The same general approach for creating the model can be adopted irrespective of whether you intend to run a staged construction analysis or not. The model can be created, loads can be applied and design load combinations generated in the normal fashion.

A staged construction load combination will also need to be created at some point but this can be done after the construction stages have been specified.

The reason for splitting the model into construction stages is to allow for the fact that not all forces will be applied at the same time, and also to cater for materials with time dependent effects.

In Tekla Structural Designer construction stage definition takes place in the Review View regime.

To see the default stages that are created automatically, select the Show/Alter State command on the Review ribbon and then the Staged Construction attribute in the Properties window.

With the mode set to New Structure by Stage, the default construction stages are shown and their durations indicated in a legend.

For tall structures click the buttons underneath the legend to see more stages.

Floor levels (specifically, levels marked as floors) denote potential construction stages. Default stages are automatically created so that members in a floor level or attached to that level from below form an individual stage.

Initially each stage defaults to a stage duration of 4 weeks.

Default stages can be modified as required by clicking the Edit button next to Stage Data.

This displays the Edit Stage Data dialog box which allows the number of stages and the stage durations to be edited.

Each row in the table corresponds to a level that has been marked as a floor in the Construction Levels dialog box.

The number of construction stages can be controlled by adjusting the active/inactive setting in the Active Stage column.

Initially each floor defaults to either Auto (Active), or Auto (Inactive):

• Auto (Active) - the floor level is an active stage if it contains a slab, (a level with beams and no slabs is not automatically active).

• Auto (Inactive) - the floor level is an inactive stage if it doesn't contain a slab.

• The one exception to the above is the top floor level which is always automatically active.

• The auto defaults can be overridden by manually setting a level to be an active or an inactive stage.

Stage durations can be edited in the above table, or via the Properties window.

The Stage time (which can’t be edited) is the sum of durations of current and previous stages; it only affects concrete creep allowance during the construction stages.

If you have made edits to stages and/or durations but then change your mind, you can revert back to the original defaults by clicking the Reset All button in the Properties window.

Once the active construction stages have been set, members can be reassigned between stages if necessary. Add to Stage and Remove from Stage editing modes are provided in the Properties window for this purpose.

While the standard design combinations should have already been defined, you will not be able to run a staged construction analysis until a dedicated staged construction combination has been created.

This combination has to be added manually in the Loading dialog box, taking care to set its class to Staged Construction.

You would typically want to define this combination so that self weight plus an additional construction loading allowance are applied to the most recent construction stages, while at the same time a different construction allowance and some proportion of dead load is applied to older stages.

The resulting construction stage combination would then effectively describe the loading for every construction stage in a building of any size.

To make this possible, two load combination groups are provided; one for the recent stages and one for older stages. Both groups have their own set of load factors. There is provision for you to say how many stages are included in the recent stages group and also to specify a different construction loading allowance for each group.

By adopting a staged construction approach the load dependent nature of creep and cracking in concrete is catered for by the application of modification factors that are appropriate to the persistent or transient nature of loading. Furthermore, separate factors take account of the difference between service and ultimate load levels.

They can be reviewed by selecting Settings on the Analyze ribbon and then navigating to the appropriate Modification Factors > Staged Construction page in the Analysis Settings dialog.

Default values have been specifically calibrated for the construction stages, and for each of the design stages.

For further information, see: Staged construction modification factors

Before you run a batch design you must specify which analysis type(s) are to be run. This is configured via the Analysis page in Design Settings.

When staged construction analysis is included, by default both chasedowns are also included and 3D building analysis is excluded.

In effect this means that the staged construction analysis results are replacing the 3D building analysis results at one end of the design envelope. Refer to design comparison - with and without staged construction to find out more about the implications of this.

Once the analysis type(s) have been set as required, you can then proceed to run the combined analysis and design. This is initiated by selecting the required design choice (e.g. Design All (Static)) from the Design ribbon.

The choices you made on the Analysis page in Design Settings determine the analysis types that will be performed and also whether a first-order or second-order analysis is used for staged construction analysis and/or 3D building analysis.

If there are any non-linear elements in the model the staged construction analysis and/or 3D building analysis will run as non-linear, otherwise it will be linear.

The Staged Construction combination is analyzed for each construction stage sequentially to determine the evolution of forces during the construction stages. The forces at the final construction stage then become a starting point for the analysis of design stages.

The gravity and lateral combinations are each assigned to a design stage (according to loadcase types they contain), they are then analyzed and designed accordingly.

Once the model has been designed you are taken to the Review View from where the design can be examined.

If you switch to the Results View regime and select the staged construction method from the Result Type group in the Results ribbon, you can then investigate the analysis results for the staged construction loading combination and each of the design combinations. When the staged construction loading combination is selected in the Loading toolbar, a Stage list is added to Result Type group to allow you to select each of the construction stages.

If you switch to the Solver Model View regime and select the staged construction method in the Solver ribbon a Stage list is added to the Solver ribbon. This allows you to select and review the solver model applicable for each construction stage and design stage.

Reports and drawings are created in the normal way from the Report ribbon and Draw ribbon respectively.