Consider The Impact Of Hole Conditions, The Cellular Beam Design Calculations

Castellated steel beams can save amount of materials and facilitate passage of pipes, being of practical value for engineering application. However, castellated beams are not classical menbers which accord with Bernoulli's assumption of section remaining plane. Their design remains unsatisfactorily solved. There is no technical standard for castellated beams in China. Therefore, further studies are necessary. In this paper, how to account for the effect of the geometry of openings in design is investigated with particular refernce to castellated beams with the comman shapes of opening, i.e. hexagon and circle. The main contents are as follows.1. A methodology is put forth to determine the equivalent flexural stiffness of castellated beams, which is reversely derived from the results of finite element analysis (FEA) of castellated beams under pure bending. It is simple, accurate, economical, and high efficent. A rational formulation is presented to calculate the equivalent flexural stiffness, in which the redution factor of stiffness for web with openings is obtained by FEA for various cases of opening and expressed by a half-empirical equation for web with hegaxonal and circular holes. The defficiencies in the stiffness calculation implied in the existing approaches of defletion prediction are pointed out by comparion with the results of stiffness determined here in this paper.2. FEA is made with ANSYS for hegaxon- and circle-castellated beams. From the results a bilinear assumption is suggested to simplify the computation of normal stresses at the mid-pier section. The relationship between the bending moment, the extreme normal stresses at the mid-pier section and the depth of the stressed area is established and empirial expression are gained by correlation. A direct approach is also proposed for prediction of the maximum stress. In addition, the stress distribution around the boudary of holes and along longitudinal direction are discussed. 3. On the basis of Vierendeel analogy to open web truss, the expression of deflection is derived for hegaxon-castellated beams. Then it is used to evaluate the deflection of circle-castellated beams and the relevant parameters are given by correlation to the FEA results .4. Expression of cirtical bending moments for flexural-torsional buckling are derived by equilibrium method and energy method for castellated beams with the opening of hexagon and circle under typical loading. The relevent stiffnesses are determined. The apllicapbility of these formulae are verified by good coincidence with the FEA results.