DESIGN OF BUILT-UP MEMBERS WITH ANGLES

Built-up steel members are frequently used for civil and industrial structures, owing to the high ratio between the load carrying capacity and the self-weight. Important applications are for cranes, from the tower and port cranes to the derricks for mining applications, that are the core of the present paper. The built-up components are usually realized by using single angles, with secondary (panel) elements directly welded to the chords. Design is usually carried out by using commercial finite element analysis packages offering only the traditional beam formulations developed for bi-symmetric crosssection members. The important effects associated with the buckling interaction between axial force and bending moments as well as the effects of the warping torsion are hence currently neglected in routine design, also because not included in the verification check equations proposed by standard codes. The paper deals with derrick cranes, despite the proposed outcomes can be also directly extended to other structures having built-up elements realized with angles. In particular, reference is made to 2 derricks differing for the panel geometry, each of them analyzed in 6 configurations accordingly to the General Method proposed by Eurocode 3. For each case, the results associated with the traditional design procedure are compared with the ones obtained by fully accounting for the key features of monosymmetric components (i.e. angles) both in the structural analysis as well as in the verification checks.