Abstract: A majority of lifting machineries contain the mechanisms for positioning heavy weights. These additional mechanisms constrain the locations of boom structures after deformation under loads, which can be considered as generalized applied forces related to structure and mechanism displacements. Boom structures are divided into several substructures along the longitudinal direction, and internal displacements of each substructure are reduced to the displacements of its left and right ends. Based on the Co-rotational method, an embedded coordinate system is defined, and a set of generalized nodal internal forces for substructure elements are formulated. Taking main and sub-boom structures of crawler cranes for an example and considering that the boom structures are constrained and controlled by derricking mechanisms, the additional nodal external forces and their derivatives on the substructure element nodes are obtained. At last, a numerical example of sub-boom working conditions for a kind of crawler crane is presented, in which the displacements of boom structures and mechanisms under different load conditions are obtained. The numerical example proves the validity and rationality of the analytical procedure.