structure shell import command

Syntax

structure shell import keyword

Primary keywords:

from-file    from-geometry

Create a shell as a collection of shell finite elements, where the elements are obtained from an outside source. Newly created nodes will attach to the first valid object (e.g., zones in FLAC3D and 3DEC, particles in PFC3D) found at their location, with attachment conditions appropriate to a shell (see this table in the topic Structural Element Links). A shell can also be created by the structure shell create command.

from-file s [shellimportblock]

Create elements from the geometry file s.

from-geometry s [shellimportblock] <range>

Create elements from the geometry set named s. The range applies to the list of edges in the geometry set.

structure shell import Keyword Block

The following keywords may be supplied after the two primary keywords from-file and from-geometry.

cross-diagonal <b >

If specified, a cross-diagonal mesh of four triangles will be created with a node lying at the centroid of all quadrilaterals; otherwise, a cross-hatch mesh of two triangles will be created dividing the quadrilateral.

When connecting elements to the grid, it is best to locate nodes at gridpoints. If the finite-element type can resist bending (DKT, DKT-CST, or DKT-(CST Hybrid) elements), then incompatibilities can develop along element faces and zone faces, because the transverse (out-of-plane) displacement field varies cubically across element faces, but varies only linearly across zone faces. Thus, when connecting bending-resistant elements rigidly to zone faces, it is best to utilize a cross-hatch mesh, because the middle node of the cross-diagonal mesh will be constrained to translate according to the linear displacement field of the zone face. This over-constrains the elements and can produce near-zero moments at these mid-nodes when present in a nonzero moment field.

distinct

Eliminate sharing of nodes among created elements. Every element will create a new set of nodes, even if they are at the same location in space and elements share the same ID number. This option is most commonly used with a later structure node join command to create links connecting nodes at the same location in order to apply custom inter-element behavior.

element-type keyword

Specify the type of finite element to be used by each structural element. If no element type is specified, then the element type will be DKT-CST. Note that the type of finite element is associated with each structural element when it is created and cannot subsequently be altered. The finite element type of existing structural elements is listed by the structure shell list element-type command. Plastic material behavior is supported by the DKT, CST and DKT-CST finite elements. The value of the keyword supplied must be one of the following three-noded shell finite elements:

s

Attempt to match the string s to one of the available keywords below, and treats as that option

cst

CST (6 degrees-of-freedom) finite element. This is a membrane element; it resists membrane, but not bending, loading.

csth

CST Hybrid (9 degrees-of-freedom) finite element. This is a membrane element; it resists membrane, but not bending, loading.

dkt

DKT (9 degrees-of-freedom) finite element. This is a plate-bending element; it resists bending, but not membrane, loading.

dkt-cst

DKT-CST (15 degrees-of-freedom) finite element. This is a shell element that combines the DKT and CST elements to resist both bending and membrane loading.

dkt-csth

DKT-(CST Hybrid) (18 degrees-of-freedom) finite element. This is a shell element that combines the DKT and CST Hybrid elements to resist both bending and membrane loading.

format keyword

Specify the format of the file. Can only be given with the from-file keyword.

This keyword can only be used with the following keywords of the structure shell import command: from-file.

dxf

Specify the DXF file format.

geom

Specify the geometry file format.

stl

Specify the STL file format.

group s1 <slot s2 >

Assign the created elements to group s1. The group is assigned to the slot named s2 if supplied; it is assigned to the slot named Default if not. Use of the group logic is described in Groups.

id i

Specify the ID (this is the collection ID) that will be assigned to all new elements created by this command. If this value is not given, then the next available ID will be used. The ID controls potential joining of the element nodes to an existing element as follows. At each potential new node location, a new node is created unless all of the following conditions are fulfilled: 1) the ID is given; 2) an existing node is found “near” the potential new node location; and 3) the found node is part of an element of the same type with ID equal to i.

maximum-length f

Break the element into segments no greater than length f. The segments setting, if provided, is overridden as needed by this setting.

offset v

Specify the translational offset of the shell.

segments i

Break the element into i equal segments, creating new nodes as needed. The default value is 1, indicating that only one element will be created.