# External Diaphragm

This section defines external diaphragms that connect the two Concrete U Girders to ensure they work together structurally.

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**Navigation:** Superstructure > Diaphragm > Custom Diaphragm

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

### Step 1: Navigate to External Diaphragm

Navigate to **Diaphragm > Custom Diaphragm** in the tree view.

![Navigation](https://openbrim.atlassian.net/wiki/download/attachments/2258862092/image-20230829-074149.png?api=v2)

### Step 2: Select Support Line Locations

Choose the specific locations (support lines) where you want to create external diaphragms.

![Select Locations](https://openbrim.atlassian.net/wiki/download/attachments/2258862092/image-20230829-105853.png?api=v2)

### Step 3: Select Girders

Click the **three-dots icon** on the **Girders** cell and pick the two Concrete U Girders (**CUG1** and **CUG2**) between which the external diaphragm will be placed.

![Select Girders](https://openbrim.atlassian.net/wiki/download/attachments/2258862092/image-20230829-110421.png?api=v2)

### Step 4: Assign Properties

Assign **Thickness** and **Material** properties to all external diaphragms.

![Properties](https://openbrim.atlassian.net/wiki/download/attachments/2258862092/image-20230829-110830.png?api=v2)

## Verification

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After completing these steps, the external diaphragms should appear as shown below.
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![Completed External Diaphragms](https://openbrim.atlassian.net/wiki/download/attachments/2258862092/image-20230829-111615.png?api=v2)