Analysis types in Tekla Structural Designer
The following analysis types can be run in Tekla Structural Designer:
1st order linear
1st order linear static analysis is suitable for structures where secondary effects are negligible. Any nonlinear springs or nonlinear elements present are constrained to act linearly.
Loadcases and Combinations to be considered in the analysis can be pre-selected.
The processes performed when this analysis type is run can be summarized as follows:
Process | Description |
---|---|
Model validation | Model validation checks are performed to detect specific issues before the analysis process begins. |
3D pre-analysis processes | In preparation for analysis a number of
pre-analysis processes are undertaken as necessary, such as:
The actual pre-analysis processes performed will vary depending on the specific model that has been defined. |
3D analysis |
A traditional frame first-order linear analysis of the entire 3D model. Nonlinearity Included:
|
Related concept: Features of 3D analysis and chasedown analysis
Related task: Run 1st order linear analysis
1st order non-linear
This is a nonlinear analysis with loading applied in a single step.
It is suitable for structures where secondary effects are negligible and nonlinear springs/elements are present.
Loadcases and Combinations to be considered in the analysis can be pre-selected.
The processes performed when this analysis type is run can be summarized as follows:
Process | Description |
---|---|
Model validation | Model validation checks are performed to detect specific issues before the analysis process begins. |
3D analysis: First-order linear | A 1st order linear analysis (see above), is automatically performed prior to the non-linear analysis. |
3D analysis: First-order non-linear |
A traditional frame first-order non-linear analysis of the entire 3D model, with an option to mesh floors. Nonlinearity Included:
|
Related concept: Features of 3D analysis and chasedown analysis
Related task: Run a 1st order non-linear analysis
1st order modal
This is an unstressed modal analysis which can be used to determine the structure's natural frequencies.
The structure is assumed to be in an unstressed state and nonlinear elements are constrained to act linearly.
The processes performed when this analysis type is run can be summarized as follows:
Process | Description |
---|---|
Model validation | Model validation checks are performed to detect specific issues before the analysis process begins. |
3D pre-analysis processes | In preparation for analysis a number of
pre-analysis processes are undertaken as necessary, such as:
The actual pre-analysis processes performed will vary depending on the specific model that has been defined. |
3D analysis First-order Modal |
A first-order modal analysis of the entire 3D model, with an option to mesh floors. Nonlinearity Included:
|
Related concept: Modal analysis
Related task: Run a 1st order modal analysis
2nd order linear
This is a 2-stage P-Delta analysis which is suitable for structures where secondary effects are of comparable magnitude to primary effects. Any nonlinear springs or nonlinear elements present are constrained to act linearly.
Loadcases and Combinations to be considered in the analysis can be pre-selected.
The processes performed when this analysis type is run can be summarized as follows:
Process | Description |
---|---|
Model validation | Model validation checks are performed to detect specific issues before the analysis process begins. |
3D analysis: First-order linear | A 1st order linear analysis (see above), is automatically performed prior to the 2nd order linear analysis. |
3D analysis: Second-order linear |
A traditional frame 2nd order linear analysis of the entire 3D model, with an option to mesh floors. Nonlinearity Included:
|
Related concept: Features of 3D analysis and chasedown analysis
Related task: Run a 2nd order linear analysis
2nd order non-linear
This is a nonlinear analysis with loading applied in a single step.
It is suitable for structures where secondary effects are of comparable magnitude to primary effects and nonlinear springs/elements are present.
Loadcases and Combinations to be considered in the analysis can be pre-selected.
The processes performed when this analysis type is run can be summarized as follows:
Process | Description |
---|---|
Model validation | Model validation checks are performed to detect specific issues before the analysis process begins. |
3D analysis: First-order linear | A 1st order linear analysis (see above), is automatically performed prior to the 2nd order non-linear analysis. |
3D analysis: Second-order non-linear |
A traditional frame 2nd order non-linear analysis of the entire 3D model, with an option to mesh floors. Nonlinearity Included:
|
Related concept: Features of 3D analysis and chasedown analysis
Related task: Run a 2nd order non-linear analysis
2nd order buckling
This is a linear buckling analysis which can be used to determine a structure's susceptibility to buckling.
The stressed state of the structure is determined from linear analysis; therefore nonlinear elements are constrained to act linearly.
Loadcases and Combinations to be considered in the analysis can be pre-selected.
The processes performed when this analysis type is run can be summarized as follows:
Process | Description |
---|---|
Model validation | Model validation checks are performed to detect specific issues before the analysis process begins. |
3D pre-analysis processes | In preparation for analysis a number of
pre-analysis processes are undertaken as necessary, such as:
The actual pre-analysis processes performed will vary depending on the specific model that has been defined. |
3D analysis Second-order buckling |
A second-order buckling analysis of the entire 3D model. Nonlinearity Included:
|
Related task: Run a 2nd order buckling analysis
FE chasedown
This analysis type cannot be run in isolation, it is only performed when it is required as part of one of the following batch analysis/design processes:
- Analyze All (Static)
- Design Concrete (Gravity)
- Design Concrete (Static)
- Design All (Gravity)
- Design All (Static)
It is only required in the above processes if the model contains meshed slabs.
Process | Description |
---|---|
FE chasedown |
Separate analyses are performed for a series of 3D sub models each containing the members between two horizontal planes with fully meshed floors. See: Solver Model used for FE Chasedown. The complete series of models is chased down from top to bottom so loads are carried from the level above to the level below. The results are always used for slab design and optionally used for concrete beam, column and wall design. Note: You can
use Design Settings to turn off
'Design for FE Chasedown analysis results' for concrete
beams, columns or walls if required. This option is located
under Concrete
> Cast-in-place, then Beam/Column/Wall >
General Parameters (as appropriate).
|
A significant consideration when opting to design for the FE chasedown results is that the slabs will tend to carry a significant proportion of the load direct to the columns.
Consequently, for beam design in particular, it is unlikely that an FE chasedown could result in a more critical set of design forces than would be already catered for by a Grillage chasedown.
Accounting for lateral loading in chasedown results
It is important to note that the chasedown analysis procedure is only valid for gravity loads. The chasedown analysis results for any lateral loadcase (wind / EHF) or from the direct analysis of any combination that includes a lateral loadcase are not valid.
Therefore in order to generate a set of forces suitable for design, the chasedown analysis results are merged with the 3D building analysis combination results as follows:
- Start with the building analysis combination result
- Identify all gravity cases used in the combination and the relevant load factor
- For each included gravity
loadcase:
- Subtract the 1st order linear building analysis result multiplied by the relevant load factor
- Add the chasedown result multiplied by the relevant load factor
- For results with live/imposed load reduction, subtract the relevant % of the chasedown result for each reducible loadcase.
Following this procedure means that chasedown analysis of lateral loadcases or combinations is not required.
Related concept: Features of 3D analysis and chasedown analysis
Grillage chasedown
We know from experience that a 3D Analysis on its own does not give the gravity results engineers have traditionally used or want - staged construction analysis reduces but doesn't resolve this. Therefore, in Tekla Structural Designer a grillage chasedown is used to emulate a traditional analysis and establish an alternative second set of design forces for concrete beams, columns and walls.
Grillage chasedown analysis cannot be run in isolation, it is only performed when it is required as part of the following processes:
- Analyze All (Static)
- Design Concrete (Gravity)
- Design Concrete (Static)
- Design All (Gravity)
- Design All (Static)
In each of the above processes grillage chasedown is only performed if the model contains concrete beams, columns, or walls.
Process | Description |
---|---|
Grillage chasedown |
Separate analyses are performed for a series of 3D sub models each containing the members between two horizontal planes, floors only being meshed at those levels where they have also been meshed in 3D Analysis. The complete series of models is chased down from top to bottom so loads are carried from the level above to the level below. See: Solver Model used for Grillage Chasedown |
Accounting for lateral loading in chasedown results
It is important to note that the chasedown analysis procedure is only valid for gravity loads. The chasedown analysis results for any lateral loadcase (wind / EHF) or from the direct analysis of any combination that includes a lateral loadcase are not valid.
Therefore in order to generate a set of forces suitable for design, the chasedown analysis results are merged with the 3D building analysis combination results as follows:
- Start with the building analysis combination result
- Identify all gravity cases used in the combination and the relevant load factor
- For each included gravity loadcase:
- Subtract the 1st order linear building analysis result multiplied by the relevant load factor
- Add the chasedown result multiplied by the relevant load factor
- For results with live/imposed load reduction, subtract the relevant % of the chasedown result for each reducible loadcase.
Following this procedure means that chasedown analysis of lateral loadcases or combinations is not required.
Related concept: Features of 3D analysis and chasedown analysis
Analyze All (Static)
This is batch process that includes the full series of analyses required to enable a static design to be performed.
- 3D analysis
- 1st order linear/non-linear
- 2nd order linear/non-linear (only if this has been specified by the user in Design > Design Settings > Analysis)
- FE chasedown (if required)
- Grillage chasedown (if required)
The processes performed when this analysis type is run can be summarized as follows:
Process | Description |
---|---|
Model validation | Model validation checks are performed to detect specific issues before the analysis process begins. |
3D pre-analysis processes | In preparation for analysis a number of
pre-analysis processes are undertaken as necessary, such as:
The actual pre-analysis processes performed will vary depending on the specific model that has been defined. |
3D analysis |
A traditional frame analysis of the entire 3D model, with an option to mesh floors. This analysis generates a first set of results that can be used for the design of beams, columns, walls and slabs. You can control whether a first, or a second order 3D Analysis is run by making the appropriate selection on the Analysis page in Design Settings. The actual options that are presented will vary depending on the design code being worked to. The choice of linear or non-linear analysis is made automatically:
|
FE chasedown | An FE chasedown analysis is only performed if required, (see above FE Chasedown topic) . |
Grillage chasedown | A Grillage chasedown analysis is only performed if required, (see above Grillage chasedown topic). |
Stability checks | Sway/Drift checks and Wind Drift checks are performed for all columns and walls, (apart from any that have been manually excluded from the check |
Related concept: Features of 3D analysis and chasedown analysis
Related concept: Why chasedown analyses are included in Analyze All (Static)
Related task: Run Analyze All (Static)
3D only (Static)
This is a batch process similar to Analyze All (Static) but which excludes chasedowns to save time during scheme design, (for example while addressing overall stability, sway, drift, wind drift, etc.)
The processes performed when this analysis type is run can be summarized as follows:
Process | Description |
---|---|
Model validation | Model validation checks are performed to detect specific issues before the analysis process begins. |
3D pre-analysis processes | In preparation for analysis a number of
pre-analysis processes are undertaken as necessary, such as:
The actual pre-analysis processes performed will vary depending on the specific model that has been defined. |
3D analysis |
A traditional frame analysis of the entire 3D model, with an option to mesh floors. This analysis generates a first set of results that can be used for the design of beams, columns, walls and slabs. You can control whether a first, or a second order 3D Analysis is run by making the appropriate selection on the Analysis page in Design Settings. The actual options that are presented will vary depending on the design code being worked to. The choice of linear or non-linear analysis is made automatically:
|
Stability checks | Sway/Drift checks and Wind Drift checks are performed for all columns and walls, (apart from any that have been manually excluded from the check |
Related task: Run 3D only (Static)
1st order RSA seismic
This is a Modal Response Spectrum Analysis used to determine the peak response of the structure to earthquakes. Any nonlinear springs or nonlinear elements present are constrained to act linearly. For RSA Seismic Combinations, the peak responses are enveloped around the static results for 1st Order Linear Analysis
Related task: Run a 1st order RSA seismic analysis
2nd order RSA seismic
This is a Modal Response Spectrum Analysis used to determine the peak response of the structure to earthquakes. Any nonlinear springs or nonlinear elements present are constrained to act linearly. For RSA Seismic Combinations, the peak responses are enveloped around the static results for 2nd Order Linear Analysis
Related task: Run a 2nd order RSA seismic analysis
Analyze All (RSA)
This is the same Modal Response Spectrum Analysis that would be carried out as part of Design All (RSA), but with no design. Any nonlinear springs or nonlinear elements present are constrained to act linearly.
Related task: Run Analyze All (RSA)
Rigorous slab deflection analysis
Tekla Structural Designer's rigorous slab deflection analysis provides a rigorous approach to slab deflection estimation. It comprises (i) Sequential Loading Analysis, (ii) iterative cracked section analysis and (iii) simple modelling of creep and shrinkage effects.
See: Slab deflections