Overall Stability Research Of Hexagon-hole Castellated Beams Considering Diameter-depth Ratio And Space-depth Ratio

Castellated beams are a kind of steel beam with regular holes on the web on thebasis of conventional solid web beams. Castellated beams have a high practical valuebecause of its advantages of economy for floor height, beautiful look and low price;therefore, castellated beams are being more widely used.Castellated beams should ensure its overall stability, because it can easily occurflexural-torsional buckling in the presence of overall instability. Elastic instabilityeasily happens whenl i yis large while the elastic-plastic instability easily happenswhenl i yis medium.The equation of total potential energy of elastic flexural-torsional buckling is builtin the basis of energy method and the critical moment expression of elasticflexural-torsional buckling is solved by using principle of stationary total potentialenergy and Raylleigh-Ritz method in this thesis. The lateral flexural rigidity ofcastellated beams is calculated through the weighted average of the webs’segmentation of moment of inertia, on this basis, free torsional stiffness and warpingstiffness is solved. Verified by the finite element method, the theoretical formulasdeducted by this method are right and relatively orthodox.Analyzed castellated beams’ elastic-plastic overall stability by using the finiteelements method software ANSYS. In consideration of initial defect, geometricnonlinearity and material nonlinearity, three kinds of typical load, five kinds ofd hwand six kinds ofs hw are calculated.The ratio of the overall stability critical moment between solid web beams andcastellated beams is the correction factor k.After comparing results of the elastictheoretical derivation of the formula, elastic-plastic finite element method and thecorresponding equivalent solid web beams, we find that the correction factor k isdifferent in three typical load and different hole condition, varying from1.01to1.09.After analyzing the factors which influence the k, we find out that the influence ofd hw is greater thans hw,and the influence of elastic-plastic instability is greaterthan elastic instability. Taken the above calculation and analysis results, k=1.1isgot to simplify things. On the basis of the above understanding, the hexagon holesimply supported castellated beams’ overall stability devise formulas is put forward, providing a reference for engineering design personnel.