DSpace Angular :: Browsing by Author "Vásquez P., Jorge"

Browsing by Author "Vásquez P., Jorge"

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A macro-element model for inelastic building analysis
(2000) Llera Martin, Juan Carlos de la; Vásquez P., Jorge; Chopra, Anil K.; Almazán Campillay, José Luis
A three-dimensional model for approximate inelastic analysis of buildings is presented herein. The model is based on a single macro-element per building storey. The inelastic properties of the model are characterized by the so-called ultimate storey shear and torque (USST) surfaces. Different algorithms for the construction of these surfaces, as well as their applications in building modelling, are presented and discussed. Two alternative procedures are developed to integrate the force-deformation constitutive relationship of the macroelements. The first one follows the exact trajectory of the load path of the structure on the USST, and the second uses linear programming without ever forming the USST surface. The accuracy of the model and integration procedure is evaluated by means of the earthquake response of single-storey systems. The model and integration procedure developed is finally used to compute the inelastic response of a seven-storey R/C building. The results of this investigation show that the model proposed, although approximate, can be effective in estimating the inelastic deformation demand of a building. It also enables the engineer to capture and interpret important features of the three-dimensional inelastic response of a structure even before performing any inelastic dynamic analysis. Copyright (C) 2000 John Wiley & Sons, Ltd.
A regularized fiber element model for reinforced concrete shear walls
(2016) Vásquez P., Jorge; Llera Martin, Juan Carlos de la; Hube Ginestar, Matías Andrés
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
Comparative assessment of nonlinear static and dynamic methods for analysing building response under sequential earthquake and tsunami
(2019) Rossetto, Tiziana; Barra, Camilo de la; Petrone, Crescenzo; Llera Martin, Juan Carlos de la; Vásquez P., Jorge; Baiguera, Marco
This paper presents a comprehensive comparison of different dynamic and static approaches for assessing building performance under sequential earthquakes and tsunami. A 10-storey reinforced concrete seismically designed Japanese vertical evacuation structure is adopted as a case study for the investigation. The case study building is first assessed under sequential earthquake and tsunami nonlinear response history analyses: the first time this is done in the literature. The resulting engineering demand parameters are then compared with those obtained when the analysis procedure is systematically simplified by substituting different static approaches for the nonlinear response history analyses in both the earthquake and tsunami loading phases. Different unloading approaches are also tested for the cases when an earthquake pushover is adopted. The results show that an earthquake nonlinear response history analysis, followed by a transient free vibration and a tsunami variable depth pushover, provides the best alternative to full dynamic analyses in terms of accuracy and computational efficiency. This structural analysis combination is recommended and has the advantage that it does not require the tsunami inundation time history to be known in advance. The proposed double pushover approach is instead deemed only suitable for the collapse assessment of regular low to mid-rise buildings and for the development of collapse fragility functions. An important observation made is that sustained earthquake damage seems not to affect the tsunami resistance of the case study building when the fully dynamic analysis is carried out for the sequential loading. This observation will be the subject of future work.
Earthquake damage assessment for deterministic scenarios in Iquique, Chile
(2018) Aguirre Aparicio, Paula; Vásquez P., Jorge; Llera Martin, Juan Carlos de la; González, Juan; González, Gabriel
Risk evaluation and loss analysis is key in foreseeing the impact of disasters caused by natural hazards and may contribute effectively in improving resilience in a community through the pre-evaluation of preparedness and mitigation actions. The pilot study presented herein is for the Chilean city of Iquique, which is located at the core of a seismic gap that extends from south Perú to north Chile, and has strategic geopolitical and economic importance for the country. The region was hit April 1, 2014, by an Mw 8.2 earthquake that caused only moderate damage, but seismological evidence suggests that there is still a potential for a much larger event in the region. Therefore, a careful damage assessment study is fundamental to anticipate the possible physical, social, and economic consequences that Iquique may face in the future. In this work, the HAZUS-MH platform was adapted and used to simulate a set of ten plausible physics-based future seismic scenarios with magnitudes ranging from Mw 8.40 to Mw 8.98, which were proposed based on an analysis of interplate locking and the residual slip potential remaining after the April 1, 2014, earthquake. Successful application of this damage assessment methodology relies on the construction of a comprehensive exposure model that takes into account regional features and a good characterization of the physical vulnerabilities. For Iquique, a large body of public and local data was used to develop a detailed inventory of physical and social assets including an aggregated building count, demographics, and essential facilities. To characterize the response of the built environment to seismic demand, appropriate HAZUS fragility curves were applied, and outcomes were validated against the damage observed in the 2014 earthquake. After satisfactory testing, a deterministic earthquake damage assessment study was carried out for the collection of predictive scenarios aimed to estimate their expected impacts. This analysis provides data for future evaluations of different physical and social mitigation measures for the city.
Earthquake damage assessment for Iquique: case study for implementation of Hazus-MH in Chile
(National Information Centre of Earthquake Engineering, 2017) Aguirre Aparicio, Paula; Vásquez P., Jorge; Llera Martin, Juan Carlos de la; González López, Gabriel; González, Juan; Shrivastava, Mahesh
Risk evaluation and loss analysis is key in foreseeing the impact of disasters caused by natural hazards, and may contribute effectively in improving resilience in a community through the pre-evaluation of preparedness and mitigation actions. The pilot study considered herein is the city of Iquique, located in north Chile where a large megathrust earthquake and tsunami is expected to eventually cover the south of Peru and north of Chile. Although the region was recently hit by an Mw 8.2 earthquake April 1st 2014, damage caused was only moderate. Geophysical evidence suggests that there is still a potential for a much larger event in the region. Therefore, a thorough risk assessment is key to anticipate its possible physical, social, and economic consequences. Consequently, HAZUS-MH was used to simulate a set of earthquake hazard scenarios generated from estimates of plate interlocking and the residual slip potential remaining from the April 1st 2014 rupture fault mechanism. Successful application of the HAZUS-MH methodology relies on the construction of a comprehensive exposure model that takes into account regional features and a good characterization of the physical vulnerabilities. For Iquique we have used a large body of public and local data to develop a detailed inventory of physical and social assets including an aggregated building count, demographics, essential facilities, infrastructure, and lifelines. To characterize the response of the built environment to seismic demand, HAZUS fragility curves and downtime models were applied, and outputs were calibrated using the observed damage after the April 1st 2014 earthquake. Using such calibration, a deterministic seismic risk assessment for the collection of generated scenarios and their expected impacts on all physical assets, population, and essential facilities were estimated. This analysis sets a basis for the simulation and evaluation of different physical and social mitigation measures for the city in the future.
Fiber model for reinforced concrete walls
(National Information Centre of Earthquake Engineering, 2017) Vásquez P., Jorge; Llera Martin, Juan Carlos de la; Hube Ginestar, Matías Andrés
Due to the taller reinforced concrete (RC) buildings that have been constructed in recent years, shear walls at lower levels are subjected to higher axial loads and bending moments. Although complex finite element inelastic models for shear walls can effectively couple several effects at the stress-strain level, they are computationally demanding, and hence robust and computationally efficient models are necessary to quickly assess the earthquake performance of these buildings. Herein, a pure two-node fiber element model that takes into account axial and bending components only, was modified to produce objective results under common loading conditions of the walls identified in Chilean buildings, i.e., high axial loads with linear bending moment variation between floors. A regularization is required to predict results independent of the element size and a shear model based on the modified compression field theory was added into this element to simulate the behavior of shear walls adequately. This investigation focuses in the formulation of the proposed model, its validation with experimental tests reported in the literature, and its application to actual RC walls of buildings. It was found that the steel stress-strain constitutive behavior, the inclusion of shear deformation, and the strain penetration effects played an important role in reproducing the experimental behavior of walls. Additionally, the proposed model is able to predict the observed collapse mechanisms of walls in buildings damaged during the 2010 earthquake. Since the element is capable of reproducing experimental tests and earthquake response, and since it is numerically more efficient than other approaches, its use for complete 3D inelastic dynamic analysis of buildings is promising.
Impact on chilean hospitals following the 2015 Illapel earthquake
(National Information Centre of Earthquake Engineering, 2017) Favier, Philomène; Rivera Jofré, Felipe Andrés; Poulos Campbell, Alan John; Vásquez P., Jorge; Llera Martin, Juan Carlos de la; Mitrani-Reiser, Judith
In a post-disaster environment, hospitals play a critical role in healthcare services continuities to the population while effectively coping with eventual losses of functionality. These losses come from physical damage to the facility, loss of utility lifelines, failure in supply chains, and reduction of personnel. However, data describing the detailed performance of hospitals during past earthquakes are scarce. Consequently, following the 2015 Mw 8.3 Illapel earthquake in central Chile, an exhaustive field campaign was carried out in the Coquimbo region to collect substantial perishable data to describe physical damage to hospitals and functionality losses. This study presents first the baseline information obtained in nine surveyed government hospitals, including size, location and type of infrastructure. Then, the seismic impact was analyzed and classified to show the main physical structural and non-structural damage, lifeline interruptions, losses in hospital units, and variations in flow of patients and staff. Transfers, discharges and evacuations of patients that occurred after the event were also reported. We found that the earthquake did not affect strongly the healthcare service despite the fact that most of the structural and non-structural damage was localized in the largest regional hospital. The archival nature of the data collected may deepen our understanding of the post-earthquake healthcare system performance, which is very useful in improving disaster preparation and overall resilience.
Study of the damage of reinforced concrete shear walls during the 2010 Chile earthquake
(2016) Jünemann Ureta, Rosita; Llera Martin, Juan Carlos de la; Hube Ginestar, Matías Andrés; Vásquez P., Jorge; Chacón, Matías F.
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. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.
The 2010 Chile Earthquake: a five-year reflection
(Australian Earthquake Engineering Society, 2015) Llera Martin, Juan Carlos de la; Mitrani-Reiser, Judith; Rivera Jofré, Felipe Andrés; Fortuño, C.; Jünemann Ureta, Rosita; Poulos Campbell, Alan John; Vásquez P., Jorge
At 3:34AM local time, on February 27th, 2010, a moment magnitude Mw 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.
Three-dimensional nonlinear response history analyses for earthquake damage assessment : A reinforced concrete wall building case study
(2020) Vásquez P., Jorge; Jünemann Ureta, Rosita; Llera Martin, Juan Carlos de la; Hube Ginestar, Matías Andrés; Chacón, Matías F.
Nonlinear dynamic analysis techniques have made significant progress in the last 20 years, providing powerful tools for assessing structural damage and potential building collapse mechanisms. The fact that several reinforced concrete shear wall residential buildings underwent severe structural damage in walls at the lower building levels during the 2010 Maule earthquake (Chile) presents a scientific opportunity to assess the predictive quality of these techniques. The objective of this research is to compare building responses using two completely different three-dimensional nonlinear dynamic models and study in detail the observed damage pattern and wall collapse of one reinforced concrete shear wall building in Santiago, Chile. The first model is a mixed fiber-shell model developed in MATLAB, and the second is a shell finite element model developed in the software DIANA. Results of both models are consistent with the hypothesis that high axial loads trigger a limited ductility failure in critical walls at roof-to-base drift ratios less than 0.34% with little capacity of hysteretic energy dissipation, which contradicts the ductile design philosophy of current code provisions.

Browsing by Author "Vásquez P., Jorge"

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