About Zone Loads Processing

Read-in the raw element forces for each subcase.

The first step is to read the raw element forces from the FEA results file. If a FEA subcase is associated with multiple time increments (as in a transient or non-linear analysis), only the last time increment is used.

Combine the subcase element forces into Design Load Case element forces

Design Load Cases are defined as any linear combination of subcases. For example, a run deck may contain three subcases: 101, 102, and 103. Load case 1 can then be defined as \(1.1*101 + 1.2*102 + 1.3*103\). This is equivalent to the subcom feature in Nastran. After element forces are read-in for each subcase, they are combined to form Design Load Cases according to the respective Design Load Case definitions.

Define a set of strength and buckling criteria for each active Design Load Case

Strength loads are used for material strength, crippling, sandwich, and local buckling failure analyses. Buckling loads are used for panel buckling, stiffener buckling, and beam buckling. For a more detailed description of this distinction, see Strength vs. Buckling loads.

The method used to compute the strength and buckling loads is one of the following:

Applied pressure and temperature deltas are always averaged.

Repeat steps 2-3 for mechanical limit vs. ultimate and thermal help vs. thermal hurt

A distinction is made between limit and ultimate loads so that separate margins can be written for each. Limit and ultimate load factors are applied during the Design Load Case creation in step #2. Limit/ultimate factors can also be defined for each Zone (Right Click> Zone Settings).

If there are thermal subcases present, hurt and help factors are applied to the thermal subcases in Step #2. Since thermal loads can either reduce or increase stress, the two factors are applied to ensure that the thermal loads are applied in a conservative manner. Thermal factors are defined per Zone on the Zone Settings Form.

See Load Factors for an explanation of all load factor considerations.

Add additional loads from Superimposed Results (if applicable)

The term 'Superimposed loads' refers to Panel Pressure and Beam-Column analyses. They are "superimposed" in that their results are computed separately and then added directly to the results from the primary input loads. There is also the options for "Zero Curvature" which occurs during load processing. Since this is an optional flag, it is also considered a 'Superimposed Load' for the sake of bookkeeping.