PSI - Issue 70

Nithin A V et al. / Procedia Structural Integrity 70 (2025) 215–222

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After a few load increments, fine hairline cracks emerged at mid-span, aligned with the longer span direction. With continued loading, these cracks propagated further and additional finer cracks formed. Eventually, the crack paths diverged from their initial trajectories and extended diagonally toward the corners, forming a failure mechanism, as illustrated in Fig.4 (a). Simultaneously, numerous micro-cracks developed and interconnected across the slab surface. Final failure was attributed to the widening of these cracks along yield lines. Among the tested specimens, slabs made with the F30H30G40-0CS mix exhibited the highest rate of crack widening. The energy absorption capacity, represented by the area under the load – deflection curve, is presented in Table 3. A marginal increase of approximately 9.2% was observed in the slab constructed with the optimum mix, indicating improved post-cracking performance. Ductility Index, defined as the ratio of ultimate to yield deflection, also showed a slight improvement across the tested slabs. The reinforcement bars in the F30H30G40-40CS based TBGC slab yielded at a slightly higher load of 28.6 kN compared to the other specimens, subsequently entering the plastic deformation stage. The enhanced flexural capacity facilitates greater load redistribution and strain accumulation, enabling the reinforcement bars to reach higher yield values. The reinforcement bars in the TBGCS specimen with mix F30H30G40 yielded at a higher load of 28.6 kN, outperforming the other slabs and subsequently entering the plastic deformation phase. In comparison, the control specimen (F60G40) exhibited a lower yield load capacity of 24.3 kN (Fig 4. (b)).

Table 3. Flexural Properties of TBGC Slabs Slab Type

First Crack Load (kN)

Yield Load (kN)

Ultimate load (kN)

Yield Deflection (mm)

Mid-span deflection (mm)

Ductility Index

Energy Absorption Capacity (kN-mm)

F60G40

12.9 11.5 16.4

24.3 17.0 28.6

54.4 48.6 78.7

11

42.1 44.8 28.4

3.8 3.1 4.3

1623 1540 1771

F30H30G40-0CS F30H30G40-40CS

14.3

6.7

Fig.3. Load-deflection curves of TBGCS