2.2.3.2. Newton-Raphson Option.
Use this analysis option only in a nonlinear analysis. This option specifies how often the tangent matrix
is updated during solution.You can specify one of these values:
- Program-chosen (default)
- Full
- Modified
- Initial stiffness
- Full with unsymmetric matrix
Command(s):NROPT
GUI: Main Menu> Solution> Unabridged Menu> Analysis Options
2.2.3.3. Prestress Effects Calculation
Use this analysis option to perform a prestressed analysis on the same model when the base analysis
is linear (such as a prestressed modal analysis). The prestress effects calculation controls the generation
of the stress stiffness matrix. The default for the prestress effects calculation is OFF.
Command(s):PSTRES
GUI: Main Menu> Solution> Unabridged Menu> Analysis Options
If the base analysis is nonlinear, the linear perturbation procedure is recommended. In this case, the
prestress effects are automatically included and PSTRES is not needed.
2.2.3.4. Mass Matrix Formulation
Use this analysis option if you plan to apply inertial loads on the structure (such as gravity and spinning
loads). You can specify one of these values:
- Default (depends on element type)
- Lumped mass approximation
NoteFor a static analysis, the mass matrix formulation you use does not significantly affect the
solution accuracy (assuming that the mesh is fine enough). However, if you want to do a
prestressed dynamic analysis on the same model, the choice of mass matrix formulation may
be important; see the appropriate dynamic analysis section for recommendations.
Command(s):LUMPM
GUI: Main Menu> Solution> Unabridged Menu> Analysis Options2.2.3.5. Reference Temperature
This load step option is used for thermal strain calculations. Reference temperature can be made mater-
ial-dependent with the MP,REFT command.
Command(s):TREF
GUI: Main Menu> Solution> Load Step Opts> Other> Reference Temp
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