Page Comparison

This pages describes the staged construction operations available in SAP2000. The same staged construction operations are available in CSiBridge, but the screenshots below apply to SAP2000.

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h1. Change Section

The default "Change Section Properties" operation essentially involves removing a stressed object and replacing it with unstressed object. This is documented in CSI Analysis Reference Manual, chapter "Nonlinear Static Analysis", section "Staged Construction > Changing Section Properties".

h1. Change Modifiers

To model staged construction for a composite section (for example, a girder initially supporting its own weight and the weight of wet concrete slab will become a composite girder after the concrete slab hardens), you could use one of the following approaches:

(1) If the composite section is modeled is a single frame element, model initially only the supporting girder and then use the "Change Modifiers" staged construction operation to account for the increased stiffness and weight of the composite section:

!Change_modifiers_operation.png!

Please note that you would need to first create frame property modifiers via "Define > Named Property Sets > Frame Modifiers" menu command.

(2) Explicitly model the individual components (such as the girder by frame elements and the slab by shell elements) of the [composite section|kb:Composite behavior]. To model hardening of the deck concrete, the deck could be initially added with negligible stiffness and full weight and then the stiffness can be increased to full stiffness via property modifiers.


h1. Change Supports

While it is not possible to directly change the support or restraint type in the staged construction in SAP2000 V15.0.1 and CSiBridge V15.1.1 (these are the current versions as of 9/2011), this can be accomplished by using frame releases and a dummy frame element:

# Define short and stiff frame element to represent the bearing.
# Use "Define > Named Property Sets > Frame Releases" menu command to define frame releases representing the final bearing condition for the frame element defined in step 1.
# Define "Change Releases" operation in the staged construction load case to change the frame releases.

!Change_releases.png!

Alternatively, you could also use link elements at the supports and then remove the{info}
Please note that the following applies (see CSI Analysis Reference Manual, chapter "Frame Element", section "End Releases > Named Property sets" for details):

_"When property modifiers are changed in a staged construction Load Case, they do not change the response of the structure up to that stage, but only affect subsequent response. In other words, the effect is incremental."_

This means that the approach described above will work well when supports are being changed by adding restraints, as it is adequate to use the incremental approach in this case. However, the above approach will not capture redistribution of internal forces when supports are being changed by removing restraints. For this case, modeling change of supports by adding and removing link elements would be more appropriate.

When using links, the procedure to change supports would be to remove link element(s) simulating the old support condition and replace it by a link element(s) simulating the new support condition.
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Related Incidents:

* {incident:no=38146|comments=Changing supports in staged construction.}
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h1. Change Frame Releases

* Use "Define > Named Property Sets > Frame Releases" menu command to define the frame end releases.
* Define "Change Releases" operation in the staged construction load case to apply the frame releases.