This study evaluates the seismic risk of weak first-story reinforced concrete (RC) structures retrofitted with inerter dampers at their ground level when subjected to narrow-band seismic excitations. The main advantages brought about by the ground-level inerters are the reductions in seismic demands (e.g., drifts, floor accelerations). This study shows that structures with inerters are reliable systems in terms of peak story drifts for large ground motions. For moderate ground-motion intensities, the opposite could occur, mainly for soft soil sites. The reliabilities of structures with inerter dampers at their ground level are in general higher for buildings under seismic intensities associated to limit state of incipient collapse, especially for low-height buildings. This could be reversed for intensities associated to the limit state of damage limitation. The findings of this study could guide practicing engineers to use inerter-based dampers in retrofitting ductile structures consisting of moment-resisting reinforced concrete (RC) frames subjected to narrow-band earthquake excitations in regions such as Mexico City.
RESUMENSe propone una expresión para estimar el desplazamiento de Newmark en términos de la relación entre la aceleración crítica, a c (umbral de aceleración del suelo para iniciar un movimiento del talud) y la aceleración máxima del suelo, a max , para obtener el deslizamiento traslacional de laderas por sismo que de manera aproximada estimen esta amenaza a escala regional. Con los resultados que se obtienen de la ecuación de desplazamiento propuesta es posible definir un mapa de peligro por deslizamiento traslacional a nivel regional inducido por sismos. Para llevar a cabo lo anterior, se asumen valores promedio de propiedades mecánicas del suelo como la cohesión, peso volumétrico y ángulo de fricción a partir de mapas geológicos y litológicos a escala 1:1'000,000, así como la pendiente de deslizamiento potencial a partir de modelos de elevación digital del terreno. Se presenta un mapa de peligro de deslizamiento de la República Mexicana asociado a la aceleración máxima del suelo que se presenta con un periodo de retorno de 150 años, y un ejemplo de un mapa empleando como detonador el sismo de Tecomán en Colima de magnitud M=7.6 ocurrido el 21 de enero de 2003; este ejemplo se compara con el obtenido a través del método Mora-Vahrson que es ampliamente utilizado para elaborar este tipo de mapas de deslizamientos.Palabras clave: mapas de deslizamiento traslacional; desplazamiento de Newmark; intensidad sísmica; evaluación del peligro por deslizamiento
ABSTRACTWe propose to obtain translational landslides due to earthquake in Mexico estimating Newmark displacements in terms of the relationship between the critical acceleration, a c (the peak ground acceleration threshold to start the landslide) and the peak ground acceleration, a max . With the obtained results from a proposed displacement equation it is possible to define a translational landslide map at regional level induced by earthquakes. Soil parameters such as cohesion, volumetric weight and angle of friction are inferred from geological maps, scale 1:1'000,000, and a digital elevation map is employed to obtain the slope of the potential landslide. We present a landslide hazard map for Mexico associated to a peak strong ground motion acceleration with a return period of 150 years at regional level, and an example map of displacements triggered by the Artículo recibido el 15 de febrero de 2011 y aprobado para su publicación el 27 de agosto de 2013. Se aceptarán comentarios y/o discusiones hasta cinco meses después de su publicación.(1)
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