Shaped Boom Beams Cantilever Flexural Torsional Buckling Of Research

Steel I-shaped horizontal beam is a commonly used component in the structure of combined bridge deck system. The main bridge of the fourth Xiangjiang River bridge in Xiangtan is a cable-stayed flying swallow type of concrete-filled steel tubular tied arch bridge with the span arrangement of 120+400+120m. Its bridge deck system, which is composed of steel horizontal beam, steel longitudinal beam and concrete slab, is a suspended system. With the background of this bridge, based on relevant theories of flexural-torsional buckling, this paper studies critical load of flexural-torsional buckling of cantilever I-shaped horizontal beam and comparatively analyses the result. It mainly includes the following content:1. Based on moment-equilibrium method and energy method, this paper deduces analytical formula of bifurcate flexural-torsional instability problem for cantalever beams of double symmetrical constant section, mono-symmetrical constant section and mono-symmetrical variable height. Then, based on the examples of 4-meter-length and 17.5-meter-length cantilever beams, the paper analyses critical loads of the components under different working conditions such as when load is imposed on the Centroid, the upper flange and lower flange of the cross section of free end. To verify the reliability of the method in the paper and calculation accuracy, the calculation results in the paper are compared with that of reference literature.2. The author considers that the suspender loads on the cross beam may be inclined, which can cause the simultaneous action of vertical and lateral loads. Under this circumstance, the instability problem of cantilever component transforms into maximum point instability problem. Based on the moment-equilibrium method and linear elastic constitutive relation, the paper deduces analytic formula of maximum point instability problem for the cantilever beam while the suspender is initially deflected, and analyses different P-Φcurves and critical loads of instability under different initial deflection angles of suspenders.3. This paper establishes finite element models of the above mentioned cantilever cross beams with plate elements (SHELL63) of the large finite element program ANSYS, analyses linear-elastic stability of the beams, and compares the results to that of analytical solution.4. Based on the analysis methods of geometric nonlinearity and double nonlinearity, by means of using ANSYS software, the paper analyses critical loads of cantilever beams under different initial deflection angles of suspenders, compares the results to that of analytical solution, and analyses the yielding stress field of the components under ultimate loads.5. Based on Timoshenko's idea of magnification factor for the analysis of maximum point instability, by means of using regression analysis method, the analytic formula of the magnification factor when the influence of the suspender's initial deflection angle is considered is given, for engineering application.