuned to the fundamental lateral vibration mode of the structure. An extended physical on-off controller, a special current driver, a new real-time structural displacement sensor, and an MR-damper force sensor were all developed for this application. The physical damper and control were experimentally validated using a suite of cyclic and seismic signals. The real-time displacement sensor developed was validated by first using a scaled down building prototype subjected to shaking table tests, and then a real-scale free vibration test on the sensor installed horizontally at the foundation level of a building. It is concluded that the proposed TM and MR-damper solution is technically feasible, and for an equivalent key performance index also defined herein, more economical than a solution based on passive viscous dampers.
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    Earthquake defence and the price of a telescope
    (2010) Infante Lira Leopoldo; De La Llera Martin Juan Carlos
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    Experimental analysis of large capacity MR dampers with short- and long-stroke
    (2014) Zemp Rene; De La Llera Martin Juan Carlos; Weber, Félix
    The purpose of this article is to study and characterize experimentally two magneto-rheological dampers with short- and long-stroke, denoted hereafter as MRD-S and MRD-L. The latter was designed to improve the Earthquake performance of a 21-story reinforced concrete building equipped with two 160 ton tuned pendular masses. The MRD-L has a nominal force capacity of 300 kN and a stroke of ±1 m; the MRD-S has a nominal force capacity of 150 kN, and a stroke of ±0.1 m. The MRD-S was tested with two different magneto-rheological and one viscous fluid. Due to the presence of Eddy currents, both dampers show a time lag between current intensity and damper force as the magnetization on the damper changes in time. Experimental results from the MRD-L show a force drop off behavior. A decrease in active-mode forces due to temperature increase is also analyzed for the MRD-S and the different fluids. Moreover, the observed increase in internal damper pressure due to energy dissipation is evaluated for the different fluids in both dampers. An analytical model to predict internal pressure increase in the damper is proposed that includes as a parameter the concentration of magnetic particles inside the fluid. Analytical dynamic pressure results are validated using the experimental tests. Finally, an extended Bingham fluid model, which considers compressibility of the fluid, is also proposed and validated using damper tests.
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    Multiphysics behavior of a magneto-rheological damper and experimental validation
    (2014) Sternberg Cunchillos Alan Phillip; Zemp Rene; De La Llera Martin Juan Carlos; Pontificia Universidad Católica de Chile, National Research Center for Integrated Natural Disaster Management
    This investigation deals with the design, manufacturing, and testing of a large-capacity MR damper prototype. The MR damper uses external coils that magnetize the MR-fluid as it moves out of the main cylinder through an external cylindrical gap. In its design, multi-physics numerical simulations are used to better understand its force-velocity constitutive behavior, and its eventual use in conjunction with tuned mass dampers for vibration reduction of high-rise buildings. Multi-physics finite element models are used to investigate the coupled magnetic and fluid-dynamic behavior of these dampers and thus facilitate the proof-of-concept testing of several new designs. In these models, the magnetic field and the dynamic behavior of the fluid are represented through the well-known Maxwell and Navier-Stokes equations. Both fields are coupled through the viscosity of the magneto-rheological fluid used, which in turn depends on the magnetic field strength. Some parameters of the numerical model are adjusted using cyclic and hybrid testing results on a 15 ton MR damper with internal coils. Numerical and experimental results for the 15 ton MR damper showed very good agreement, which supports the use of the proposed cascade magnetic-fluid model. The construction of the 97 ton MR damper involved several technical challenges, such as the use of a bimetallic cylinder for the external coils to confine the magnetic field within a predefined magnetic circuit. As it should be expected, test results of the manufactured MR damper show that the damping force increases with the applied current intensity. However, a larger discrepancy between the predicted and measured force in the large damper is observed, which is studied and discussed further herein. (C) 2014 Elsevier Ltd. All rights reserved.
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    Tall building vibration control using a TM-MR damper assembly: Experimental results and implementation
    (WILEY, 2011) Zemp Rene; De La Llera Martin Juan Carlos; Almazan Campillay Jose Luis
    This paper summarizes the relevant results of the design, construction, testing, and implementation of a nominal 120 kN magnetorheological damper developed to control a free-plan tall building in Santiago, Chile, equipped with two 160-ton tuned masses. Cyclic as well as hybrid simulation tests were performed on the prototype damper. Global building responses using measured MR properties showed good correlation with analytical estimations. Also, a proposed physical controller for the MR damper was validated through hybrid and building pull-back tests. Its performance is essentially equivalent to that of an LQR controller, but the information needed in its implementation is considerably less. Pull-back tests of 10 cm amplitude were performed on one mass along the flexible edge of the building and its response controlled using the passive and controlled modes of the MR damper. The MR damper was capable of controlling the TM displacements very effectively, as well as the simulated building response for different ground motions and harmonic excitation. Copyright (C) 2010 John Wiley & Sons, Ltd.
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    Torsional balance of seismically isolated asymmetric structures
    (2013) Seguin Ruiz Carlos Eugenio; Almazan Campillay Jose Luis; De La Llera Martin Juan Carlos