Experimental Study on Effective Preloading Performance of Prestressed Concrete with Given Water Content at Different Ultralow Temperatures

Through the experiments of concrete with normal water content experiencing cryogenic temperatures of 0 ℃, -20 ℃, -40 ℃, -60 ℃, -80 ℃, -100 ℃, -120 ℃, -140 ℃ and -160 ℃, the changing regularity of the preloading stress of prestressed concrete under different cryogenic temperatures was discussed, and the difference of the effect of higher water content on it was given by the experiments from lower and higher cryogenic temperature actions. The test results showed that the preloading stress loss rate of prestressed concrete at the cooling target points and the temperature uniformity target points increased rapidly first and then slowly with the decreased in the exerted cryogenic temperatures. But its preloading stress changing rate at the cooling stages was different from that at the constant temperature stages. The former showed a trend of rapid increase first and then basically linear decrease, and the latter showed a trend of rapid first and then gradually slow decrease. The loss of preloading stress of the prestressed concrete no longer increased but recovered at the constant temperature stages after reaching the cooling target points. The influence of water content on the preloading stress loss rate and the preloading stress changing rate of prestressed concrete was complex, and it was related to the exerted cryogenic temperatures. These results could provide a reference for the design and safety evaluation of prestressed concrete structures as LNG storage tanks.