Behavior of Crane Beams in Bending and Restraint Torsion

Abstract

AbstractA common solution in foreign worldwide practice is the use of crane beams without brake bracing structures or only with braces to the upper flange of the beam in the support zones. In this case, when lateral forces from the crane act on the thin-walled crane beam of an open profile (as usual it is I-beam), it experiences restrained torsion, and requires a special approach for the analysis of its stress–strain state. The article considers the calculation of a crane I-beam without a brake structure and with braces to the upper chord in the support zones. It is shown that the account of restraint torsion for a free I-section crane beam is mandatory. For this case of combined bending and restraint torsion of the beam, finite element analysis with the use for modeling of the beam either simple beam finite elements with 7 degrees of freedom or plate elements shows the most accurate results. In addition, for engineering analysis, it is possible to use a modified beam model using finite elements with 6 degrees of freedom, the calculation results of which turned out to be quite close to the theoretical ones. It is shown that the braces in the supporting zones fix the beam from torsion quite well, allow reducing stresses and beam deformability, and can be used for beams for light-duty cranes with small load capacity. For medium and heavy duty cranes, such solutions are not recommended due to the possibility of fatigue failure of the beam, and full-length brake structures should be provided along the upper flange of the beam.KeywordsCrane beamBrake structureRestraint torsionWarpingBimoment