Wall beams and wall beam stiffness

Within Tekla Structural Designer, wall beams are automatically generated internal elements. These elements are a key component of the idealized analysis model. Generally, wall beams do not contribute to the global stiffness or lateral stability of the overall structure. Instead, they are designed to resolve localized finite element meshing challenges.

However, when engineers use Tekla Structural Designer to investigate local stress concentrations, the inherent rigidity of these internal wall beams can artificially disrupt local stress contours. To support these kinds of investigation, we have introduced an option to reduce wall beam stiffness.

CAUTION:

Reducing this stiffness removes the local load-distribution 'safety net' that wall beams provide and reintroduces mesh sensitivity. Therefore, this feature should be used with extreme caution and careful engineering judgment.

Why wall beams are needed

The connection of 1D elements (beams, columns) to 2D elements (meshed shells), or the connection of independent 2D meshes to one another, introduces mathematical discontinuities in a stiffness matrix. Wall beams act as localized "load distributors" to prevent mesh-sensitive anomalies. There are three primary cases where they are essential:

Case 1: Connection of beams and columns to walls

Beam connections (rotational stiffness): When an out-of-plane beam connects directly to a wall mesh node, the connection's rotational stiffness is highly dependent on the mesh size. Without a wall beam, a finer wall mesh results in greater local distortion (rotation) at that single node, artificially weakening the connection. The wall beam ensures consistent in-plane and out-of-plane joint stiffness regardless of mesh discretization.
Column connections (axial stiffness): If a 1D column element terminates directly on a 2D wall mesh, it introduces a point load that causes a theoretical stress singularity. In a fine mesh, the column will physically "sink" into the wall, overestimating local deflections. The wall beam acts as a rigid boundary that distributes the column's axial load across multiple shell nodes.

Case 2: Connecting mismatched wall/wall meshes

When two intersecting walls have mismatched mesh densities (e.g., due to different element sizing rules or openings), their nodes do not naturally align. Wall beams act as a continuous "zipper" along the intersection line. They collect forces from the nodes of one wall and distribute them to the non-aligned nodes of the intersecting wall, maintaining kinematic compatibility and preventing load loss.

Case 3: Connecting mismatched slab/wall meshes

Similarly, when a horizontal slab mesh connects to a vertical wall mesh, the 2D elements may not align perfectly due to differing meshing parameters. The wall beam at the floor level ensures that vertical shears, in-plane diaphragm forces, and bending moments are continuously transferred from the horizontal slab elements into the vertical wall elements without requiring a perfectly contiguous node-to-node mapping.

How to adjust wall beam stiffness

To adjust wall beam stiffnesses, you must first expose the wall beam stiffness modification factor. Once this factor is exposed, you can either apply the same modification factor to all wall beams in your model (a global adjustment) or adjust the factor for specific wall beams only. Adjustments can be made directly in the Properties window. However, if you are updating multiple walls, it can be more efficient to apply the adjustments graphically in a Review View, as this approach makes it easier to see where different factors have been applied.

What is adjusted

Major Moment of Inertia Modification Factor: Users can define a multiplier between 0.001 and 1.0.
- A value of 1.0 (default) applies the standard, unadjusted calculated properties.
- Values < 1.0 will linearly reduce the major axis moment of inertia of the internally generated wall beam.
Shear Area Loaded Parallel to Minor Axis: Based on the modified Major Moment of Inertia, the software automatically calculates an “effective height” for the wall beams. This reduced effective height is then used to proportionally scale down the relevant shear area.
The cross-sectional area, major shear area, and the torsion constant of the wall beams remain unchanged, regardless of the modification factor applied.

CAUTION:

Reducing this stiffness may resolve local stress contour visualization issues, but it reintroduces the mesh sensitivity issues outlined above. If you reduce the wall beam stiffness, you must ensure your local mesh is sufficiently refined and verify that beam/column end connections are not experiencing unrealistically high local stress, deflection, or rotation.

To expose the wall beam stiffness modification factor

On the Home ribbon, click Model Settings
In the Model Settings dialog, open the Analysis Model page.
Under the Wall beams heading, select Enable option to adjust wall beam stiffness.
Click OK

To globally adjust the stiffness of all wall beams

Once you have exposed the wall beam stiffness modification factor (as described in the preceding instructions), you can adjust the factor for all wall beams in the model as follows.

In the Structure window, click Structure.
In the Properties window, locate the Wall Beams section.
Adjust the Major Moment of Inertia Modification Factor as required.

To adjust the stiffness of selected wall beams in a Structural View

Once you have exposed the wall beam stiffness modification factor (as described in the preceding instructions), you can adjust the factor for selected wall beams in a Structural View as follows.

Ensure the view containing the wall is set as a Structural view regime.
Select one or more wall beams.

The properties should then be displayed in the Properties window as 'Wall Elements'.
In the Properties window, locate the Wall Beams section.
Select Override Factor
Adjust the Major Moment of Inertia Modification Factor as required.

To adjust the stiffness of selected wall beams in a Review View

Although there is no specific Show/Alter State command for this action, you can adjust the wall beam stiffness modification factor in a Review View. First, ensure the factor is exposed (as described in the preceding instructions). Then you can make the adjustment using the generalized Any Property command as follows.

Switch the view regime to Review View.
Open the Scene Content window and ensure Walls > Wall Elements is selected.
On the Review ribbon, click Show/Alter State.
In the Properties window, locate the Attribute list and select Any Property.
In the Properties window, select Editable Properties
Select a wall element that you intend to edit.
When the element has been selected, the command prompt asks you to select a property.
In the Properties window, under the Wall Beams section change Override Factor from unselected to selected. This has the effect of applying the override to the currently selected wall element.
In the Properties window, change [M]ode to Copy.
Select the other wall elements for which you want to override the factor. Note that the legend updates accordingly.
In the Properties window, select Major Moment of Inertia Modification Factor
Adjust the Major Moment of Inertia Modification Factor to the value you require.
Select the same wall beams to which you applied the override.
When finished, change [M]ode back to Review and use the legend to check that each of the wall beams with an Override Factor has the required factor applied.
Press [Esc] to end.

Example: Adjustment of wall beam stiffness when modeling a stepped slab

To model a “folded” or “stepped” concrete slab in Tekla Structural Designer, the upper and lower areas would need to be created as separate slabs.

To achieve continuity between the slabs, a short wall could then be inserted along the dividing line between them as shown below. Because the lower slab is detected when the wall is placed, the wall's "Generate Support" setting is automatically disabled.

To avoid unwanted 3D effects as a result of the step, diaphragm action should also be switched off in the slabs to either side of the step.

As described here, a wall beam element is automatically introduced at the top of the short wall, and because its "Generate Support" setting is not enabled a second wall beam element is also introduced at the bottom of the wall.

In the resulting solver model, quadrilateral 2D solver elements in the wall provide continuity between the two slabs

Results based on the default wall beam stiffnesses

An initial set of results can be generated for the above model by running the analysis while leaving the wall beam adjustment option unselected in Model Settings (as shown below).

The deflections based on the unadjusted wall beam stiffnesses are as follows.

Adjusting wall beam stiffness

Before a stiffness modification factor can be applied, it is necessary to activate the wall beam adjustment option.

The next step is to select the wall beam elements to be adjusted. In this example, we only need to adjust the wall elements running along the top and bottom of the short wall. (Either by boxing around them, or by selecting one, then the other while pressing Ctrl).

The properties of the selected wall beam elements are displayed in the Properties window. Note that, because the option to adjust wall beam stiffness has been activated, an extra "Wall Beams" section has been added.

To adjust the stiffness, select Override Factor and then enter the factor required.

Results after adjusting wall beam stiffness

When the analysis is rerun, the adjusted wall beam stiffness is apparent when the deflections are reviewed.