Timber member design workflow
The essentials of design of timber members using Tekla Tedds can be thought of as being very similar to Interactive concrete member design within the program:
Just like the concrete beam/ column/ wall interactive design dialog, the Tedds Timber member design calculation interface lists the design forces and settings for a selected member/ group, populated from the model and analysis, the design pass/fail status and individual check results and utilization ratios. You can make changes in the interface - such as to section size and/ or grade - and immediately see the design results for these. All the data you input and changes you make are updated to and stored in the model. You can then re-analyze and run a check on all designed members to ensure the design results are up to date. You can perform design and analysis loops as necessary so that all members are passing, and to cater for any other changes to the model or loading.
Design Groups work in a similar manner also - these are automatically created for Timber members and listed in the Project Workspace Groups Tree. The resulting groups can be reviewed and customized as necessary. Group design is enabled by default ( in Design Settings > Design Groups > Timber Beams/ Columns/ Braces) and can be run both via the model and from the Groups Tree.
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, ASD or 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 head code that has been selected.
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.
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.
- Multi-stack columns - splices should be specified in the stack properties when the column is being defined 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.
Create load combinations and set load duration/time effect factors
Loads are applied in the standard manner. Once load combinations have been created you should review their load duration/ time effect factors.
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.
You have control to adjust the default value on a combination by combination basis.
Configure timber design settings
Certain timber design settings which apply to the entire building can be specified on the Timber page of the Design Settings dialog.
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.
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.
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
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).
Establish design forces by running the analysis
Timber members can only be designed provided a set of analysis results exist. These can be generated from the Analyze ribbon by running Analyze All (Static).
A design force envelope is established, which if designing to the US head code considers the selected design method (ASD or LRFD) only.
Provided load combinations have been created, once analysis has been performed the Design using Tekla Tedds options become available.
Design using Tekla Tedds
Once the analysis has been performed, a Design or Check using Tekla Tedds can be initiated from the Project Workspace or any graphical view of the model. To do this right-click over any individual member in the Project Workspace, or make a graphical selection, then right-click to open the context menu listing the Tekla Tedds design options.
You can then select Design of the Member, Group or Selection as appropriate. Design of a Selection can also be used for example to design all members of a truss - which can be selected with one click - in one operation.
Check the design after changes
If changes are made to the model you can run a 'check' design to determine if the existing sections are still sufficient. 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.
The updated utilizations can then be reviewed in a Review View.
Output the calculations
The Tekla Tedds design results are returned to the Tekla Structural Designer model.