# Commands

Structural elements are explicit finite-element based objects formulated using shell and beam theory. As with zones, all element force-displacement calculations are incremental.

Each individual element is connected to others via structural nodes. Interactions with other objects (primarily zones) are handled by structural links associated with the nodes.

There are six types of structural elements supported—each specifies both a default internal behavior and a default link formulation. There are three linear elements (beam, cable, and pile) and three two-dimensional plate elements (shell, liner, and geogrid).

The structural element logic differs from other modules in how it handles id numbers. Within this module, id numbers refer to collections of elements, identifying a given beam or cable structure that may be constructed of any number of individual elements. Each element is identified by a component-id number, which is unique to that element. Nodes and links may be selected by id number, which selects nodes that are attached to element collections with those numbers. Nodes and links also have their own individual component-id numbers.

For more detail, please see General Formulation of Structural-Element Logic.

[CS: previous sentence had this following “see”: the detailed :flag2:-structural element formulation- section. : check with DR that link supplied above is correct; also check whether that section is properly located (it could reasonably be moved adjacent to this topic)]

Structural Commands

Commands that affect the structural element logic in general.

beam commands

Commands that apply to beam elements.

cable commands

Commands that apply to cable elements.

geogrid commands

Commands that apply to geogrid elements.

liner commands

Commands that apply to liner elements.

pile commands

Commands that apply to pile elements.

shell commands

Commands that apply to shell elements.

node commands

Commands that apply to structural nodes elements.

Commands that apply to structural links elements.