# 3. Properties

This section defines the material properties, sections, rebars, and bolt properties used throughout the bridge model.

{% hint style="info" %}
Define these properties before modeling structural components. Once imported, they appear in property selection dropdowns throughout the workflow.
{% endhint %}

## Properties to Define

| Property Type                                                                                                                    | Description                                                        |
| -------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------ |
| [Materials](https://docs.openbrim.org/examples/steel-bridge-examples/example-steel-i-girder-bridge-ex1-sig/broken-reference)     | Steel and concrete material definitions (A709 Grade 50, f'c=4 ksi) |
| [Rebars](https://docs.openbrim.org/examples/steel-bridge-examples/example-steel-i-girder-bridge-ex1-sig/broken-reference)        | Reinforcement bar definitions for deck and substructure            |
| [Sections](https://docs.openbrim.org/examples/steel-bridge-examples/example-steel-i-girder-bridge-ex1-sig/broken-reference)      | Cross-frame member sections and other structural shapes            |
| [Bolt Property](https://docs.openbrim.org/examples/steel-bridge-examples/example-steel-i-girder-bridge-ex1-sig/broken-reference) | Bolt specifications for field splices and connections              |

## Materials Used in This Example

* **Structural Steel**: AASHTO M270, Grade 50 (Fy=50 ksi, Fu=65 ksi)
* **Concrete**: f'c=4 ksi, unit weight=150 pcf
* **Reinforcing Steel**: AASHTO M31, Grade 60 (Fy=60 ksi)