PSI - Issue 60

Sarmili Swain et al. / Procedia Structural Integrity 60 (2024) 553–563 Sarmili Swain / Structural Integrity Procedia 00 (2024) 000 – 000

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Case 2 Instantaneous loss of Edge column at ground floor In this case, progressive collapse potential is analysed by the loss of peripheral middle (edge) column at the ground floor. The results are presented in Table 5 and Fig. 7 for all three scenarios (ambient temperature, 30 minutes, and 60 minutes). It can be observed from the results that, at the ground floor periphery the local structural components (Beams: B3 to B8) as depicted in Fig.7 (a), have survived the load changes as well as the fire exposure up to 60 minutes of duration. However, other structural components (Beams: B9 to B12) have got severely deteriorated particularly due to its exposure to fire and appears to have reached collapse state. In addition, the adjacent structural components connecting the lost column member (Beams: B1& B2) have exceeded the collapse capacity mainly attributed to its fire exposure and can be termed as failed in resisting the load changes. Moreover, the DCR values of the adjacent columns to the lost column as depicted in Fig.7 (b), have reached its threshold collapse state (DCR > 2) at ambient temperature itself. Therefore, the initiation of global failure or loss of structural integrity of the building occurs even before its exposure to fire and can be perceived to have been accelerated due to the deterioration undergone under fire exposure. Table 5. Moment Carrying Capacities of typical floor beams under various Fire Load durations for Case 2: 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

23.6 23.6 8.12 8.66 8.47 8.46 8.54 8.14 21.4

46.326 46.324 25.454 31.012 31.246 31.331 30.973 39.592 39.107 37.027 39.126 25.48

52.8

52.766 28.607 28.605 23.196 28.645 28.581 23.228 39.976 37.034 35.103 36.973

B10 B11 B12

13.66 10.37 13.67

b

Case-2: Instantaneous removal of Edge Column

a

3

2.5

2

1.5

1

0.5

0

Demand capacity ratio (DCR)

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

Typical Floor Beam

Ambient Temp.

30 min 60 min

Fig. 7. (a) DCR value of typical floor beams for Case 2 (b) DCR values of adjacent components for ambient temp. of Case 2

Case 3 Instantaneous loss of Center/Middle Interior column at ground floor Here, the centre/middle interior column of the building is removed to realise the progressive collapse potential of the structure. The results are presented in Table 6 and Fig.8 for different durations of fire load (i.e., ambient temperature, 30, and 60 minutes). It can be observed that the local structural components appear to remain intact in its position, indicating its survival for the exposed fire duration. However, the DCR values indicates severe