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STAAD Commands and Input Instructions
Section 5
5-300
General Format:
SPECTRUM {Method} 1893 (TOR) X f1 Y f2 Z f3 ACC (SCALE f4)
(DAM
P f5 or MDAMP or CDAMP) (MIS f6) (ZPA f7)
SOI
L TYPE f8
The data in the first line above must be on the first line of the
command, the second line of data can be on the first or subsequent
lines with all but last ending with a hyphen (limit of 3 lines ). The
last line (Soil Type parameter) must be in a separate line.
where,
Method = SRS
S or CQC or ABS or CSM or TEN
SRSS , CQC, ABS, CSM and TEN are methods of combining the
responses from each mode into a total response. SRSS stands for
square root of summation of squares, CQC for complete quadratic
combination and ABS for Absolute method. CSM is a closely-
spaced modes grouping method where the peak response quantities
for closely spaced modes (considered to be within 10 percent of
each other) are combined by Absolute method. This peak response
quantity for closely spaced modes is then combined with those of
widely spaced modes by SRSS method. TEN PERCENT method
combines modal responses as published in US Nuclear Regulatory
Guide 1.92 Revision 1 of February 1976.
Note : CQC, SRSS and CSM Grouping methods are
recommended by IS:1893 (Part 1) –2002.
If SRSS is given, the program will internally check whether
there are any closely spaced modes or not. If it finds any such
modes, it will switch over to the CSM method. In the CSM
method, the program will check whether all modes are closely
spaced or not. If all modes are closely spaced, it will switch
over to the CQC method.
1893 indicates the analysis as per IS:1893(Part 1)-2002
procedures.