Best practices in modeling, validating and exporting for Unitechnik

Tekla Structures
Tekla Structures

Best practices in modeling, validating and exporting for Unitechnik


Before you start modeling, find out the following:

  • What are the fabrication requirements and constraints?

  • What is the complexity level of the products?

  • What information is desired from the model?

    • Production geometry for reinforcement mesh, loose rebars, embeds
    • Project and product attributes
  • What Unitechnik versions does the CAM system support?

Before your first project:

  • Model a test model with each of the typical products.

  • Choose your modeling components and modeling settings.

  • Test the Unitechnik export with each of the typical products and draft suitable settings.

  • Draft a company modeling guideline for collecting the information about modeling, drawing creation, export and other practices in one place.



Designers should aim to model with good precision taking into account the fabrication requirements of the products. The required level of accuracy varies from product to product, and some details need to have exactly correct geometry whereas others can be included as attributes that will be sufficient for production purposes.

As production only needs certain amount of information, some data needs to be in drawings that will not be used within the export files and vice versa. The goal is to have an error free model, which is modeled in a disciplined and structured fashion so that it will be easy to include or exclude information in both drawing and export file creation. All information will be used by production, and therefore it is very important to have correct information, because also export might be prevented if data is missing (such as material data or other). Any mistakes are hard to notice until the actual production stage.

Additional information can be brought to both the drawing and production file using user-defined attributes (UDAs), which can be within each object, or on the project level. UDAs are defined on the HEADER block data specification, SLABDATE block data specification, Mounting part data specification and Reinf. data specification tabs in the export dialog box. Some mandatory fields have to filled as agreed, such as project number, product type and drawing number, otherwise import is prevented. For more information about the different tabs, see Unitechnik.

The best practice is to:

  1. Finalize the detailing of a product.
  2. Do a test export of the product with ready-made setting (for that product type) and inspect the resulting file and make any adjustments if necessary.
  3. Create the drawing and edit it.
  4. Finalize the drawing and send the drawing and a production file to a team member for approval.
  5. Later on a designated person will send the production files in suitable sets.
  6. Control the design status on object-level within the model to keep track of design, approval and changes, as well as the export files sets.

Object geometry will be used for plotting and shuttering as well as fabricating the mesh, and cutting and bending the reinforcement. Each object type should have a distinct NAME and CLASS setting, to later control the export content.

In the model objects are represented hierarchically. This means that the object to be exported is a cast unit and within the cast unit there is the concrete main part. Other parts or reinforcement can be attached to the main part directly, or by first formulating a sub-assembly, which will have its own hierarchy and main part.

Unitechnik geometric objects

The 3D Tekla Structures objects are translated to suit the Unitechnik format.

(1) Contour

(2) Cutout

(3) Mountpart (embed)

(4) Rodstock (rebar)

(5) Steelmat (mesh)

(6) BGrinder (braced girder)

Contour and openings

Each object should have unified contour. There may be openings through the element.

More than one contour causes problems for plotting the contour and placing the shuttering. Having more than one contour is usually unintended, and caused by either having a concrete part that has not been designated as an embed, or the contour scanning resulting in two separate objects due to a cut or recess.

The orientation of the object and contour is controlled by the modeling direction, using the top-in-form setting within the model and the various settings within the export dialog box. Setting the top-in-form in the model is important because that is how Tekla Structures understands how the object will be produced, which affects both the export file and the drawings. As a rule of thumb, slabs and panels should be laid out on their wide face, with no extending parts or rebars towards the pallet, and any embeds and gaps that require additional filler pieces against the pallet. These filler embeds should have 0 weight and should be excluded from drawings and volume calculations.

If the edge has a shape that needs to be identified for a shuttering robot, this is indicated by using line attribute codes (for chamfers, recesses or teeth). These should be modeled using ready-made components, chamfers or cuts. These will always be in the geometrical object's contour and cutout. In export, they can be mapped automatically according to the Unitechnik standard, or you can set an automatic override in the export.

In the usual case, CUTOUT represents a full-depth opening, while recesses in the face are represented by embeds, MOUNPART.

For elements with standardized shape, such as pre-stressed slabs, the profile can be included as attribute information.

Controlling the contour in the model is done by having an object profile, which will be extruded to create the main part geometry. This basic geometry can then be adjusted by using cuts within the model. Each cut should have a distinct class or part set, so including and excluding them in export geometry can be adjusted later. We recommend that you model any cuts or filler embeds with systematic orientation, and for example, start and end handles should also be modeled in the panel length direction.

The initial cut parts are to be added to the cast unit, knowing that they will be listed on reports and shown on drawings. To exclude these purely production related elements from reports and drawings use filters and rules.

In the example below the initial cut parts were kept and added to the cast unit. The cut part name is set to "FORMWORK", the class is 111 (orange), and the material name is Zero_weight.

The following example shows exactly the same wall panel, but without the formwork parts – they have been filtered out.

Example chart of classes for modeling cuts (Cut included = as CUTOUT, mountpart included = as MOUNPART):

Type of cut Modeled Exported

Window opening

Cut with class 601 (component)

Cut included

Door opening

Cut with class 601 (component)

Cut included

Other opening through the element

Cut with class 601 (component)

Cut included

Rectangular recess in the middle of element

Cut with class 602, filler embed part with class

Cut excluded, filler mounpart included

Rectangular recess on the contour

Cut with class 602, filler embed part with class

Cut excluded, filler mounpart included

Non-rectangular recess

Cut with class 602, filler embed part with class

Cut excluded, filler mounpart included

Cuts around embed components

Cut with class 602

Cut excluded

Chamfer on the edge

Chamfer or cut with class 603

As line attribute

Groove or tongue shape on the edge

Cut with class 603 (component)

As line attribute


Embeds are presented as mountparts. Steel plates for connections, lifting embeds, electric boxes or grout tubes are examples of mountparts. Each embed should be added as a sub-assembly to the main cast unit. Embeds are usually modeled with ready-made components, and it is important to check that the tools have correct materials and attributes, and that the embed hierarchy is correct. Embeds should be classified by a distinct class (recommended 100 - 109 , other steel parts as 99). Steel parts can also be recognized automatically.

  • There are various options available for presenting the embeds: exact geometry, a bounding box or a symbol.

  • Embeds modeled as rebars can be turned into mountparts.
  • Small cuts within the embed modeling components should usually be excluded, which can be done by separately identifying them with class.

  • Insulation layers can be added as mountpart identified by class.

  • Surface treatment can be exported as mountparts. Surface objects are not supported.

  • Additional attributes can be added to each mountpart.

Remember the following:

  • Apply meaningful names or identification codes to embeds, such as the component main part.

  • Embed parts and sub-assemblies added to the cast unit must fully be added to the cast unit of Tekla Structures. Embeds or other connection entities not assigned to a cast unit of Tekla Structures will not be taken into account when exporting to UT file.

  • Use logical hierarchical structure, and select a sensible main part for an embed sub-assembly.

  • Check sub-assembly hierarchies. Only 2 levels within the sub-assembly is recommended.

  • Check placing, classes, positioning, naming.

  • Embed UDA tab settings for tailoring embed representation

  • Keep a list of all embeds and reinforcement in the project including their names and classes.

Cut and bent reinforcement and reinforcement mesh

Cut and bent reinforcement can be modeled by using standard rebar modeling functionalities or components. Rebars should be correctly attached to correct main parts, but this is rarely an issue if modeling carefully.

Usually the elements have a very high number of reinforcement but not necessarily all have to be brought into the export file, only the ones that need to be produced according to correct geometry or need to be quantified. In some cases, it is good idea to exclude the protruding rebars from cast units for better export. Bent rebar shapes will be presented as unfolded and in the xy plane in most of the viewers. 3D bent rebars are not supported by the format.

Reinforcement has automatically assigned reinforcement type to designate it in the production system. You can override this logic by manually adding reinforcement type in rebar UDAs for desired groups.

The mesh bars are automatically assigned to reinforcement types 1 and 2 or 5 and 6. The types 1, 2, 5 and 6 represent the installation layer in the form. 1 and 2 for mesh in bottom face, 5 and 6 on the top face.

Rebars can also be grouped and classified as cage objects by using rebar UDAs. It is very important to ensure that rebars are not accidentally grouped into mesh or cage.

Additional attributes can be added to each bar group as well as to each bar.

Unitechnik supports both planar mesh and bent mesh. Mesh can be modeled as mesh objects or as crossing bar groups. If modeled as bar groups, the bars need to be identified using class (recommended a double digit class, e.g. 13 - 19) or name in the export dialog. If there are no bar groups to be designated as mesh, it is important to not use this setting

The modeled cuts are also used for cutting meshes and bars within the Tekla Structures object.

Tekla Structures has several tools for creating mesh for precast objects, such as Mesh Bars, Mesh Array and Wall Panel Reinforcement.

Additional attributes can be added to each mesh object as well as to each bar within the mesh.

Remember the following:

  • Model according to production constraints.

  • Check placing, classes, positioning, naming.

  • A mesh can be designed or created in the Tekla Structures model with mesh objects but also using bar groups. If mesh is bent in two directions, it can only be modeled as bar groups. The UT file export has several options to influence the mesh creation towards the end result.

  • A mesh in the Tekla Structures cast unit, consisting of longitudinal and cross wire, should be defined either by

    • the same class (color)

    • the same name

  • Do a differentiation of name and class per mesh having for instance bottom and top mesh within one wall shell.

  • Furthermore, it is a good practice to apply loose or additional rebar to a dedicated class. Depending on the factory equipment and the processes involved it might be necessary to exclude certain rebars from a cast unit when exporting to the UT file. This can easily be achieved by excluding such rebars by class in question from the export. Class can also be used to distinguish rebars for non-automated production.

  • There are advanced functions to validate mesh, or to add additional wires for stabilizing if the mesh has openings. Check the dialog box settings on the Reinforcement tab.

In the example below the wall panel reinforcement rebar and mesh are created based on the suggested logic.

The mesh color has been set to red, class 79, its additional reinforcement to blue, class 88. Other reinforcement, also being added to the mesh manually later on in the production process, is set to yellow, class 6, and green, class 87. Reinforcement belonging to embeds are set to purple, class 7. With such a structure it is very easy to exclude rebar from automated mesh production and declare the UT file content as per factory or MC requirement.

Braced girders

Braced girders for half-cast or layered structures are identified by having a sub-assembly consisting of rebar groups and designating them with a specific class that is defined in export dialog box (recommended class 105 ). The top chord should be the main part of the sub-assembly.

Girders modeled from steel parts or rebars are both supported but rebars are recommended.

The best way to model braced girders is using modeling components such as the Braced Girders tool from Tekla Warehouse.


Strands should be modeled as rebar groups. Strand rebar groups are typically reinforcement type 9. The best way to model strands is the Hollow Core Reinforcement Strands tool.

Strands should be quite standard so in the production file they can represented with an identifier within the main part such as a Strand Code and quantity of strands. With the Hollow Core Reinforcement Strands tool this strand code can be automatically included in the slabdate data, otherwise it has to be manually controlled using UDAs.

Product information

Product information besides the geometry can be added as textual or numerical information. This data can be on any level of the hierarchy, but most important product information will be included in the HEADER and SLABDATE.

The following is automatically added:

  • Names of the order and the element (but these have to be set in the export dialog)
  • Product maximum dimensions, length, width in slab-block and thickness in product-block
  • Total weight in the slabdate block
  • Product material in the slabdate block in the layer data. Many layers can be exported but in most cases using only 1 layer provides best results.
  • Product coordinates within the project (model) in the header block
  • Product type (this needs to be set within the main part UDA) in the header block
  • Reinforcement type in the rodstock block
  • Reinforcement cage group numbers
  • Transport information

Other recommended manual information:

  • The name of the modeler
  • The design status
  • Bar and mountpart labeling
  • The quantity of the strands (if applicable)
  • Erection sequence (if applicable)

Other optional manual information:

  • Project information
  • Mountpart special instructions
  • Concreting special instructions

In addition, any UDA or manual text can be added to info fields.

Product type

As a mandatory setting, the UT product type must be set for each main part of a cast unit.

The product type is not set by default. Select a product type for the element selected from the model from the predefined list of option.

We recommend that you save the UT product type in modeling settings and components.

The most commonly used types are:

  • Solid wall

  • Element slab

  • Sandwich Element

  • Double wall (1st stage)

  • Double wall (2nd stage)

  • Solid floor

Note that it is very important to define the double wall and sandwich wall correctly for both shells.

You can also define product types of your own in addition to the predefined types.

We also recommend that you systematically gather information about the product and keep it up to date.

Company-specific modeling guidelines

  • Use classes to control element geometry and part/rebar filtering.

    • Included/excluded, automated/non-automated, mesh/loose bars
  • Define UDA content to define the product

    • Project UDAs
    • Unitechnik product types, location, additional info
  • What to do with different types of element openings and recesses

    • Shuttered, plotted or excluded
  • Use standard edge shuttering shapes

  • Define standard meshes, rebars and embeds according to factory requirements

    • Wire sizes, spacings, bendings, overhangs, maximum dimensions, cutting

  • Define top-in-form face for pallet orientation
  • Create export settings for each product, and tailor them for each project

Attribute information

Project attributes

To streamline and obtain best possible results it is highly recommended to have the Tekla Structures cast units to be exported and processed by the Unitechnik file well structured. The modeling technique has a direct impact on the outcome of the UT file.

The following instructions give a guideline on the mandatory and the most needed settings to be set in the Tekla Structures model.

The UT file contains a dedicated header block with general information about the project where the cast unit to be manufactured belongs to.

Within the UT file export dialog box the content of the UT file header block can be defined by using the project settings of the Tekla Structures Structures model. All relevant information should be set in the beginning of the project in Project properties.

User-defined attributes (UDAs)

Each main part of a cast unit in Tekla Structures to be exported to an UT file requires additional information to be stored in the model. You can use user-defined attributes (UDAs) for this purpose. The UDAs are defined in the Tekla Structures objects.inp file which is present for each configuration but its content can differ per Tekla Structures user role. In the Precast configuration this file can be found in the ..\ProgramData\Tekla Structures\<version>\environments\common folder.

In UT file export the Unitechnik tab must be available for precast elements.

Element naming

The UT file contains geometric information of the cast unit to be manufactured as well as its properties such as names and materials.

We recommend that you apply a meaningful naming to all elements of a cast unit (main part, embed part, rebar), as this will improve the readability of a UT file when being reviewed on the precast production control system. In most systems, the PDF drawing name should match the Unitechnik export file name.

Element numbering

Unique numbering is usually needed. ACN numbering is very handy for making sure that the export separates each piece into its traceable own export file and PDF drawing, rebar positions can be included into bar objects using a logic that suits the production.

Element color coding

Tekla Structures elements, such as parts and reinforcements, can easily be filtered by its class.

Self-validating the export file

  • Validate after the export.
  • Go through the geometrical objects within the slab-blocks and visualize them one by one.

  • Investigate possible errors in notifications, logs and viewer.
  • Check the date modified and naming of the files.
  • Check the main attributes for HEADER and SLABDATE.
  • Check orientation on pallet.
  • Check contour and line attributes.
  • Check the quantity of exported objects.
  • Smoke test the rebar and mesh geometry. Check that the mesh production constraints have been taken into account, and translated correctly.
  • Check the resulting embed plotting.
  • If there are any issues, fix those in Tekla Structures, re-export and re-validate.
  • Do not import to CAM unless you have checked the export files properly.
  • Keep in separate folders (to be checked / faulty / checked and ready for import).
Was this helpful?