| A castellated beam is a kind of perforated beam, which is dislocation welding or in different direct-cutting hole-patterns after cutting the web of beam by I-shaped steel beam. The main types of opening include circle, hexagon and regular octagon and so on. Compared with a solid web beam, a castellated beam has many advantages, such as a higher bending rigidity and section modulus, a better economic efficiency as well as convenience of setting up pipeline facilities and an artistic appearance. Therefore, along with more studies on castellated beams, it has been widely used in the society.Since there are openings on the webs of castellated beams, the primary analysis of its bearing capacity is great different with solid web beams, therefore, more factors should be taken into account in considering its mechanic performance, such as the hole size of webs and welding quality, etc.. So far, the studies on castellated beams are mainly in the field of strength, rigidity and overall stability. Because of different opening shapes and complicated theoretical derivation, there isn't a corresponding theory solution to the local buckling of webs. Present researches to buckling performance of webs of castellated beam are mainly carried out in the state of single stress, moreover, such studies have certain differences with real buckling stress state of webs.Firstly, this paper introduced the current status of studies on castellated beams at home and abroad, simply stating the buckling theory of plate and common methods of analyzing stability.Secondly, according to the sheet stability theory, with setting webs of castellated beams as the object of study, this paper has assumed that the constraint condition of web was a four-edge simple support and analyzed the stability of a perforated web individually. This paper has establish a large numbers of models by ANSYS to do an eigenvalue buckling analysis, with concluding change rules of buckling models and critical buckling stress of castellated beams webs in the state of pure bending and pure shear. In reference to the flexural buckling coefficient formula and shear buckling coefficient formula of a solid web, with utilizing critical load concluded by ANSYS, the buckling coefficient of perforated web can be worked out by back-calculation in the state of corresponding stress state. Moreover, the numerical analysis software MATLAB could fit a corresponding buckling coefficient formula of perforated web in pure bending state and pure shear state, which could verify the accuracy of formulas. And the function of restraint on the web in castellated beams has been taken into consideration in different stress state by the adoption of constraint coeddicients.Thirdly, based on the study of webs of castellated beams in a single stress state, elastic buckling of castellated beams'webs of two typical height ratios of hole to plate with taking both flexure and shear into account. And as a result, two sets of critical condition of buckling stress could be achieved by fitting, which could be suitable for webs of castellated beams with designated height ratios of hole to plate.Finally, with a detail analysis of elastic buckling performance of castellated beams, this paper has concluded that the buckling modes web and rules of critical loads of castellated beams'webs, which has been carried out with considering the parameters such as a height ratio of hole to hole, hole number, thickness and installment of transverse stiffeners. |
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