Bearing Capacity And Construction Control Research Of Long-Span Concrete Filled Steel Tubular Arch Bridges

This paper is concentrated on the bearing capacity and construction control theory of concrete filled steel tubular (CFST) long-span arch bridges. On the background of the scientific research items about long-span concrete filled steel tubular arch bridges: the Wu Gorge Yangtze River Bridge (a 460m span, will be the longest span CFST arch bridge in the world) and the Yonghe Bridge in the city of Nanning (a 350m calculable span, will be the longest span down-supported CFST arch bridge in the world) which are still under construction, a complete analysis theory and calculation method for concrete filled steel tubular arch bridges which includes normal service time, ultimate bearing capacity and construction control are presented. The main subjects are summarized as follow: 1. In this paper, a spline finite point method is presented for the solution of the double nonlinear stability of arch structure. With the cubic B spline functions treated as displacement functions, the nonlinear stiffness equations of spline discretization are established based on the principle of minimum potential energy, and the geometrically and materially nonlinear characteristic of structure is considered. The calculation examples show that this method has advantages of higher accuracy, simple calculation and easy programming. The analyzing results correspond very well with the experimental data. 2. Based on the large deflection theory of arch bridge, this paper uses spline finite point method to analyze the geometric nonlinear internal force of arch structure. With the cubic B spline functions treated as displacement functions, a new method is introduced into. The result is compared with one of the finite element method. Numerical example study show that this method is better than other quadrature method, and the solution of the problem is satisfactory. 3. The shrinkage and creep characteristic of core concrete inside steel tube is investigated. According to the step by step finite element method and the age adjusted effective modulus method,a computing program is presented in this paper. Being aimed at design and construction needs of two long-span CFST arch bridges, basing on actual dividing constructed stages, the internal force and deformation of the arch bridge at any period of time during the whole construction course are analyzed. The results shows that the creep effect can improve the internal force and deformation state of CFST arch bridge to some extent, the redistributed internal force is considerably large. 4. For long-span concrete filled steel tubular arch bridges, it is nonlinear characteristics of material and geometric during its deformation and instability. Accounting for the effects of imperfection and large displacement of arch rib, based on the finite element technique of high accuracy beam with a rounded section, and on the constitutive relations of composite material of concrete-filled steel tube, the ultimate bearing capacities of two bridges are analyzed under static loads on the concept of structural simulation for entire bridge. The results of a model test for concrete-filled steel tubular arch have shown that the test results were in good agreement with the numerical results. 5. This paper introduces the optimization theory and method into the calculation of erecting arch ribs for the first time. The first order optimization method is used to determine the rational construction state of a concrete-filled steel tube arch bridge. The cables force and the prearranged height of arch ribs during construction are obtained, and the actual construction process of arch ribs installation is simulated. This method solves the problem, the times and the methodological restrict of adjusting cables force in the new construction technology for diagonal fastening and connecting by use of jacks and cables. 6. In this paper, an optimal control method for the segmental construction of CFST arch bridge is presented, which employs the minimum double multiplication algorithm to identify parameter, employs the Kalman's filtering metho...