Preliminary Research Of Self-Stress Theoretical Calculation And Test Of Concrete-Filled Steel Tube Arch Bridge

High-performance expansive concrete is filled in the steel tube to counteract the separation of tube and concrete. This combination is called self-stressing concrete-filled steel tube (CFST). The initial self-stress caused by expansion of concrete will influence the mechanical performance of CFST distinctly. The study of self-stress calculation and self-stress detection are in inchoate state. The main aims of the paper are to improve the theoretical calculation of self-stress, and establish the self-stress model test plan, and propose the experimental data processing.The major work and results in the paper are summarized as follows:①The analysis of computational theory of self-stress of CFSTThe self-stress computational models of concrete core in triaxial stress state are analyzed by theory. The axial-restrained elastic model and axial-free elastic model are first proposed, and the computational formulae of the models are deduced. They are totally three computational models included the plain elastic model which has existing. The computational formulae of the three models are compared with each other through parameter analysis.Based on the computational formulae of uniaxial creep and the immature theory of creep in triaxial stress state, the computational formulae of creep in triaxial stress state are proposed under varying stress. Taking account of the creep under triaxial stress state, the calculational method of self-stress of CFST is gotten in the paper. The concept of effective factor "p" is introduced in this paper. The "p" is defined as the ratio between effective free expansion rate and free expansion rate, and it is a correction factor which based on massive experimental data.②The self-stress test scheme of CFST and experimental data processingBase on the type of strain sensor and laboratory conditions, the self-stress model test plan is established. Six specimens are designed, and the axial length of everyone is 1200㎜, and the diameter is 400㎜. In the current, the model dimension of CFST is the biggest one in the laboratory. It will decrease the size effect. Vibrating wire sensor is used to measure the self-stress of CFST in lab, which never happen before. Resistance strain gauge is also adopted for comparative analysis of test result.Experimental date processing is proposed too in the paper, including the calculation processing of initial self-stress of CFST by experimental dates,calculation processing of effective free expansion rate by experimental dates and the calculation of effective factor "p".