Page Comparison

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*TO DO* (see for-name label):
* 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.
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{live-template:Test Problem}

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This test problem showsdemonstrates how construction stage analysis can be done for bridges that are simply supported for dead load and continuous for live load.

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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

* CreateUse the BrIM template to create a 2-span precast -girder concrete bridge from BrIM template, with . Designate double bearings at the interior pier.

* Manually define 15 continuity [links|kb:Link] connectingat girdersthe andinterior deckpier ofto spanconnect 1the with girders and deck ofbetween span 21 atand thespan interior pier2.

* Create 3three groups to be used for the construction stage analysis forof continuity links, deck, and all other remaining objects.

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

* Set up construction stage analysis with separate stages to:
** (1)\\
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*# add and load girders;
the\\
girders\\
**# (2) add deck shell elements;
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** (3)\\
*# reduce the stiffness of the deck shell elements to simulate fresh concreteconcrete placement;
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**# (4) apply the deck dead load;
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**# (5) reset the stiffness of the deck shell elements to simulate the hardenedhardening of concrete; and
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**# (6) add the 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. OtherModeling modeling comments

* The bridge has fixed bearings (at the bent which restrain vertical, longitudinal, and transverse translation. translationsSliding fixed)bearings at the bentabutments and sliding bearings (only restrain vertical and transverse translationstranslation. fixed)For atall theother abutments.bearing HoweverDOF, *it is requirednecessary to add small stiffness for other bearing DOFs* to stabilize the girder before the deck is erected., Otherwiseotherwise 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 bridgecondition.

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


h2. Additional screen shots
screenshots
The Momentmoment atdiagram theupon endcompletion of staged construction, (after all loads are applied to a simply supported model beams) 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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LiveMoment loadinduced momentsby (live load is, 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

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

* Manually define 15 continuity [links|kb:Link] connectingat girdersthe andinterior deckpier ofto spanconnect 1the with girders and deck ofbetween span 21 atand thespan interior pier2.

* Create 3three groups to be used for the construction stage analysis forof continuity links, deck, and all other remaining objects.

* Set up construction stage analysis with separate stages to:
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**# (1) add and load the girders;
** (2)\\
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*# add deck shell elements;
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**# (3) reduce the stiffness of the deck shell elements to simulate fresh concrete
** (4) concrete placement;
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*# apply the deck dead load;
** (5) \\
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*# reset the stiffness of the deck shell elements to simulate the hardening hardenedof concrete; ** (6) add theand
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*# add continuity links to the model.


h1. Attachments

* [SAP2000 file, Model B |Staged construction for precast-girder bridges^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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