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Constructing a typical steel bridge requires defining at least four stages: pier/foundation construction, girder and bracing construction, application of deck loads on non-composite girders, and deck stiffness gain. Introducing deck pouring stages will require additional stages for non-composite and composite stages. For example, if the deck is poured in three stages, six stages will be necessary (three for deck load application on girders and three for deck stiffness gain stages).
For permanent loads, such as wearing surface loads and barriers, two extra stages may be required.
Additional stages will be necessary for each transient load, such as wind loads, braking loads, live loads, and temperature loads.
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Stage
Prior Stage: The continuity of stages is maintained using the prior stage parameter, which instructs the software on which stage to analyze next. For the first stage, the prior stage will be none. If users wish to apply temporary loads like wind or live load, they can select the final permanent load stage as the prior stage for all transient loads. (screenshot for the transient load example)
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Active[Yes/No]: Users can deactivate specific stages to expedite the model's runtime, especially if they are interested in something from the earlier stages. However, if the deactivated stages negatively affect the continuity of stages, the staged construction analysis will fail to run successfully. Therefore, when users deactivate certain stages, they must ensure that all active stages' prior stages are still active.
Time Dependent
Typically, in a steel I-girder design project, time-dependent staged construction analysis is not necessary. However, if the bridge owner requests CEB-FIP 1990 creep/shrinkage computations for the substructure, or if post-tensioned tendons are employed for the pier cap or pier columns, time-dependent analysis can be conducted. In such cases, the following parameters can be used:
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PT Losses from Structure[Include/Ignore]: Elastic shortening losses refer to the reduction in the length of a prestressed concrete member caused by the initial stress generated during the pre-tensioning process or other external loads that could alter the length of the member. To account for this effect in the analysis, it is essential to select both the material and stage settings that include it.
AASHTO N-3N
Material: Choose the deck material to override for short-term and long-term properties
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