Issue 50

C. C. Silva et alii, Frattura ed Integrità Strutturale, 50 (2019) 264-275; DOI: 10.3221/IGF-ESIS.50.22 273 C ONCLUSION he union between the potential of the continuous composite beams and the castellated steel profiles is promising for material savings. Despite this, the construction of these beams runs into deficiency of studies about their behavior. In the case of continuous composite beams, the ultimate limit state of lateral distortional buckling deserves special attention. This ultimate limit state depends fundamentally on the web rotational stiffness. In castellated sections the openings in the web of the composite beams reduce the web rotational stiffness of these profiles when compared to those without openings, which makes these beams more susceptible to this buckling mode. According to the standards EN 1994-1- 1:2004 [4] and ABNT NBR 8800:2008, in order to obtain the lateral distortional buckling resistant moment, it is necessary to calculate the elastic critical moment which depends on the geometric properties of the steel profile and the rotational stiffness of the composite beam. In this paper, three different adjustment coefficients (β) were proposed for the Anglo-Saxon, Litzka and Peiner typologies of castellated beams, 0.53, .054 and 0.55, respectively, for the calculation of the web rotational stiffness of the castellated sections, fundamental variable for obtaining the rotational stiffness of the composite beam and, consequently, the elastic critical moment of lateral distortional buckling. As the web rotational stiffness is reduced, the elastic critical moment will also be smaller and, consequently, the resistant moment. The coefficients were obtained (one for each of the opening patterns) from a parametric numerical study performed in the software ANSYS 17.0 [25]. The proposed coefficients provided an excellent adjustment between the results obtained numerically and those obtained from the classical formulation of the plate theory. The maximum deviation between the numerical results and the proposed methodology was 2%, considering different adjustment coefficients for each opening pattern. The adjustment coefficient equal to 0.53 (value obtained for the Anglo-Saxon typology) can be used in the proposed equation for composite beams with three typologies of openings (Anglo Saxon, Liztka and Peiner), resulting in a deviation maximum equal to 4% of the numerical results. A CKNOWLEDGMENT he authors would like to acknowledge the support provided by the Government agencies of Brazil: CAPES, CNPq, FAPEMIG and IFMG. NOTATION a distance between the parallel beams of the inverted "U-frame" mechanism d 0 height opening d g web height of the castellated section h o distance between the geometric centers of the flanges of the steel profile k spring stiffness k g coefficient that takes into account effects caused by the presence of the slab in the model k s rotational stiffness of the composite beam k 1 cracked slab bending stiffness k 2 web rotational stiffness k 2 ,an,sol analytic stiffness of the web without openings k 2, num,cast numeric stiffness of the castellated web k 2, num,sol numerical web rotational stiffness without openings k 3 shear strength stiffness n number of half-waves of the buckling mode C w,d warping constant D plate bending stiffness E Young's modulus of the structural steel (EI) 2 bending stiffness of the homogenized composite section of the slab F force G transverse elastic modulus of the steel I afy second moment of area of the compressed flange in relation to the y axis J St. Venant torsion constant of the profile L beam span M cr elastic critical moment α g related factor to the cross-section geometry β adjustment coefficient β simplified simplified adjustment coefficient δ lateral displacement δ 2 web lateral displacement δ 2, ext displacement of the end plate T T