Abstract
This paper presents a study on flexural behavior of unbonded post-tensioned concrete T-beams (UPC) externally strengthened by CFRP sheets under static loading with or without the presence of U-strip CFRP anchorage systems. A total of nine UPC T-beams in large size including one control unstrengthened beam and eight beams externally strengthened with varied number of CFRP sheets (2, 4, and 6 plies) were tested. Two types of transverse CFRP U-strip anchorage system were also retrofitted in the shear span. The results showed that CFRP sheets significantly increased the flexural capacity (up to 37%), decreased deflection in serviceability state, improved ductility, and reduced crack width (up to 48%) of the tested beams. The maximum strain in CFRP sheets in strengthened UPC T-beams ranged from 38.7 to 69.3% of the rupture strain of the CFRP sheets and tended to decrease with a large number of CFRP sheets. Strain in tendons of strengthened beams was significantly affected by the CFRP sheets and transverse U-strip anchorage system.
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Abbreviations
- AN1:
-
U-strip anchorage system with one 300-mm-wide strip and three 100-mm-wide strips installed within the distance of L/4Â =Â 1350Â mm from each end of CFRP sheet
- AN2:
-
U-strip anchorage system with six 100-mm-wide strips evenly spaced within the distance of L/4Â =Â 1350Â mm from each end of CFRP sheet
- an :
-
number of CFRP U-strip 100-mm-wide anchorage
- a cr,exp :
-
crack width of tested beam, mm
- a cr,u,CFRP :
-
maximum crack width of FRP-strengthened beam, mm
- a cr,u,0 :
-
maximum crack width of the control beam, mm
- t f :
-
thickness of one ply of the CFRP sheet, mm
- a cr,CFRP :
-
crack width of FRP-strengthened beam, mm
- a f :
-
width of the CFRP reinforcing plies, mm
- n :
-
number of plies of CFRP sheet
- s f :
-
spacing of CFRP U-strip, mm
- w f :
-
width of CFRP U-strip anchors, mm
- P cr,exp :
-
cracking load of test beam, kN
- P exp :
-
test load, kN
- P u,0,exp :
-
ultimate load of the control beam, kN
- P u,exp :
-
ultimate load of test beam, kN
- δ u,exp :
-
maximum displacement at midspan of test beam, mm
- δ exp,mid :
-
displacement at midspan of test beam, mm
- ε ten,u,mid :
-
maximum tensile strain in unbonded tendon at midspan, ‰
- δ u,0 :
-
maximum displacement at midspan of the control beam, mm
- ε cu :
-
maximum concrete strain, ‰
- ε CFRP :
-
tensile strain in CFRP sheets, ‰
- ε su :
-
maximum tensile strain in non-prestressed reinforcement at the ultimate load, ‰
- ε fu,end :
-
maximum tensile strain in CFRP sheets at the ends of the bond length, ‰
- ε fu,L/3 :
-
maximum tensile strain in CFRP sheets of test beam at the loading locations, ‰
- ε fu,mid :
-
maximum tensile strain in CFRP sheets of test beam at midspan, ‰
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Acknowledgements
This research was funded by Dong Thap province’s Department of Science and Technology and Department of Transport.
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Truong, Q.P.T., Phan-Vu, P., Tran-Thanh, D., Dang, T.D., Nguyen-Minh, L. (2018). Flexural Behavior of Unbonded Post-Tensioned Concrete T-Beams Externally Bonded With CFRP Sheets Under Static Loading. In: Nguyen-Xuan, H., Phung-Van, P., Rabczuk, T. (eds) Proceedings of the International Conference on Advances in Computational Mechanics 2017. ACOME 2017. Lecture Notes in Mechanical Engineering. Springer, Singapore. https://doi.org/10.1007/978-981-10-7149-2_19
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DOI: https://doi.org/10.1007/978-981-10-7149-2_19
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