Timber member design workflow

Tekla Structural Designer
2022
Tekla Structural Designer

Timber member design workflow

Key aspects of the Tedds integrated timber design process and workflow in Tekla Structural Designer are:

Set the timber design code

The timber design code is set from the Home ribbon by clicking Model Settings > Design Codes > Resistance Codes.

  • If working to US codes, there are two different methods, NDS ASD or NDS LRFD to choose from and also a choice of code year to apply. The design forces consider only the selected design method.

  • If working to Eurocodes, the timber design code will be applied with a national annex that is appropriate to the regional code that has been selected.

The selected design code is automatically applied in all Tedds timber member designs.

Configure timber design settings

Certain timber design settings which apply to the entire building can be specified from the Design ribbon by clicking Settings > Timber.

  • If working to US codes:
  • If working to Eurocodes:

By ensuring the defaults are set correctly you can avoid having to manually set the values in each Tedds timber calculation as it is run.

You still have control within individual calculations to adjust these settings on a member by member or group basis.

Note: Tedds data is retained from one run of the design to the next unless changes are made in Tekla Structural Designer that force the Tedds calculation data to be re-established.

If you change timber design settings after a member has already been designed you would need to manually clear the Tedds data from the design in order to have it use the revised design settings. To do this highlight the member, right-click and select Clear Tekla Tedds Data from the context menu.

Define and place timber members

To place timber members, select the appropriate member type from the Timber group on the Model ribbon, ensure the values in the Properties window are as required and then pick the points to locate the members in position.

Note the following with regard to the properties:
  • Section shapes - When defining a timber model in Tekla Structural Designer it may appear that the range of timber sections is somewhat limited. This is because Tekla Structural Designer doesn't currently have a facility to specify timber sections by simply inputting a breadth and depth. Instead you have to select the required size from Tekla Structural Designer's database of timber sections.

    While this might seem to be a significant limitation, it is actually not too great an issue, because the Tedds timber calculation allows you to override the original size to input the breadth and depth you require. Then when the member data is transferred back from Tedds to Tekla Structural Designer the new size is automatically added to the timber section database.

    Once the new section is in the section database it becomes available for future Tekla Structural Designer models also.

  • Timber fabrication and grade - You can specify timber, glulam, or structural composite lumber fabrication types.

    Initially the grade must be selected from the existing grades in the Tekla Structural Designer materials database, although if the grade is changed in the Tedds timber calculation, when the member data is transferred back from Tedds to Tekla Structural Designer the new grade is automatically added to the materials database.

    Note: If a situation arises such that the material properties in the programs don’t align, Tedds ignores unmatched data and selects calculation defaults.
  • Deflection limits - for beams you can specify limits for individual load type deflections and also for the total load deflection. For more information, see: Timber beam deflection checks - US or Timber beam deflection checks - EC as appropriate.
  • Column splices - for columns, splices should be specified in the stack properties if a change in cross section is required between stacks. If a splice has not been specified before the column is designed in Tedds the change in section size will not be correctly returned to the Tekla Structural Designer model. For further information, see: Timber column stacks and lifts.

Create load combinations and review load duration/time effect factors

Loads are applied and load combinations defined in the standard manner.

Once your load combinations have been created you should review the default factors associated with load duration that have been applied. (Load duration factor - NDS ASD and EC, Time effect factor - NDS LRFD).

These factors are set on the Timber design tab on the Combinations page of the Loading dialog once you have selected an individual combination from the list in the dialog. The value is set automatically according to the constituent loadcases.

  • ASD combination:
  • LRFD combination:
  • Eurocode combination:

You have control to adjust the default value on a combination by combination basis if required.

Load combinations are automatically grouped into timber combination sets to enable appropriate design cases to be created when the design is performed. For further details see: Timber combination sets and strength design cases.

Generate timber design envelopes

Design envelopes can be generated for each of the timber combination sets so that the design forces can be easily reviewed.

You can create these from the Envelopes page of the Loading dialog by clicking Generate... > Timber Design Envelopes.

Configure timber groups

When timber members are placed in the model, to make editing easier they are automatically grouped according to a set of rules.

These initial groups can be reviewed from the Groups tab of the Project Workspace - you can add new groups and move members between groups as required.

Groups are not only useful for editing, they can (optionally) be activated for design purposes also. There are a number of reasons why you would choose to do this.

Set the Tedds results output level

You can choose the output level for the Tedds timber calculations in advance from the Home ribbon by clicking Settings > Report > Tedds Reports.

By ensuring this is set correctly beforehand you can avoid having to manually set the level in each Tedds timber calculation as it is run.

The setting applies to all Tedds linked calculations (precast and timber).

Run analysis

Timber members can only be designed provided a set of analysis results exist. These can be generated by running Analyze All (Static) from the Analyze ribbon.

Once the analysis has been performed the Design using Tekla Tedds options become available.

Design using Tekla Tedds

Once the analysis has been performed, a design using Tekla Tedds can be initiated from the Project Workspace or any graphical view of the model.

You can choose to design a member, group, selection, or all timber members in the model.

Note: Design of a selection provides a useful means to design all members of a truss - which can be selected with one click - in one operation.
When the design is initiated a Tedds calculation interface appropriate to the timber design code being worked to is displayed (the NDS ASD version being shown below).
The main areas within the interface are:

Drop list for selecting the design case.

Design forces for selected design case.

Duration of loading (for NDS ASD and EC), or time effect factor (NDS LRFD) for the selected design case.

Timber section details for the span under consideration.

Design pass/fail status and individual check results and utilization ratios for the selected design case.

Overall design status and utilization ratio.

You can make changes in the interface - such as to section size and/ or grade - and the design results are immediately refreshed.

When you click Finish, all the data you input and changes you make are updated to and stored in the model.

Check the design after changes

If changes are made to the model you can re-analyze and then run a 'check' design to determine if the existing sections are still sufficient. You can conrtinue to perform as many design and analysis loops as necessary so that all members are passing. A check is quicker to perform than a design because the Tedds calculation runs in the background without having to display the Tedds calculation dialog.

You can check the whole model from the Design ribbon, or you can make a graphical selection, then right-click to open the context menu listing the available check options. You can also run checks from the Project Workspace.

The updated utilizations can then be reviewed graphically in a Review View, or as a table in a Design Summary Tabular Data View as described in the next section.

Output the calculations

The Tekla Tedds design results are returned to the Tekla Structural Designer model.

At this stage you can graphically display member design status and utilization ratios from a Review View:
From the Review ribbon, by clicking Tabular Data and making appropriate selections you can also display the design status table in a Design Summary Tabular Data View:
Detailed Tekla Tedds calculations for timber members do not exist within Tekla Structural Designer itself, instead they are available by exporting to Tekla Tedds.
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