Research into the dynamic behaviour of structures is present in mechanical and civil engineering. Structures of various purposes are exposed to variable influences. These influences can be common [1], which are variable only in time, and influences of moving loads, which are variable in time and space [2] and [3]. The action of these influences on structures is reflected in the occurrence of dynamic displacements, velocities, and accelerations of the structure. In mechanical engineering, this problem is present, above all, in the field of crane engineering. One of the representatives of crane machines, which are the subject of this paper, is the portal-rotating crane. These are crane machines with a boom that is connected to the portal and that has the possibility of a 360° rotation. These cranes are interesting for dynamic analysis due to their high carrying capacities and the fact that they have a small base in proportion to their height. In portal-rotating cranes, there are influences that are variable in time. Load swing contributes significantly to the dynamic loading of cranes. The importance of the problem of load swing is considered and confirmed in papers [1] and [4]. Furthermore, the importance of this problem is defined in standards [5]. The first papers considered planar dynamic models, and later papers published specifically in

This thesis refers to an access during forming of dynamic model of a boom of portal crane. The first step defines the incentive of portal crane. In the second step simplified spatial dynamic model of a boom of portal crane has been formed and worked out. In other words, the laws of spatial oscillating of the cargo caused by the previously defined incentive have been determined. Final step defines dynamic load on the dynamic model formed.

U ovom radu je opisana uporedna modalna analiza sa FEM pristupom dva portala tipa ″H″ i ″X″ portalnih dizalica. Ova dva tipa portala imaju iste glavne geometrijske mere. Razlikuju se samo na srednjem nivou u horizontalnoj ravni. Prvi portal na srednjem nivou ima ram tipa ″H″, dok drugi portal na srednjem nivou ima ram tipa ″X″. U radu su upoređeni odgovarajući modalni parametri dva tipa portala, koji su dobijeni tokom modalne analize. Data je prva ocena koji od dva razmatrana tipa noseće konstrukcije ima povoljniju dinamičku stabilnost protiv prevrtanja.

Fakultet za mašinstvo i građevinarstvo, Univerzitet u Kragujevcu, Kraljevo (Srbija) U mašinskom inženjerstvu relativno je čest slučaj da izvedena rešenja konstrukcija nisu i optimalna. Dinamička analiza nosećih konstrukcija dizaličnih mašina je vrlo bitna za unapređenje tehničkih karakteristika dizalica. U dinamičkoj analizi frekventna analiza predstavlja prvu fazu u proceni dinamičke stabilnosti. U tom smislu, u ovom radu je razmatran problem slobodnih oscilacija noseće konstrukcije portalnih dizalica.

Introduction/purpose: The aim of this paper is to analyse the numerical methods for solving differential equations of dynamic equilibrium in technical problems. Methods: The paper gives an overview of the following numerical methods: the method of central difference, the method of linear acceleration, the Newmark method, and the Wilson th method. Results: Various problems in applying numerical methods in dynamics of structures have been solved. Conclusion: It has been shown that the application of numerical methods has a fundamental importance in dynamics of structures.