The test results of eight concrete beams reinforced with carbon fiber reinforced polymer （CFRP） sheets subjected to an aggressive environment under a sustained load are presented. The beams are 1 700 mm long with a ...The test results of eight concrete beams reinforced with carbon fiber reinforced polymer （CFRP） sheets subjected to an aggressive environment under a sustained load are presented. The beams are 1 700 mm long with a rectangular cross-section of 120- mm width and 200-mm depth. The beams are precracked with a four-point flexural load, bonded CFRP sheets, and placed into wet-dry saline water（ NaCl） either in an unstressed state or loaded to about 30% or 60% of the initial ultimate load. The individual and coupled effects of wet-dry saline water and sustained bending stresses on the long term behaviour of concrete beams reinforced with the CFRP are investigated. The test results show that the coupled action of wet-dry saline water and sustained bending stresses appears to significantly affect the load capacity and the failure mode of beam strengthened with CFRP, mainly due to the degradation of the bond between CFRP and concrete. However, the stiffness is not affected by the coupled action of wet-dry cycles and a sustained load.展开更多
This paper discusses the method of determining the tensile strength and modulus of elasticity of continuous carbon fiber sheet.Five simply supported beams strengthened by CFS were tested.Based on th experiment,a compu...This paper discusses the method of determining the tensile strength and modulus of elasticity of continuous carbon fiber sheet.Five simply supported beams strengthened by CFS were tested.Based on th experiment,a computer analysis program is developed and a simplified formula is proposed.The calculated results agree well with the experimental results.The design method suggested by this paper can meet the engineering requirements.展开更多
Eighteen reinforced concrete beams, including 16 beams strengthened with CFRP laminate at different levels of preload and 2 control beams, were tested to investigate the influence of preload level on flexural behavior...Eighteen reinforced concrete beams, including 16 beams strengthened with CFRP laminate at different levels of preload and 2 control beams, were tested to investigate the influence of preload level on flexural behavior of CFRP-strengthened RC beam. The experimental parameters include rebar ratios, number of plies of CFRP laminates and preload level at the time of strengthening. Theoretical analysis was also carried out to explain the experimental phenomena and results. The experimental and theoretical results indicated that the preload level has more influence on the stiffness and deflection of the strengthened beam, both at post-cracking and post-yielding stage, than that on the yielding and ultimate flexural strength of the strengthened beam. The main failure mode of CFRP-strengthened beam is the intermediate crack-induced debonding of CFRP laminates, provided that the development length of CFRP laminates and shear capacity of the beam are sufficient.展开更多
This research was conducted to investigate the ductility behavior of timber beams strengthened with CFRP （carbon fiber reinforced polymer） plates. The surface to be bonded was spiked by punching small holes of 2 mm ...This research was conducted to investigate the ductility behavior of timber beams strengthened with CFRP （carbon fiber reinforced polymer） plates. The surface to be bonded was spiked by punching small holes of 2 mm in diameter with 10 mm spacing. The aim is to increase bonding capacity by having small studs. Five beams with the dimension of 100 mm x 200 mm x 3,000 mm were tested where one of the beams was used as control beam （unstrengthened）. The remaining beams were strengthened with different configurations before tested to failure under four-point loading. The results showed that the ductility was increased as the percentage of CFRP increased. The ductility was dramatically improved where the highest ductility index based on deflection method was 2.2 where the percentage increase was 37.5%, whereas the highest ductility index based on energy method was 3.2 where the percentage increase was 88.2%. From this study, it was found that 0.3% is the optimum value of CFRP area to achieve maximum ductility index. Ductility index obtained from energy method gives higher values when compared to deflection method. All beams in this study did not fail due to peel off or debonding. It was also proved that the spikes that have been made at the wood surface were very effective for bonding.展开更多
基金The National Natural Science Foundation of China(No.50608013)Special Prophase Project on Basic Research of the National Department of Science and Technology(No.2004CCA04100)
文摘The test results of eight concrete beams reinforced with carbon fiber reinforced polymer （CFRP） sheets subjected to an aggressive environment under a sustained load are presented. The beams are 1 700 mm long with a rectangular cross-section of 120- mm width and 200-mm depth. The beams are precracked with a four-point flexural load, bonded CFRP sheets, and placed into wet-dry saline water（ NaCl） either in an unstressed state or loaded to about 30% or 60% of the initial ultimate load. The individual and coupled effects of wet-dry saline water and sustained bending stresses on the long term behaviour of concrete beams reinforced with the CFRP are investigated. The test results show that the coupled action of wet-dry saline water and sustained bending stresses appears to significantly affect the load capacity and the failure mode of beam strengthened with CFRP, mainly due to the degradation of the bond between CFRP and concrete. However, the stiffness is not affected by the coupled action of wet-dry cycles and a sustained load.
基金Supported by Ministry of Education,Science,Sports and Culture ofJapan under constract No.1 0 0 4 50 55
文摘This paper discusses the method of determining the tensile strength and modulus of elasticity of continuous carbon fiber sheet.Five simply supported beams strengthened by CFS were tested.Based on th experiment,a computer analysis program is developed and a simplified formula is proposed.The calculated results agree well with the experimental results.The design method suggested by this paper can meet the engineering requirements.
基金Project (No. 03HK03) supported by the Science and Technology Development Foundation for College and University of Shanghai, China
文摘Eighteen reinforced concrete beams, including 16 beams strengthened with CFRP laminate at different levels of preload and 2 control beams, were tested to investigate the influence of preload level on flexural behavior of CFRP-strengthened RC beam. The experimental parameters include rebar ratios, number of plies of CFRP laminates and preload level at the time of strengthening. Theoretical analysis was also carried out to explain the experimental phenomena and results. The experimental and theoretical results indicated that the preload level has more influence on the stiffness and deflection of the strengthened beam, both at post-cracking and post-yielding stage, than that on the yielding and ultimate flexural strength of the strengthened beam. The main failure mode of CFRP-strengthened beam is the intermediate crack-induced debonding of CFRP laminates, provided that the development length of CFRP laminates and shear capacity of the beam are sufficient.
文摘This research was conducted to investigate the ductility behavior of timber beams strengthened with CFRP （carbon fiber reinforced polymer） plates. The surface to be bonded was spiked by punching small holes of 2 mm in diameter with 10 mm spacing. The aim is to increase bonding capacity by having small studs. Five beams with the dimension of 100 mm x 200 mm x 3,000 mm were tested where one of the beams was used as control beam （unstrengthened）. The remaining beams were strengthened with different configurations before tested to failure under four-point loading. The results showed that the ductility was increased as the percentage of CFRP increased. The ductility was dramatically improved where the highest ductility index based on deflection method was 2.2 where the percentage increase was 37.5%, whereas the highest ductility index based on energy method was 3.2 where the percentage increase was 88.2%. From this study, it was found that 0.3% is the optimum value of CFRP area to achieve maximum ductility index. Ductility index obtained from energy method gives higher values when compared to deflection method. All beams in this study did not fail due to peel off or debonding. It was also proved that the spikes that have been made at the wood surface were very effective for bonding.
