Web rotational stiffness of continuous steel-concrete composite castellated beams

Continuous composite beams can present a global instability known as lateral distortional buckling (LDB). The design code EN 1994-1-1:2004 provides a procedure for the verification of this ultimate limit state, in which the resistant bending moment is calculated considering the behavior of the inverted "U-frame" mechanism. An essential parameter for the determination of this moment is the rotational stiffness of the composite beam, which depends on the web stiffness. The EN 1994-1-1:2004 procedure is restricted to composite beams with solid-web steel sections without openings. This paper presents several numerical analyses of the web rotational stiffness of castellated sections such as Anglo-saxon, Litzka and Peiner typologies. Finally, based on numerical results obtained, three different adjustment coefficients were proposed for the Anglo-Saxon, Litzka and Peiner typologies for the calculation of the web rotational stiffness of the castellated profile. The proposed coefficients provided an excellent adjustment between the results obtained numerically and those obtained from the classical formulation of the plate theory, with an average deviation of 2%, indicating low dispersion and homogeneous results.