Browsing by Author "De La Llera Martin, Juan Carlos"
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- ItemAccidental torsion in buildings due to base rotational excitation(1994) De La Llera Martin, Juan Carlos; Chopra, Anil K.This investigation is concerned with accidental torsion in buildings resulting from rotational excitation (about a vertical axis) of the building foundations as a result of spatially non-uniform ground motions. Because of this accidental torsion, the displacements and deformations in the structural elements of the building are likely to increase. This increase in response is evaluated using actual base rotational excitations derived from ground motions recorded at the base of 30 buildings during recent California earthquakes. Accidental torsion has the effect of increasing the building displacements, in the mean, by less than 5 per cent for systems that are torsionally stiff or have lateral vibration periods longer than half a second. On the other hand, short period (less than half a second) and torsionally flexible systems may experience significant increases in response due to accidental torsion. Since the dependence between this increase in response and the system parameters is complex, two simplified methods are developed for conveniently estimating this effect of accidental torsion. They are the ‘accidental eccentricity’ and the ‘response spectrum’ method. The computed accidental eccentricities are much smaller than the typical code values, 0.05bb or 0.1b, except for buildings with very long plan dimensions (b ≥ 50 m). Alternatively, by using the response spectrum method the increase in response can be estimated by computing the peak response to each base motion independently and combining the peak values using the SRSS rule.
- ItemAnalytical model of structures with frictional pendulum isolators(2002) De La Llera Martin, Juan Carlos
- ItemImpact of earthquake magnitude on the estimation of tsunami evacuation casualties(2018) Castro, S.; Poulos, A.; Urrutia, A.; Herrera, J. C.; Cienfuegos, R.; De La Llera Martin, Juan CarlosThe importance of evacuation plans has been widely proven in recent tsunami events. Several evacuation models have been proposed to develop these plans and estimate city evacuation times. Typically, single extreme earthquake scenarios are used in these estimations; however, the impact of earthquake damage on the evacuation routes is usually neglected in these models. This article deals with the evaluation of the effect of three different earthquake magnitudes and the following tsunamis. Several spectral accelerations were sampled for each magnitude to estimate city damage, and from there the reduced capacity of evacuation routes due to earthquake debris. An agent-based evacuation model was used to assess the evacuation times for the city of Iquique, located in north Chile. Results show significant variability for different magnitude scenarios, thus leading to an observed increment on evacuation times up to 40% and an increase in the number of casualties due to the evacuation delay caused by earthquake debris spread on the evacuation routes
- ItemMitigating Risk through R&D+Innovation: Chile’s National Strategy for Natural Disaster ResilienceDe La Llera Martin, Juan Carlos; Rivera, Felipe; Gil, Magdalena; Schwarzhaupt, ÚrsulaWith an annual average expense of more than $2,800 million USD, Chile leads the OECD countries with the largest percentage of the GDP spent in disaster losses per year (almost 1.2% GDP). This was the motivation of the Chilean President in 2015 to ask a group of experts to prepare a national Research, Development, and Innovation (R&D+i) strategy for disaster resilience. The strategy was developed by a group, called by the acronym CREDEN, and involved more than 80 experts representing different national stakeholders from the academia, public and private sectors, NGOs, and the armed forces. The work of CREDEN finished December 2016 and produced an R&D+i roadmap composed of five enabling conditions and 14 tasks. The implementation of this strategy demands a total investment of $914 million USD in 20 years, which is expected to have a benefit-cost ratio of 2.32, and annual savings of about $106 million USD. The first stage in this process is the design of a National Institute of R&D+i for Disaster Resilience (ITReND), which will oversee the implementation of the strategy. ITReND’s design was completed in 2017 and its implementation is expected to begin in 2018. This strategy can be considered as an example of how to position R&D+i in the basis of public policy for disaster resilience. Both, the contents of this strategy and its implementation process, have unique aspects and may help guide other disaster-prone countries in their pursuit of larger resilience to the increasing occurrence rate of extreme natural events
- ItemResponse of Reinforced Concrete Buildings in Concepción during the Maule Earthquake(2012) De La Llera Martin, Juan Carlos
- ItemSlip model of the 2015 Mw 8,3 Illapel (Chile) earthquake from inversion of sentinel 1A and GPS dataDe La Llera Martin, Juan CarlosThe Mw 8.3 earthquake that occurred on September 16th 2015 west of Illapel, Chile, ruptured a ~200 km section of the plate boundary between 29°S and 33°S. SAR data acquired by the Sentinel 1A satellite was used to obtain the interferogram of the earthquake, and from it, the component of the displacement field of the surface in the line of sight of the satellite. Based on this interferogram, the corresponding coseismic slip distribution for the earthquake was determined based on different plausible finite fault geometries. The model that best fits the data gathered is one whose rupture surface is consistent with the Slab 1.0 model, with a constant strike angle of 4° and variable dip angle ranging from 2.7° near the trench to 24.3° down dip. Using this geometry the maximum slip obtained is 7.52 m and the corresponding seismic moment is 3.78·1021 equivalent to a moment magnitude Mw 8.3. The interferogram processed is also used to analyze specific site effects, such as deformations found in areas of affected mining tailing dams. A comparison between this earthquake rupture model and the inversion models of two previous earthquakes, the Mw 8.2 Pisagua (Chile, 2014) and the Mw 8.8 Maule (Chile, 2010) is done to study different earthquake characteristics, and provide a suite of methodologically consistent and spatially detailed characterizations of the fault rupture mechanisms and the permanent superficial effects of megathrust events along the Chilean coastline. These results are a key input for the generation of synthetic seismic records that combine deterministic and stochastic methods for representation of low- and high-frequency components of ground motions, respectively, and will hence enable us to characterize the seismic demand for both flexible and rigid structures in earthquake-affected areas, and thereby investigate the direct damage and losses that may be expected during future events