Load Rating [SIG]

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 clause6.10.1.1.1b , 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).