In the first part of this paper an algorithm is proposed to obtain demand hazard curves and, from them, seismic-response spectra with uniform annual failure rates for single-degree-of-freedom (SDOF) systems with energy-dissipating devices (EDDs). In the second part, a performance-based dual-level approach is proposed for the design of buildings with EDDs. The criterion establishes acceptance conditions (related to serviceability—and to ultimate limit-states) that correspond to the main system and to the dissipating elements. The uncertainties implicit in the transformation between the response of SDOF and MDOF systems with EDDs are taken into account by means of their demand hazard curves. The reliability-based dual-level design criterion proposed is illustrated by means of a ten-story reinforced concrete building rehabilitated with steel energy-dissipating devices.
The hysteretic energy (EH) dissipated in posttensioned steel frames (PTSF) with hysteretic dampers is calculated by using equivalent single-degree-of-freedom systems (ESDOFS), where the nonlinearity of both the steel bars (beam and columns) and the connections of the structural frame is separately considered. Five multi-degree-of-freedom (MDOFS) PTSF and their corresponding ESDOFS are studied under the action of 30 seismic motions recorded in soft ground, scaled in terms of the spectral pseudoacceleration evaluated at the fundamental period of the structures. Several simple mathematical expressions are proposed. The first expression is useful to calculate modifying factors (FMEH) to relateEHof the ESDOFS with that of the MDOFS; the second is to determine the interstory drift (γ) as a function of the seismic intensity. The third equation is to calculate the factor of the relative participation of the energy that the connections dissipate with respect to the total energyEHand the fourth equation, which is function of theγ, is to obtain the distribution factors ofEHthrough the height of the structure. The methodology proposed can be used for the design or the structural revision of PTSF with dampers.
Se usa la dispersión de las ondas de Rayleigh en su modo fundamental, correspondiente a dos explosiones nucleares efectuadas en Nevada, USA, y registradas en la estación sismológica UNM, en la ciudad de México, para estimar la estructura de la velocidad de la onda de cizalle en un perfil que corre aproximadamente a lo largo del flanco oriental de la Sierra Madre Occidental, México. Los datos observados de la dispersión de la velocidad de grupo para el rango de períodos de 10 a 21 segundos pueden explicarse con 5 capas horizontales, elásticas y homogéneas sobre un semiespacio. El espesor promedio obtenido para la corteza es del orden de 40 km. Las velocidades de cizalle y los espesores obtenidos son los siguientes: Sedimentos, Vs1 = 1.5 km/s, h1= 1.2 km;Granito, Vs2= 2.90 km/s h2= 2.2 km y VS3= 3.56 km/s, h3= 26 km;Basalto, VS4= 4.10 km/s, h4= 10.0 km;Manto Superior VS5= 4.50 km/s, h5= 10.0 km; Manto, VS6=4.15 km/s, h6=∞. Se presupone una razón de 1.78 para el cociente Vp/VS.Este modelo de velocidades sugiere que la estructura del flanco oriental de la Sierra Madre Occidental es transicional entre una de tipo Alpino y otra de tipo Basin and Range. El modelo concuerda satisfactoriamente con resultados anteriores basados en estudios de refracción hechos en los alrededores de la región y con las ideas sobre la evolución tectónica cenozoica del oeste del continente norteamericano.
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