There Several methods are several ways available to account for deformed shaped in staged construction and for placing newly added joints into their deformed position.
Modify Undeformed Geometry
The most useful approach in many cases structural deformation during staged construction. These methods, which involve adding joints to displaced configuration, are discussed as follows:
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Modify undeformed geometry
In many cases, the most useful approach to account for structural deformation is to start with coordinates representing which represent the desired final deflected shape of the structureconfiguration. After running the staged - construction analysis, use the command select Analyze > Modify Undeformed Geometry to change the modify joint coordinates so such that the deflected shape at the end of the staged construction case matches the originally geometry initially specified geometry. Iterate a few times until the coordinates A few iterations may be necessary for coordinates to converge to the desired shape.
This approach automatically gives you provides the joint location desired location of joint at the time it a joint is added to the structure, and the deflected . Deflected shape is therefore meaningful. It also has the benefit of calculating camber for you.
The Concept of "Ghost Structure"
(1) Define two Named Property Sets of type Another benefit is that bridge camber is calculated automatically.
Implement a ghost structure
Another method which accounts for structural deformation during staged construction is the implementation of a ghost structure, which is done as follows:
- Define two Frame (or Shell) Modifiers
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- named property sets through Define >
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- Named Property Sets
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- . The first may be named Ghost, and the second
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- , Full
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- . In the named property set
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- Ghost
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- , set all stiffness modifiers to a small value,
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- perhaps 1e-4, and
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- Full
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- , set all modifiers to 1.0.
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- In the first construction stage
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- , add the whole structure
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- and apply the named property set
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- Full
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- to
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- all objects
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- which are present at the
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- beginning of staged construction. Load these objects, then apply named property set
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- Ghost
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- to the rest of the structure.
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- In subsequent stages,
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- apply the named property set
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- Full
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- to objects which are added to the
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- structure, then load this set of objects.
At each stage, the entire structure deflects, but only the objects set to "Full" contribute significant stiffness. This results in joints being activated in a deformed location that may be meaningful. Note that this approach can be modified as needed by considering will deflect while only objects of the named property set Full will contribute to stiffness. As a result, joints are activated in meaningful displaced locations. This approach may be modified through consideration of partial or multiple ghost structures.
The same approach can be used by changing An alternative approach is to change sections instead of changing modifiers. For example, you could use a plywood section for deck shells, and later change them deck shells may be modeled using plywood sections which are later changed to concrete slab sections.
Both options are discussed A discussion of ghost structure application using both sections and modifiers is available in the CSI Analysis Reference Manual, chapter " (Chapter XXIII Nonlinear Static Analysis".
Manually Modifying Joint Coordinates
For unusual cases, you can manually get the initial joint coordinates by running multiple analyses.
Start with a model having preliminary joint coordinates, and , Staged Construction).
Implement a ghost structure with two parallel structures
Another approach is to develop the actual structure in parallel with the ghost structure. The color of objects within the ghost structure may be modified to better visualize the staged-construction process. This method also enables better control over the age at which objects are added, improving the simulation of time-dependent effects. The Staged construction of a five-story column test problem demonstrates the development of actual and ghost structures in parallel.
Manually modify joint coordinates
Initial joint coordinates may be retrieved manually by running multiple analyses to gauge the structural behavior of unusual staged construction applications. Begin with a model which has preliminary joint coordinates, then run the first stage of construction. Modify the coordinates of the joints that which will be added in the second stage so such that they have are in the correct location with respect relative to the deflected shape of the first stage. Re-run the Run analysis again for these two stages, locate the joints for the third stage, and then continue this process recursively until all joints in the model have been are located.
See Also
- CableStaged construction of a five-story column test problem on ghost and parallel ghost structures
- Camber article
- Fabric structure
- Modify undeformed geometry form
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