Study On Design Theory For Self-stressing Concrete Filled Steel Tube

With the advantages of high bearing capacity, economical efficiency, practicability and beauty, Concrete-Filled Steel Tube (CFST) is widely used in high-rise buildings and long-span bridges. However, traditional CFST has some shortcomings that shrinkage and hardening of concrete will result in cavities and unstick. Self-Stressing Concrete-Filled Steel Tube (SCFST) is a new type of CFST, which can ensure concrete and steel to work together by micro expansion performance of concrete.Based on the Western Transportation Science and Technology Construction Project-Development Test and Applied Research on the Self-Stressing Concrete-Filled Steel Tube, contents and achievements of this dissertation are described as follows:①Based on the results of our past experiments, the impacts of the expansion agent to the self-stressing concrete mechanical property and fits the young's modulus curve were discussed in this dissertation;②According to past free expansion experimental data, correlation between young's modulus and age is established by using curve fitting.③The general calculation methods of the ultimate bearing capacity and design bearing capacity of SCFST are summed up, and comparion with the calculation result of test-piece is done.④Enhanced coefficient of bearing strength of self-stressing concrete is introduced, and the effect of the self-stress on the load carrying capacity of CFST stub column is drawn.⑤The axial loading test specimens of stub column have been numerically simulated by ANSYS program. Expansion of concrete is simulated by heating concrete in steel tube, and then the Finite element analysis models are set up for CFST stub column and SCFST stub column. Calculation result shows that mechanical property of SCFST is better than CFST. The reasons how to increase ultimate bearing increment is discussed. Finally, author compares initial self-stress influences and microstructure influences on the load carrying capacity increment of SCFST.