3.7.2.1 BeamView

The "BeamView" component manages the display options for beams and trusses (refer to Fig. 3.7.2.1.1). This includes the visualization of cross-section forces, resultant displacements, the stress-to-strength ratio of materials, axial stress, buckling lengths, second order theory normal forces NII and utilization.

In previous versions of Karamba3D, the term "utilization" was used in place of "Stress/Strength ratio". However, this caused confusion: the stress-wise utilization (or stress-to-strength ratio) only describes the condition at a specific point in the cross section. In contrast, the "Utilization of Elements" component calculates the overall utilization of the entire cross section, accounting for factors such as plastic behavior and buckling. Therefore, the stress/strength ratio and utilization values may differ for the same beam under the same loads.

Display of cross section forces and moments

The “Section Forces” sub-menu lets you plot section forces and moments as curves, meshes and with or without values attached. All generated curves and meshes get appended to the “BeamView”-component's “Curves” and “Mesh” output. The graphical representation is oriented according to the local coordinate axes of the beam and takes the deflected geometry as its base. The subscript of bending moments indicates the local axis about which they rotate, for shear forces it is the direction in which they act (see also fig. 3.7.2.1.2). The cross-section forces refer to the section which is defined by the element's local coordinate system. In fig. 3.7.8.4 the cross section forces need to be applied to the right side of the beam to be in equilibrium with the external point load since the local X-direction points to the left side.

The size of the cross section forces diagrams can be scaled separately for forces and moments by the two sliders in the "SectionForces"-menu.

Customize the mesh-colors of the cross section forces diagrams via "karamba.ini". The slider “Length/Subdivision” in sub-menu “Render Settings” of the “ModelView”-component controls the number of interpolation points.

The “Display”-submenu

This submenu of the "BeamView" component offers several options for rendering beam axes or meshes according to specified result properties.

When activated, options such as "Cross Section", "|Disp|-CroSec", "Stress/Strength Ratio" and "Axial Stress" display the corresponding calculation results using a cross-sectional representation. "Stress/Strength Ratio" illustrates the ratio between axial, normal stresses and the material strength, with shear and buckling effects not considered. Consequently the maximum "Stress/Strength Ratio" value in fig 3.7.2.1.3. lies slightly below the utilization according to EC3 as calculated with the "Utilization"-component.

The color range for the results extends from the minimum to the maximum values. Users can adjust color ranges for all result quantities via the "Karamba3D/Settings" menu. Alternatively, predefined color ranges can be selected from the component's context menu: right-click on the component, navigate to "Colors", and choose a color range. A "Legend" component allows inspection of the corresponding values for each color.

The mesh used for rendering is accessible via the "Mesh" output of the "BeamView" component. Two sliders control the mesh resolution of rendered beams: the "Length/Segment" slider in the "ModelView" component sets the size of sections along the beam’s middle axis, while the "Faces/Cross section" slider in "BeamView" controls the number of faces per cross section (see fig. 3.7.2.1.4). For circular hollow cross-sections, the "Faces/Cross section" value is multiplied by six to ensure a smooth visual appearance.

Visualizing tension and compression within a beam can be insightful. To display axial stresses along the beam’s length, enable the "Axial Stress" checkbox in the "Display" menu. Red (similar to brick) indicates compression, while blue (similar to steel) represents tension. In some models there may exist small regions with high stresses with the rest of the structure having comparatively low stress levels. This results in a stress rendering that is predominantly white and not very informative. With the sliders for “Upper Result Threshold” and “Lower Result Threshold” of the “ModelView” you can set the range of the color-scale (see section 3.6.1). Result values beyond the upper limit appear yellow, below the lower threshold green.

For certain result types, only a single value per beam is available, or the variations across the cross-section are minimal. In such cases, results are represented using colored beam axes.

• |Disp|-MidAxis: Displays a color representation of the absolute beam displacements. It provides the same information as the cross-section-based |Disp|-CroSec option but with less detail.

• Buckling Length: The options "Buckling Length Y," "Buckling Length Z," and "Buckling Length LT" plot the buckling lengths of beam elements in the local Y and Z directions, as well as for lateral-torsional buckling, respectively. Negative values indicate that Karamba3D generated the values, while positive values denote user-defined inputs via the "ModifyBeam" component. There is no such thing as a negative length - only the absolute values enter the code equations. Since the absolute values of the buckling lengths significantly impact code-based utilization calculations, accuracy is crucial. The square of a beam’s buckling length is approximately inversely proportional to its buckling resistance—an underestimated buckling length results in unsafe calculations.

• NII (Geometric Stiffness Normal Force): Plots the normal forces used to determine a beam’s geometric stiffness in the currently active result selection, which is set in an upstream "ModelView" component. A negative NII value indicates compression, reducing stiffness, whereas positive values increase stiffness—similar to how a pre-tensioned rope behaves.

• Utilization: Displays the highest building-code-based utilization value for the currently active result selection. Currently, only EC3 is supported, and buckling effects are considered. To analyze the contribution of individual cross-section forces to overall utilization, the options "Utilization-N" to "Utilization-Mz" can be enabled:

  • N: Normal force

  • Vy, Vz: Shear forces in the local Y and Z directions

  • Mt, My, Mz: Torsional moment and bending moments about the local Y and Z axes

  Enabling the "Utilization-LcInd" option highlights the index of the load case within the currently selected load-case combination that leads to the maximum utilization at a specific location. Load cases are indexed from zero within their respective combinations.

When plotting results in axis mode, the "Line Thickness" slider in the "Render Settings" menu controls the thickness of the result lines (see Fig. 3.7.2.1.4).