We have noticed that, under certain configurations, the “Effective Length Calculator” tool in STAAD.Pro may yield results that are not conservative, which poses a risk to the structural safety of the project. Allowing users to validate and manually adjust these parameters would help ensure that the design is both safe and truly representative of the constructed reality.
After our review, we identified two specific cases in which the current functionality does not correctly detect the unbraced length of elements, affecting the proper assignment of the Ly and Lz parameters:
Columns:
In the attached image, a structural frame is shown where certain beams are highlighted. These highlighted beams are not effective in providing lateral bracing to the columns, as they are not connected to a rigid system that truly restrains lateral displacement. Therefore, the LY parameter should only be measured between levels with effective lateral bracing, ignoring intermediate beams that do not fulfill this function. Currently, the “Effective Length Calculator” may incorrectly consider all beams as lateral support points, underestimating the buckling length and potentially resulting in an unsafe design.
Beams:
In the second image, a beam system is shown where only one of the panels between columns has lateral bracing, thanks to the direct connection of the secondary beam to a horizontal bracing element. Only the portion of the beam that is laterally braced should be assigned a reduced buckling length (Lz equal to the distance between bracing points), while the unbraced spans should be assigned the length between columns. However, the software may incorrectly assign the same bracing length to all segments, without distinguishing between the actually braced and unbraced panels.
Improvement proposal:
We kindly request that you consider implementing the following improvements in the “Effective Length Calculator”:
The tool should consider only levels with effective bracing for columns and correctly distinguish between braced and unbraced segments for beams.
The dialog window should allow users to manually adjust the effective lengths (Ly and Lz) for each element and to select whether elements should be considered as partially braced, to address specific situations that the automatic detection may not identify.
These enhancements would allow for more precise control of structural safety and better alignment with the actual construction conditions of the project.
We look forward to any further information you may require regarding this proposal.
