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 cross frames, 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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