(Available for: Spectrum)
Specifies the method for combining individual modes into the total system response.
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GROUP - Grouping Method
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10% - Ten Percent Method
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DSRSS - Double Sum Method
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ABS - Absolute Method
The response spectrum yields the maximum response at any time during the course of the applied load, and each of the modes of vibration usually have different frequencies. As a result, the peak responses of all modes do not occur simultaneously and an appropriate means of summing the modal responses must be considered.
Nuclear Regulatory Guide 1.92 (published in February 1976) defines the requirements for combining modal responses when performing seismic response spectra analysis for nuclear power plants. The four options presented there are available, along with one other, for modal combinations under non-nuclear seismic and force spectrum analyses.