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Bonding behaviour of CFRP composite strengthened tunnel structure under fire exposure

By: Contributor(s): Publication details: Borås : RISE Research Institutes of Sweden AB, 2023Description: s. 602-617Subject(s): Online resources: In: Proceedings from the Tenth International Symposium on Tunnel Safety and Security, Stavanger, Norway, April 26-28, 2023Abstract: In order to improve the safety and durability of the structure, a growing number of shield tunnels with structural damage of metro lines have been reinforced by carbon fiber reinforced polymers (CFRP). After a long-term operation, there is a great concern with the fire resistance of the epoxy bonded CFRP strengthened tunnel structure. In this study, a series of experimental studies were conducted on specimens of the epoxy resin and the CFRP composite-concrete to investigate the residual bond behavior of interfaces of CFRP-strengthened shield tunnel subject to elevated temperature. The experimental specimens were for both the tension and the shear test. The influences of the different levels of the exposure temperature were considered and contained seven groups for 20, 50, 100, 200, 250, 300, and 400 °C in a controlled condition. Based on fitting and regression on the experimental results of the CFRP composite-concrete interfacial bond performance, the interfacial constitutive relationships for both tensile and shear properties were established. Combined with the experimental results, a numerical model of the reinforced shield tunnel structure, including tunnel lining segments, longitudinal joints, and CFRP composites, was also established to analyze the temperature distribution and mechanical behaviors of the debonding of CFRP under four fire scenarios. The numerical results suggest that the CFRP-strengthened shield tunnel may face a challenge when a large fire occurs and sustains for a considerable duration. As bonding interface extends with the heating, the cohesive elements start to fail gradually from the joint to the segment span, and the complete failure of the interface is mainly due to the complete failure of the interface shear performance. The significance of the shear properties of the CFRP-strengthened tunnel bonding interface precedes that of the tensile properties.
Item type: Reports, conferences, monographs
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In order to improve the safety and durability of the structure, a growing number of shield tunnels with structural damage of metro lines have been reinforced by carbon fiber reinforced polymers (CFRP). After a long-term operation, there is a great concern with the fire resistance of the epoxy bonded CFRP strengthened tunnel structure. In this study, a series of experimental studies were conducted on specimens of the epoxy resin and the CFRP composite-concrete to investigate the residual bond behavior of interfaces of CFRP-strengthened shield tunnel subject to elevated temperature. The experimental specimens were for both the tension and the shear test. The influences of the different levels of the exposure temperature were considered and contained seven groups for 20, 50, 100, 200, 250, 300, and 400 °C in a controlled condition. Based on fitting and regression on the experimental results of the CFRP composite-concrete interfacial bond performance, the interfacial constitutive relationships for both tensile and shear properties were established. Combined with the experimental results, a numerical model of the reinforced shield tunnel structure, including tunnel lining segments, longitudinal joints, and CFRP composites, was also established to analyze the temperature distribution and mechanical behaviors of the debonding of CFRP under four fire scenarios. The numerical results suggest that the CFRP-strengthened shield tunnel may face a challenge when a large fire occurs and sustains for a considerable duration. As bonding interface extends with the heating, the cohesive elements start to fail gradually from the joint to the segment span, and the complete failure of the interface is mainly due to the complete failure of the interface shear performance. The significance of the shear properties of the CFRP-strengthened tunnel bonding interface precedes that of the tensile properties.