> For the complete documentation index, see [llms.txt](https://docs.enercalc.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.enercalc.com/e3d-training-manual/building-the-model/general-modeling-theory/strutural-entities.md).

# Structural Entities

Understand the four entities used to build ENERCALC 3D models: nodes, members, shells, and bricks.

There are four different structural entities to model with in ENERCALC 3D:

**Nodes:**

![](https://3750289988-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FlRZtG5Ynp58kYzLHYbR7%2Fuploads%2Fgit-blob-ab9e6a92a18c5221f57eeda15092ab1d7f217313%2FNode.jpg?alt=media)

* Also known as "joints".
* Serve as points of connectivity and load transfer in a model.
* Think of a node as a beam to column connection, or a column base, or the point where chevron braces connect to a beam.

**Members:**

![](https://3750289988-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FlRZtG5Ynp58kYzLHYbR7%2Fuploads%2Fgit-blob-146d1940060e4548e16a38db023dff922c939de2%2FMember.jpg?alt=media)

* Also known as "beams".
* One dimensional structural members that can have axial stiffness as well as biaxial flexural and shear stiffness.
* Members are useful for modeling beams, columns, braces, truss webs and chords, struts, hangers, brackets, outriggers, posts, links, etc.

**Shells:**

![](https://3750289988-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FlRZtG5Ynp58kYzLHYbR7%2Fuploads%2Fgit-blob-5f2c32942ae886f7d6cb29668d0f90af668bcada%2FShell.jpg?alt=media)

* Also known as "plates"
* Two-dimensional quadrilateral elements that have the ability to span in two directions and that have in-plane shear (racking) stiffness.
* Shells are useful for modeling masonry walls, concrete walls and floors, plywood walls, etc.

**Bricks:**

![](https://3750289988-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FlRZtG5Ynp58kYzLHYbR7%2Fuploads%2Fgit-blob-bea3ea201f11e7f0b192b6daf197039b5ca756c1%2FBrick.jpg?alt=media)

* Three dimensional solid elements defined by 8 nodes.
* Bricks are useful for modeling thick things like a massive combined footing or the face of a dam or stem of a retaining wall.
* More useful than shells in situations where the through-thickness effects have a significant role in the behavior of the element.


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