PSI - Issue 6

Vimal Kumar et al. / Procedia Structural Integrity 6 (2017) 95–100 Author name / Structural Integrity Procedia 00 (2017) 000 – 000

98

4

observed in slabs RC1, RC2 and PC was 60.2, 87.3 and 107.2 kN, respectively, see column d of Table 2. Prestressed concrete has reported highest reaction due to increase in the stiffness of the slabs by induced initial stress.

120

120

120

90

90

90

60

60

60

30

30

30

Reaction (kN)

Reaction (kN)

Reaction (kN)

0

0

0

0

5

10

15

20

0

5

10

15

20

0

5

10

15

20

Time (ms)

Time (ms)

(c) Slab PC Time (ms)

(b) Slab RC2

(a) Slab RC1

Fig. 2. Reaction-time response for prestressed and reinforced concrete slabs

4.3. Displacement-time history The displacement was measured using laser technique at the center span of the slabs. The displacement-time history obtained for the slabs has presented in Fig. 3. The displacement for slab RC1 could not be recorded properly because initiation of crack at the location where the displacement was measured. The influence of prestressing was apparently noticeable in the displacement of the slabs due to increase in the stiffness of the slab, see Fig. 3(a) and 3(b). The prestressed concrete slab PC has undergone approximately 28% lesser displacement in comparison with slab RC2, see Table 2.

20

20

15

15

10

10

5

5

0 Displacement (mm)

0 Displacement (mm)

0

10 20 30 40 50

0

10 20 30 40 50

(b) Slab PC Time (ms)

Time (ms)

(a) Slab RC2

Fig. 3. Displacement-time history for prestressed and reinforced concrete slabs

4.4. Acceleration-time history The accelerations were measured using accelerometers mounted on the rear surface of the slab at the center and quarter span. The response has shown a high magnitude vibration after the impact, see Fig. 4. However, the acceleration found to be more dominant for the initial 5 ms of the impact duration. The magnitude of the acceleration at the center has found to increase with increase in the drop height of the impactor and induced prestress in the concrete. A similar phenomenon was also recorded at the quarter span due to increase in the drop height. An increase of 77 and 33% was noticed in the first peak acceleration due to increase in the drop height. However, due to induced prestressing the increase was only observed at the center of the slab PC compared with slab RC2. This could be due to the fact that only the localized concrete at the impact point offered more resistance against the applied impact load. The increase in the peak acceleration at the center of slab PC was about 18% of that slab RC2.