This paper presents the analysis of a fracture due to the local increase in stress at the point of connection between the hydrocylinder and the first segment of the truck crane boom. The connection between the hydrocylinder support and the body of the first boom segment is accomplished by welding. The first part of the paper defines the relevant load for calculation of the hydrocylinder support, by using the manufacturer’s data to perform analytical calculation of the critical section. It is followed by the FEM analysis and fatigue analysis, for the most unfavourable load case. It has been established that the critical value of stresses is at the point of connection between the hydrocylinder support and the structure of the first boom segment. Experimental testing has shown that the fracture did not occur due to an error in the material and that the material type is adequate for this type of structure. The superposition of negative influences: fatigue of the material and a pronounced difference in material thicknesses in the cross section at the point of fracture are the main causes of damage of the hydraulic truck crane structure.

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