Mechanical Properties of Reinforced Concrete Members at Cryogenic Temperatures.

This study analyzed the mechanical properties of reinforced concrete flexural and axial-tension members at low temperatures ranging from 273.15 to 108.15 K based on experimental and theoretical analyses. Special test chambers were used to separately apply mechanical forces and low temperatures to the test members. The steel strain caused by the mechanical and thermal restraint forces was obtained using the self-compensation test method. The effects of low temperatures on the tensile and flexural stiffness behaviors of reinforced concrete beams, as well as the internal forces generated because of the different linear expansion coefficients of concrete and steel at low temperatures, were analyzed. Analytical models were developed to predict the restraint stress corresponding to different temperatures. The accuracy of the analytical models was verified using the test results. The results show that the deformation stiffness of both flexural and axial-tension members increases linearly with decreasing temperature. The difference between the thermal deformation of concrete and steel bars becomes more considerable as the temperature decreases, resulting in nonnegligible restraint stress in the steel bars. The study can provide a basis for the design of structures in service at low and ultralow temperatures, such as liquefied natural gas storage tank structures. Practical Applications: Liquefied natural gas (LNG) is primarily composed of methane. After extraction from gas fields, it goes through a purification process; thereafter, it is subjected to a series of ultralow-temperature liquefaction steps and transported through specialized LNG carriers. LNG has extensive applications in various aspects of daily life, including energy supply, transportation, industrial use, and power generation. Compared with traditional fuels, LNG offers higher efficiency and environmental benefits. Nonetheless, optimizing the design of LNG storage facilities presents several technical challenges. Presently, reinforced concrete is the predominant material used in the construction of LNG storage facilities. To fully exploit the advantages of concrete structures in ultralow-temperature environments and reduce construction costs, comprehensive studies on the performance of concrete under such extreme conditions are crucial. This study is of immense scientific value and offers promising prospects for practical applications. [ABSTRACT FROM AUTHOR]