Castellated Beams The Overall And Local Stability Analysis

Castellated beams, characterized by rational section form, large flexural stiffness, high carring capacity and prominent economic efficiency, and so on , are often used in the projects of workshops, office buildings, high-rise buildings, bridges and steamships. The researches about castellated beams also become more and further. However, analysis and researchers of stability are not development enough. Therefore, it is necessary to do more researches on stability. This thesis mainly makes analysis of overall stability and local stability, and the main research work covers the following aspects:Flanges and web of a castellated beam separated, finite element analyses are made by using ANSYS for web with circular openings to obtain the lateral deflection under lateral pure bending. Then the lateral flexural stiffness is determined inversely from its classical relationship with the deflection and divided by the lateral stiffness of solid web with equal section to obtain the reduction coefficient k_y. An expression of k_y is brought forward with linear fitting method to correlate with diameter-depth ratio and space-depth ratio of web. The achieved k_y makes it possible to amend the free torsional stiffness of castellated beam. The formula for flexural-torsion critical moment of solid I-beam is adopted by substituting the stiffness of castellated beam to predict the critical moment for the latter under pure bending. At last ANSYS is applied to analyze a series of castellated beams subjected to different conditions of load and with different spans and opening to work out the critical moments in numerical procedure. Comparisons indicate that the formula existing for solid beam and the stiffness here achieved for castellated one can be combined to give satisfactory results for overall stability analysis of the latter.Web of castellated beams is treated as simply supported plate with openings. The stability of plate with openings is studied under pure bending and uniform shear by using ANSYS and the characteristics of buckling are described. When plate length,height,thickness and the number of openings keep constant, a series of finite element analyses are carried out by using ANSYS to achieve the variation relationship of resistance capacity with diameter-depth ratio and space-depth ratio of web. The buckling coefficient of web with openings is obtained and an expression of it is brought forward with linear fitting method to correlate with diameter-depth ratio and space-depth ratio of web. The formula for buckling of thin plate is adopted by substituting the original buckling coefficient. At last, the stability of web is analysised under lateral loads. A simplified method is presented to check the local stability of web.