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IEEE IEC 60980-344-2020 pdf free download
IEEE IEC 60980-344-2020 pdf free download.Nuclear facilities – Equipment important to safety – Seismic qualification.
5.6.3 Time history
A time history is a form of earthquake-induced motion defined in terms of acceleration as a function of time. The simulated motion is derived from existing or artificially generated earthquake records. For application at any floor, the time history record generated includes the dynamic filtering and amplification effects of the building and other intervening support structures. It is possible by knowing time history displays to determine, through discrete Fast Fourier Transform (FFT) analysis, acceleration as a function of frequency. There is no one-to- one relationship between a response spectrum and a time history, since a given response spectrum can be fulfilled by several different time histories.
5.6.4 PSD function
The Power Spectral Density (PSD) is the mean squared acceleration of the vibratory motion and is characterized in terms of the PSD as a function of frequency. PSD gives an indication of the frequency distribution of power in the acceleration signal (measure of signal power over the frequency range) and is typically used to characterize broadband stationary random vibration motion. For vibration data, PSD amplitude is in units of [mIs2]2 /Hz or g2 /Hz. According to Parseval’s theorem the square root of the total area under the PSD-curve is equal to the root mean square (RMS) acceleration calculated in the time domain. The PSD provides information regarding the excitation directly without including the effects on an array of SDOF oscillators as is done for the response spectrum. The PSD function does not define the exact waveform or duration of the excitation but enables significant frequency-dependent properties of the motion to be seen at a glance from one curve. The PSD allows application of relationships between excitation and response by way of the transfer functions for linear systems.
Damping is the generic name ascribed to the numerous energy dissipation mechanisms in a system. In practice, damping depends on many parameters, such as the structural system, mode of vibration, strain, normal force, velocity, materials, joint, and slippage. IEEE IEC 60980-344-2020 pdf free download.
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