The Research Of Concrete Shrinkage And Creep Experiment

Shrinkage and creep are very important long-term performance of concrete materials. They are parameters that exert great influence on the precamber setting, splitting resistance, durability and safety of structures,considering which shrinkage and creep are factors which must be taken into use when it comes to compute the long-term deflection of concrete structures. Nowadays there are still no united conclusions over shrinkage and creep of concrete and most of the models about shrinkage and creep in use are based on the plain concrete structures as the experimental objects.The models do not take the influence which the steel exert on the concrete structures into consideration and which lead errors when they are put into use on the positive constructures.The thesis is based on the Ministry of Communications western traffic construction technology project'key laboratory open fund [10KA10] of Changsha University of Science and Technology bridge engineering'.Experimental areas are set up and the experimental observation is carried on both in the lab and outdoors. Eight concrete columns are made and four of which are plain concrete columns(two columns are loaded to measure the creep and two columns are not loaded to measure the shrinkage), and the left four columns are reinforced concrete columns(two columns are loaded to measure the creep and two columns are not loaded to measure the shrinkage)The highlight of this thesis is about the influence of shrinkage and creep the steel exert on the concrete structures. And conclusions are listed as below:First, conclusions of shrinkage: The shrinkage analysis Comparison between the reinforced concrete columns and the plain concrete columns shows that the steel has effectively suppressed the shrinkage of concrete. The coefficient of steel influence to the shrinkage of plain concrete is concluded through the experiment. The comparisons between the measured value and standard value show that to reinforced structural unit the code has obviously underestimated the influence of shrinkage which the steel exert on the structural unit. The comparisons of standard values between different cods show that the standard value of chaina communications code are above that of CEB-FIP code.Second,conclusions of creep:The shrinkage contrast test of concrete column point out that the steel has effectively suppressed the shrinkage of concrete.The influence coefficient of creep is concluded which the steel act on the plain concrete column.to reinforced structures, the comparisons between the measured value and the standard value point out that the influence of creep prescribed by code which the steel act on the structures has been underestimated.Comparisons of standard values between different codes are made, which shows that in the lab setting the china communications 04 code is much more precisely than that of CEB-FIP code to reinforced concrete columns, and to plain concrete columns the standard value of CEB-FIP fit in the stress-curve of plain concrete columns better than that of china communications. Based on the measured values of creep strain, an accurate prediction model for concrete creep is concluded. The influence coefficient of creep which the plain bars act on the concrete structures is acquired via the least square method.