On behalf of Kalmar Industries AB, Ingenjörsdata AB has undertaken the sizing of a truck frame. The truck has a lifting capacity of 10 ton hoisted to an elevation of 21 m. In its retracted/ lower configuration the frame has a height of approx. 10 m. Each lifting cylinder also measures around 10 m as retracted, whereas it measures approx. 20 m fully extended. In the process of lifting one frame part (upper) 10 m relative to the base frame, a load platform is hoisted (on the upper frame) by chain action from ground until 21 m elevation. Stability was one of the dominating sizing criterions. The stability analyses were made using rather detailed models, where all mechanisms (lifting cylinders, chains etc) were represented and including a level of details such that the effect of hollow pressurized pistons could be studied. In the model exhibited below, though, the pistons were modelled using beam elements. The FE-simulations were of the type non-linear with large displacements. Simulations based on linear buckling (bifurcation) were also performed as a reference. The figure below shows the deformation of the frame at a load level of 210 % of max allowed, i.e. at an extreme overload.

Keywords: Kalmar Industries AB, FEM-calculation, non-linear, large displacements, PERMAS, MEDINA, truck frame, container lifting, stability analysis, sizing of steel structure