Create a concrete lofted slab

Added May 4, 2021 by Tekla User Assistance

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Create a concrete lofted slab

Create a concrete lofted slab

With lofted slabs you can create curved and double-curved slabs or walls, for example.

Prerequisites and examples of lofted slabs

Before you can create lofted slabs, you need to have construction objects in your model. Tekla Structures creates the shape of the lofted slabslab that is created by using construction objects

Lofted slabs can be used to model curved or double-curved slabs or walls, for example.

according to the geometry of the used construction objects, by connecting the start point of the first construction objectmodeling aid that helps in creating and placing other objects

Construction object can represent a point, line, arc, or plane, for example.

to the start point of the second construction object. The end points of construction objects are connected in similar way.

You can connect the following construction objects as a lofted slabplate that represents a concrete structure

In Tekla Structures, a slab is created by picking three or more points.

Slab may be part of a floor, for example.


  • construction lineconstruction object that represents a line between two points

    to construction line

    For example:

  • construction line to construction arcconstruction object that represents an arc defined by three points

    For example:

  • construction arc to construction arc

    For example:

  • construction circleconstruction object that represents a circle

    to construction circle

    For example:

  • construction polycurveconstruction object that represents a polycurve passing through several picked points

    Construction polycurves can have straight and curved segments.

    to construction polycurve

Note that rebar sets do not work with lofted slabs.

Create a lofted slab

  1. Create the needed construction objects in the model. The shape of the lofted slab is based on the construction objects' shape.

    You need to have

    • construction lines

    • construction arcs

    • construction circles


    • construction polycurves

      With polycurves, use the Create arc by tangent or Create tangent line options on the construction polycurve toolbar. To create polycurves only with straight segments, use the Create line option . Note that the construction polycurves do not need to have the same number of segments, as long as both of them are tangential.

  2. When you have created the needed construction objects, go to the Concrete tab and click Slab > Create lofted slab.
  3. On the toolbar that appears, click a button to specify whether to create the lofted slab by using two construction objects, or by using a construction object and a point.
    • Use two construction objects to create a lofted slab:

      1. Select the first construction object: line, arc, circle, or polycurve.

        For example, if you are using two construction circles to create a lofted slab:

      2. Select the second construction object:

        Tekla Structures creates the lofted slab between the selected construction objects, using the Lofted slab properties in the property panecontrol element in Tekla Structures user interface in the form of a side pane window

        The property pane can be used to show and modify the properties of model objects.

        The property pane can be customized by using the property pane editor.


    • Use one construction object and a point to create a lofted slab:

      1. Select the first construction object: line, arc, circle, or polycurve.

        For example, if you are using a construction polycurve and a point to create a lofted slab:

        Tekla Structures shows a preview of the part geometry. Use the preview to set the direction and height of the lofted slab.

      2. Pick a point.

        Tekla Structures creates the lofted slab based on the preview.

Modify the shape of a lofted slab

Use direct modificationfunction that activates the mode where the model objects can be modified by using handles

Direct modification enables additional handles and modification options.

dimension handles and dimension values to modify the lofted slab shape.

  • Modify, for example, the height and radius of the lofted slab.

  • For lines and arcs: drag the arc symbol at the midpoint of a line or an arc to modify the lofted slab shape.

Split a lofted slab

Note that you cannot split closed cylindrical or conical lofted slabs.

  1. On the Edit tab, click Split.
  2. Select the lofted slab you want to split.
  3. Pick a point for the dividing line.

    Tekla Structures splits the lofted slab.

    For example:

Swap the end handle points to correct the geometry of a lofted slab

In some cases when you try to create a lofted slab, the geometry of the slab would become self-intersecting, meaning that the start and end points of the top and bottom construction object are opposite of each other. In these cases the slab is not created.

You can try to resolve the situation and create the lofted slab by changing the modeling direction of the construction lines or arcs.

  1. Select the construction line or the construction arc.

    With construction lines, ensure that the Direct modification switch is not active. You can then see the yellow and magenta object handles.

  2. On the contextual toolbarfloating toolbar that contains commands for modifying the most common object properties

    The user can customize the contextual toolbar.

    , click Swap ends.

    Tekla Structures changes the modeling direction of the selected construction object, and the lofted slab can be created correctly.

With construction circles you can try to resolve the situation by moving either of the circles.

Modify concrete lofted slab properties

  1. If the property pane is not open, double-click the lofted slab to open the Lofted slab properties.
  2. Change the properties as needed.
  3. Click Modify.

Lofted slab properties

Use the Lofted slab properties in the property pane to view and modify the properties of a concrete lofted slab. To open the properties, double-click the concrete lofted slab. The file name extension of a concrete lofted slab property fileobject type specific file that contains values of properties or settings used in the property pane or a dialog box

Property files are saved in the current model folder. The user can create and modify property files and copy them to the project or firm folders for future use.

User-defined attributes related to a specific object type are stored in a separate property file.

is *.lsl.

If you have customized the property pane layout, the list of properties may be different.





User-definable name of the lofted slab.

Tekla Structures uses part names in reports and in Document manager, and to identify parts of the same type.


Thickness of the slab.


Material of the lofted slab.


Type of finish.


Use to group lofted slabs.

For example, you can display parts of different classes in different colors.

Face type

Face type

Select whether the top and bottom faces of the slab are flush with the plane.


The top and bottom faces of the slab are non-linear.

Bounded by curved planes:

The top and bottom faces of the slab are planar.

Cast unit

Cast unit numbering

Part prefix and start number for the part position number.

Cast unit

Indicate whether the slab is precast or cast in place.

Pour phase

Pour phase of the cast-in-place parts. Use to separate pour objects from one another.

Concrete covers for rebar sets

Coordinate system

Select whether the concrete cover thickness of the rebar sets in the part is defined in the global coordinate system, or in the part's local coordinate system.

The default global and local cover thickness values are defined in the Options dialog box.

If you select the empty option, Tekla Structures uses the global values.

Top, Bottom, Sides, Front , Back, Start, End

To override global or local default values from the Options dialog box, define the cover thickness at each required part face.



Click the User-defined attributes button to open the user-defined attributes (UDAs) of the part. UDAs provide additional information about the part.

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