Steel and composite beam - autodesign optimization
Note: The autodesign optimization features
described here are only available for the United States Regional code.
In some circumstances (auto) Design of an individual beam following analysis could select a more optimized section than a full Steel Design process with the autodesign property enabled. This can occur for both composite and non-composite beams potentially, generally to do with the influence of the self weight of presize sections. Additional autodesign settings for the United States can be used to improve section optimization in such cases - the settings are located in Design Settings > Autodesign as shown in the picture below.
Beam design section step back
This relates to the design of steel beams in general and adds further
control of the autodesign iterative process. The steel beam autodesign process
sequentially loops through the steel section order list (from top to bottom) to
identify a passing section together with analysis results to update the beam self
weight each time there is a section change. For subsequent analysis and design
iterations, looping through the section list starts by default from the most
efficient passing section identified in the previous iteration which, depending on
the change in self weight, might not always be the most optimum.
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The option allows you to specify where the iterative looping starts in the section list in relation to the optimum section from the prior iteration - either at the same section (a value of 0) or up to 5 sections before it in the list. Hence it is termed the section ‘step back’ value. Occasionally using this with a value 1-5 can improve design efficiency, however with a potential to impact design times particularly for larger models.
Prefer fewer connectors over section weight
This relates specifically to steel composite beam design and the influence
of studs (connectors) and section size on optimization - for a similar moment
capacity you can potentially have a solution of more studs with a lighter section,
or less studs with a heavier section. A designer may consider either of these
solutions the ‘optimum’ in terms of overall economy - hence this setting which
allows the designer to specify their preferred criteria:
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When enabled (default) - autodesign seeks the smallest possible number of studs in lieu of a potentially heavier section.
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When disabled - autodesign seeks the lightest possible section potentially requiring more studs.