PSI - Issue 37

Jamal A. Abdalla et al. / Procedia Structural Integrity 37 (2022) 660–667 Abdalla et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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Similarly, specimens experiencing small eccentricity ratio (e x /b x = 0.25), the nonlinear and linear models were able to predict the axial loading capacity with an average MAPE of 5% and 14%, respectively. The nonlinear models were close to perfect fit with the experimental results, except for the (8S2W) strengthening mechanism which could be due to the strip contribution to the axial capacity of the specimen. On the other hand, linear models were in reasonable agreement with the experimental results and close to perfect fit on the same case of (8S2W).

Table 5. Comparison between normalized axial capacity of experimental and empirical predictions

Experimental Capacity Ratio (P u /P o )

Empirical (L) MAPE (%)

Empirical (L) Capacity Ratio (P u /P o )

Empirical (NL) MAPE (%)

Number of Strips and Wraps

Empirical (NL) Capacity Ratio (P u /P o )

Eccentricit y Ratio

P Exp (kN)

111 7 152 0 166 7 546 902 891 808 272 474 423 531 182 290 316 348

1.00 1.36 1.49 0.49 0.81 0.80 0.72 0.24 0.42 0.38 0.48 0.16 0.26 0.28 0.31

0.94 1.37 1.42 0.50 0.78 0.80 0.82 0.27 0.44 0.45 0.49 0.15 0.25 0.25 0.29

0.89 1.27 1.35 0.61 0.90 0.94 0.71 0.34 0.53 0.54 0.50 0.06 0.16 0.13 0.30

6.0 0.6 5.1 3.4 3.4 0.3

11.3

0S0W 4S2W 4S4W 0S0W 4S2W 4S4W 8S2W 0S0W 4S2W 4S4W 8S2W 0S0W 4S2W 4S4W 8S2W

7.0 9.9

e x / b x = 0

25.1 11.1 17.9 38.0 24.6 41.4 63.0 38.3 53.8 2.0 5.9

e x / b x = 0.25

12.9 11.4

4.8

e x / b x = 0.50

18.2

2.9

10.6

2.5

e x / b x =0.75

11.1

5.8 6.6

4.6

Average MAPE

23.6

Conversely, for medium and large eccentricity ratio (e x /b x = 0.5 and e x /b x = 0.75), the nonlinear models were able to predict the axial capacity of strengthened columns (4S2W and 8S2W) with an average MAPE of less than 4%, but slightly deviated for non-strengthened specimen and 4S4W specimen with an average MAPE of 12%. This behavior could be attributed to the presence of higher eccentricity which offsets the effect of the CFRP confinement (Abowkiek et al. 2021). On the other hand, the linear models were offset the experimental results with an average MAPE of 27% and 39% for medium and large eccentricity ratio (e x /b x = 0.5 and e x /b x = 0.75), respectively. This is predicted as the relation between the eccentricity ratio and axial capacity is exponentially decreasing with the increase in eccentricity ratio rather than a linear reduction. It is clear from the comparison and analyses provided by the prediction models and the experimental results, the models are able to fairly predict the capacities of eccentrically loaded columns in uniaxial direction. These models may be used in lieu of exhaustive experimental analysis to predict the capacity of non-strengthened and strengthened columns using NSM-CFRP composites with an overall average MAPE of 6.6% and 23.6% for nonlinear and linear models, respectively. Both former and latter models may be used to predict and check the axial capacity of an eccentrically loaded columns.