Research On Calculation Models For Hydration Heat, Shrinkage And Creep Of Concrete-Filled Steel Tubes

The characteristics of temperature field due to cement hydration heat and atmospherictemperature, the shrinkage and creep of core concrete in CFST (Concrete-Filled Steel Tube)members, have been the interests of structural engineers. The main achievements of this paper can be summarized as followings:1. Temperature field of CFST members in cement hydration stage was tested, and the parameter is sectional dimension. The experimental results show that the varying rules of temperature field of CFST members are similar to the concrete members, and the sectional dimension has significant influence on temperature field characteristics of CFST members.2. Shrinkage of core concrete in CFST members and plain concrete was tested, and the experimental parameters are sectional dimension and sectional shape. The test results show that there has great difference of shrinkage behaviors between CFST members and plain concrete ones, and shrinkage of core concrete in CFST members is far less than that of plain concrete.3. Based on the determination of model of cement hydration heat and calculation method of temperature field of core concrete in CFST members, the temperature field was calculated by means of computing program, and the calculating results agree well with those of the tests.4. Concrete shrinkage model proposed by ACI209 (1992) specifications was improved. A more fitting method for calculating the shrinkage of core concrete in CFST members was suggested, and the calculating results have a good agreement with the test results.5. Based on the improved shrinkage model, deformation curves of axially and eccentric loaded CFST members under long-term sustained loads were calculated and analyzed. The achievements in this paper may be reference for practical engineering and theoreticalresearch of CFST.