Calculation method of equivalent bending stiffness of castellated beams and analysis of its influence factors

There is no applicable method for calculating internal force of castellated beams in moment resisting frame or portal frame structure. Based on the calculation method of small deformation deflection in the classic mechanics of materials and the principle of same deformation in every small region between castellated beams and equivalent solid-web girders, the equivalent bending stiffness of castellated beams was deduced by utilizing Simpson formula in the web-post of castellated beams. The method to determine the equivalent flexural rigidity of castellated beams with several common web opening shapes in engineering was put forward. Through a comprehensive finite element analysis for different web opening shapes of castellated beams, the proposed calculation method of equivalent bending stiffness was verified. It is concluded that equivalent bending stiffness of various web opening shapes of castellated beams is affected by the ratio of hole diameter to beam depth and the space-to-depth ratio, where the former is a crucial factor while the latter has minor influence on equivalent bending stiffness. Compared with the analogy method that is represented by the Vierendeel open-web truss analogy and other calculation methods of bending stiffness of castellated beams, the proposed method is accurate, efficient and has wide applicability. © 2018, Editorial Office of Journal of Building Structures. All right reserved.