# 2. Bridge Geometry

This section defines the geometric layout of the bridge, including alignments, support locations, and girder positions.

{% hint style="info" %}
Complete these definitions in order. Each subsequent step depends on the previous definitions.
{% endhint %}

## Geometry Definitions

| Definition                                                                                                                                                            | Description                                         |
| --------------------------------------------------------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------- |
| [Roadway Alignment](https://docs.openbrim.org/examples/steel-bridge-examples/example-steel-i-girder-bridge-ex1-sig/bridge-geometry-ex1-sig/roadway-alignment-ex1-sig) | Horizontal and vertical alignment of the roadway    |
| [Bridge Alignment](https://docs.openbrim.org/examples/steel-bridge-examples/example-steel-i-girder-bridge-ex1-sig/bridge-geometry-ex1-sig/bridge-alignment-ex1-sig)   | Bridge centerline referencing the roadway alignment |
| [Support Lines](https://docs.openbrim.org/examples/steel-bridge-examples/example-steel-i-girder-bridge-ex1-sig/bridge-geometry-ex1-sig/support-lines-ex1-sig)         | Pier and abutment locations along the alignment     |
| [Insertion Point](https://docs.openbrim.org/examples/steel-bridge-examples/example-steel-i-girder-bridge-ex1-sig/bridge-geometry-ex1-sig/insertion-point-ex1-sig)     | Reference points for girder positioning             |
| [Girder Layout](https://docs.openbrim.org/examples/steel-bridge-examples/example-steel-i-girder-bridge-ex1-sig/bridge-geometry-ex1-sig/girder-layout-ex1-sig)         | Lateral spacing and arrangement of girders          |

## Geometry Parameters for This Example

| Parameter               | Value                       |
| ----------------------- | --------------------------- |
| Span Configuration      | 160 ft - 210 ft - 160 ft    |
| Horizontal Curve Radius | 700 ft                      |
| Number of Girders       | 4                           |
| Girder Spacing          | Variable (curved alignment) |
| Deck Width              | 40.5 ft                     |
| Superelevation          | 5%                          |

## Workflow

1. **Roadway Alignment**: Define horizontal curve and vertical profile
2. **Bridge Alignment**: Reference the roadway alignment for the bridge centerline
3. **Support Lines**: Place 4 support lines at pier and abutment locations
4. **Insertion Points**: Define 4 insertion points with transverse offsets
5. **Girder Layout**: Create 4 girder layouts connecting the insertion points


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