Introduction to staged construction analysis
What is staged construction analysis?
A staged construction analysis,
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Is a static analysis procedure
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It recognizes the changing state of a structure over time
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It is more relevant for taller (typically concrete) buildings
It typically assumes,
- Buildings are constructed in stages
- Stages are story based
- Not all forces and stiffnesses are in effect from day one (unlike a full 3D analysis).
At each “stage” any or all of the following may change:
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The physical members/supports included in the model
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Material properties (Time dependent effects)
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The applied loading
Benefits of staged construction analysis
By running a staged construction analysis in Tekla Structural Designer you can take advantage of the following benefits:
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Transfer levels are loaded more realistically,
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but not to the same extent as a traditional hand calculation - this is more closely emulated by Tekla Structural Designer’s existing chasedown procedures - see this example for details.
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Axial deformations are reduced to give a more realistic assessment.
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This is due to the structure evolving over time, as opposed to being formed instantly.
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Deflection due to wind and other short term loading events in concrete structures is determined using different properties to those used for sustained loading.
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This is achieved through the use of load type dependent design cases, each with appropriate modification factors - see Staged construction modification factors for more details.
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- A more optimized design is delivered.
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The engineer can choose between staged construction analysis or 3D building analysis with either or both of FE chasedown and grillage chasedown.
- The different analyses mean that an envelope of possible design forces have been considered.
- Swapping out 3D building analysis for staged construction analysis (more realistic) will
reduce this envelope of design forces, leading to a more optimized design,
potentially reducing the quantities of materials.
For further details, see: Design comparison - with and without staged construction
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Note however that staged construction analysis in Tekla Structural Designer doesn’t enable you to examine design conditions on partially completed structures (e.g. wind effects on a half built building).
Scope in Tekla Structural Designer
Staged construction analysis is
applicable to both concrete and steel structures.
- All of the concrete design codes available in Tekla Structural Designer take account of staged construction analysis design forces.
- If working to the AISC steel design codes or Eurocode steel design codes these will take account of staged construction analysis design forces. If working to British Standards, Indian, or Australian steel design codes, only 3D building analysis results are considered.
- The Staged Construction load combination can be analyzed using either 1st or 2nd order linear, 1st or 2nd order nonlinear analysis.
- The static part of a Seismic RSA design combination can also come from a staged construction analysis.
Structures in other materials that can be designed via Tekla Tedds (e.g. timber, precast) also consider staged construction analysis results.
Implementation in Tekla Structural Designer
In Tekla Structural Designer staged construction has been implemented in a way that is both simple and intuitive:
- Set up, review and edit the construction stages
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A series of construction stages are defined by the engineer to idealize the evolution of the structure.
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- Define a Staged Construction load combination.
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A single staged construction load combination is defined, typically consisting of self weight plus an additional construction loading allowance.
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- In Design Settings choose to include staged construction analysis.
- The available choices allow you to control which types of analysis results get considered in design - either of 3D building analysis or staged construction analysis with either or both FE chasedown and grillage chasedown.
- Run Design in the normal way.
- Analysis results can be reviewed on a stage by stage basis.
- The design is the same, but with new forces.