Flexural Performance of Stone Beams Strengthened with Prefabricated Prestressed CFRP-Reinforced Stone Plates
Publication: Journal of Composites for Construction
Volume 27, Issue 5
Abstract
A strengthening technique incorporating prefabricated prestressed carbon fiber–reinforced polymer (CFRP) was proposed and evaluated. The flexural performance of bare stone beams strengthened with prefabricated prestressed CFRP-reinforced stone plates was investigated by testing 11 stone beams. The test variables considered involved the diameter and prestress level of the CFRP bars, the reinforcement ratio, and the surface condition of the stone plate. The stress transfer efficiency between different components during the prestressing and strengthening processes was monitored with the aid of strain gauges that were attached to the CFRP bars and stone beams. The monitoring results showed that the CFRP bars prestress could be effectively maintained by the temporary device and then transferred to the stone beam to be strengthened. Further four-point bending tests indicated that the strengthened stone beams exhibited a failure mode with obvious deflection and multiple flexural cracks. The strengthened beams presented three stages of load versus deformation responses and showed significantly higher load-carrying and deformation capacities than the bare stone beams. The flexural behavior of the strengthened stone beams for different parameters was analyzed. Finally, models were proposed to calculate the cracking and ultimate moments, and the initial stiffness of the strengthened stone beams.
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Acknowledgments
This research is supported by the National Natural Science Foundation of China (Grant No. 52178485) and the Science and Technology Project of Fujian Province, China (Grant No. 2020Y4011). The support is highly appreciated.
Notation
The following symbols are used in this paper:
- Af
- total cross-sectional area of CFRP bars;
- Af1
- cross-sectional area of CFRP bar;
- Bs
- sectional stiffness of strengthened stone beams;
- Bs,e
- experimentally measured initial stiffness;
- Bs,c
- calculated initial stiffness;
- b
- width of cross section;
- c1
- height of compressive zone at prestressing state;
- c2
- height of compressive zone at cracking state;
- c3
- height of compressive zone at ultimate state;
- df
- diameter of CFRP bar;
- Ef
- elastic modulus of CFRP bars;
- Es
- elastic modulus of stone;
- e
- elongation at breakage;
- F
- applied vertical load;
- Fc1
- compressive stress resultant of stone at prestressing state;
- Fc2
- compressive stress resultant of stone at cracking state;
- Fc3
- compressive stress resultant of stone at ultimate state;
- Fd
- design prestressing force;
- Ff
- breaking force;
- Ff1
- tensile stress resultant of CFRP bars at cracking state;
- Ff2
- tensile stress resultant of CFRP bars at ultimate state;
- Fre
- prestressing force after removing the hydraulic jack;
- Ft
- applied prestressing force;
- Ft1
- tensile stress resultant of stone at cracking state;
- Ft2
- tensile stress resultant of stone at ultimate state;
- Fps
- total effective prestressing force;
- ff
- ultimate tensile strength of CFRP bars;
- fst
- tensile strength of stone;
- h
- height of cross section;
- h0
- effective height;
- I0
- section inertia moment;
- K
- flexural stiffnesses;
- l
- length of beam specimen;
- l0
- span length of beam specimen;
- Mcr
- cracking moment;
- Mcr,c
- calculated cracking moment;
- Mcr,e
- experimentally measured cracking moment;
- Mp
- peak moment;
- Mp,e
- experimentally measured peak moment;
- Mp,c
- calculated peak moment;
- Mu
- ultimate moment;
- nf
- number of CFRP bars;
- S
- section modulus of stone beam;
- w
- average crack width;
- αcr
- percentage increase in cracking moment;
- αp
- percentage increase in peak moment;
- β
- prestress level;
- βa
- actual prestress level;
- γs
- coefficient that considers the plastic development of stone material;
- Δ
- midspan deflection;
- Δcr
- midspan deflection that corresponds to first crack;
- Δh
- midspan deflection that corresponds to the end point of crack propagation stage;
- Δp
- midspan deflection that corresponds to peak moment;
- Δu
- midspan deflection that corresponds to ultimate;
- ɛb1
- stone compressive strain in bottom layer of cross section at prestressing state;
- ɛb2
- stone tensile strain in bottom layer of cross section caused by externally loading at cracking state;
- ɛf
- tensile strain of CFRP bars;
- ɛfu
- ultimate tensile strain of CFRP bars;
- ɛf1
- CFRP strain caused by externally loading at cracking state;
- ɛf2
- ɛfu, for instance, ultimate tensile strain of CFRP bars;
- ɛre
- strain after removal of the hydraulic jack;
- ɛs
- strain of stone;
- ɛt
- applied strain;
- ɛt1
- stone tensile strain in top layer of cross section at prestressing state;
- ɛt2
- stone compressive strain in top layer of cross section caused by externally loading at cracking state;
- ɛt3
- stone compressive strain in top layer of cross section at cracking state;
- κ
- stiffness reduction coefficient;
- λcr
- ratio of calculated and measured cracking moments;
- λp
- ratio of calculated and measured peak moments;
- λs
- ratio of calculated and measured initial stiffness;
- μ
- ductility index, for instance, the value of Δu/Δh;
- ρf
- reinforcement ratio;
- σb1
- stone compressive stress in bottom layer of cross section at prestressing state;
- σb2
- stone tensile stress in bottom layer of cross section caused by externally loading at cracking state;
- σe
- effective prestress;
- σf
- stress of CFRP bars;
- σf1
- CFRP stress caused by externally loading at cracking state;
- σf2
- ff, for instance, ultimate tensile strength of CFRP bars;
- σre
- prestress after removal of the hydraulic jack;
- σs
- strain of stone;
- σt
- applied prestress;
- σt1
- stone tensile strain in bottom layer of cross section at prestressing state;
- σt2
- stone compressive stress in top layer of cross section caused by externally loading at cracking state; and
- σt3
- stone compressive stress in top layer of cross section at cracking state.
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Published In
Journal of Composites for Construction
Volume 27 • Issue 5 • October 2023
Copyright
© 2023 American Society of Civil Engineers.
History
Received: Sep 25, 2022
Accepted: May 12, 2023
Published online: Jul 5, 2023
Published in print: Oct 1, 2023
Discussion open until: Dec 5, 2023
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