# 13. Load Rating

This section performs load rating per AASHTO Manual for Bridge Evaluation (MBE) to determine the safe load capacity of the bridge.

{% hint style="info" %}
Load rating determines rating factors for design, legal, and permit vehicles to assess the bridge's load-carrying capacity.
{% endhint %}

## Load Rating Checks

| Rating                                                                                                                                                                              | Description                        |
| ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------- |
| [Steel I Girder Load Rating](https://docs.openbrim.org/examples/steel-bridge-examples/example-steel-i-girder-bridge-ex1-sig/load-rating-ex1-sig/steel-i-girder-load-rating-ex1-sig) | Rating factors for girder capacity |

## Rating Levels

| Level                  | Purpose                                              |
| ---------------------- | ---------------------------------------------------- |
| **Design Load Rating** | Rating at Inventory and Operating levels using HL-93 |
| **Legal Load Rating**  | Rating for legal trucks (Type 3, 3S2, 3-3)           |
| **Permit Load Rating** | Rating for overweight permit vehicles                |

## Rating Factors

Rating Factor (RF) = (Capacity - Dead Load Effect) / (Live Load Effect)

* **RF > 1.0**: Bridge can safely carry the rated load
* **RF < 1.0**: Load posting may be required


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