Issue 74

V. J. Kalyani et alii, Frattura ed Integrità Strutturale, 74 (2025) 89-114; DOI: 10.3221/IGF-ESIS.74.07

values below 5%, indicating high consistency and reliability of the bond test results. Although slightly higher CoV values are observed for the ultimate load and bond strength in the SGS configuration and for rupture strain in SS configuration, however they also remain within acceptable experimental limit. These findings, combined with narrow confidence intervals observed in graphical data representations, affirm the consistency and repeatability of the results.

Ultimate Load

Bond Strength

Stiffness

Rupture Strain

Specimen Configuration

Epoxy

SD 1.65 0.57 1.99 0.90 1.83 0.88 4.14 0.65 1.10 0.96 0.86 0.56 0.94 1.58 1.70 0.19

CoV (%)

SD 3.45 1.28 4.49 2.25 3.13 1.57 8.56 1.20 2.59 2.30 2.06 1.44 1.70 3.05 3.66 0.39

CoV (%)

SD

CoV (%)

SD 0.58 0.16 0.11 0.03 0.47 0.20 0.33 0.07 0.18 0.15 0.16 0.09 0.37 0.55 0.22 0.17

CoV (%)

GG GS SG

3.80 1.00 4.30 4.51 2.70 1.51 7.93 2.33 3.36 3.33 3.25 3.28 2.19 3.92 4.98 0.84

3.80 1.00 4.30 4.51 2.70 1.51 7.93 2.33 3.36 3.33 3.25 3.28 2.19 3.92 4.98 0.84

106.36 152.44 137.76 304.12 219.89 205.91 382.46 195.72 228.19 147.54 294.14 821.48 179.62 193.18 482.20 303.63

4.58 1.88 1.23 0.82 2.72 1.63 3.04 1.53 1.75 2.29 2.82 2.58 2.85 5.81 2.74 3.66

3.15 1.57 1.51 3.68 5.56 3.47 4.51 2.18 6.90 1.90 3.88

Sikadur 30LP

SS

GGG GSG SGS

SSS GG GS SG

Sikadur 330

SS

10.26 4.83 3.30 6.43 3.71

GGG GSG SGS

SSS

SD = standard deviation, CoV - coefficient of variance

Table 7: Statistical indicators for mechanical parameters obtained from bond tests.

70

10 12 14 16 18 20

90

10 12 14 16 18 20 22 24

Standard Deviation Confidence Interval

Standard Deviation Confidence Interval

Load Stiffness

Load Stiffness

SD

SD

80

60

70

50

60

40

50

40

30

0 2 4 6 8

30 Load (kN)

Load (kN)

0 2 4 6 8

20

Stiffness (kN/mm)

Stiffness (kN/mm)

20

10

10

0

0

GG GS SG SS GGG GSG SGS SSS 1.64 0.57 0.16 0.56 1.99 0.11 0.89 0.03 1.82 0.46 0.87 0.20 4.14 0.32 0.65 0.07 Specimen Configuration

GG GS SG SS GGG GSG SGS SSS 1.10 0.18 0.15 0.96 0.86 0.16 0.56 0.09 0.94 0.37 1.58 0.55 1.70 0.22 0.19 0.17 Specimen Configuration

(a) use of Sikadur 30 LP adhesive (b) use of Sikadur 330 adhesive Figure 15: Comparison of ultimate load and stiffness for dumbbell specimens with different strengthening configuration Comparison of ultimate load capacity and stiffness for dumbbell specimen strengthened using different configurations using Sikadur 30 LP and Sikadur 330 is presented in bar chart form in Fig. 15. A comparative evaluation of the two-layer and three-layer specimens reveals the superior performance of hybrid wrap configurations. Among the two-layer wraps, the GS and SG configurations, demonstrated higher load carrying capacity as compared to the GG and SS specimen. For specimens prepared using Sikadur 30 LP, GS recorded an average ultimate load of 56.82 kN, which is 30.86% higher than 43.42 kN of GG and nearly 2.85 times higher than 19.90 kN of SS. Similarly, ultimate load capacity of SG is 46.36 kN, surpassing GG by 6.77% and 2.33 times higher as compared to SS. This indicates that the hybrid wraps are effectively enhances bond behaviour. The hybrid benefit is still evident, when adhesive Sikadur 330 is used. Specimen GS and SG recorded 28.78 kN and 26.38 kN, respectively, while GG and SS showed 32.68 kN and 17.08 kN. Although GS and SG are slightly lower than

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