GMNA, or Geometrically and Materially Nonlinear Analysis, represents a significant advancement in analyzing hollow section member connections in structural engineering. This method provides a more accurate representation of real-world behavior compared to traditional materially nonlinear analysis (MNA).
Prior to version 10.0 of IDEA StatiCa Connection, the MNA method, employing an elastoplastic working diagram, was the standard. While sufficient for many connections, MNA falls short when analyzing hollow sections, particularly those with slender walls, under point loading. These scenarios can lead to significant local deformations impacting overall stability, a factor not fully captured by geometrically linear analysis. This can result in an inaccurate assessment of the joint’s load resistance.
GMNA addresses this limitation by incorporating geometrically nonlinear effects, providing a more precise understanding of connection behavior under complex loading conditions. This advanced analysis has been rigorously validated against established finite element software like ANSYS and ABAQUS. The image below illustrates the differences in deformation patterns captured by GMNA. The more pronounced buckling behavior clearly demonstrates the importance of considering geometric nonlinearity.
Implementing GMNA in IDEA StatiCa
Within IDEA StatiCa Connection, GMNA is automatically enabled for new projects involving hollow section members. However, older projects retain their original settings. Users can manually activate GMNA within the code setup dialog. Importantly, GMNA only applies to hollow sections; if the member is not hollow, the solver defaults to traditional analysis regardless of the GMNA setting.
This difference in analysis methods between versions can lead to variations in results. Generally, GMNA produces less conservative results for tension members and more conservative results for compression members. Consequently, connections designed in earlier versions, especially those optimized to meet code limits, might require reevaluation in version 10.1 using GMNA. Collaboration with IDEA StatiCa support or local resellers is recommended to understand and address any discrepancies.
Conclusion: Enhanced Accuracy with GMNA
GMNA offers a crucial refinement in structural connection analysis, especially for hollow sections. By accounting for both material and geometric nonlinearities, GMNA delivers a more realistic prediction of connection behavior under complex loading, leading to safer and more reliable designs. This enhanced accuracy ensures that engineers can confidently assess the true capacity of connections, particularly in critical applications where the behavior of hollow sections under point loading is paramount.
