# Truss Load Rating \[TB]

Performs an AASHTO MBE load rating for an individual truss member. The object pulls its global settings (load rating combinations, effective length factor, condition and system factors, Rp hole reduction) from a Truss Load Rating template, then evaluates strength and service ratings for the selected truss member using section properties, connection eccentricity, and weld length. Design, legal, emergency, and permit live-load cases defined on the combination table are all reported.

## General

**Truss:** Pick the truss member to rate. The member's section properties and length are used for capacity calculations, and its element name is used to extract analysis results from the staged construction model. The user must provide a value.

**Load Rating Template:** Pick the Truss Load Rating template that holds the generic inputs (strength and service load rating combinations, effective length factor, condition and system factors, Rp reduction factor for holes). All global settings applied to the rating come from this template.

**PDF Name (Export):** Name used when the load-rating report is saved as a PDF. When renaming, avoid characters that interfere with parametric equations (see the [Illegal Characters](https://docs.openbrim.org/faq/general/faq-illegal-chars) page).

## Shear Lag Factor

Inputs used to compute the shear lag factor U for the net section in tension per AASHTO LRFD 6.8.2.2.

**Truss Member - Connection Eccentricity:** The eccentricity between the connection centroid and the centroid of the connected part of the member cross-section, used as x in the shear lag factor formula U = 1 - x / L. The default is auto-computed from the truss section type (y or z section dimension depending on whether the section is a channel, tee, angle, or tube); override it when the connection detail requires a value different from that auto-computed default. Enter a positive length.

**Truss Member - Max Length of the Longitudinal Welds:** The length L of the longitudinal welds at the end connection, used as the denominator in U = 1 - x / L. Enter the longer of the two weld lines when welds of unequal length are used. Enter a positive length.


---

# 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/templates/truss-bridge-workflow/load-rating-tb/truss-load-rating-tb.md?ask=<question>
```

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.