GMNA, or Geometrically and Materially Nonlinear Analysis, represents a significant advancement in analyzing steel connections, especially those involving hollow section members. This method provides a more realistic prediction of structural behavior compared to traditional materially nonlinear analysis (MNA). Prior to version 10.0 of IDEA StatiCa, connection analysis relied solely on MNA, which often proved insufficient for complex scenarios involving slender hollow sections.
Why GMNA Matters: Addressing Local Deformations
In connections involving hollow sections with thin walls, concentrated loads can induce significant local deformations. These deformations, particularly in the cross-sections, can impact the overall stability of the member. Traditional MNA, with its geometrically linear approach, often fails to accurately capture these effects. This can lead to either an underestimation or overestimation of the connection’s load resistance. GMNA addresses this limitation by incorporating geometric nonlinearity into the analysis, ensuring a more accurate assessment of connection behavior under critical loading conditions.
GMNA in IDEA StatiCa: Implementation and Considerations
IDEA StatiCa version 10.0 and later incorporate GMNA by default for new projects involving hollow section members. However, projects created in earlier versions retain their original MNA settings. Users can manually activate GMNA within the code setup dialog. Importantly, GMNA only applies to hollow sections; if the bearing member is not a hollow section, the software defaults to MNA regardless of the user settings.
This difference in analysis methods between versions can lead to variations in results. Generally, GMNA tends to yield less conservative results for members under tension and more conservative results for members under compression. Consequently, connections designed in older versions, particularly those pushing design limits, might not satisfy code requirements when re-analyzed with GMNA in version 10.1 or later. It is strongly recommended to re-evaluate such connections using the updated software and consult with IDEA StatiCa support or a local reseller for guidance.
Conclusion: Improved Accuracy with GMNA
GMNA provides a more accurate and reliable method for analyzing connections involving hollow section members. By considering both geometric and material nonlinearities, GMNA delivers results closer to the actual behavior of the structure, leading to safer and more efficient designs. While transitioning to GMNA might necessitate re-evaluating existing designs, the improved accuracy and enhanced understanding of connection behavior ultimately contribute to more robust and reliable structural engineering practices.
