(Available for: Modal, Harmonic, Spectrum, Range, and Time History)
Specifies the static load case as described below. Select a load case from the list.
CAESAR II cannot perform a dynamic analysis on nonlinear systems. For dynamic analyses, a one-directional restraint must be modeled as either seated (active) or lifted off (inactive), and a gap must be either open (inactive) or closed (active). This process is automated when the static load case is selected. CAESAR II automatically sets the linear condition at the non-linear restraints in the system to correspond to their status in the selected load case. Think of this as being the loading condition of the system (such as operating load) at the time at which the dynamic load occurs. This automated linearization does not always provide an appropriate dynamic model, and you may need to select other static load cases or manually alter the restraint condition in order to simulate the correct dynamic response.
A static load case must precede the dynamics job whenever:
-
There are spring hangers to be designed in the job. The static runs must be made in order to determine the spring rate to be used in the dynamic model.
-
There are non-linear restraints in the system, such as one-directional restraints, large-rotation rods, bi-linear restraints, or gaps. The static analysis must be made in order to determine the active status of each of the restraints for linearization of the dynamic model.
-
There are frictional restraints in the job, such as any restraints with a nonzero µ (mu) value.
The most common static load cases during a typical CAESAR II analysis are:
Example 1: Analyses containing no hanger design
1 = W+P1+D1+T1+H (OPE)
2 = W+P1+H (SUS)
3 = L1-L2 (EXP)
If the operating condition is likely to exist throughout the duration of the dynamic transient, use parameter 1. If the installed condition is more likely to exist during the transient, use parameter 2. It is unlikely that expansion case 3 is correct, because it does not represent the system status at any given time but represents the difference between the first two cases.
Example 2: Analyses containing hanger design
1 = W+P1(For hanger design)
2 = W+P1+D1+T1(For hanger design)
3 = W+P1+D1+T1+H (OPE)
4 = W+P1+H (SUS)
5 = L3-L4 (EXP)
The correct static load cases to use are those in which the selected spring hangers have been included. If the operating condition is the correct load case, use parameter 3. For the installed condition, use parameter 4.