> 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/concrete-u-girder-bridge-workflow/load-rating-cug.md).

# Load Rating \[CUG]

**Staged Construction Analysis**\
For a typical load rating project, a staged construction analysis is performed in the following stages:\
**Stage 1:** Construction of girders and bracings, followed by the application of non-composite loads such as deck loads and stay-in-place formwork loads on the non-composite girder.\
**Stage 2:**(or more): The deck gains stiffness based on the deck pouring sequence.\
**Stage 3:** Barrier loads or wearing surface loads are applied on the deck.\
**Stage 4:** Influence surface-based live load analysis is conducted using various vehicles.

To comply with AASHTO clause`6.10.1.1.1b` , users are given the ability to override the modulus of elasticity of the deck at each stage AASHTO clause `6.10.1.1.1b`. For transient loads assumed to be applied to the short-term composite section, the concrete deck area is transformed using the short-term modular ratio, n. For permanent loads assumed to be applied to the long-term composite section, the concrete deck area is transformed using the long-term modular ratio, 3n.).

**Load Rating**

To compute stress values for load rating, we classify the analysis results from staged construction analysis into three categories: non-composite major axis bending moment, short-term composite bending moment, and long-term composite bending moment.

For positive flexure regions, stress is then calculated based on these three section moduli (girder only-noncomposite section, short-term composite section - deck(n)+girder, and long-term composite section-deck(3n)+girder).

For negative flexure regions, we utilize a non-composite section and a girder section with rebars (optionally with a creep correction factor).


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