# Internal Cross-frame K Top

This section defines K-type internal cross-frames inside the tub girders.

{% hint style="info" %}
**Navigation:** Superstructure > Bracing > Internal Cross-frame K-Top

For detailed parameter explanations, see the [Internal Cross-frame K-Top Reference](https://docs.openbrim.org/templates/steel-tub-girder-bridge-workflow/superstructure-stg/bracing-stg/internal-cross-frame-k-top-stg).
{% endhint %}

## Steps

### Step 1: Navigate to Internal Cross-frame K-Top

Navigate to **Bracing > Internal Cross-frame K-Top** in the tree view.

![Internal Cross-frame navigation](https://openbrim.atlassian.net/wiki/download/attachments/2168684564/image-20230220-110759.png?api=v2)

### Step 2: Assign Girder

Click the **three-dot icon** on the **Girder** cell and set **G1** to place cross-frames inside that girder.

### Step 3: Define Cross-Frame Stations

Enter the **Station** locations for each cross-frame along G1 and G2.

![Station locations](https://openbrim.atlassian.net/wiki/download/attachments/2168684564/image-20230220-113159.png?api=v2)

### Step 4: Assign Chord Sections

Navigate to the **Sections** tab and assign sections:

1. Click the **three-dot icon** on **Top Chord Section**
2. Click **Select**
3. Choose **AISCL6X6X7/8** from the imported sections
4. Apply the same section to **Diagonal Chord Sections**

![Section assignment](https://openbrim.atlassian.net/wiki/download/attachments/2168684564/image-20230220-114940.png?api=v2)

![Section selection](https://openbrim.atlassian.net/wiki/download/attachments/2168684564/image-20230220-115052.png?api=v2)

![Completed sections](https://openbrim.atlassian.net/wiki/download/attachments/2168684564/image-20230220-121130.png?api=v2)

### Step 5: Configure Chord Geometry

Navigate to the **Chord Geometry** tab and enter **18** for "Diagonal Chord Inner Offset from Top Web" for all cross-frames.

![Chord geometry](https://openbrim.atlassian.net/wiki/download/attachments/2168684564/image-20230220-121520.png?api=v2)

<details>

<summary><strong>Quick Tip:</strong> End Offsets</summary>

The "Diagonal Chord Inner Offset from Top Web" parameter incorporates end offsets for truss elements in the FEA model.

</details>

### Step 6: Optional Gusset and Stiffener Settings

Modify **Gusset Plate** and **Stiffener** tabs if desired. These affect 3D visualization only, not the FEA model.

![Gusset plate](https://openbrim.atlassian.net/wiki/download/attachments/2168684564/image-20230220-122044.png?api=v2)

![Stiffener](https://openbrim.atlassian.net/wiki/download/attachments/2168684564/image-20230220-122123.png?api=v2)

## Verification

{% hint style="success" %}
The completed K-Top internal cross-frames are shown below.
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![Completed cross-frames 3D](https://openbrim.atlassian.net/wiki/download/attachments/2168684564/image-20230220-123052.png?api=v2)

![Completed cross-frames detail](https://openbrim.atlassian.net/wiki/download/attachments/2168684564/image-20230220-123142.png?api=v2)