ShapeBuilder

ShapeBuilder is a pre-processor to SectionBuilder. It enables the parametric definition of simple cross-sectional shapes that are used in mechanical and aerospace engineering.

A typical input to ShapeBuilder is of the following form, where the various entries depend on the specific shape being defined.

@SHAPE_BUILDER_ANALYSIS {
@SHAPE_BUILDER_NAME {ShbDefName} {
@SHAPE_GROUP {ShapeGroup}
@SHAPE_TYPE {ShapeType}
@OPTION_DEFINITION {o1, o2, ...}
@DIMENSIONS {
@DIMENSION_01 {d1}
...
}
@MATERIALS {
@MATERIAL_01 {Mat1}
...
}
@AIRFOIL_SHAPE_NAME {AirSName}
@NUMBER_OF_CONTROL_POINTS {Ncp}
@IS_DEFINED_IN_FRAME {FrameName}
@MESH_DENSITY {md}
@COMMENTS {CommentText}
}
}

NOTES

  • Parameters ShapeGroup and ShapeType defines the type of shape to be defined. They can be chosen from the following options.
  • Shape Groups Shape Types Shape Types Shape Types Shape Types Shape Types
    Solid sections Circular section Rectangular section Triangular section
    Open sections C-Section I-Section L-Section T-Section Circular arc
    Closed sections Rectangular box Double box Circular tube Tube with fins Flattened tube
    Airfoil sections No shear web One shear web IH-60 section High-lift device
    Table 1. Summary of the cross-sectional shapes that can be defined by ShapeBuilder
  • For specific shape types, options are available. For instance, the top and bottom flanges of an I-section can be reinforced or not. The option flags, denoted o1, o2, etc., take values of 1 or 0, if a particular option is activated or not. If no options are available for this shape type, keyword @OPTION_DEFINITION should not appear.
  • The geometry of the shapes is parameterized and depends on a number of dimensions, d1, d2, ..., etc. These could represent the height of a web, the thickness of a reinforcement, or the inclination of a flange with respect to the horizontal.
  • The physical properties of the section must be defined as well. For homogeneous material, material properties can be defined and for heterogeneous, anisotropic materials, it is more convenient to define solid properties directly. A number of materials, Mat1, Mat2, .., etc., will be defined for the section.
  • Some of the cross-sections defined by ShapeBuilder are airfoil sections, such as those listed in the last line of table 1. The outer contour of these sections are defined based on aerodynamic considerations. The airfoil shape, AirSName, defines the shape of the aerodynamic contour precisely.
  • The definition of the geometry of the cross-section relies on the concept of NURBS curves. Ncp control points will be used for the definition of these NURBS curves. (Default: Ncp = 2,048)
  • Sectional shapes are defined in their own local coordinate system, which is assumed to coincide with the global coordinate system. If a fixed frame, FrameName, is specified, the local coordinate system coincides with this fixed frame.
  • The mesh density parameter, md, determines the level of mesh refinement. (Default: md = 4)
  • It is possible to attach comments to the definition of the object; these comments have no effect on its definition.