Ring Load, Free
A load applied to a point, not located at the axis of revolution, in an axisymmetric model actually represents a ring load. Add a Ring Load, Free node to describe concentrated loads with locations specified by coordinates. Such loads do not have to be placed in a geometrical point or in a mesh node. This is particularly useful for the following cases:
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Imported meshes, where there may not be suitable points for load application
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Moving loads
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Several point loads, in which case it may be impractical to create points at all load locations
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For each free load, there will be a search for the mesh element that is closest to the given location. For the load to be active, the location must be within a certain small distance from at least one element. The actual load location is taken as the point on the element that is closest to the given location. If no element is found, the load is silently ignored.
You can check the number of loads that were ignored through the variable <phys>.<load_tag>.num_ignored, for example shell.rlf1.num_ignored.
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The local stress field in the element where a point load acts will not be reliable.
Location and Force
Select a Through-thickness location — Top Surface, Midsurface, or Bottom Surface. The default is that the load is applied at the midsurface. The effect of using another surface than the midsurface is that for a tangential load, the distance from the midsurface is used to compute an additional equivalent moment load.
To place the load at another distance from the midsurface, select the Offset check box, and enter a value for the offset, zoffset.
The coordinates that you enter for the load location are not affected by this setting; they should always refer to the reference surface, that is the coordinates of the mesh.
If the material model is Section Stiffness, there may physically not be a well-defined top and bottom surface. If the load is applied at such a surface, the thickness value used to compute the load is taken from the settings in the Thickness and Offset node.
Select a Frame — Material or Spatial that determines how the given coordinates are interpreted in case of a geometrically nonlinear analysis. When Material is selected, the load location on the body is interpreted with respect to the initial configuration. When Spatial is selected, then the load location is given in space fixed coordinates, which usually means that the material point on the body where the load is applied will change with deformation even if the coordinate values are constant.
For each row in the table, enter the data for one load. If material frame input is used, then the location is specified in terms of the material coordinates (R, Z). If spatial frame input is used, then the spatial coordinates (r, z) are used. Then, enter the force and moment values, Fxl, Fzl, and Myl. The force and moment components are interpreted in the coordinate system selected in the Coordinate System Selection section.
Linear Buckling
To display this section, click the Show More Options button () and select Advanced Physics Options in the Show More Options dialog box.
If you are performing a linear buckling analysis with a combination of live and dead loads, select the Treat as dead load check box to indicate that the load contributions from this node are constant. The default is that a load is proportional to the load factor.
For more information about live and dead loads, see Buckling Analysis.
 
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You can specify this load to be a Harmonic Perturbation in a frequency domain analysis.
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You can assign this load to a load group. See Load Cases in the Structural Mechanics Modeling chapter.
Location in User Interface
Context Menus
Shell>Ring Load, Free
Ribbon
Physics tab with Shell selected:
Global>Shell>Ring Load, Free