# Tub Girder

This section defines the steel tub girder geometry with station-dependent plate dimensions.

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**Navigation:** Superstructure > Steel Girders > Tub Girder

For detailed parameter explanations, see the [Tub Girder Reference](https://docs.openbrim.org/templates/steel-tub-girder-bridge-workflow/superstructure-stg/steel-girders-stg/tub-girder-stg).
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## Steps

### Step 1: Navigate to Tub Girder

Navigate to **Steel Girders > Tub Girder** in the tree view.

![Tub Girder navigation](https://openbrim.atlassian.net/wiki/download/attachments/2169077766/image-20230217-171009.png?api=v2)

### Step 2: Assign Girder Layouts

Click the **three-dot icon** on the **Girder Layout** cell and set **GL1** and **GL2**.

### Step 3: Define Top Flange Width

Click the **three-dot icon** on the top flange width cell, select **Edit**, and enter **22** for both GL1 and GL2.

![Top flange width](https://openbrim.atlassian.net/wiki/download/attachments/2169077766/image-20230220-075612.png?api=v2)

### Step 4: Define Station-Dependent Thicknesses

Click the **three-dot icon** on the top flange thickness cell and select **Edit (Spreadsheet)** to enter station-dependent values.

![Edit spreadsheet](https://openbrim.atlassian.net/wiki/download/attachments/2169077766/image-20230220-081546.png?api=v2)

![Thickness data](https://openbrim.atlassian.net/wiki/download/attachments/2169077766/image-20230220-081626.png?api=v2)

### Step 5: Set Web Depth

Enter **78** for Web Depth Projected to CL of box.

![Web depth](https://openbrim.atlassian.net/wiki/download/attachments/2169077766/image-20230220-082101.png?api=v2)

### Step 6: Define All Plate Dimensions

Use **Edit** or **Edit (Spreadsheet)** to define:

* Top flange thickness
* Web depth and thickness
* Bottom flange width and thickness
* Haunch thickness and additional haunch width

![Plate dimensions](https://openbrim.atlassian.net/wiki/download/attachments/2169077766/image-20230220-084204.png?api=v2)

### Step 7: Assign Materials

Click the **three-dot icon** on material cells and select **A709\_50W** for:

* Top Flange Material
* Web Material
* Bottom Flange Material

![Material assignment](https://openbrim.atlassian.net/wiki/download/attachments/2169077766/image-20230220-084912.png?api=v2)

### Step 8: Configure FEA Settings

Navigate to **FEA Setting** tab and assign **RigidSection** to the Rigid Section column.

![FEA settings](https://openbrim.atlassian.net/wiki/download/attachments/2169077766/image-20230220-090114.png?api=v2)

![Rigid section](https://openbrim.atlassian.net/wiki/download/attachments/2169077766/image-20230220-090234.png?api=v2)

<details>

<summary><strong>Quick Tip:</strong> Haunch Thickness Definition</summary>

**Haunch Thickness** = Distance from the bottom of the deck to the bottom of the top flange.

![Haunch definition](https://openbrim.atlassian.net/wiki/download/attachments/2169077766/image-20230220-091754.png?api=v2)

</details>

<details>

<summary><strong>Quick Tip:</strong> FE Model Generation</summary>

OpenBrIM automatically generates the FE model based on parametric relationships. Flanges use FeLine elements and webs use FeSurface elements.

</details>

## Verification

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The completed tub girder model is shown below.
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![Completed girder 3D](https://openbrim.atlassian.net/wiki/download/attachments/2169077766/image-20230220-093437.png?api=v2)

![Completed girder cross-section](https://openbrim.atlassian.net/wiki/download/attachments/2169077766/image-20230220-093314.png?api=v2)