How does RF‑STABILITY or RSBUCK determine the buckling load? According to the manual calculation, the respective buckling loads should be about 10% higher.

Answer

The partial safety factor γM for reducing the modulus of elasticity is very likely activated in RFEM/RSTAB, but is not considered in the manual calculation.

γM can be displayed and adjusted, if necessary, within the "Edit Material" dialog box, see Image 01.

Image 01 - Partial Factor γM

Furthermore, the "Activate stiffness modifications from RFEM/RSTAB" option must be considered in General Data in the RF‑STABILITY or RSBUCK add-on module, see Iage 02.

Image 02 - Activate Stiffness Modifications in RFEM

For the effective length of 35.405 m, the second moment of area of 8,356 cm 4, the modulus of elasticity of 21,000 kN/cm², and the partial safety factor of 1.1 as a divisor, the following buckling load results (see also Image 03) according to the following formula:

Critical Load Including Partial Safety Factor

(πLcr,y)2 * E * Iy *1γM = Ncr (π3,540.5 cm)2 * 21,000 kN/cm² * 8,356 cm4 * 11.1 = 125.6 kN

Image 03 - Effective Lengths and Critical Loads

Keywords

Buckling load Critical load Manual calculation

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  • Updated 7 January 2021

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RFEM Other
RF-STABILITY 5.xx

Add-on Module

Stability analysis according to the eigenvalue method

Price of First License
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RSTAB Other
RSBUCK 8.xx

Add-on Module

Stability analysis according to the eigenvalue method

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670.00 USD