PSI - Issue 6

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

97

3

Drop mass, M (kg)

Drop height, H (mm)

Type of specimen

Specimen ID

Strength of concrete (N/mm 2 )

a

b

c

d

e

RC1

72

242.85

500

Reinforced concrete slab Prestressed concrete slab

RC2

72

242.85

1000

PC

72

242.85

1000

4. Results and discussions

4.1. Impact force response The impact load was recorded in a data-logger using a load-cell mounted on the drop weight. A rapid increase was observed in the impact force just after the establishment of contact between impactor and target slab. The magnitude of peak impact load obtained under impact experiments has been presented in column c of Table 2. The magnitude of peak impact force has found to increase up to 38% with increase in the drop height of the hammer, see Fig. 1(a) and (b). The prestressing has increased the impact resistance and stiffness of the slabs therefore an increase was also observed in the peak load. However, the influence of the prestressing was relatively lesser (4.5%), see Fig. 1(b) and (c), compared with that of the influence observed with increase in the drop height. In addition, the time duration of the impact force has found to reduce by employing prestressing in the concrete, see Fig. 1(b) and (c).

450

450

450

375

375

375

300

300

300

225

225

225

150

150

150

Force (kN)

Force (kN)

Force (kN)

75

75

75

0

0

0

0

5

10

15

20

0

5

10

15

20

0

5

10

15

20

Time (ms) (a) Slab RC1

Time (ms)

(c) Slab PC Time (ms)

(b) Slab RC2

Fig. 1. Impact-force response for prestressed and reinforced concrete slabs

Table 2. Peak impact response under drop impact loading

Impact Force (kN)

Acceleration (g)

Reaction (kN)

Displacement (mm)

Specimen ID

Types of specimen

At center

At quarter

a

b

c

d

e

f

g

RC1 RC2

287.7 396.2

60.2 87.3

-

479 849

366 486

Reinforced concrete slab Prestressed concrete slab

17.0

PC

414.2

107.2

12.3

1006

458

4.2. Reaction-time history The support reaction was recorded in the same data-logger using the load-cells placed at the corner of the slabs. The magnitude of peak support reaction obtained under impact experiments has been presented in Fig. 2. The reaction time response has reported a time-lag with load-time response as it did not start simultaneously with impact force at the instant of establishment of contact between impacting bodies. The magnitude of peak reaction has found to increase with increase in the drop height as well as incorporating initial stress in the concrete. The magnitude of reaction force