The Inner Fill Outsourcing Steel Tube Concrete Columns Bearing Capacity Analysis

The main arch structure of Darui Railway Lancang River Super Large Bridge is steel tubes filling and outsourcing concrete single cell single box girders. Aimed at matching up with project construction and scientific research project, as well as, providing theoretical basis of reasonable evaluation of the bearing capacity of Lancang River Super Large Bridge, the vault section selected to construct steel tubes filling and outsourcing concrete straight bar and short column, this thesis applied nonlinear finite element analysis and numerical integration of section limit equilibrium state to analyze and calculate the ultimate bearing capacity, and discussed the impact on ultimate bearing capacity exerted by initial stress of steel tube and relative slip between the steel tube and concrete. The main contents are as follows.1. By adopting stress-strain non-linear constitutive model of concrete and steel, and selecting the typical steel pipe concrete experimental complement from literatures, this thesis built the numerical analysis model with the assistant of large-scale finite element program. The comparison between the calculation result and the test results in literatures verified the numeral model's modeling method and rationality of preferences. It presented modeling basis of building steel tubes filling and outsourcing concrete numerical model.2. Based on the large-scale finite element program, this thesis built the ultimate bearing capacity's numerical analysis model of steel tubes filling and outsourcing concrete short column. According to the time history analysis of outsourcing concrete, steel tube filling concrete's stress and strain, it figured out the complement's ultimate bearing capacity and safety factor under vault practical internal force conditions of background project.3. The thesis derived the "numerical integration of section limit equilibrium state" formula, adopted FORTRAN to program relative calculative process, and calculated the ultimate bearing capacity of complement's section. In comparison of and verification of calculation and result of finite element analysis, it tested the reliability of the calculation result.4. Considering the initial stress which is generated by the steel tubes composite framework of main arch in the construction process, the thesis used two methods mentioned above respectively calculate the impact on complement's ultimate bearing capacity exerted by initial stress.5. In order to analyze the influence of ultimate bearing capacity exerted by relative slip between the steel tube and concrete, the author designed a complement and built the non-slip and slip numerical analysis mode between steel tubes and filling and outsourcing concrete. Through comparison and analysis, he drew some useful conclusions.6. The appraisal of bearing capacity and safety of background project's steel tubes filling and outsourcing concrete component verified the rationality of this design. The results of calculation and analysis may be for engineering design reference.