Click Directives on the Spectrum Load Cases or Static/Dynamic Combinations tabs to open the Directive Builder dialog box and select parameters for the current load case. These parameters are load-case-specific changes to the global parameters set for all dynamic analysis load cases. For more information, see Spectrum/Time History Load Cases Tab and Static/Dynamic Combinations Tab.
For most analyses, the global parameters apply. You do not need to specify the parameters
on this dialog box.
Directional Combination Method
Select SRSS or ABS. For more information, see Missing Mass Combination Method (SRSS/ABS).
Modal Combination Method
Select GROUP, 10%, DSRSS, SRSS, or ABS. For more information, see Modal Combination Method (Group/10%/DSRSS/ABS/SRSS).
Spatial Combination Method
Select SRSS or ABS. For more information, see Spatial Combination Method (SRSS/ABS).
Spatial or Modal Combination First
Select SPATIAL or MODAL. For more information, see Re-use Last Eigensolution (Frequencies and Mode Shapes).
Pseudostatic Combination Method
Select SRSS or ABS. For more information, see Pseudostatic (Anchor Movement) Comb. Method (SRSS/ABS).
Missing Mass Combination Method
Select SRSS or ABS. For more information, see Missing Mass Combination Method (SRSS/ABS).
Static/Dynamic Combination Method
Select SRSS or ABS to define how the load case is combined. The ABS method takes the absolute value of all displacement, force, and stress data for each load case and adds them. The SRSS method sums the square of all displacement, force, and stress data for each load case and then takes the square root of the result. This is the only parameter available on the Static/Dynamic Combinations tab.