> 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/templates-for-code-check-and-load-rating-tb/truss-load-rating-lfd-t-tb.md).

# Truss Load Rating (LFD) \[TB]

The Truss Load Rating (LFD) template collects the inputs that stay constant across all truss member load ratings — the mapped LFD Load Rating Combination Table, the effective length factor for compression buckling, the Rp reduction factor for holes, and the axial resistance factor. Each individual Truss Load Rating (LFD) object (under the Load Rating section) points at one template to inherit these values so they do not have to be repeated at every member.

## General

**Load Rating Combination (LFD):** The LFD Load Rating Combination Table used as the basis for all analysis results and load factors in the rating. Pick a Load Rating Combination Table (LFD) that maps the analysis result cases and their Design, Legal, Emergency, and Permit live-load stages. The user must provide a value.

## LFR Factors

**K, Effective Length Factor (compression buckling):** Effective length factor K used for compression-member buckling in the LFD column equation (AASHTO Standard Specifications Article 10.54.1.1). Typical values depend on the end-condition assumption — for example 1.0 for members effectively pinned at both ends.

**Rp Reduction Factor for Holes \[1.0 Drilled Full Size/0.90 Punched Full Size]:** Reduction factor Rp used with the net-section fracture limit state. Use 1.0 when the holes are drilled full size, and 0.90 when the holes are punched full size.

**Phi, Axial Resistance Factor (LFD):** The resistance factor φ applied to the nominal axial capacity (tension and compression). For LFD load rating this is typically 1.0.


---

# 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 by asking a question.

Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters:

```
GET https://docs.openbrim.org/templates/truss-bridge-workflow/templates-for-code-check-and-load-rating-tb/truss-load-rating-lfd-t-tb.md?ask=<question>&goal=<user_goal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case.

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.