给定初始预压应力水平混凝土不同超低温下有效预压性能试验研究

Experimental study on effective preloading performance of concrete with given initial preloading stress levels at different ultralow temperatures

通过给定初始预压应力水平混凝土经历0℃、-20℃、-40℃、-60℃、-80℃、-100℃、-120℃、-140℃和-160℃的低温作用试验,探讨不同低温作用下混凝土的预压应力变化规律.结果表明,随作用的低温降低,混凝土的降温点和温均点预压应力损失率均呈先快速上升后下降的变化趋势,其中下降时前者很平缓、后者则较明显;而降温段和恒温段预压应力变化率有所不同,但作用的低温较低时均呈下降变化态势.混凝土恒温时相较于降温时的预压应力损失率和预压应力变化率均较小,达降温点后的恒温阶段混凝土的预压应力损失还有所恢复.较低初始预压应力水平混凝土的预压应力损失率和变化率均高于较高初始预压应力水平,并且与作用的低温有关.试验结果可为低温储罐类预应力混凝土结构的设计和安全评估提供参考。

Through the experiments of concrete with given initial preloading stress levels experiencing cryogenic temperatures of 0℃,-20℃,-40℃,-60℃,-80℃,-100℃,-120℃,-140℃and-160℃,the changing regularity of the preloading stress of concrete under different cryogenic temperatures is discussed.The test results show that the preloading stress loss rate of concrete at the cooling target points and the temperature uniformity target points increases rapidly firstly and then decreases with the decrease in the exerted cryogenic temperatures,and the former is gentle while the latter is obvious for their decrease changing degree.The preloading stress changing rate at the cooling stages is different from that at the constant temperature stages.But when the exerted cryogenic temperatures are low,all the preloading stress changing rates at both the cooling stages and the constant temperature stages decrease.The loss rate and changing rate for the preloading stress of concrete at the constant temperature stages are lower than those at the cooling stages.And the loss of preloading stress will also recover at the constant temperature stages.The loss rate and changing rate for the preloading stress of concrete with lower initial preloading stress levels are higher than those with higher initial preloading stress levels,and they are related to the exerted cryogenic temperatures.These results can provide reference for the design and safety evaluation of concrete structures as LNG storage tanks.