Issue 55

F. A. Elshazly et al, Frattura ed Integrità Strutturale, 55 (2021) 1-19; DOI: 10.3221/IGF-ESIS.55.01

one longitudinal GFRP layer increased the ultimate compressive strength by 18.2%. These results indicated that using transversal layers in strengthening was more effective in increasing ultimate bearing capacity than using a combination of transversal and longitudinal layers with the same number of layers, as shown in Fig. 10 (a). Similar trend was observed in columns with 15% rubber content, as shown in Fig. 10 (b). In comparison with the column strengthened with one transversal GFRP layer, using one transversal layer in addition to one longitudinal GFRP layer increased the ultimate compressive strength by 7.3% while using two transversal GFRP layers increased the ultimate compressive strength by 13.8%. Using two transversal layers in addition to one longitudinal GFRP layer increased the ultimate compressive strength by 17.8% while using three transversal GFRP layers increased the ultimate compressive strength by 20% that led to the result that existence of transversal layers in strengthening was more effective than using a combination of transversal and longitudinal layers with the same number of layers. However, adding one longitudinal layer to transversal layers increased the ductility index of the specimen, as shown in Fig. 11. Using more than two GFRP layers led to a decrease in ductility index.

Figure 8: Ductility index of the specimens with various steel tube thickness.

(a) (b) Figure 9: Ultimate bearing capacity of the specimens with various steel tube thickness; (a) RU5 CFST, (b) RU15 CFST. Strengthening specimens with longitudinal deficiency increased the ultimate bearing capacity, as shown in Fig. 10 (c). It was observed that the orientation of the layers was impressive in enhancing the deficient columns behaviour. Using two GFRP layers in transversal direction increased the ultimate compressive strength by 9.8%, while using one transversal layer and one longitudinal GFRP layer increased the ultimate compressive strength by only 1.7%, In comparison with the column strengthened with one transversal GFRP layer. Three transversal GFRP layers increased the ultimate compressive strength by 14.7%, while using two transversal layers in addition to one longitudinal GFRP layer increased the ultimate compressive strength by only 11.7%. These results indicate that with existence of vertical deficiency, transversal GFRP layers in strengthening was more effective than using a combination of transversal and longitudinal layers with the same number of layers. The equivalent columns with 15% rubber particles replacement showed better performance. In comparison with the column strengthened with one transversal GFRP layer, using two transversal GFRP layers increased the ultimate compressive strength by 12.9%. However, using one transversal layer in addition to one longitudinal GFRP layer increased the ultimate compressive strength by only 4.17%. Three transversal GFRP layers increased the ultimate compressive strength by 18.2%, whereas two transversal layers in addition to one longitudinal GFRP layer increased the ultimate compressive strength by 14.9%.

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