Lateral torsional buckling of girders with rotational restraints – influence and application of the new rules in prEN1993‐1‐1:2020
This paper presents the results of a study that investigated the effects of the innovations introduced in the draft standard for the 2nd generation of EN 1993‐1‐1 for the lateral‐torsional buckling (LTB) verification of beams with I and H cross‐sections on the regulations for the calculation of the minimum stiffness of a rotational restraint to avoid LTB. In the first part of the paper, the background of the existing and new regulations is discussed together with previous proposals for adapting the definition of the minimum rotation bedding. Then, based on theoretical considerations and numerical calculations of the realistic load‐bearing capacity of rotationally restrained beams, it is shown that the new regulations for LTB in prEN1993‐1‐1 lead to very precise predictions of the load‐bearing capacity of rotationally restrained girders and beams, provided that rotational stiffness is also taken into account in the determination of the corresponding slenderness for LTB. In addition, it is shown that the currently valid specifications for the minimum rotational stiffness contained in the National Annex of DIN EN 1993‐1‐1 are also sufficiently accurate for practical use and do not contradict the newly introduced regulations for torsional buckling. The planned tightening of the regulations on the minimum rotational stiffness in prEN 1993‐1‐1, Annex D are thus shown to be unnecessary.