René Zemp, Juan Carlos de la Llera, Hernaldo Saldias and Felix Weber. Smart Materials and Structures, 25, 105006 (17pp), doi:10.1088/0964-1726/25/10/105006

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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Junemann R.,de la Llera J.,Hube M.,Vásquez J.,Chacón M. Earthquake Engineering and Structural Dynamics, DOI 10.1002/eqe.2750

Reinforced concrete shear wall buildings have shown, in statistical terms, an adequate performance in past seismic events. However, a specific damage pattern was observed in 2010 Chile earthquake in some shear walls located in the lower building stories, usually associated with high axial stresses, lack of transverse reinforcement, and vertical irregularity. Results show that the nature of this failure led to a sudden degradation in strength and stiffness of walls and resulted in very limited ductility. This research aims to study analytically this damage pattern of shear wall buildings during the 2010 earthquake. By starting with two-dimensional inelastic pushover finite element models using diana, two walls that were severely damaged during the earthquake were studied in detail using different load patterns and stress–strain constitutive relationships for concrete in compression. These models were validated with experimental data of four reinforced concrete walls available in the literature. It can be shown that the geometry of the damage in the building walls cannot be correctly represented by conventional pushover load patterns that ignore the lateral and axial interaction. Indeed, the failure mechanism of walls shows strong coupling between lateral and vertical deformations within the plane of the wall. Results shown for a three-dimensional inelastic analysis of the building are consistent with these two-dimensional results, and predict a brittle failure of the structure. However, these models predict a large increase in axial load in the walls, which needs to be validated further with more experimental and analytical studies.

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J.C. de la Llera, F. Rivera, J. Mitrani-Reiser, R. Jünemann, C. Fortuño, M. Ríos, M. Hube, H. Santa María, R. Cienfuegos. Bulletin of Earthquake Engineering DOI 10.1007/s10518-016-9918-3

This article presents an overview of the different processes of data recollection
and the analysis that took place during and after the emergency caused by the Mw 8.8 2010 Maule earthquake in central-south Chile. The article is not an exhaustive recollection of all of the processes and methodologies used; it rather points out some of the critical processes that took place with special emphasis in the earthquake characterization and building data. Although there are strong similarities in all of the different data recollection processes after the earthquake, the evidence shows that a rather disaggregate approach was used by the different stakeholders. Moreover, no common standards were implemented or used, and the resulting granularity and accuracy of the data was not comparable even for similar structures, which sometimes led to inadequate decisions. More centralized efforts were observed in resolving the emergency situations and getting the country back to normal operation, but the reconstruction process took different independent routes depending on several external factors and attitudes of individuals and communities. Several conclusions are presented that are lessons derived from this experience in dealing with a large amount of earthquake data. The most important being the true and immediate necessity of making all critical earthquake information available to anyone who seeks to study such data for a better understanding of the earthquake and its consequences. By looking at the information provided by all these data, we aim to finally improve seismic codes and engineering practice, which are important social goods.

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Vásquez J., de la Llera J., Hube M. Earthquake Engineering & Structural Dynamics, DOI: 10.1002/eqe.2731

Reinforced concrete shear walls are used because they provide  high lateral stiffness and resistance to extreme seismic loads. However, with the increase in building height, these walls have become slenderer and hence responsible of carrying larger axial and shear loads. Because 2D/3D finite element inelastic models for walls are still complex and computationally demanding, simplified but accurate and efficient fiber element models are necessary to quickly assess the expected seismic performance of these buildings. A classic fiber element model is modified herein to produce objective results under particular loading conditions of the walls, that is, high axial loads, low axial loads, and nearly constant bending moment. To make it more widely applicable, a shear model based on the modified compression field theory was added to this fiber element. Consequently, this paper shows the formulation of the proposed element and its validation with different experimental results of cyclic tests reported in the literature. It was found that in order to get objective responses in the element, the regularization techniques based on fracture energy had to be modified, and nonlinearities because of buckling and fracture of steel bars, concrete crushing, and strain penetration effects were needed to replicate the experimental cyclic behavior. Thus, even under the assumption of plane sections, which makes the element simple and computationally efficient, the proposed element was able to reproduce the experimental data, and therefore, it can be used to estimate the seismic performance of walls in reinforced concrete buildings.

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S. Brunet, J.C. de la Llera, E. Kausel

This article considers the effectiveness of a seismic isolation system composed of a shallow layer of soil mixed with sand and rubber from shredded tires. Athorough review of past work is first provided, which is then followed by an evaluation of the constitutive properties of sand-rubber soil mixtures when these undergo large states of deformation and slip. Finally, a comprehensive set of simulations that involve a structure underlain by a strongly non-linear, seismic isolating layer when subjected to a variety of actual earthquakes scaled to various peak accelerations, are considered in detail. It is shown that the concept of using soil-rubber mixtures for the purposes of seismic isolation appears promising. A thickness for the rubber–soil mixture of just2–3 m is likely to be enough to achieve good levels of reductions in the seismic response of the structure. This suggests the desirability of following these analyses with large-scale experimental verifications, not only to fully validate the concept, but also to quantify and assess the
numerical predictions with our simple even if non-linear mechanical models, and verify the large-strain constitutive properties of the soil mixtures inferred from laboratory analyses.

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R. Jünemann, J.C. de la Llera, M. Hube, L.A. Cifuentes, and E. Kausel. Engineering Structures, 82:168-185

This research article investigates the correlation between a suite of global structural parameters and the observed earthquake responses in 43 reinforced concrete shear wall buildings, of which 36 underwent structural damage during the M_w 8.8, 2010, Maule earthquake. During the earthquake, some of these buildings suffered brittle damage in few reinforced concrete walls. Damage concentrated in the first two building stories and first basement, and most typically, in the vicinity of important vertical irregularities present in the resisting planes. This research consolidates in a single database information about these 36 damaged buildings for which global geometric and building design parameters are computed. Geometry related characteristics, material properties, dynamic and wall-related parameters, and irregularity indices are all defined and computed for the inventory of damaged buildings, and their values compared with those of other typical Chilean buildings. A more specific comparison analysis is performed with a small benchmark group of 7 undamaged buildings, which have almost identical characteristics to the damaged structures, except for the damage. A series of ordinal logistic regression models show that the most significant variables that correlate with the building damage level are the region where the building was located and the soil foundation type. Most of the damage took place in rather new medium-rise buildings, and was due in part to the use of increasingly thinner unconfined walls in taller buildings subjected to high axial stresses due to gravity loads, which in turn are increased by dynamic effects. Time–history analyses are performed in five damaged buildings to analyze in more detail the dynamic effect in these amplifications of the average axial load ratios. Finally, a simplified procedure to estimate this dynamic amplification of axial loads is proposed in these buildings as an intent to anticipate at early stages of the design the seismic vulnerability of these structures.

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C. Alarcón, M.A. Hube, R. Jünemann, and J.C. de la Llera. Bulletin of Earthquake Engineering, 13(4):1119-1139

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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J. Pardo-Varela and J.C. de la Llera. Earthquake Engineering & Structural Dynamics, 44 (3):333-354

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.

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A. Lemnitzer, L.M. Massone, D.A. Skolnik, J.C. de la Llera, and J.W. Wallace. Engineering Structures, 76:324-388

Between March 13th and 28th 2010, a team of U.S. researchers, professionals, and local collaborators instrumented four reinforced concrete (RC) buildings in Santiago, Chile, to measure aftershock response data following the February 27, 2010 MW 8.8 earthquake. The selected buildings, designed according to NCh433.Of96 (similar to ACI 318-95), represent typical construction, e.g. moderate to high rise office buildings with large office space and inner core shear walls and mid-rise residential shear wall buildings. Two of the instrumented buildings were undamaged, whereas one building suffered only minor nonstructural damage and the fourth building exhibited more significant structural damage such as column buckling and shear wall cracking. Instrumentation consisted mainly of uni-axial and tri-axial accelerometers as well as some displacement transducers. Records for several aftershocks were captured during a period of one month. Collected data were processed and system identification algorithms were used to determine dynamic building- and modeling parameters (e.g. building periods, acceleration amplification, inter-story drifts, building rocking and torsion, and assessment of diaphragm in-plane rigidity). A comparison between linear elastic models used in engineering practice and measured data was performed for one building. Information related to the instrumented buildings, data collected, and analytical results is presented, along with practical lessons learned conducting monitoring studies in the aftermath of this very strong earthquake.

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C. Fortuño, J.C. de la Llera, C.H. Wicks, and J.A. Abell. Bulletin of the Seismological Society of America, 104(6):2735

Conventional acceleration records do not properly account for the observed coseismic ground displacements, thus leading to an inaccurate definition of the seismic demand needed for the design of flexible (long period) structures. Large coseismic displacements observed during the 27 February 2010 Maule earthquake suggest that this effect should be included in the design of flexible structures by modifying the design ground motions and spectra considered. Consequently, Green’s functions are used herein to compute synthetic low‐frequency seismograms that are consistent with the coseismic displacement field obtained from interferometry using synthetic aperture radar (SAR) images. In this case, the coseismic displacement field was determined by interfering twenty SAR images of the Advanced Land Observation Satellite (ALOS)/PALSAR satellite taken between 12 October 2007 and 28 May 2010. These images cover the region affected by the 2010 M_w 8.8 Maule earthquake. Synthetic broadband seismograms are built by superimposing the low‐pass filtered synthetic low‐frequency seismograms with high‐frequency strong‐motion data. The broadband seismograms generated are then consistent with the coseismic displacement field and the high‐frequency content of the earthquake. A sensitivity analysis is performed using three different fault and slip parameters, the rupture velocity, the corner frequency, and the slip rise time. Results show that the optimal corner frequency of the low‐pass filter f_c=1/T_c, leads to a trade‐off between acceleration and displacement accuracy. Furthermore, spectral response for long periods, say T≥8  s, is relatively insensitive to the value of T_c, whereas shorter periods are strongly dependent on both the slip rise time and T_c. In general, larger displacements consistent with coseismic data are obtained using this technique instead of digitally processing the acceleration ground‐motion records.

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B. Briones and J.C. de la Llera. Engineering Structures, 79:309-321

The behavior of a bi-directional energy dissipation device made of copper was investigated. The development considered four phases: (1) characterization and numerical modeling of the cyclic plastic behavior of Electrolytic Tough Pitch copper using the Chaboche constitutive model; (2) generation of a finite element model including large deformations and the inelastic constitutive model of the material; (3) numerical design of the device using the response surface methodology; and (4) design and testing of two different proof-of-concept devices subjected to both, a unidirectional and a bi-directional displacement load path. The cyclic response of the device showed significant energy dissipation capacity even for very small deformations. It was also capable of sustaining 20 large cycles prior to failure. The numerical model used was capable of representing the cyclic response characteristics of the damper very accurately, and the proposed design process was validated using the measured response of the tested devices. It is concluded that annealed copper is an interesting material for energy dissipation and that the design procedure developed proved to be cost-effective and applicable to other metallic dampers.

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R. Zemp, J.C. de la Llera, and F. Weber. Smart Materials and Structures 23(12)

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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M.A. Hube, A. Marihuén, J.C. de la Llera, and B. Stojadinovic. Engineering Structures, 80:377-388

Residential reinforced concrete buildings performed well during the 2010 Mw 8.8 Maule, Chile earthquake. However, brittle damage was observed in reinforced concrete structural walls. The most frequent observed damage in such walls was crushing of concrete due to flexural-compressive interaction, buckling and fracture of longitudinal reinforcement, and opening of the horizontal reinforcement. The main objective of this study is to understand the observed damage in slender walls after 2010 Maule earthquake and to reproduce and analyze experimentally the seismic behavior of such walls. The second objective is to provide recommendations to estimate the lateral displacement and the effective stiffness of slender walls. To achieve these objectives, six ½-scale slender reinforced concrete walls were tested using a conventional quasi-static cyclic incremental lateral displacement test protocol with a constant axial load. The test results are compared to a reference wall tested previously in the same research project. The variables analyzed in this study are: wall thickness, wall aspect ratio, use of uniformly distributed vertical reinforcement, detailing of 135-degree hooks for the horizontal reinforcement, addition of closed stirrups in the wall boundaries, and addition of transverse cross-ties. The observed damage in the tested walls was similar to that observed in walls of buildings damaged during the 2010 Maule earthquake. The behavior of the tested walls was dominated by bending due to their relatively large aspect ratio. The failure, determined by the loss of ability to carry axial load, occurred suddenly as a compression failure along the entire cross section at the base of the tested walls. Test results showed that a 25% reduction in wall thickness reduced the ultimate displacement capacity, ductility, and energy dissipation ability of the wall. Closed stirrups and cross-ties were effective in increasing displacement capacity and ductility, and closed stirrups were effective in preventing out-of-plane buckling of the wall after compression failure. The average effective stiffness ratio of the tested walls was 0.39, which is slightly larger than the ACI 318 suggestion of 0.35.

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A. Sternberg, R. Zemp, and J.C. de la Llera. Engineering Structures, 69:194-205

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.

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C. Alarcón, M.A. Hube, and J.C. de la Llera. Engineering Structures, 73:13-23

About 2% of Reinforced Concrete (RC) buildings taller than nine stories suffered serious damage in structural walls during the 2010 Chile earthquake. The observed damage involved mostly crushing of concrete, buckling of vertical reinforcement, and opening of the horizontal reinforcement. This damage is attributed to poor concrete confinement in the web and boundaries, inadequate horizontal reinforcement detailing, and high axial loads. This research aims to reproduce the observed damage and evaluate the influence of axial loads in the seismic behavior of RC walls with unconfined boundaries. To achieve these objectives, three identical wall specimens were tested. The wall specimens were designed with characteristic wall detailing obtained from data of five damaged buildings. These wall specimens were tested under equal lateral displacement cycles and subjected to different axial load ratios. The flexural-compressive failure mode exhibited by damaged walls during the earthquake was reproduced in these tests. Experimental results indicate that high axial load has a significant effect on the seismic performance and failure mode of RC walls. Indeed, it triggers a dangerous brittle concrete crushing failure which occurs immediately after spalling of the concrete cover.

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J. Encina and J.C. de la Llera. Engineering Structures, 56:738-748

In early stages of the design of a free-plan building different structural layouts should be evaluated to achieve a satisfactory level of seismic performance. However, the urgency of initial stage decisions needed by architects and developers makes the use of complex 3D structural models impractical. For this reason, a tool that can evaluate with acceptable accuracy the expected seismic performance of these configurations is necessary. This paper introduces a simplified building model that includes the flexural contribution of the slabs, and models the shear wall cores using a wide column analogy that includes warping effects. The model introduces kinematic constraints to account for the interaction between walls and slabs. Comparison of modal and response-histories with those given by a 3D finite element model shows that the proposed model has good accuracy, leading to errors usually less than 15%. Finally, the model has been devised to include other shear-wall structural configurations, energy dissipation systems, and the inelastic behavior of walls.

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Segui C.E., Almazán J., de la Llera J. Engineering Structures 46, 703-717.

 

Seismic isolation systems reduce the destructive effects of earthquakes through introducing a flexible interface between the superstructure and the foundation. Numerous studies, both analytical and experimental, have shown that such devices can control the translational response of the superstructure. However, no generally consistent design recommendations to control the torsional response are available. The objective of this paper is to present a methodology that lead to achieve optimal torsional control. The assumption behind is that the isolation–superstructure system can be split into an isolated base and superstructure subjected to the filtered ground motion excitation produced by the base response. The superstructure acts as a rigid body subjected this filtered acceleration responses which are applied as quasi-static inputs into the superstructure. Under rather weak assumptions, this simplification provides excellent results in estimating the response of the system. Such response has been used in this study to choose the optimal eccentricity and torsional stiffness parameters of the isolation system that minimize the lateral-torsional response of the superstructure. Results are obtained using probabilistic techniques and show that the response of the superstructure may be substantially improved if the isolation system is torsionally flexible, and if the center of stiffness of the isolated base should lie in the vicinity of the (average) center of stiffness of the superstructure.

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Westenenk B., de la Llera J., Junemann R., Hube M., Besa J.J., Lüders C., Inaudi J.A.,Riddell R., Jordán R. Bulletin of Earthquake Engineering,  11 (1),  69-91.

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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J.A. Vásquez, J.C. de la Llera, M. Rendel. Insights and Innovations in Structural Engineering, Mechanics and Computation. Proceedings of the Sixth International Conference on Structural Engineering, Mechanics and Computation, Cape Town, South Africa.

Customary Seismic design assumes a reduced design spectrum with a certain ductility level of the structure. Although proven successful, the design method provides little information about the inelastic behavior of a structure, which is expected to be large in severe earthquakes. This study deals with the inelastic dynamic response analysis of a large prestressed building to be constructed in Chile. Because of regularity of the structure, a 2D reinforced concrete frame was modeled using fiber elements regularized with a modified stress-strain constitutive relationship using the software Opensees. Therefore, damage may occur anywhere along the element characterized by variable reinforcing steel and internal forces. Results of the inelastic analysis show that inelastic deformations localize in a few places around the nodes, but the building is able to withstand a maximum credible earthquake demand without collapse.

Vasquez et al (2016)

J.C. de la Llera, J. Mitrani-Reiser, F. Rivera, C. Fortuño, R. Jünemann, A. Poulos, and J. Vasquez. 10th Pacific Conference of Earthquake Engineering, Keynote Lecture

At 3:34AM local time, on February 27^th, 2010, a moment magnitude M_w 8.8 megathrust earthquake struck offshore the coast of Chile. The earthquake ruptured a 540 by 200 km mature seismic gap of the underlying subduction pacific plate interlocking mechanism. More than 75% of the 16 million Chileans spread over several large urban areas in the center-south of the country were affected by the earthquake, which caused 521 fatalities with 124 of them due to the tsunami, and an overall damage estimate of USD 30 billion. Because the earthquake struck the most densely populated area of the country, it represents a very unique opportunity to reflect on its ubiquitous impact over many different physical and social systems. The reflection contained in this article occurs five years later, once reconstruction and recovery are complete from this longitudinal wound of the country. Seismic codes have changed, research on the supposedly indestructible reinforced concrete shear walls has been done, new seismic protection technologies have been incorporated, and whole new seismic standards have been adopted by communities and people. The price it took was quite high, but we can confidently say that Chile is better prepared today for the next large earthquake.

10PCEE Paper_210 de la Llera et al

A. Poulos, P. Favier, J. Vásquez, and J.C. de la Llera. 10th Pacific Conference of Earthquake Engineering

Hospitals are critical facilities that are essential to the response of communities to disasters such as earthquakes. The seismic performance of these facilities is highly dependent on the structural behaviour and content damage. However, earthquake induced building damage has not been considered directly yet when assessing hospital loss of functionality. Previous models are mainly based on holistic approaches (fault trees) or simplified numerical models, thus reducing the effect of the hospital damage to penalty factors. Our approach uses inelastic structural analysis to compute the earthquake response, fragility functions to assess non-structural and component damage, and a discrete event model to simulate the response of the emergency room of the hospital. Further, the seismic performance of the hospital is characterized by the increase in patient waiting times after the earthquake. The model is then tested with the Mw 8.2 2014 earthquake in Pisagua, northern Chile. Analyses show that hospital performance is mainly affected by two factors: the arrival rate of patients and the downtime of healthcare units. The model is applicable to a big range of seismic scenarios, which is key in estimating risk for the loss of performance of hospitals during an earthquake.

10PCEE Paper_156 Poulos et al

J.C. de la Llera, J. Vásquez, A. Poulos, and P. Favier. ACHISINA Congress, Keynote Lecture

This article describes some of the new trends observed in research and design of structures equipped with seismic protection systems (SPS). This field of earthquake engineering has almost 40 years of formal development and techniques have gained increasing acceptance through time in design practice, especially due to the successful performance of these structures during the severe ground shaking of recent earthquakes. The time window considered in this investigation of the field is 10 years, defined mainly by research and practical applications after the important cluster of severe earthquakes starting with Sumatra in 2004, Haiti and Chile in 2010, and Japan and New Zealand in 2011. A brief overview of the research done in the field around the world is presented first to provide a general context to the reader, and also identify possible trends in research and practice that could lead the future development of the field. The article then highlights some results and applications derived from current research in earthquake behavior and seismic protection of buildings in Chile, followed by an overview of the design methodologies available in the literature. Furthermore, some details and results are provided for a robust design procedure that has been used to design a number of buildings equipped with SPS technologies in Chile. And finally, a list of the Chilean structures known up to now to be equipped with seismic protection was generated as future reference for the local development of the field.

Achisina2015_de la Llera et al (2015)

R. Zemp, J. C. de la Llera, H. Saldias, F. Weber

F. Tocornal, A. Poulos, J. C. de la Llera, J. Mitrani-Reiser, F. Rivera

M. A. Hube, J. C. de la Llera

M. Chacón, J. C. de La Llera, J. Marques, M. Hube, A. Lemnitzer

R. Jünemann, J. C. de la Llera, M. A. Hube

C. Fortuño, J. C. de la Llera, C. Wicks, J. Abell

Maureira, N., J.C. de la Llera

F. X. Flores, F. A. Charney, D. Lopez-Garcia, J. C. de la Llera. ACHISINA.

Hube M.A., Marihuén A., de la Llera J.C. Proceedings of the Second European Conference on Earthquake Engineering and Seismology

Hube MA, Marihuén A, De la Llera JC, Stojadinovic B. DOI: 10.4231/D3X34MS4R

C. Alarcon, M. A. Hube, J.C. de la Llera. Proceedings of Vienna Congress on recent advances in earthquake engineering & structural dynamics.

Real-Time Structural Measurement (RTSM), CHILE, 2626-2012, 21/09/2012

Disipador de Tabique, CHILE, 2687-2011, 27/10/2011

Autocentrando FRI-UC, CHILE, 2273-2011, 13/09/2011

Magneto-reológico MRDA-UC, CHILE, 2688-2011, 27/10/2011

U-SHAPE, PERU, 1977-2009, 27/11/2008

U-SHAPE, MEXICO, MX/2012/9429, 30/01/2012, 27/11/2008

U-SHAPE, ECUADOR, SP-08-8911, 26/11/2008, 26/11/2008

UFP,  CHILE, 3404-2007, 27/11/2007, 27/11/2007

Sistema de tirantes y deslizador, COLOMBIA, 07-076.272, 15/03/2007

Sistema de tirantes y deslizador, PERU, 961-2007, 15/03/2007