Buckling Analysis - Missing Modes

jessica_ritchieT5UBT — Thu, 29 Jun 2023 13:40:58 GMT

Hello,

I am reviewing the design of a series of tri chord trusses which have no horizontal members tieing the top chords together and are joined by Y lacers at approx 3m centres (profile snip included below). I am running buckling analysis to determine whether we have an issue with buckling and also will feed in to to determining the effective length to consider for the chords in compression. Initially when running between 10 - 20 modes the software would give me the critical coefficient for 10 - 20 modes. However now when I run the buckling analysis for 20 modes I am only getting output for 1 or 2 modes. The biggest change I have made since being able to run larger number of modes is adjusting the combination used for the check (which results in lower design forces).

I am also getting missing eigenvalues when running the buckling analysis whilst also considering buckling mode as initial deformation but struggling to find any guidance on what this means (running with sturm check ticked).

Any words of wisdom or suggestions gratefully received!!

Thanks

Jess

topic Buckling Analysis - Missing Modes in Robot Structural Analysis Forum

Buckling Analysis - Missing Modes