Three-dimensional Nonlinear Analysis Of Long Span Concrete Filled Steel Tube Arch Bridge By The Method Of Laminated Element

For its so many merits, CFT (Concrete filled steel tube) has gotten extensive application in the engineering practice, especially in long-span bridges and high-rise buildings. Researches and investigations on the bearing capacities of CFT and its time-dependent behavior have been widely carried out. Based on the summarizations the prevenient research results and taken into account the primary problems in those researches on CFT structures, this paper proposes the three-dimensional nonlinear virtual laminated element (3D-NVLE) to investigate the loading capacities and time-dependent behaviour of CFT specimens.In theoretical investigation of the loading bearing capacities of CFT specimens, this paper proposed the three-dimensional stress-strain relationship module of core concrete. The Total Lagrangian Description (T.L. Description) is adopted to consider the large deformation effects, which is in relation to the deformation history. Many factors are considered in the study of the nonlinear buckling bearing capacities of the representative concrete filled circular and square steel tube columns, these factors include the sectional form, the slenderness ratio, the steel ratio, and the eccentricity ratio. The comparison between the test and calculating results shows that they have a good agreement.In theoretical investigation of the time-dependent behaviour of CFT specimens, based on the three-dimensional viscoelastic theory, this paper proposed the three-dimensional finite element model of creep of core concrete, in which a linear three parameters visoelastic model was adopted. After the evaluation of the three parameters in the proposed creep model, which is based on the large numbers of experimental measurements of concrete creep, the influential regularities of concrete filled steel tube columns under long-term loading are investigated. By dispersing time, the method of tangent modulus is adopted to study the relation of creep strain and load time. In the end, this paper took CFT specimens with representative geometry and sectional dimensions as examples and adopted the proposed method as an approach to investigate the influencing regularities of many factors, which include the ratio of long-term load to strength, the slenderness ratio, the eccentricity ratio, and the intensity grade of concrete, on CFT structures. The comparison between the test and calculating results shows that they have a good agreement.In the end, the steel-reinforced concrete arched bridge (Chun'an Weiping Bridge), which span is198m, is analyzed by the proposed three-dimensional nonlinear finite element method and also those gained conclusions are directly adopted in the computation. The universal stability coefficient and nonlinear buckling stability coefficient of the bridge are respectively computed, in which the Dead Load and the Live Load are assembled according to the criterion. On the other side, the regularities of creep deformation and subsidiary stress of the investigated bridge under the first-stage Dead Load are carefully researched.The proposed analytical method and those research findings can be consulted in the engineering practice, the buckling bearing capacities, and the time-dependent behaviour design of CFT columns and CFT arched bridges.