# External Diaphragm

This section defines external diaphragms that connect adjacent tub girders.

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**Navigation:** Superstructure > Bracing > External Diaphragm

For detailed parameter explanations, see the [External Diaphragm Reference](https://docs.openbrim.org/templates/steel-tub-girder-bridge-workflow/superstructure-stg/bracing-stg/external-diaphragm-stg).
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## Steps

### Step 1: Navigate to External Diaphragm

Navigate to **Bracing > External Diaphragm** in the tree view.

![External Diaphragm navigation](https://openbrim.atlassian.net/wiki/download/attachments/2169274402/image-20230220-140857.png?api=v2)

![External Diaphragm spreadsheet](https://openbrim.atlassian.net/wiki/download/attachments/2169274402/image-20230220-141002.png?api=v2)

### Step 2: Select Girders

Click the **three-dot icon** on **Girders** cell and pick both tub girders (**G1 & G2**) between which the external diaphragm will be placed.

### Step 3: Define Diaphragm Locations

Create 5 external diaphragms with appropriate station values and skew angle = 0.

![Diaphragm inputs](https://openbrim.atlassian.net/wiki/download/attachments/2169274402/image-20230220-141430.png?api=v2)

### Step 4: Set Diaphragm Types

* Assign **Pier-End** type for the first 4 rows (at support locations)
* Assign **Intermediate** type for the last row (mid-span location)

![Diaphragm types](https://openbrim.atlassian.net/wiki/download/attachments/2169274402/image-20230220-142557.png?api=v2)

### Step 5: Configure Pier/End References

Click the **three-dot icon** on **Select Pier/End** cell and pick the appropriate support locations. Enter station = 260 for the intermediate diaphragm.

![Pier/End selection](https://openbrim.atlassian.net/wiki/download/attachments/2169274402/image-20230220-143116.png?api=v2)

### Step 6: Set Offset Values

Enter **Offset from Pier/End** values as required.

![Offset values](https://openbrim.atlassian.net/wiki/download/attachments/2169274402/image-20230220-145507.png?api=v2)

### Step 7: Assign Material

Click the **three-dot icon** on **Material** cell and assign **A709\_50W** to all external diaphragms.

### Step 8: Optional Settings

Modify **Section Details** and **Stiffener** tabs if desired.

![Section details](https://openbrim.atlassian.net/wiki/download/attachments/2169274402/image-20230220-143817.png?api=v2)

![Stiffener](https://openbrim.atlassian.net/wiki/download/attachments/2169274402/image-20230220-143837.png?api=v2)

## Verification

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The completed external diaphragms are shown below.
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![Completed external diaphragm plan](https://openbrim.atlassian.net/wiki/download/attachments/2169274402/image-20230220-144630.png?api=v2)

![Completed external diaphragm 3D](https://openbrim.atlassian.net/wiki/download/attachments/2169274402/image-20230220-144500.png?api=v2)

![Completed external diaphragm detail](https://openbrim.atlassian.net/wiki/download/attachments/2169274402/image-20230220-144525.png?api=v2)