# 3.3.6: Modify Cross Section

In Karamba3D cross section properties fall into four categories:

|                   |                                                                                                                  |
| ----------------- | ---------------------------------------------------------------------------------------------------------------- |
| **“General”**     | parameter which set the name, family, color, material and element identifier                                     |
| **“Geometry”**    | properties that determine the cross section size and eccentricity                                                |
| **“Deformation”** | these parameters influence the elastic behavior of a structure                                                   |
| **“Resistance”**  | properties which are used by cross section design procedures in order to determine the load-bearing capabilities |

The meaning of the input-values in the menu sections "Deformation" and "Resistance" are given in the help-texts associated to each input-plug.

The **“Modify Cross Section”**-component allows to change these properties. Two operation modes exist for this component:

**Flow through:** When a Cross section is provided as input, the result on the left side is the same cross section by default. Only those properties get changed, for which values are supplied as input.

**Agent:** The cross sections which shall be modified can be selected via the **“Elem-Ids”**-input. It is possible to apply regular expressions. The resulting cross section agent is of type **“Cross Section”** and gets active when being plugged into an **“Assemble”**-component.

<figure><img src="https://2671626451-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F6rkhS8IteqWJRfUuJlL5%2Fuploads%2FDq07OwDjbyPQ5dJh9hGm%2FModifyCrossSection.PNG?alt=media&#x26;token=e7fa9c8f-2285-4374-857e-da0b2420bd64" alt=""><figcaption><p>Fig. 3.3.6.1: ModifyCroSec Component</p></figcaption></figure>

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Fig. 3.3.6.1: the definition of a simply supported beam under uniform load. A **“Modify CroSec”**-component can be used to impose shear rigidity in local z-direction on a cross section. Now the calculated maximum displacement coincides with the result of the formula without shear effects. Textbook formulas for calculating the maximum displacement of such a system usually neglect the influence of shear-deformations. In order to make a cross section nearly rigid in shear the **“Modify Cross Section”**-component is used to set the shear area $$A\_z$$ to a very large value.

In case the height or thickness of a cross section is changed along with deformation- or resistance parameters, the evaluation proceeds from top to bottom: First, all parameters get updated according to the new cross section dimensions, these may then be overwritten by new values for deformation of resistance properties. The drop-down list at the bottom of the component allows to switch between beam- and shell-cross sections.

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