Wall beams and wall beam stiffness

In Tekla Structural Designer, wall beams are automatically generated internal elements that form a critical part of the idealized analysis model. In general, 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, as engineers increasingly 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 this type of advanced analysis, we have introduced an option to reduce wall beam stiffness.

CAUTION:

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

Why wall beams are needed

Connecting 1D elements (beams, columns) to 2D elements (meshed shells), or connecting 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: Connecting beams and columns to walls

Connecting beams (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.
Connecting columns (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 mis-matched wall / wall meshes

When two intersecting walls have mis-matched 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 mis-matched 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.

Adjusting wall beam stiffness: guidelines and implementation

To allow engineers to capture specific local stress behaviors, we have provided an option to allow you to expose the wall beam stiffness modification factor. Once this is exposed you can then globally adjust the major moment of inertia factor applied to all wall beams in the model.

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 adjust the wall beam stiffness modification factor

Once the wall beam stiffness modification factor is exposed you can adjust it 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.

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.

Recommendation:

Reducing this stiffness may resolve local stress contour visualization issues, but it re-introduces 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.