Sub models

Tekla Structural Designer
2021
Tekla Structural Designer

Sub models

In both grillage and FE chasedown analysis, (performed as part of the Analyze All, Design Concrete, or Design All processes), Tekla Structural Designer performs the analysis one sub model at a time. The topmost sub model being analyzed first, and then its support reactions are applied as loads for the analysis of the sub model below. The sequence continues until all sub models have been analyzed down to the foundation level.

Slab mesh parameters can be specified individually for each sub model if required.

As part of the chasedown analysis process, (if they don't already exist), sub models are automatically created for every level specified as a Floor in the Construction Levels dialog box.

You can also define sub models manually in the Sub Models dialog box and you can modify the default support conditions applied to individual sub-models, if necessary.

Definitions of sub model characteristics

  • Sub model: a part of the 3D model between two horizontal sub model divide planes.

    Each sub model contains all members entirely between the two horizontal planes. For the columns, wall and braces split by a divide plane, the stacks and brace length above the top plane are included in the sub model, as are the stacks and brace length below the lower plane.

  • Sub model divide planes: horizontal planes that you can add, delete or move in the 3D structure. Sub model divide planes are notional and infinite. Tekla Structural Designer only allows the planes to cut through the structure where they only split the following members:

    • Column stacks

    • Wall stacks

    • Steel braces

  • Sub model supports: the artificial supports that Tekla Structural Designer defines for the column and wall stack ends and braces that pass through the divide planes

  • Structure supports: the supports that the user has defined in the 3D structure

  • Column and wall stacks: the span length of a column or wall.

  • Volume of the sub model: the 3D space that exists between any two adjacent sub model divide planes.

Basic rules of sub models

When all sub models are considered together, they form the complete structure. Only column stacks, wall stacks, and braces that are split by sub model divide planes can be in several sub models. This means that:
  • Each member in the 3D model is in at least one sub model.

  • A sub model cannot contain a member that is already in another sub model, unless that member is a column, wall, or brace divided by a sub model divide plane.

  • A sub model must contain at least one beam member, one truss member, or one slab item.

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