Mechanical Property And Simplified Calculation Research On Continuous Curved Composite Box Bridges In Construction Stage

Channel section is usually used in curved composite box bridge, in which the lateral coupling system is arranged evenly. During the construction stage, the mechanical behavior of the steel beam is complicated and different from the open or closed section beam. In theory, The fine finite element model established by the shell element and solid element can be used to calculate the stress condition of the structure precisely. However, some drawbacks directly restrict its application in practical engineering, including huge processing workload, long computational time and requiring heavy internal memory and external memory. In this case, it is very valuable to establish a simple and accurate calculation model. For this purpose, some discussion was made in this thesis. The research contents and contributions are as follows:Shell element model of steel beam was generated using the finite element analysis software ANSYS. Mechanical behaviors of the structure in the construction stage were calculated, and the properties are defined. Main influence parameters (including cross section form of steel beam, arrangement distance and the style of lateral coupling system) in curved composite box girder construction stage were studied.Introducing the concept of equivalent torsional stiffness, equivalent torsion parameters were calculated by using Vlasov restrained torsion theory and constrained torsion initial parameter method for thin-walled open section beam, deducing the formula of rotation angle, and establishing the sectional model composed of shell elements. The modeling method of frame system finite element was established. In addition, the more simple calculation methods of equivalent free torsion constant I1 is provided in this thesis. The structure is equivalent to an closed section, which consist of a elastic thin roof. The formula of roof thickness is provide.Using a built continuous curved composite box girder bridge as an example, frame system finite element models during the important stage in the construction process were established by using formula and calculation process to getting equivalent torsion parameters in the thesis. Comparing the stress and deformation between frame system finite element models and fine finite element models, the correctness and applicability of this method were verified.The calculation results show that the torsion type of curved channel steel beam with the lateral coupling system was restrained torsion. Warp deform occurred along the bridge and distortion of cross section is very small. The characteristics of this structure are consistent with the analysis results of the constrained torsion theory of open thin-walled members. An additional torque is existed in the unsymmetrical section steel beam under the action of dead load or symmetrical load, which stays the same with the change of curve radius. The lateral coupling system can significantly improve the torsional stiffness of the steel beam with the channel section and the relationship keep the positive correlation. It is same for the influence on the overall mechanical behavior of open-section box girders between the diaphragm type lateral coupling system and the truss type lateral coupling system. The calculated equivalent torsion parameters are reasonable when open-section box girder with uniform lateral coupling system is regarded as homogeneous thin-walled beam. Engineers can ignore the influence of the cross links during calculating the equivalent warping constant and the coordinate of torsional center. The deformation and stress results calculated by the frame system finite element model and fine finite element model are in good agreement, which proves that the frame system finite element model is precise and practical, which can provide a calculation method for the design and analysis of the bridges.