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Optimized earthquake response of multi‐storey buildings with seismic isolation at various elevations
The response of multi‐storey structures can be controlled under earthquake actions by installing seismic isolators at various storey levels. By vertically distributing isolation devices at various elevations, the designer is provided with numerous options to appropriately adjust the seismic performance of a building. However, introducing seismic isolators at various storey levels is not a straightforward task, as it may lead to favourable or unfavourable structural behaviour depending on a large number of factors. As a consequence, a rather chaotic decision space of seismic isolation configurations arises, within which a favourable solution needs to be located. The search for favourable isolators' configurations is formulated in this work as a single‐objective optimization task. The aim of the optimization process is to minimize the maximum floor acceleration of the building under consideration, while constraints are specified to control the maximum interstorey drift, the maximum base displacement and the total seismic isolation cost. A genetic algorithm is implemented to perform this optimization task, which selectively introduces seismic isolators at various elevations, in order to identify the optimal configuration for the isolators satisfying the pre‐specified constraints. This way, optimized earthquake response of multi‐storey buildings can be obtained. The effectiveness of the proposed optimization procedure in the design of a seismically isolated structure is demonstrated in a numerical study using time‐history analyses of a typical six‐storey building. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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The caustic of SKP is found at an epicentral distance ΔC = 129.5° for surface foci and at ΔC = 128.9° for foci at 400 km depth, by means of amplitude-distance graphs based upon short-period time-domain measurements. These results are essentially confirmed by long-period time-domain measurements of SKP as well as by frequency-domain studies, even though the spectra are less accurate for such determinations. The average period of SKP is from short-period records, significantly different from the corresponding PKP-period of 1.00 ± 0.31 sec. Likewise, the long-period averages of SKP = 10.8 ± 4.5 sec and of PKP = 7.7 ± 3.0 sec are significantly different from each other. A travel-time table of SKP1 is deduced, covering the epicentral distance range of 130–143° and the focal depth range of 100–700 km. All results are based on measurements on seismograms of the Swedish network of stations, deriving almost exclusively from earthquakes in the southwest Pacific area. 相似文献
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In earth and environmental sciences applications, uncertainty analysis regarding the outputs of models whose parameters are spatially varying (or spatially distributed) is often performed in a Monte Carlo framework. In this context, alternative realizations of the spatial distribution of model inputs, typically conditioned to reproduce attribute values at locations where measurements are obtained, are generated via geostatistical simulation using simple random (SR) sampling. The environmental model under consideration is then evaluated using each of these realizations as a plausible input, in order to construct a distribution of plausible model outputs for uncertainty analysis purposes. In hydrogeological investigations, for example, conditional simulations of saturated hydraulic conductivity are used as input to physically-based simulators of flow and transport to evaluate the associated uncertainty in the spatial distribution of solute concentration. Realistic uncertainty analysis via SR sampling, however, requires a large number of simulated attribute realizations for the model inputs in order to yield a representative distribution of model outputs; this often hinders the application of uncertainty analysis due to the computational expense of evaluating complex environmental models. Stratified sampling methods, including variants of Latin hypercube sampling, constitute more efficient sampling aternatives, often resulting in a more representative distribution of model outputs (e.g., solute concentration) with fewer model input realizations (e.g., hydraulic conductivity), thus reducing the computational cost of uncertainty analysis. The application of stratified and Latin hypercube sampling in a geostatistical simulation context, however, is not widespread, and, apart from a few exceptions, has been limited to the unconditional simulation case. This paper proposes methodological modifications for adopting existing methods for stratified sampling (including Latin hypercube sampling), employed to date in an unconditional geostatistical simulation context, for the purpose of efficient conditional simulation of Gaussian random fields. The proposed conditional simulation methods are compared to traditional geostatistical simulation, based on SR sampling, in the context of a hydrogeological flow and transport model via a synthetic case study. The results indicate that stratified sampling methods (including Latin hypercube sampling) are more efficient than SR, overall reproducing to a similar extent statistics of the conductivity (and subsequently concentration) fields, yet with smaller sampling variability. These findings suggest that the proposed efficient conditional sampling methods could contribute to the wider application of uncertainty analysis in spatially distributed environmental models using geostatistical simulation. 相似文献
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Nikolaos Theodulidis Zafeiria Roumelioti Areti Panou Alexandros Savvaidis Anastasia Kiratzi Vassilios Grigoriadis Petros Dimitriu Theodoros Chatzigogos 《Bulletin of Earthquake Engineering》2006,4(2):101-130
The densely populated city of Thessaloniki (Northern Greece) is situated in~the vicinity of active seismic faults, capable of producing moderate to strong earthquakes. The city has been severely affected by such events several times during the last 15 centuries. The most recent event occurred on 20 June 1978 (M6.5) in the Mygdonian graben, with an epicentral distance of about 30 km, causing extended damage in the city, with macroseismic intensities between MSK V+ and VIII+. The majority of buildings affected by the earthquake were of reinforced-concrete typology, typical to many southern European metropolitan areas. The source properties of the normal-faulting causative event and the source-to-city propagation path are well known from previous studies. The soil structure under the metropolitan area of Thessaloniki is assigned NEHRP categories B, C, D on the basis of geotechnical and geologic information and single-station ambient-noise measurements. A finite source model and various rupture scenarios of the June 1978 earthquake are used to perform forward stochastic modeling of strong ground motion in terms of peak ground and spectral acceleration. Rock motion is assessed under the city and it is transferred to the surface in accordance with the respective soil category. A GIS tool is employed to compare the estimated strong-motion parameters with the observed detailed damage pattern induced by the 1978 earthquake. For selected natural periods, a satisfactory correlation is established between macroseismic intensity and peak ground and spectral acceleration, thus encouraging the application of stochastic modeling for generating realistic ground-shaking scenarios in metropolitan areas. 相似文献
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A new method is presented for the determination of the parameters of the pulse contained in pulse‐like records. The Mavroeidis and Papageorgiou (M&P) wavelet is used for the mathematical representation of the pulse, but the proposed methodology could be modified to cover other types of wavelets as well. First, the period of the pulse is determined from the peak of the Sd × Sv product spectrum, a new concept that is introduced herein and is defined as the product of the velocity and the displacement response spectra. The remaining parameters of the M&P wavelet are derived from the targeted response spectrum of the ground motion applying a new relationship that is established between the cumulative absolute displacement (CAD) of a wavelet and its peak spectral amplitude. The method follows a well‐defined procedure that can be easily implemented in a computer code for the automatic determination of the pulse parameters of a given ground motion. As an application, the pulses contained in 91 NGA records that have been classified as pulse‐like by Baker are determined. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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