TORSION OF LOWER BELT OF CRANE SECONDARY TRUSS

The lower belt of the crane secondary truss, along which the crane moves, is made of a thin-walled box profile. The largest local concentrated crane forces applied with eccentricity to the lower belt of truss made of thin-walled welded box cause its restrained torsion. The calculation method of the crane secondary truss does not consider the inclusion in the work of the lower belt for torsion and horizontal bending of the webs. A beam with a span equal to the span of the crane secondary truss is taken as the design scheme of the lower belt along which the crane moves. In fact, the work of the belt during torsion is different from the work of the beam. The objectives of the work are to assess the impact on the operation of the lower belt during torsion of the webs and the upper belt and to clarify the methodology for calculating the lower belt. The study of the influence of webs on the angular malleability and torque of the lower belt has been carried out. Various ratios of the stiffness of the belt and the entire crane secondary truss are considered. The design scheme of the belt for the calculation of torsion is proposed – a beam angular elastic supports at the points of junction of the webs. The formula for determining the stiffness of elastic supports has been adopted. The error in determining the bending moments in the lower belt according to the proposed method relative to the results of numerical calculation of the rod design scheme of the entire crane secondary truss does not exceed 2%. The stresses in the lower belt, considering the torsion component, are analytically determined. The results were verified numerically using shell finite elements and a full-scale examination.