Vector-IM-based assessment of alternative framing systems under bi-directional ground-motion

Earthq Engng Struct Dyn

2018

Summary The seismic behaviour of a wide variety of structures can be characterized by the rocking response of rigid blocks. Nevertheless, suitable seismic control strategies are presently limited and consist mostly on preventing rocking motion all together, which may induce undesirable stress concentrations and lead to impractical interventions. In this paper, we investigate the potential advantages of using supplemental rotational inertia to mitigate the effects of earthquakes on rocking structures. The newly proposed strategy employs inerters, which are mechanical devices that develop resisting forces proportional to the relative acceleration between their terminals and can be combined with a clutch to ensure their rotational inertia is only employed to oppose the motion. We demonstrate that the inclusion of the inerter effectively reduces the frequency parameter of the block, resulting in lower rotation seismic demands and enhanced stability due to the well‐known size effects of the rocking behaviour. The effects of the inerter and inerter‐clutch devices on the response scaling and similarity are also studied. An examination of their overturning fragility functions reveals that inerter‐equipped structures experience reduced probabilities of overturning in comparison with uncontrolled bodies, while the addition of a clutch further improves their seismic stability. The concept advanced in this paper is particularly attractive for the protection of rocking bodies as it opens the possibility of nonlocally modifying the dynamic response of rocking structures without altering their geometry.

\overset{μ}{true}

and

\overset{β}{true}

, that maximize the likelihood of reproducing the observed data, such that

false{\overset{μ}{true}, \overset{β}{true} false} = \max_{μ, β} true \prod_{j = 1}^{n} normalΦ {((), \frac{\ln x_{j} - μ}{β})}^{z_{j}} {((), 1 - normalΦ ((), \frac{\ln x_{j} - μ}{β}))}^{1 - z_{j}},

where Φ is the normal cumulative distribution function and x j the intensity measure values.…”

Section: Response Under Real Pulse‐like Ground Motionsmentioning

confidence: 99%

Seismic protection of rocking structures with inerters

Thiers-Moggia

Earthq Engng Struct Dyn

2018

“…Indeed, orientational analysis principles demand that the variables under consideration have a predefined set of orientations instead of orientations that change over time. This also hints to the formal orientational superiority of peak orthogonal displacements as structural demand parameters in contrast with other measures like the maximum geometric mean, whose orientation is time‐dependent 20,47 …”

Section: Bidirectional Yielding Structuresmentioning

confidence: 89%

Strong‐motion duration and response scaling of yielding and degrading eccentric structures

Earthq Engng Struct Dyn

2020

Plan irregular structures, whose complex response represents a generalisation of the simpler de-coupled motion ascribed to symmetric buildings, make up a large proportion of the failures during major earthquakes. This paper examines the seismic response scaling of degrading and no-degrading eccentric structures subjected to bidirectional earthquake action and its relationship with the duration of the ground motion by means of dimensional and orientational analyses. Structures with reflectionally symmetric stiffness distribution and mass eccentricity subjected to orthogonal pairs of ideal pulses are considered as the fundamental case. The application of Vaschy-Buckingham's Π-theorem reduces the number of variables governing the peak orthogonal displacements leading to the emergence of remarkable order in the structural response. If orientationally consistent dimensionless parameters are selected, the response becomes self-similar. By contrast, when degradation is introduced, peak inelastic displacements are dramatically affected and the self-similarity in the response is lost immediately after the onset of inelastic deformations. Conversely, if the uniform duration, instead of the period, of the strong motion is adopted as a timescale, a practically self-similar response is observed. This offers unequivocal proof of the fundamental role played by the ground-motion duration in defining the peak displacement response of degrading structures even at small inelastic demands, although its importance increases with increasing deformation levels. Finally, the existence of complete similarities, or similarities of the first kind, are explored and the practical implications of these findings are briefly outlined in the context of real pulse-like ground motions with varying degrees of coherency.

“…To this end, the parameters of the fragility function (i.e., its median and standard deviation ) required in Eq. (22), can be calculated by maximizing the likelihood function (Dimitrakopoulos and Paraskeva 2015;Málaga-Chuquitaype and Bougatsas 2017). For a N number of ground motions, the likelihood function can be written as:…”

Section: Dimensionless Fragility Analysismentioning

confidence: 99%

“…Non-dimensional terms normalized to S a (T 0 ). Dimensionless terms Π 1 = a max /P GA, Π 2 = ω 0 /ω g = T p /T 0 Regression analysis for MP Pulses4 Acceleration response and regression analysis for real records4.1 Alternative time and length scales for real recordsA number of recent studies have investigated the challenging issue of selecting appropriate time and length scales for earthquake response analysis(Dimitrakopoulos and Paraskeva 2015;Málaga-Chuquitaype 2015;Málaga-Chuquitaype and Bougatsas 2017).…”

mentioning

confidence: 99%

Dimensionless fragility analysis of seismic acceleration demands through low-order building models

Psaltakis

Kampas³

et al. 2019

Bull Earthquake Eng

Self Cite

This paper deals with the estimation of fragility functions for acceleration-sensitive components of buildings subjected to earthquake action. It considers ideally coherent pulses as well as real non-pulselike ground-motion records applied to continuous building models formed by a flexural beam and a shear beam in tandem. The study advances the idea of acceleration-based dimensionless fragility functions and describes the process of their formulation. It demonstrates that the mean period of the Fourier Spectrum, T m , is associated with the least dispersion in the predicted dimensionless mean demand. Likewise, peak ground acceleration, PGA-, and peak ground velocity, PGV-based length scales are found to be almost equally appropriate for obtaining efficient 'universal' descriptions of maximum floor accelerations. Finally, this work also shows that fragility functions formulated in terms of dimensionless -terms have a superior performance in comparison with those based on conventional non-dimensionless terms (like peak or spectral acceleration values). This improved efficiency is more evident for buildings dominated by global flexural type lateral deformation over the whole intensity range and for large peak floor acceleration levels in structures with shear-governed behaviour. The suggested dimensionless fragility functions can offer a 'universal' description of the fragility of acceleration-sensitive components and constitute an efficient tool for a rapid seismic assessment of building contents in structures behaving at, or close to, yielding which form the biggest share in large (regional) building stock evaluations.