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For modern infrastructures, structural concrete has been widely adopted for various components and structures such as railway stations, platforms, walkways, railway bridges, tunnelling, concrete sleepers, concrete foundation of overhead wiring structures, etc. These infrastructures are subject to various changes of time, operation, and environment. Environmental conditions are a considerably influential factor to life cycle and durability of concrete structures. This study aims at identifying the influence of climate change on the performance and durability of concrete structures using statistical regression analysis of a number of pertinent experimental and field data. The study into the influence of elevated temperature on compressive strength and splitting tensile strength also has been carried out using experimental data on the basis of environmental temperature and relative humidity, as well as CO 2 concentration to the concrete carbonation and steel corrosion rates. The results indicate that environmental temperature, CO 2 concentration, and a certain range of relative humidity play an important role in the concrete carbonation rates. Temperature and relative humidity affect the rate of steel corrosion as well. In addition, it is found that there exists a nearly direct correlation between the environmental temperature and the concrete carbonation rates, as well as the corrosion rate of steel embedded in concrete from 25 • C to 60 • C, and a nearly inverse proportion between the environmental relative humidity and the concrete carbonization from 48.75% to 105%. Indeed, the results exhibit that even in extreme natural high temperature, the capacity of compressive strength and splitting tensile strength is not affected significantly.

No abstract

Prestressed concrete sleepers are generally designed taking into account the influence of the dynamic wheel load. In Japan, the dynamic wheel load factor of 2.0 has been typically used for the serviceability limit state since the 1950s. However, there are few examples that have proved its validity. In this study, field measurement tests and three-dimensional numerical analysis were conducted for prestressed concrete sleepers laid on a straight section of a railway track with continuously welded rails. According to the results of the field tests, the measured dynamic wheel load factor was less than the conventionally used dynamic wheel load factor of 2.0, and the bending moments exceeding the full prestress condition, i.e. the compressive stress on all sections, were generated in some cases. Furthermore, even with the prestressed concrete sleepers of the same type laid continuously, the bending moment was increased more than three times due to the support conditions of the prestressed concrete sleepers and the rail roughness. Results of the numerical analyses also revealed that the bending moment was increased more than two times because of the hanging (unsupported) sleepers, and the tensile stress of the prestressed concrete sleeper exceeded 3 N/mm2 when the rail roughness was approximately 2 mm or more. Based on this investigation, the validity of the dynamic wheel load factor of 2.0 was proved.