Load Duration (DSRSS) (sec) - CAESAR II - Help

CAESAR II Users Guide

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CAESAR II
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CAESAR II Version
12

(Available for: Spectrum/DSRSS and Time History)

Specifies the duration of the applied dynamic load, as described below.

Spectrum Analysis

For a time history analysis, this parameter specifies the total length of time over which the dynamic response is simulated. The load duration divided by the time step size from Closely Spaced Mode Criteria/Time History Time Step (ms) gives the total number of integration steps making up the solution. CAESAR II limits the number of time steps to 5000 or as permitted by available memory and system size. The duration should be at least equal to the maximum duration of the applied load plus the period of the first extracted mode. This allows simulation of the system response throughout the imposition of the external load, plus one full cycle of the resulting free vibration. After this point, the response dies out according to the damping value used. For example, if the applied load is expected to last 150 milliseconds and the lowest extracted frequency is 3 Hz, set the load duration to a minimum of 0.150 plus 1/3, or 0.483 seconds.

Time History Analysis

For a spectrum analysis using the double sum (DSRSS) modal combination method (as defined by USNRC Regulatory Guide 1.92), this value specifies the duration of the earthquake. This duration is used to calculate the modal correlation coefficients based on empirical data. For more information, see Modal Combination Method (Group/10%/DSRSS/ABS/SRSS).