ship crane pedestal strength assessment
A strength assessment of the Upper Deck crane equipment with a local hull strengthening
The strength assessment of the design for a new crane pedestal located on the Upper Deck of a bulk carrier/raid loader “Iron Destiny” has been performed. The Transloader “Iron Destiny” was built in 1981 and modernized by installation of the 4 crane pedestals with a similar design. The necessary modifications of upgrading the Transloader structure (near the pedestals) were analyzed with the finite element method. Two different load cases for linear stress levels and plate buckling checks were considered.
A few existing conveyor constructions have been investigated due to significant deformation of some structural parts, particularly "cheek" plates.
Static load distribution taken into account by the assumption of longitudinal direction mass of cargo gives 560 kg/m.
The new designed strengthened crane pedestal is located on the Upper Deck. The strong set of the pedestal continued strongly under the deck. The model structure was modeled and tested in accordance with the requirements of the Russian Marine Register (RMRS).
Liebherr crane SBG 350 should be installed on the foremost crane pedestal supporting structure which was considered for the analyses.
There are two load cases were considered:
1) when the boom of the crane is maximum outreached to the port side;
2) when the boom is directed along the longitudinal plane of the ship.
And the crane carries maximum allowable weight.
The finite element model is built up using plate elements for panels, stiffeners, and columns. The general element size of the coarse plate element is 150x150 mm, with local refinements where needed. The total number of elements used for modeling pedestal’s structure is approximately 158000. The lightweight is about 552 metric tons.
After analyses of 2 basic load cases of the original design, there are no areas were marked as critical, where stresses exceeded critical stress (184,6 MPa for the crane pedestal, 220,5 MPa for the hull) or the buckling checks reached levels above a critical value.