PSI - Issue 78

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

637

S 2

S 1

(a)

(b) Fig. 7. Column removal scenarios: (a) Scenario S 1 ; (b) Scenario S 2 .

0.9

0.8

0.8

0.7

0.7

0.6

0.6

0.5

0.5

0.4

0.4

0.3 Load Factor

0.3

Load Factor

PUSHDOWN Beam connection Yielding Brace connection Failure

PUSHDOWN Beam connection yielding Brace connection failure Beam connection failure

0.2

0.2

0.1

0.1

0

0

0

5

10

15

20

25

30

0

5

10

15

20

25

30

(a)

(b) Fig. 8. Pushdown curves: (a) Column Removal Scenario S 1 ; (b) Column Removal Scenario S 2 . Displacement (mm) Displacement (mm)

(a)

(b) Fig. 9. Dynamic response: (a) Column Removal Scenario S 1 ; (b) Column Removal Scenario S 2 .

4. Conclusions This study analyzed the progressive collapse behavior of rack structures under column removal scenarios simulating seismic or forklift impact events. It focused on collapse mechanisms, particularly the role of connections in internal force redistribution and catenary action development. After central column failure, connections experienced combined axial and bending forces, and adjacent columns saw increased axial loads, affecting both column and base plate performance. Member behavior under these conditions was assessed through experiments, FEM, and EN 15512 based properties considering local buckling. Beam-to-column connections behaved ductilely under bending, but axial tension led to brittle failure. Base-plate connections showed direction-dependent behavior, with greater ductility in out-of-plane loading and reduced rotational capacity when bolts were engaged. Cold-formed steel columns also exhibited asymmetric bending resistance due to their geometry. Two collapse scenarios were studied. In Scenario S 1 , the structure showed ductile behavior with catenary action and effective energy dissipation. Scenario S 2 , with added bracing, experienced early brittle failure and limited deformation. These results underscore the need for well-balanced bracing and connection design to enhance ductility and prevent progressive collapse in steel rack systems.