Effect of Suspended Mass on Modal Vibration of a Port Crane Modeled by Shell Elements

This paper aims at the modal analysis of a particulartype of port crane, regarding the effect of a hangingcontainer on the modes of vibration. The study of bothlocal and global natural modes is enabled by using shellfinite elements to model the crane in detail. Thecontainer and the cables are modelled by using solid andtruss elements respectively. The local mode shapes aredistinguished from global ones where only a part or fewparts of the structure are deformed in a mode shape. Thecrane structure is analyzed without and with thesuspended mass. For the crane with the suspended mass,seven positions on the crane boom are considered. Theresults of modelling show that the mode shapes for themodels without and with hanging mass are verydifferent so that the frequencies of the same modenumbers are not comparable. However the modenumbers that have similar mode shapes are found andtheir corresponding frequencies are compared. For thecrane without the suspended mass, the first ۲۰ to ۲۴vibration modes correspond to the local vibration of theflange beams. This means that the natural frequenciesfor the local vibration of the flange beam are lower thanthat for the global structure. The last global mode isobserved at the ۱۱۸th mode shape, from this mode afteronly local modes are seen concerning the deformationof cross contact beams, flange beams as well as braces.

کلیدواژه ها:

Port crane ، Modal analysis ، Shell element ، Moving suspended mass ، Finite element method