# Parametric Bridge Engineering ## Access an Example Steel Bridge Model {% hint style="info" %} Follow the steps below to open the **Steel I-Girder Training Example**. {% endhint %} 1. Log in to your account and locate **Project** in the top-right corner. ![](https://openbrim.atlassian.net/wiki/download/attachments/2231271425/image-20230703-094719.png?api=v2) 2. Click **Project**, then click **NEW** in the top-left corner. ![](https://openbrim.atlassian.net/wiki/download/attachments/2231271425/image-20230703-094913.png?api=v2) 3. Under **Example Project**, click **New Project** within **Steel I-Girder Training Example**. ![](https://openbrim.atlassian.net/wiki/download/attachments/2231271425/image-20230703-141313.png?api=v2) ![](https://openbrim.atlassian.net/wiki/download/attachments/2231271425/image-20230711-113454.png?api=v2) 4. Provide a name for your project and open the example. ![](https://openbrim.atlassian.net/wiki/download/attachments/2231271425/image-20230711-113559.png?api=v2) ![](https://openbrim.atlassian.net/wiki/download/attachments/2231271425/image-20230705-110649.png?api=v2) {% hint style="warning" %} The initial download of the library components **takes approximately 2 minutes 30 seconds**. Subsequent openings of the same project are noticeably faster because OpenBrIM library objects are cached in your browser; loading then **takes less than 2–3 seconds**. {% endhint %} ![](https://openbrim.atlassian.net/wiki/download/attachments/2231271425/image-20230703-153825.png?api=v2) *** ## OpenBrIM Parametric Modeling This section demonstrates how OpenBrIM's cloud-based parametric approach updates every connected output (3D model, FEA model, drawings, reports) when you change a single input. {% hint style="info" %} In the steps below, you will modify the **Web Depth** parameter of a girder in the spreadsheet. Both the 3D model and the FEA model will update automatically. {% endhint %} 1. Click the **DATA** button in the bottom-middle of the screen to open the spreadsheet. ![](https://openbrim.atlassian.net/wiki/download/attachments/2231271425/image-20230705-082508.png?api=v2) ![](https://openbrim.atlassian.net/wiki/download/attachments/2231271425/image-20230705-083136.png?api=v2)
2. Click **Plate Girder** under **Superstructure** in the workflow tree. *All project girders and their parameters appear in the spreadsheet.* ![](https://openbrim.atlassian.net/wiki/download/attachments/2231271425/image-20230705-083410.png?api=v2) 3. To compare the FE model before and after the change, open the sliding menu in the top-left corner and click **FEA** to switch to the Finite Element view. The menu also offers **MODEL**, **CAD**, **DOCS**, **SUPPORT**, and **USER SETTINGS**. ![](https://openbrim.atlassian.net/wiki/download/attachments/2231271425/image-20230713-082055.png?api=v2) ![](https://openbrim.atlassian.net/wiki/download/attachments/2231271425/image-20230713-082436.png?api=v2) ![](https://openbrim.atlassian.net/wiki/download/attachments/2231271425/image-20231025-193909.png?api=v2)

Zoom with the mouse scroll wheel. Pan by holding the scroll wheel down while moving the mouse. To recenter the view, click the Zoom Extents button in the top-right corner; after selecting an object, Zoom Extents orbits the view around that object. Rotate by dragging with the left mouse button.

![](https://openbrim.atlassian.net/wiki/download/attachments/2231271425/Screenshare%20-%202023-07-13%2010_59_28%20AM-20230713-080117.gif?api=v2) 4. The current Finite Element model uses an 84 in web depth. To change it for girder **G4**, click the **Web Depth** cell for that girder and enter **55** inches. ![](https://openbrim.atlassian.net/wiki/download/attachments/2231271425/image-20230713-082823.png?api=v2) ![](https://openbrim.atlassian.net/wiki/download/attachments/2231271425/image-20230713-083033.png?api=v2)

After the change, the 3D model and Finite Element model take roughly 10 seconds to refresh. OpenBrIM recompiles using your inputs to regenerate the 3D model, FEA model, CAD drawings, and dynamic reports (such as the quantity report) so all outputs stay in sync.

5. The new Finite Element model now reflects the updated web depth. ![](https://openbrim.atlassian.net/wiki/download/attachments/2231271425/image-20230713-083348.png?api=v2) 6. Open the sliding menu again from the top-left corner and click **MODEL** to switch back to the 3D view. ![](https://openbrim.atlassian.net/wiki/download/attachments/2231271425/image-20230713-083959.png?api=v2) 7. The change is visible in both the 3D and Finite Element views. ![](https://openbrim.atlassian.net/wiki/download/attachments/2231271425/image-20230713-084708.png?api=v2) {% hint style="info" %} For a full description of girder plate dimensions, see [Plate Girder \[SIG\]](/templates/steel-i-girder-bridge-workflow/superstructure-sig/steel-girders-sig/plate-girder-sig.md). For a worked example, see [Plate Girder \[EX1-SIG\]](https://docs.openbrim.org/examples/steel-bridge-examples/example-steel-i-girder-bridge-ex1-sig/superstructure-ex1-sig/steel-girders-ex1-sig/plate-girder-ex1-sig). {% endhint %} *** ## OpenBrIM Spreadsheets: Excel-Like Functionality with Parametric Dependencies This section shows how OpenBrIM spreadsheets behave like Excel — cells can reference one another to keep related parameters in sync. {% hint style="info" %} Cross-frame skew, roadway skew, and support-line skew are independent inputs by default, so the same value must be entered in three places. The steps below link them so that changing the support-line skew updates the others automatically. {% endhint %} 1. Click **Support Line** under **Bridge Geometry** in the workflow to access the skew angle parameter. ![](https://openbrim.atlassian.net/wiki/download/attachments/2231271425/image-20230705-095956.png?api=v2) 2. To change the skew angle of **Abut1**, click the corresponding cell (marked in red). ![](https://openbrim.atlassian.net/wiki/download/attachments/2231271425/image-20230705-112143.png?api=v2) 3. With the skew angle of **Abut1** set to 0, the bridge appears as shown. ![](https://openbrim.atlassian.net/wiki/download/attachments/2231271425/image-20230705-102036.png?api=v2) 4. With the skew angle of **Abut1** set to **−15°**, the bridge appears as shown. ![](https://openbrim.atlassian.net/wiki/download/attachments/2231271425/image-20230705-103455.png?api=v2) {% hint style="info" %} The cross-frames are no longer aligned with the support line. To link them parametrically: 1. Copy the support line's skew angle value with **Copy Parameter**. 2. Paste the parametric expression into the cross-frame's skew angle. 3. The cross-frame skew now follows the support line skew automatically. {% endhint %} 4. Click the skew angle cell for **Abut1**. Click the three-dot menu that appears on the right side of the cell, then choose **Copy Parameter**. The skew angle parameter (not the value) is copied. ![](https://openbrim.atlassian.net/wiki/download/attachments/2231271425/image-20230705-105048.png?api=v2)

The parameter copied: =Abut1.s_skew

5. Expand **Cross Frames** under **Superstructure** in the workflow, then click **Cross-frame K Top** to access its parameters. ![](https://openbrim.atlassian.net/wiki/download/attachments/2231271425/image-20230705-104914.png?api=v2) 6. Click the skew angle cell for **CFTK1**. Open the three-dot menu that appears on the right side of the cell and choose **Paste**. ![](https://openbrim.atlassian.net/wiki/download/attachments/2231271425/image-20230705-110050.png?api=v2)

You can also paste the copied parameter into the active cell with CTRL+V.

7. Repeat the paste for **CFKT28** and **CFKT29**. *The cross-frames are now aligned with the support line.* ![](https://openbrim.atlassian.net/wiki/download/attachments/2231271425/image-20230705-110452.png?api=v2) 8. Cross-frame skew angles are now parametrically linked to the support-line skew, so changing one updates the others. ![](https://openbrim.atlassian.net/wiki/download/attachments/2231271425/image-20230712-084553.png?api=v2) {% hint style="success" %} The cross-frame skew now references the support line's skew the way one Excel cell references another. OpenBrIM cells accept arithmetic, functions, and logical operators, so more complex equations are supported. See [Mathematical Functions](https://docs.openbrim.org/developers/paramml-developer-guide/functions/mathematical-functions) in the ParamML documentation. {% endhint %} *** ### Aligning Roadway with Skew Angle {% hint style="info" %} Use the same Copy Parameter approach to align the roadway with the skew angle of the support line. {% endhint %} 1. Expand **Superstructure Attachments** in the workflow and click **Roadway** to access the roadway alignment parameters. 2. Open the three-dot menu on the right of the **Roadway Dimensions** cell and click **Edit**. 3. Paste the skew angle copied from **Abut1** into the **Skew** parameter at station 0. ![](https://openbrim.atlassian.net/wiki/download/attachments/2231271425/image-20230705-111028.png?api=v2) ![](https://openbrim.atlassian.net/wiki/download/attachments/2231271425/image-20230705-111816.png?api=v2) --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.openbrim.org/quick-guides/parametric-bridge-engineering.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.