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STAAD Commands and Input Instructions
Section 5
5-336
Simple SRSS Combination
LOAD COMBINATION SRSS 8 DL+SEISMIC
1 1.0 2 -0.4 3 0.4
This (LOAD COMBINATION SRSS 8) illustrates a pure SRSS
load combination with a default SRSS factor of 1. The following
combination scheme will be used -
v= 1.0 1 x L1
2
- 0.4 x L2
2
+ 0.4 x L3
2
where v = the combined value and L1 - L3 = values from load
cases 1,2 and 3. Since an SRSS factor is not provided, the default
value of 1.0 is being used.
Algebraic & SRSS Combination in the Same Load Combination
Case
Example 1
LOAD COMBINATION SRSS 9
-1 0.75 2 1.3 3 2.42 0.75
The combination formula will be as follows -
v = 0.75 x L1 + 0.75 1.3 x L2
2
+ 2.42 x L3
2
where v = combined value
L2 & L3 = values from load cases 2 & 3.
In the above specification, a minus sign precedes load case 1.
Thus, Load 1 is combined algebraically with the result obtained
from combining load cases 2 and 3 in the SRSS manner. The SRSS
factor of 0.75 is applied on the SRSS combination of 2 and 3.