Browsing by Author "De La Llera Martin, Juan Carlos"

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    Accidental 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.
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    Analytical model of structures with frictional pendulum isolators
    (2002) De La Llera Martin, Juan Carlos
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    Fragility curves for unanchored medical equipment accounting for building and content interaction
    (2026) Guamán Cabrera, Jaime Wilson; De La Llera Martin, Juan Carlos; Rossetto, Tiziana; Enberg Castro, Luis Fernando; Ioannou, Ioanna
    Currently, construction codes and standards require nonstructural fragility information to define nonstructural performance objectives and expectations for low- and design-intensity earthquake motions. To address this knowledge gap, this study focuses on the development of analytical fragility curves for unanchored medical equipment commonly found in hospital critical rooms, taking into account the building’s performance, damage progression, and content interaction simultaneously. To achieve this goal, a fully equipped emergency room, intensive care unit, and operating room are simulated on the first, fourth, and fifth floors of a mid-rise hospital building, respectively, and subjected to service, design, and maximum considered earthquake levels under fixed-to-the-base (FB) and base-isolated (BI) support conditions. The building’s floor acceleration responses are used as input motions to assess the performance of several pieces of medical equipment using rolling and sliding nonlinear models. This study has included a comprehensive uncertainty analysis to propagate different sources of uncertainty into the fragility curves. Fragility results indicate that, under FB support conditions, equipment malfunctions and failures are expected to occur during low-intensity earthquake motions, even if the hospital building experiences minor structural damage. Furthermore, knowing the damaged condition of medical equipment (malfunction/failure) is crucial for determining its availability and subsequent use to stabilize critical condition patients or save their lives. Finally, these fragility curves can be used to plan post-disaster recovery and make risk-informed decisions in healthcare facilities.
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