1,721,498 research outputs found
Envelope process statistics for linear dynamic system subject to nonstationary random vibrations
No full textEnvelope process statistic plays a central role in evaluation of threshold crossing of many dynamic physical systems subject to random inputs. Commonly used envelope definition in stationary condition deals with modulus of a complex process, whose real part is the original process itself and imaginary part is its Hilbert transformation. A simplified envelope process definition is commonly used in technical literature for nonstationary modulated situations. This is to overcome some physical and computational inconveniences that take place when the stationary envelope definition is directly extended to the nonstationary case. This simplification consists in replacing, in the imaginary part of the above defined complex process, the response to the Hilbert transform of a Modulated stationary Input (HMI) with the response to a Modulated Hilbert transform of a stationary Input (MHI). In this work the efficiency of this approximation has critically evaluated, showing that it is able to extend the un-symmetry of original state space and its Hilbert transformation envelope covariance matrix, that is true in stationary conditions. Moreover, it is also shown that above approximation will induce some errors in envelope statistics, which are not negligible when input modulation function has a very fast variation rat
Un test psicometrico delle trasformazioni di un gruppo :costruzione di uno strumento diagnostico sul gruppo
No full textPerformance reliability based optimization criterion for elastic structures subject to random loads
No full textA stochastic optimization which makes use of a reliability constraint, expressing a performance requirement, is proposed for linear elastic systems subject to random dynamic loads. The criterion selected for the optimum design is the minimization of a deterministic measure, whereas the constraint condition requires that system failure probability must be smaller than a given allowable level, where failure is associated to the first exceeding of system response from a safe domain. The proposed method is then developed for the optimum design of a Tuned Mass Damper, utilized for reducing undesirable vibrations originated in structures by random loads. Unlike conventional TMD designs based on minimizing the mean-square response, a reliability-based performance measure is then considered in the proposed design, which properly accounts for uncertainties in loads. A sensitivity analysis is carried out and results are shown in a useful manner for TMD design decision suppor
Effect of pounding on the seismic response of two adjacent asymmetric buildings under single uni-directional ground motion
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Sensitività della resistenza a compressione del calcestruzzo all’incertezza del rapporto acqua-cemento
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