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.
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:
In this format:
JOINT COORDINATESdefines node locations in global or local coordinate systems.CONNECTIVITY - FRAMEdescribes 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:
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) 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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