The theory is base on an analysis of the bifurcations of multiple eigenvalues of non-self-adjoint differential operators that depend on parameters. A theory is constructed for the qualitative and quantitative description of the “destabilization paradox” in these systems, one manifestation of which is an abrupt drop in the critical load and frequency when small dissipative forces are taken ino account. This due to the unknown fatigue effect, which is not analysed in this thesis.The effect of small internal and external damping on the stability of distributed non-conservative systems is investigated. The formula is accurate for small damages and is gradually more conservative for larger damages. The formula is developed to fit the numerical results of damage at the main girders at the back of the boom.

Damages at other locations of the boom were surprisingly insignificant for the buckling load.Īn empirical formula is developed to determine the reduction in SWL (Safe Working Load) due to damage. The most critical location of the damage was found to be at the main girders at the back of the boom. Impact damage, with various grade of indentation depth and deflection were analysed at different locations of the crane boom, with different lifting radii. The indentation depth of the dent and the deflection of the member were found as the parameters with highest influence on the buckling load.įurther, global analyses of the crane boom are performed. A parametric study of damage of one of the bracing members of the boom are conducted, including the parameters indentation depth of dent, radius of impact object, deflection of bracing and location of damage. The capacity of the crane boom is determined from the buckling load of nonlinear buckling analyses. This includes loads from two different hoisting systems, wind, and sidelead load caused by sideways displacement of the load on the supply vessel deck due to motion of the vessel. Relevant crane loads are identified and established for different lifting radii. The crane boom is modelled and analysed in the FE program, Abaqus. The geometry and dimensions of Wolffcran's HDK 1000 HM crane is used as basis for a finite element (FE) model of a latticed boom. This thesis targets to detect the important parameters of such impact damage, and how they effect the capacity of the crane. Offshore cranes with latticed boom are exposed for unwanted collision with other objects, damaging the load-carrying structure. Cranes are important constructions on offshore installations.

Crane boom radius