Methods for Strengthening Reinforced Concrete Columns Using Carbon Fiber in China

Introduction. China's construction industry developed in three phases: the first peak occurred in the 1950s, and the second one in the 1980s and 1990s. Generally, buildings constructed during the construction boom were characterized by relatively low design and construction standards resulting in poor quality. Currently, buildings constructed during the first and second phases are entering a phase of "aging" due to some factors such as low construction standards and outdated construction methods. Both the buildings themselves and their structures are flawed. Over time, most buildings exhibit varying degrees of deterioration and serious damage requiring urgent inspection, repair, and reinforcement. To meet the needs of social development, proper repair, reinforcement, and reconstruction of existing buildings is essential. The aim of this study is to identify the possibilities of reinforcing defective building structures with modern composite materials manufactured in China. Materials and Methods. The object of the research are methods of strengthening reinforced concrete pillars. The author suggests using a systematic approach that accounts for the adjacent functional areas, their mutual influence and an expert assessment of their significance. Research Results. The analysis showed that the strengthening mechanism for reinforced concrete columns subjected to axial compression and strengthened with carbon fiber sheets is a combination of carbon fiber sheets and concrete influenced by a host of factors. The strengthening method is strictly regulated, and the lateral restraint provided by the carbon fiber sheets under loading is capable of improving the compressive strength, structural stability, and durability of the columns. Discussion and Conclusion. The strengthening methods for existing buildings vary widely, each with its own unique advantages and limitations. For example, bonded steel is fast to construct but requires a high quality; section enlargement is cost-effective but reduces space; carbon fiber strengthening offers numerous advantages but has limitations in investigating nodes and calculating load-bearing capacity. Although extensive research has been conducted on strengthening reinforced concrete axial compressed columns, the effectiveness depends on a host of factors. The discussion demonstrates that the choice of a strengthening method should be tailored to actual conditions. Carbon fiber strengthening requires further research, while strengthening axial compressed columns requires technological optimization. Furthermore, existing standards and regulations should be revised to reflect new advances and best practices.