PSI - Issue 78

Tahir Ahmad et al. / Procedia Structural Integrity 78 (2026) 631–638

634

Moment

Moment

Specimen 1SXP Specimen 2SXP Specimen 3SXP

Axial Force

Moment

Rotation

Rotation

(a) (c) Fig. 2. (a) Experimental Moment-rotation curves; (b) Bilinear idealization (EN 15512, 2020); (c) Idealized interaction P - M diagram. (b)

(b) (c) Fig. 3. Column base-plate connection: (a) Stresses for bending in X-direction; (b) Stresses for bending in Y-direction; (c) M -  curves.

(a)

500

500

0 Axial Force ( P ) -2

0 -1 Axial Force ( P )

22

-500

-500

Bending Moment ( M y )

Bending Moment ( M x )

(a)

(b) (c) Fig. 4. Interaction P-M diagrams of column base-plate connection. (a) PMM; (b) PMx; (c) PMy.

To fully characterize the upright's PMM interaction surface, a combination of compressive axial loading and imposed displacements in both the local X- and Y-directions was applied in a controlled sequence. This enabled the extraction of multiple moment–rotation curves for various combinations of axial force and bending directions, providing the necessary data to construct the complete PMM interaction surface, as illustrated in Fig. 4. 2.3. Cold-formed steel columns The cold-formed steel columns are of Class 4 according to UNI EN 1993-1-1 (2005). Therefore, effective section properties due to local buckling were defined following the EN 15512 standard (2009). This standard provides guidelines for accounting for the localized reduction in load-carrying capacity and stiffness caused by holes or perforations in cold-formed steel members. The effective thickness t i of a perforated thin-walled steel section, particularly for the column upright where holes are located, is calculated using the following formula: