PSI - Issue 60

Sarmili Swain et al. / Procedia Structural Integrity 60 (2024) 553–563

559

Sarmili Swain / Structural Integrity Procedia 00 (2024) 000 – 000 7 structural response is presented in terms of bending moments & shear forces. The demand estimation on the structural components are arrived using two approaches: linear static analysis (using SAP2000) which is used as bench mark and structural fire analysis (using SAFIR) for various fire exposure durations. This assessment aids at comprehensive understanding of structural load changes within the building which, in turn dictate the performance of building’s structural components quantified using respective DCR as per the guidelines. Case 1 Instantaneous loss of corner column at ground floor The linear static analysis is performed on the building structure after the removal of the corner column as depicted in Fig.6 , resulting in altered structural loads for the adjacent structural components. Therefore, the bending moments experienced by these structural components increases significantly (shown in Table 4). Further, when subjected to fire load scenarios it was found that the load bearing structural components appears to have severely deteriorated in resisting 30 minutes of fire exposure (Temperature rise is around 800 o C to 850 o C) and reached collapse for 60 minutes of fire exposure duration (Temperature rise is around 900 o C). Table 4. Moment Carrying Capacities of typical floor beams under various Fire Load durations for Case 1: Progressive collapse

Demand (KN-m)

Beam no.

Capacity (KN-m)

Ambient Temperature

30 minutes

60 minutes

B1 B2 B3 B4 B5 B6 B7 B8 B9

19.8 19.8 19.8 19.8 19.8 19.8 19.8 19.8 19.8 19.8 19.8 19.8

26.23

39.03 35.37

37.6 35.7

8.25 8.78 9.96 9.96 8.78 8.36

29.257 33.278 33.194 29.451 35.297 36.308 37.609 37.628 36.329 39.04

28.96

33.228

33.15 29.13

35.4 39.9

26.23 13.66 12.07 12.09 13.64

36.015 37.331 37.488 36.175

B10 B11 B12

a

b

Case-1: Instantaneous removal of Corner Column

2.5

2

1.5

1

0.5

0

B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11 B12

Typical Floor Beam

Demand capacity ratio(DCR)

Ambient Temp.

30 min

60 min

Fig. 6. (a) DCR value of typical floor beams for Case -1 (b) DCR values of adjacent components for ambient temp. of Case 1

It can be observed From Fig.6 (a), that the adjacent beams of the corner column (B1 and B8) have experienced higher demand capacity ratio (DCR) for all the (three) cases of fire scenarios, compared to all other beams in the floor. This can be attributed to the structural load changes initiated due to loss of load bearing structural column. However, the B8 structural component (beam) appears to have reached collapse state for 30 minutes of fire exposure whereas, most of the other beam components have managed to resist up to 60 minutes of fire exposure albeit the structural deterioration. This can be envisaged by the DCR values presented in Fig.6 (b), Moreover the adjacent columns appear to have been severely stressed with DCR values approaching a maximum of 1.754 during ambient temperature conditions and found to exceed the threshold limit leading to global failure under fire exposure of 30 minutes duration. These results clearly describe the buildings vulnerability in resisting the load changes due to its exposure to fire.