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{live-template:Test Problem}

{action-request}
* The model should be revised to use the same maximum submesh size as is the discretization for the deck to avoid disconnected points.
* Revise the model to the latest version of SAP2000.
* Provide a discussion for interpreting the deck deflections due to weight of wet concrete.
{action-request}

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h1. Model screenshot

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!Staged_construction_for_precast_girder_bridge.png|align=center,border=0!

{center-text}Figure 1 - Deflected configuration{center-text}


h1. Approach 1 - Using section modifiers (Model B)


h2. Key modeling steps

* Use the BrIM template to create a 2-span precast-girder bridge. Designate double bearings at the interior pier.

* Manually define 15 continuity [links|kb:Link] at the interior pier to connect the girders and deck between span 1 and span 2.

* Create three groups for the construction stage analysis of continuity links, deck, and all other objects.

* Use the Define > Named Property Sets > Area Modifiers command to define property modifiers for the deck [shell|kb:Shell] elements. This will simulate the hardening of concrete.

* Set up construction stage analysis with separate stages to:
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*# add and load girders;
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*# add deck shell elements;
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*# reduce the stiffness of deck shell elements to simulate concrete placement;
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*# apply the deck dead load;
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*# reset the stiffness of the deck shell elements to simulate the hardening of concrete; and
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*# add continuity links to the model.

* Save the results at the end of each stage.

* Define [moving-load analysis|kb:Moving-load analysis], starting from the end of [staged-construction|kb:Staged construction] analysis.


h2. Modeling comments

* The bridge has fixed bearings at the bent which restrain vertical, longitudinal, and transverse translation. Sliding bearings at the abutments restrain vertical and transverse translation. For all other bearing DOF, *it is necessary to add small stiffness* to stabilize the girder before the deck is erected, otherwise stability problems may occur.


h2. Results

* Check bridge forces and stresses for each step of the staged construction analysis to ensure that moments are as expected for a simply-supported condition.

* Check moments for the results of moving-load analysis to ensure that moments are as expected for a continuous-girder system.


h2. Additional screen shots

The moment diagram upon completion of staged construction, after all loads are applied to simply-supported beams elements, is shown in Figure 2:

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!Moment_at_the_end_of_staged_construction_(simply_supported).png|align=center,border=0!

{center-text}Figure 2 - Moment diagram at the end of staged construction{center-text}

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Moment induced by live load, applied to a continuous span, is shown in Figure 3:

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!Moment_for_live_load_(continuous).png|align=center,border=0!

{center-text}Figure 3 - Live load moment diagram{center-text}

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*Important Comments:*

As of V14.1.0., *forces for each stage are reported to the centroid of the full bridge deck section.* You may need to transform the forces to the centroid of the section that is active when the forces are applied. See [bridge modeler forces and stresses diagrams|kb:Locations for reporting bridge superstructure and girder forces DRAFT] for additional information.
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h1. Approach 2 - Change section properties (Model C)


h2. Key modeling steps

* Use the Quick Bridge template to create a 2-span precast-girder bridge with double bearings at the interior pier.

* Manually define 15 continuity [links|kb:Link] at the interior pier to connect the girders and deck between span 1 and span 2.

* Create three groups for the construction stage analysis of continuity links, deck, and all other objects.

* Set up construction stage analysis with separate stages to:
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*# add and load the girders;
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*# add deck shell elements;
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*# reduce the stiffness of the deck shell elements to simulate concrete placement;
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*# apply the deck dead load;
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*# reset the stiffness of the deck shell elements to simulate the hardening of concrete; and
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*# add continuity links to the model.


h1. Attachments

* [SAP2000 file, Model B |Staged -construction analysis of two-span precast girder bridge^SAP2000 V12.0.2 model B.zip] (zipped SDB file)

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*To do:* Show powerpoint presentation with screenshots for model B.
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