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STAAD Commands and Input Instructions
Section 5
5-296
remaining spectrum cases. The format is shown below. fn
may not be more than 72 characters in length.
Modal Combination Description
SRSS Square Root of Summation of Squares method.
CQC Complete Quadratic Combination method. Default.
ASCE ASCE4-98 method.
ABS Absolute sum. (Very conservative worst case)
TEN Ten Percent Method of combining closely spaced modes.
NRC Reg. Guide 1.92 (1976).
Description
This command should appear as part of a loading specification. If
it is the first occurrence, it should be accompanied by the load data
to be used for frequency and mode shape calculations. Additional
occurrences need no additional information. Maximum response
spectrum load cases allowed in one run is 4.
See Sections
1.18.3, 5.30,
and 5.34
Results of frequency and mode shape calculations may vary
significantly depending upon the mass modeling. All masses that
are capable of moving should be modeled as loads, applied in all
possible directions of movement. For dynamic mass modeling, see
sections 5.32 and 1.18.3. An illustration of mass modeling is
available, with explanatory comments, in Example Problem No.11.