STRUCTURAL ANALYSIS OF BUILT-UP MEMBERS WITH ANGLES

Built-up steel members are frequently used in lifting equipment structures, such as tower cranes, gantry cranes, mobile cranes jibs and so on. Mining stiffleg derricks are the subject of the present paper. Derricks design is usually carried out using commercial finite element analysis packages (FEAP): these packages often offer only beam formulations developed for bi-symmetric cross-section members. So, important effects associated with buckling interaction between axial force and bending moments, as well as with the presence of warping torsion, are currently neglected in analysis design. These interactions are not yet included in standard provisions. The paper is focused on built-up members for stiffleg derricks made by angles, focusing on the analysis phase. Key features of single angles are presented, stressing out the importance of capturing the buckling loads for compression, bending and compression plus bending. An applicative part is also proposed: two stiffleg derricks, differing only in panel geometry, have been studied, considering each in six geometrical configurations. Structural analyses have been carried out by using two FEAPs differing for the degree of refinement of the implemented beam formulations. Research outcomes highlight the important influence of effects that are currently neglected in routine design.