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Title |
Development Lengthof GFRP Rebars Based on Pullout Test
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Keywords |
GFRP 보강근 ; 인발실험 ; 정착길이 ; 수정 인발실험 ; 상부근 효과 |
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Abstract |
The development length equations of the GFRP rebars are suggested based on the pullout tests performed in this study. A total of 48 pullout and modified pullout tests were completed. Test variables included embedment length (L=10, 15, 20, and 30db), vertical and horizontal installation of the rebars, height of the rebars (H=100 and 300 mm), and cover thickness (C=2~5db). D13 GFRP rebars domestically developed were used in the experimental program. The average of the bond strength of all vertically installed GFRP rebars was 6.39 MPa with a 5% fractile of 4.63 MPa. A basic development length equation was derived that resulted in an equation equivalent to the one proposed in the ACI 440.1R-03. Careful reevaluation of the bond strength using the modified pullout test indicated that a modification of the design equation was necessary so that the basic development length increases by 11%. The top bar effect of the horizontally installed rebars as well as the effect of the cover thickness were determined and included in the set of suggested equations. Since the current equations were derived from testing rebars embedded in relatively low strength concrete (fck=20~24 MPa), they result in conservative development lengths when applied to bars embedded in higher strength concretes.
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