Load Pattern

Use the Load pattern option to define influence surfaces for plate and shell structures.

The influence surface is a diagram of the relationship between a certain result quantity (such as, force or displacement at a given point) and a position of the unit force on the load surface. A value of the influence surface at any point on the surface is the value of the selected result quantity if the unit force is positioned at this point.

Color maps obtained from using this option indicate the regions in which the influence surface assumes positive or negative values. This lets you determine the position of the planar loads that produce the most adverse effect on the resultant quantity described by a given influence surface.

The engineer designing the structure must decide for which quantities the influence lines should be generated and analysis be performed. It is the engineer, who selects which quantities and which structure points are decisive for structure design.

Influence surfaces are saved as a mesh of points with a determined division. Values between points are subjected to linear interpolation. You can specify a dimension of mesh division. Coarse mesh division might (in extreme cases) lead to obtaining incorrect solutions. As the dimension of mesh division decreases, the accuracy of solution grows; however, it requires a longer calculation time.

The Load pattern option is available for the following structure types: plate design and shell design.

There are several steps to using the Load Pattern option:

1. Define the data, load surface, and select the result types and the points for the influence surface.
2. Generate the model and start calculating the auxiliary case with unit loads.
3. Result analysis and defining the calculation cases and loads.

In the Load Pattern dialog, you can define a surface on which a unit load (and consequently, an influence surface) will be generated. A list of quantities for which influence surfaces are to be generated can be specified there, as well.

After defining the data and the list of influence surfaces and after clicking Generate In the Load Pattern dialog, the second step starts. The previous dialog closes and the calculation phase begins. During this step, the following operations are performed:

• Mesh generation on the panel and whole structure.
• Generation of an auxiliary load case with components. (In each component, a unit force is applied to a node of the panel mesh.)
• Preparation for structure calculations.
• Calculation of the auxiliary case. All other user-defined cases are in this calculation phase. They are specified as auxiliary, that is, not undergoing the solution process.

When this step is completed, the Load Pattern - Loads dialog opens for result analysis (3rd step).