The calculation of the critical load factor according to second-order analysis in RSTAB results in a value that differs significantly from the one of the RSBUCK calculation.
Check if the settings for considering the favorable effect by tension forces are the same in RSTAB and RSBUCK.
RSTAB determines the critical load factor according to a nonlinear calculation method: The loading is increased gradually by the value of the load factor increase until the system becomes unstable. RSBUCK, however, carries out a linear eigenvalue analysis. Therefore, elements acting nonlinearly like failing members or supports may have different effects in RSTAB and RSBUCK.