PSI - Issue 6

Author name / Structural Integrity Procedia 00 (2017) 000 – 000

4

Vimal Kumar et al. / Procedia Structural Integrity 6 (2017) 11–18

14

Table 2. Peak impact-force for PC and RC slab under multiple impacts. Reinforced concrete slab ID Peak impact force (kN) Prestressed concrete slab ID Impact force (kN)

Increase in impact force due to prestressing (%)

a

b

c

d

e

f=(e-c)/c, (%)

Fresh slab

RC0 RC1 RC2 RC3

259.100 238.000 156.522 118.271

PC0 PC1 PC2 PC3

287.781 252.113 244.644 180.255

11.07

1 st repetition 2 nd repetition 3 rd repetition

5.93

56.30 52.41

4.2. Displacement response under multiple impacts The displacement response was measured at two locations center and quarter span of the slabs using laser displacement sensors. The magnitude of peak displacement at the center span of slabs under the multiple impact experimentations has presented in Fig. 2 and Table 3. Similarly, the magnitude of peak displacements at the quarter span of slabs under the multiple impact have presented in Table 4 and Fig. 3. The displacement sensors were removed after first repetition in the impact to avoid any damage to expensive sensors. The magnitude of peak displacement was increased under successive impacts. The increase in the displacement at center and quarter span of the slab was due to reduced stiffness of the concrete slabs owing to some permanent damage. Moreover, for a given repeat of the drop hammer, the peak displacement in the prestressed concrete slab was found to be smaller than that observed for reinforced concrete slab. Therefore, prestressed concrete slab was found to have improved stiffness under multiple impacts due to induced initial stresses.

Table 3. Peak displacements for PC and RC slab at the center of span. Reinforced concrete slab ID Displacement (mm) Prestressed concrete slab ID

Reduction in disp. due to prestressing (%)

Displacement (mm)

a

b

C

d

e

f=(c-e)/c, (%)

Fresh slab

RC0 RC1

9.760

PC0 PC1

8.397 9.133

13.97 16.45

1 st repetition

10.931