Experimental Investigation On Behavior Of Reinforced Concrete At Low And Ultra-low Temperatures

Nowadays,China's economy has been developing rapidly,which promotes the high-end technology improved continually and which drives the building technology used in extreme environment frequently as well.Specially,reinforced concrete is widely used in low and ultra-low temperatures environment and the LNG storage tank is one typical structure among them.Reinforced concrete would behavior quite different if the temperature changes.Therefore,it is the basis for constructing LNG storage tank safely and economically to master the material properties of reinforced concrete at low and ultra-low temperatures.With the help of tests and finite element software,the mechanical properties of a LNG reinforced concrete storage tank in various cryogenic temperatures was studied here.As one part of Natural Science Foundation of Shandong Province,“Study on the performance in low temperature and optimization design on large LNG prestressed concrete storage tank”,this paper include the following contents:1.The equipment used in tests and the characteristic of tests were introduced here.In order to overcoming the limitations of existing test techniques and equipment,to making tests operation easy,fast and safe,to improve the level of study and accuracy,a new test device mentioned in this paper was designed by ourselves.What's more,for the purpose of comparing and analyzing the data with that in room temperature,the testing program set here was made according to the corresponding test criterions in room temperature.2.Studied the variation in thermal conductivity and mechanical indicators when the temperature changes from-160? to 20?,and obtained a constitutive relation between thermal velocity and temperature in low and ultra-low temperatures.Results showed that the larger temperature difference was,the higher moisture content was,or the more times freeze-thaw cycle was,the faster thermal velocity.of concrete would be.Besides,Specimen size and shape also had influence on the thermal velocity.3.Mechanical properties of concrete in low and ultra-low temperatures were tested.Results showed that the values of mechanical indicators became large with temperature decreasing,and increasing speed was separated.Some equations associated with spilling tensile strength,compressive strength and temperature were fitted.Besides,size effect coefficient and strength conversion coefficient formula in various temperatures between-160 ? to 20 ? were proposed and analyzed,comparing results with f the existing conclusions.All for making contribution to design LNG storage tank on our own feet and drawing up China concrete criterions in low and ultra-low temperatures.4.By doing reinforced tensile test in low and ultra-low temperature,values of reinforced strength and plasticity indexes in different temperature were gained.5.With the help of formula in criterions,the test data of concrete was converted into design value in various temperatures.Simulated a large LNG prestressed concrete tanks with ABAQUS finite element software,analyzing the role material properties played in temperature field formed and stress state in storage tank.A conclusion was got that the characteristic of reinforced concrete helps overcome the adverse effects of temperature stress when structure is suffering from low temperature environment,which promise the material a brilliant future in low temperatures field.