Krzysztof
Lasek, Renata Kotynia and Michał Staśkiewicz
Lodz University of Technology, Poland
Strengthening for flexure with initially prestressed Carbon Fiber Reinforced Polymers has been a subject of numerous research programs. Results of conducted tests lead to conclusion that the efficiency of such strengthening is relatively low due to premature Carbon Fiber Reinforced Polymers strip debonding from the surface of concrete member, usually induced by intermediate cracks. Research also showed that the strengthening ratio depends on numerous other factors, such as type of the Carbon Fiber Reinforced Polymers composite, reinforcement ratio of the reinforced concrete structure as well as load and bending moment distribution on the tested member Strengthening with non-prestressed Carbon Fiber Reinforced Polymers strips increased the load capacity of reinforced concrete members, but had no positive effect on serviceability state of the structure in terms of deflections and cracking moment. To improve the overall efficiency of the strengthening and the utilization of the Carbon Fiber Reinforced Polymers tensile strength, an introduction of tensile force in the Carbon Fiber Reinforced Polymers strip prior to its application was proposed. Such technique of strengthening allows not only to increase the load capacity and stiffness, but also reduce the deflections and width of the cracks in strengthened member, as well as to reduce stress in the longitudinal rebars and concrete strains.
The biggest challenge related to strengthening reinforced concrete structures with prestressed Carbon Fiber Reinforced Polymers is proper anchorage of the composite strip’s ends. A significant shear stresses occur in the area where the tensile force from the strip is transferred to the concrete surface. In this work, a series of reinforced concrete beam strengthened for flexure with prestressed Carbon Fiber Reinforced Polymers laminates has been tested in the laboratory of Lodz University of Technology. The members varied in the initial exhaustion level- beams were strengthened under the load corresponding to 14%, 25% or 76% of the load capacity of non-strengthened beam. Results of the test program have proven high efficiency of flexural strengthening with prestressed Carbon Fiber Reinforced Polymers both for ultimate and serviceability limit state, also for highly exhausted structures. During the tests members reached load capacity from ca. 1.5 to 2.2 times higher than the load capacity of reference member.
References
KOTYNIA, R., KAMIŃSKA, M.E.: Ductility and failure mode of reinforced concrete beams strengthened for flexure with CFRP. Report No. 13, Department of Concrete Structures Technical University of Lodz, Poland 2003
Lodz University of Technology, Poland
Strengthening for flexure with initially prestressed Carbon Fiber Reinforced Polymers has been a subject of numerous research programs. Results of conducted tests lead to conclusion that the efficiency of such strengthening is relatively low due to premature Carbon Fiber Reinforced Polymers strip debonding from the surface of concrete member, usually induced by intermediate cracks. Research also showed that the strengthening ratio depends on numerous other factors, such as type of the Carbon Fiber Reinforced Polymers composite, reinforcement ratio of the reinforced concrete structure as well as load and bending moment distribution on the tested member Strengthening with non-prestressed Carbon Fiber Reinforced Polymers strips increased the load capacity of reinforced concrete members, but had no positive effect on serviceability state of the structure in terms of deflections and cracking moment. To improve the overall efficiency of the strengthening and the utilization of the Carbon Fiber Reinforced Polymers tensile strength, an introduction of tensile force in the Carbon Fiber Reinforced Polymers strip prior to its application was proposed. Such technique of strengthening allows not only to increase the load capacity and stiffness, but also reduce the deflections and width of the cracks in strengthened member, as well as to reduce stress in the longitudinal rebars and concrete strains.
The biggest challenge related to strengthening reinforced concrete structures with prestressed Carbon Fiber Reinforced Polymers is proper anchorage of the composite strip’s ends. A significant shear stresses occur in the area where the tensile force from the strip is transferred to the concrete surface. In this work, a series of reinforced concrete beam strengthened for flexure with prestressed Carbon Fiber Reinforced Polymers laminates has been tested in the laboratory of Lodz University of Technology. The members varied in the initial exhaustion level- beams were strengthened under the load corresponding to 14%, 25% or 76% of the load capacity of non-strengthened beam. Results of the test program have proven high efficiency of flexural strengthening with prestressed Carbon Fiber Reinforced Polymers both for ultimate and serviceability limit state, also for highly exhausted structures. During the tests members reached load capacity from ca. 1.5 to 2.2 times higher than the load capacity of reference member.
References
KOTYNIA, R., KAMIŃSKA, M.E.: Ductility and failure mode of reinforced concrete beams strengthened for flexure with CFRP. Report No. 13, Department of Concrete Structures Technical University of Lodz, Poland 2003
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KOTYNIA,
R., WALENDZIAK, R., STOECKLIN, I., MEIER, U.: Reinforced
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under Monotonic and Cycling Loading., Journal of Composites for
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