> 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/templates/truss-bridge-workflow/construction-tb/changes-tb.md). # Changes \[TB] An analysis may require parameters to be redefined across several stages to ensure the stability of the bridge. To achieve this, changes to various elements can be defined based on a specific sequence and stage. -A common scenario is that girders without cross-frames and bracings can sometimes be in an unstable condition, which may cause the Finite Element Analysis (FEA) to fail or remain incomplete. If the bracings are constructed after the erection of the girders, the **Bearing Fixity Change** section can be utilized to successfully complete the analysis. -Another use case arises during seismic analysis, where factors such as **cracked inertia** are essential. These factors can be assigned to pier columns based on the defined construction stage. In such cases, the **Pier Section Property Override** object is employed to accurately reflect the structural behavior during different phases of construction. For the objects that can be defined in this section, please refer to the related page for detailed explanations of the parameters. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## 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, and the optional `goal` query parameter: ``` GET https://docs.openbrim.org/templates/truss-bridge-workflow/construction-tb/changes-tb.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. 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.