Strengthening of RC structures with externally bonded FRP （fiber reinforced polymers） has become an important challenge in civil engineering. Epoxy is the main bonding agent used so far, but in the case of a fire, i...Strengthening of RC structures with externally bonded FRP （fiber reinforced polymers） has become an important challenge in civil engineering. Epoxy is the main bonding agent used so far, but in the case of a fire, it is subjected to complete loss of his bonding capabilities. Mineral based composites strengthening systems consist of FRPs and a cementitious bonding agent which form a repair or strengthening system that is more compatible with the concrete substrata, and roved its efficiency. The current research introduces the use of a special cementitious material ＂Grancrete＂ as a bonding agent. Test results of 32 T-section RC beams strengthened with various FRG （fiber reinforced Grancrete） strengthening systems are presented. The results demonstrated that most of the specimens were likely to fail by debonding of the FRP from the concrete either at the ends or at intermediate flexural cracks. This paper presents an in-depth study aimed at the development of a better understanding of debonding failures in RC beams strengthened with externally bonded FRP systems. Different analytical models, published in the literature for plate end debonding, are reviewed and compared to test results. The results also demonstrated that when using U-wraps, the specimens were likely to fail by FRP sheet rupture.展开更多
According to the analysis of the macro and micro characteristics of the center of continuous casting blooms by acid wash, SEM, metallographic and scanning-type electron microscope, there was a serious segregation and ...According to the analysis of the macro and micro characteristics of the center of continuous casting blooms by acid wash, SEM, metallographic and scanning-type electron microscope, there was a serious segregation and some shrinkage cavities in the slab; Cracks occurred at the end of the columnar crystal and spread along the boundary of the primary dendrite. At the crack enriched a large number of impurity elements, carbon, phosphorus, sulfur, whose crystal boundary segregation is the internal factor of the intermediate cracks. Determining the originated location of intermediate cracks and calculating the total strain in this area during solidification process of slab, it is found that the load is the ex- ternal factor of cracks’ generation and expansion.展开更多
文摘Strengthening of RC structures with externally bonded FRP （fiber reinforced polymers） has become an important challenge in civil engineering. Epoxy is the main bonding agent used so far, but in the case of a fire, it is subjected to complete loss of his bonding capabilities. Mineral based composites strengthening systems consist of FRPs and a cementitious bonding agent which form a repair or strengthening system that is more compatible with the concrete substrata, and roved its efficiency. The current research introduces the use of a special cementitious material ＂Grancrete＂ as a bonding agent. Test results of 32 T-section RC beams strengthened with various FRG （fiber reinforced Grancrete） strengthening systems are presented. The results demonstrated that most of the specimens were likely to fail by debonding of the FRP from the concrete either at the ends or at intermediate flexural cracks. This paper presents an in-depth study aimed at the development of a better understanding of debonding failures in RC beams strengthened with externally bonded FRP systems. Different analytical models, published in the literature for plate end debonding, are reviewed and compared to test results. The results also demonstrated that when using U-wraps, the specimens were likely to fail by FRP sheet rupture.
文摘According to the analysis of the macro and micro characteristics of the center of continuous casting blooms by acid wash, SEM, metallographic and scanning-type electron microscope, there was a serious segregation and some shrinkage cavities in the slab; Cracks occurred at the end of the columnar crystal and spread along the boundary of the primary dendrite. At the crack enriched a large number of impurity elements, carbon, phosphorus, sulfur, whose crystal boundary segregation is the internal factor of the intermediate cracks. Determining the originated location of intermediate cracks and calculating the total strain in this area during solidification process of slab, it is found that the load is the ex- ternal factor of cracks’ generation and expansion.
