> For the complete documentation index, see [llms.txt](https://manual.karamba3d.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://manual.karamba3d.com/beta/3-in-depth-component-reference/3.7-export/3.8.6-export-model-to-sap2000-.s2k.md).

# 3.8.6 Export Model to SAP2000 (.s2k)

Karamba3D can export structural models to the `.s2k` text format used by **SAP2000**. The `.s2k` format is a plain-text, table-based representation of a structural model, designed for interoperability and direct import into SAP2000.

<figure><img src="/files/uycoUOovjLcMfto2ciF5" alt=""><figcaption><p>Fig. 3.8.6.1: SAP2000 export component.</p></figcaption></figure>

### Overview

Similar to the `.e2k` format used by ETABS, `.s2k` organizes model data into a sequence of **TABLE** blocks. Each table defines a specific category of information, such as geometry, connectivity, material properties, cross-sections, supports, and loads.

Example structure:

```shellscript
TABLE:  "JOINT COORDINATES"
   Joint=0   CoordSys=GLOBAL   CoordType=Cartesian   XorR=0   Y=-2   Z=0   SpecialJt=No
   Joint=1   CoordSys=GLOBAL   CoordType=Cartesian   XorR=0.30944860558263226   
   
TABLE:  "CONNECTIVITY - FRAME"
   Frame=0   JointI=0   JointJ=1   IsCurved=No   Length=0.3489830496720493
```

In this format:

* `JOINT COORDINATES` defines node locations in global or local coordinate systems.
* `CONNECTIVITY - FRAME` describes frame elements by referencing their start (`JointI`) and end (`JointJ`) nodes.
* Additional tables specify section assignments, material definitions, restraints, loads, and analysis settings.

The exporter converts Karamba3D objects into their corresponding SAP2000 entities as follows:

| Karamba                   | SAP2000 counterpart                                                                    |
| ------------------------- | -------------------------------------------------------------------------------------- |
| Supports                  | Joint restraint assignments (plus local axes if defined)                               |
| Linear Elements           | Frame elements with connectivity, section, design procedure and load-transfer settings |
| Surface Elements          | A single polygonal area                                                                |
| Beam joints (releases)    | Frame release assignments                                                              |
| Beam/Shell cross-sections | Frame/Area section properties                                                          |
| Materials                 | Material properties (general + basic mechanical)                                       |
| Point loads               | Joint forces                                                                           |
| Imposed displacements     | Joint ground displacements                                                             |
| Element loads             | Frame distributed loads                                                                |
| Load cases                | Load patterns + load cases                                                             |
| Load case combinations    | Combination definitions                                                                |

#### Limitations

The `.s2k` exporter supports most standard Karamba3D model components, but several limitations apply, particularly for shell elements and mesh-based loads.

**Non-planar shells are not fully supported**

Karamba3D attempts to export shell elements as native SAP2000 **area objects** whenever possible. For successful export, the shell mesh must have an associated **underlying Brep** (see [3.9.1 *Mesh Breps*](/beta/3-in-depth-component-reference/3.8-utilities/3.8.1-mesh-breps.md)) and meet SAP2000’s geometric requirements.

If the exporter encounters:

* a mesh **without an underlying Brep**, or
* **non-planar geometry**, or
* curved boundary edges

the shell cannot be exported as a single native area object. In such cases, Karamba3D attempts to export each individual mesh face separately as an area element. Depending on mesh complexity, this may lead to fragmented geometry and reduced editability in SAP2000.

**Variable shell thickness is not supported**

Shell elements with **non-uniform or variable thickness** cannot be transferred through the `.s2k` exporter. Only shells with a **constant thickness** can be exported.

**Mesh loads are not exported**

Loads applied directly to mesh elements are not included in the `.s2k` export.

Before exporting, **mesh-based loads must be converted into equivalent nodal (point) loads** to ensure they are transferred correctly into SAP2000.


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