Timber limitations and assumptions

The following limitations and assumptions apply to the design of timber beams, columns and braces in Tekla Structural Designer:

A compatible version of Tekla Tedds must be installed and licensed.
The locale must be set correctly in Tekla Tedds before attempting to run the design from Tekla Structural Designer.
Design is supported for NDS LRFD, NDS ASD, base Eurocode, and the following Eurocode National Annexes: UK; Ireland; Norway; Finland; Sweden.
- If the Singapore or Malaysia Eurocode National Annex is selected, the calculation will adopt base Eurocode recommended values.
For models with seismic loading using the RSA method, RSA analysis results are not considered when determining the design forces populated to the Tedds timber design calculation.
- This limitation can be worked around as follows: the engineer should review the RSA Analysis results for the Seismic Combinations for timber members being designed using Tedds, and note the critical values for design from these where they are greater than those of the static analysis/ combinations. The noted values can then be manually entered into the Tedds timber design calculation when design using Tedds is run.
If working to the NDS code, size classifications taken from the NDS supplement 'Design Values for Wood Construction' are used in the Tedds calculation to distinguish which grades are valid for particular timber species. The same classification rules are not implemented in Tekla Structural Designer itself. Therefore, after a member has been designed in Tedds, if the member size or grade is subsequently changed in Tekla Structural Designer the associated Tedds calculation is deleted, so that the member cannot be checked and a redesign is required.
Column design: If designing a multi-stack column you must indicate a splice in the stack properties before running the design if a change in cross section is required between stacks. If a splice has not been specified the change in section size will not be correctly returned to the Tekla Structural Designer model.
When working to the NDS code, the following assumptions have been made:
- The moisture content of structural composite lumber or glulam sections is less than 16% and the temperature remains below 100°F - analysis modification factors may need to be applied if this is not the case.
- Glulam sections will be loaded perpendicular to the wide faces of the laminations (bending about the x-x axis).
- Glulam grades comply with the characteristic properties outlined in AWC NDS supplement 2018.
- The engineer has verified that the E_analysis value of the member is suitable for the particular application.
- The section and strength class are compatible.
When working to Eurocodes, the following assumptions have been made:
- Loading will be perpendicular to the wide faces of the laminations (bending about the major axis).
- Moisture content of the sections will be less than 15% - analysis modification factors may need to be applied if this is not the case.
- Glulam grades comply with the characteristic properties outlined in BS EN 14080:2013.
- The engineer has verified that the E_analysis value of the member is suitable for the particular application.
- The section and strength class are compatible.