GENERAL PURPOSE MODULES
Structural analysis is usually performed on an idealized, geometrically perfect model. However, nothing is perfect in the real world. The structural geometry, the material behaviour and the position of the loads are all imperfect. Geometrically and materially nonlinear analysis with imperfections included (GMNIA) may be used effectively instead of linear methods for strength and stability verification of structures, structural elements and details. This is especially true in the case of complex structural details and parts where the stability and load-bearing capacity can be hardly verified with simpler methods.
The IMP module of AxisVM allows users to account for such geometric imperfections, which can be created by scaling and then superimposing the buckling-mode shapes. The effect of imperfections can be taken into account via a geometrically nonlinear analysis on a load combination, which includes imperfection-type load cases.
Requirements / recommendations
- NL or PNL (e.g. NL1S, PNL3P) configuration is required to account for geometric imperfections based on buckling mode shapes
The IMP module is design code independent
- scaling and superimposing of buckling mode shapes
- displaying of created imperfect geometries
- including imperfection-type load cases in load combinations
- performing nonlinear analysis on models with geometric imperfections
CREATING EQUIVALENT GEOMETRIC IMPERFECTIONS
The imperfect geometry can be compiled from the mode-shapes obtained from a buckling analysis, even corresponding to multiple load cases. Displacement components and the respective maximum values for each buckling mode shape can be specified. The created geometric imperfections can be included in load combinations.
NONLINEAR ANLYSIS OF MODELS WITH EQUIVALENT GEOMETRIC IMPERFECTIONS
Internal forces may be obtained on models with geometric imperfection via a geometrically nonlinear analysis include large-displacement effects. The loss of stability mode can be determined with a displacement-controlled nonlinear analysis. Finite element simulation-based design is also possible by using nonlinear material models and geometric imperfections together.
Design codes/standards provide guidance for the inclusion of wind pressure factors only for structures with close to regular geometry. In the case of more complex or compound structures, these methods are not applicable, and the pressure coefficients must be determined individually by a fluid dynamics simulation (CFD modeling) or a wind tunnel test. The CFD module allows for importing these results into AxisVM.
The CFD module is a generic interface which enables defining pressures caused by flowing substances over domains or load panels.
Requirements / recommendations
- the module is an option in the basic packages (analysis options), which is recommended when designing structures with loadings from flowing substances
The CFD module is design code independent
- it is recommended for structures with irregular geometry or with loads not covered by design codes/standards
- currently it can only apply static pressure loads (constant functions of time)
- it interpolates pressure values from CFD simulations on the contour of the surface elements of the structure
- it is sufficient to specify the spatial coordinates of the measurements and the corresponding pressure values, from which the program determines the surface load values perpendicular to the surfaces