> For the complete documentation index, see [llms.txt](https://docs.openbrim.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.openbrim.org/examples/concrete-bridge-examples/example-concrete-u-girder-bridge/combinations-ex1-cug/design-load-combinations-ex1-cug/limit-states-ex1-cug.md).

# Limit States

This section defines AASHTO LRFD limit state categories for design load combinations.

{% hint style="info" %}
**Navigation:** Combinations > Design Load Combinations > Limit States

For detailed parameter explanations, see the [Limit States Reference](https://docs.openbrim.org/templates/concrete-u-girder-bridge-workflow/combinations-cug/design-load-combinations-cug/limit-states-cug).
{% endhint %}

## Steps

### Step 1: Navigate to Limit States

Navigate to **Combinations > Design Load Combinations > Limit States** in the tree view.

### Step 2: Configure Strength Limit States

Define strength limit states per AASHTO LRFD:

* **Strength I:** Basic load combination for normal vehicular use
* **Strength II:** Load combination for owner-specified special vehicles
* **Strength III:** Load combination for wind on structure
* **Strength IV:** Load combination for very high dead/live load ratio
* **Strength V:** Load combination for normal vehicular use with wind

### Step 3: Configure Service Limit States

Define service limit states:

* **Service I:** Normal operational use
* **Service II:** Steel yielding and concrete cracking control
* **Service III:** Tension in prestressed concrete

### Step 4: Configure Extreme Event Limit States

Define extreme event limit states as needed:

* **Extreme Event I:** Earthquake
* **Extreme Event II:** Ice, collision, vessel impact

<details>

<summary><strong>Quick Tip:</strong> AASHTO Limit State Reference</summary>

Refer to AASHTO LRFD Bridge Design Specifications Section 3.4.1 for detailed limit state definitions and load factor requirements.

</details>

## Verification

{% hint style="success" %}
After completing these steps, limit states are defined for load combination analysis.
{% endhint %}


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