Design Settings > Analysis and General

Tekla Structural Designer
Tekla Structural Designer

Design Settings > Analysis and General

> Analysis

Setting Description


Allows you to select if a first or second order 3D building analysis is performed.


For steel structures in particular you should consider running a first-order analysis for the initial gravity design before switching to a second-order analysis for the final design.

In addition, Solve lateral loadcases in isolation if non-linear analysis is required during design allows you to try to solver lateral loadcases in isolation if non-linear analysis is required. However, in non-linear analysis, lateral loadcases often fail to solve or take a long time to converge when considered in isolation, especially for compression only foundation mats. Therefore, we recommend that you leave the option cleared.

If you need to see the results for the individual lateral loadcases, you can either run the analysis directly on the Analyze tab, or select the option if you know that the analysis does not fail.

Stability coefficient tolerance

United States head code (ACI/AISC) head code only

Stack height / ratio allows you to adjust the value of deflection that can safely be ignored. Selecting the option prevents any small deflections from causing erroneously high stability coefficients in stability coefficient calculations.


If the second order drift is less than the tolerance specified in Stack height /, the stability coefficient value is returned as N/A with a note that states that the drift is small enough to be ignored.

Reduced stiffness factor

United States head code (ACI/AISC) head code only

This factor is only exposed once the analysis is set to second-order.

It is applied to the stiffness (EI and EA) of all steel members in addition to any settings made on Analysis Options, Modification Factors.

For correct design to the AISC Specification using the DAM, it should be set to 0.8.


As an alternative to setting the analysis to first-order to explore the reason for any second order analysis failure, it is possible to alter this factor. If you set it to a value of say 10, this will stiffen both the Modulus of elasticity (E) and the shear modulus of elasticity (G) by a factor of 10 in the second order analysis. Although the results will not be able to be used for a valid design, it should now be possible to run the analysis to see which member might fail a design and hence be the cause of the analysis instability. This factor can then be reduced towards 0.8 for further investigation.

> General

Setting Description

Fix column nodes horizontally

Allows you to automatically apply lateral translational fixed supports to column nodes for the 3D building analysis performed during the gravity design processes.

The option is useful at the early design stage when lateral systems have not been established. The automatic lateral supports can remove unwanted lateral displacements that may prevent the analysis from completing and produce unrealistic forces.

The option does not apply to:
  • The column nodes that are in a rigid floor diaphragm
  • An analysis run as a separate process
  • The Analyze All (Static) command
  • The 3D building analysis performed during any Design (Static) command
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