# Steel Tub Girder - Additional Bearing Construction and Deconstruction

{% hint style="info" %}
Follow the steps below to construct and deconstruct temporary bearings on a steel tub-girder model.
{% endhint %}

This article walks through adding temporary bearings on the steel tub-girder model shown below. Two extra supports are added at the 25 ft and 75 ft stations of the 100 ft girder. The construction is staged in three steps.

![image-20250513-153553.png](https://openbrim.atlassian.net/wiki/download/attachments/3113451523/image-20250513-153553.png?api=v2)

1. Create the additional support lines.

   ![](https://openbrim.atlassian.net/wiki/download/attachments/3113451523/image-20250513-153858.png?api=v2)
2. Create additional insertion points on the new support lines. The insertion points could also be added to existing support lines using a longitudinal offset, but a new support line is usually easier to manage.

   ![](https://openbrim.atlassian.net/wiki/download/attachments/3113451523/image-20250513-154219.png?api=v2)
3. Include the new insertion points in the girder layout. The girder is configured to generate bearings on the same support lines as the insertion points listed in its layout.

   ![](https://openbrim.atlassian.net/wiki/download/attachments/3113451523/image-20250513-154307.png?api=v2)
4. In the tub girder's **FEA Setting** tab, select all bearing insertion points related to the girder in the **Support** input. The insertion points marked with the blue arrow in the screenshot are the additional bearings.

   ![](https://openbrim.atlassian.net/wiki/download/attachments/3113451523/image-20250513-154409.png?api=v2)
5. Define bearing fixity for the new insertion points.

   ![](https://openbrim.atlassian.net/wiki/download/attachments/3113451523/image-20250513-154555.png?api=v2)
6. Construct the bearings stage by stage under **Bearing Construction**.

   ![](https://openbrim.atlassian.net/wiki/download/attachments/3113451523/image-20250513-155102.png?api=v2)
7. Select the additional bearings to be removed under **Bearing Deconstruction**.

   ![](https://openbrim.atlassian.net/wiki/download/attachments/3113451523/image-20250513-155210.png?api=v2)

Animation of the resulting deformation across construction stages:

![](https://openbrim.atlassian.net/wiki/download/attachments/3113451523/tubgirder_deformation.gif?api=v2)

Final deformed shape after all stages:

![](https://openbrim.atlassian.net/wiki/download/attachments/3113451523/image-20250513-160339.png?api=v2)

{% hint style="info" %}
Place additional insertion points so they coincide with web nodes, or add an **internal diaphragm** at the same station. An internal diaphragm is a transverse stiffener inside the tub that ties the two webs together; without it, the local stiffness at a midspan support is low and you may see exaggerated deformations at that station.
{% endhint %}


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