2,243 publications from this institution
Summary When performing loss assessment of a geographically dispersed building portfolio, the response or loss (fragility or vulnerability) function of any given archetype building is typically considered to be a consistent property of the building itself. On the other hand, recent advances in record selection have shown that the seismic response of a structure is, in general, dependent on the nature of the hazard at the site of interest. This apparent contradiction begs the question: Are building fragility and vulnerability functions independent of site, and if not, what can be done to avoid having to reassess them for each site of interest? In the following, we show that there is a non‐negligible influence of the site, the degree of which depends on the intensity measure adopted for assessment. Employing a single‐period (e.g., first‐mode), spectral acceleration would require careful record selection at each site and result to significant site‐to‐site variability of the fragility or vulnerability function. On the other hand, an intensity measure comprising the geometric mean of multiple spectral accelerations considerably reduces such variability. In tandem with a conditional spectrum record selection that accounts for multiple sites, it can offer a viable approach for incorporating the effect of site dependence into fragility and vulnerability estimates. Copyright © 2017 John Wiley & Sons, Ltd.
Summary The response of a non‐circular structure strongly depends on the orientation of the horizontal ground motion components vis‐à‐vis the structure's principal axes. At the same time, the structural response is also a function of accelerogram characteristics that give rise to considerable record‐to‐record variability even when the incident angle is neglected. Therefore, when the structural orientation relative to the fault geometry is unknown and we have limited resources for estimating the distribution of structural response given the seismic intensity, the question arises as to whether it is preferable to use (1) few records rotated to multiple orientations, (2) many records, each at a random incident angle, or (3) some combination of the two. To this purpose, we subjected several single‐degree‐of‐freedom systems and one plan‐asymmetric multi‐degree‐of‐freedom structure to a pulsive and a non‐pulsive set of ground motions using different combinations of record set size and incident angle rotations. In all cases, the natural record‐to‐record variability of the (unrotated) waveforms clearly outweighed the influence of the record orientation. In addition, the choice of an intensity measure that utilizes the geometric mean of spectral accelerations in both horizontal axes at one or more periods of vibration was found to further enhance this difference, essentially nullifying the already small effect of the incident angle. In all cases, spending any significant proportion of the limited number of dynamic analyses to incorporate the effect of incident angle was detrimental to the fidelity of the estimated performance.
Lime-based composites have been extensively used throughout the years as plasters/renders and jointing mortars in building construction. However, the low f
This chapter addresses the equation of motion for the response of nonlinear single-degree-of-freedom (SDOF) oscillators, its solution, common hysteretic models, inelastic response trends and estimates, inelastic spectra, and the influence of P-Δ effects on response. Nonlinear SDOF oscillators provide an excellent basis for estimating the displacement response of multi-degree-of-freedom (MDOF) systems. ElaΔstic systems are conservative or non-dissipating systems and do not dissipate energy during any quasi-static complete cycle of loading. Linear elastic response implies that there is no damage to the structural system. Various hysteretic models are available to represent in an idealized, approximate manner the response observed in experimental tests. Superposition relies upon linearity, and is implicit in the use of other mathematical approaches such as frequency domain solutions. Different strategies exist for the solution of nonlinear systems. The peak displacement response of a yielding oscillator may be higher or lower than the response of an elastic oscillator of the same period and viscous damping for any individual record.