Challenging and dangerous material-handling applications in construction have motivated the study of the dynamics and control of tower cranes. Manipulating tower cranes is difficult while moving large-size payloads because of the inevitable payload swing and twisting about the cables. Although significant work has been directed at reducing the swing of point-mass loads, much less effort has been directed at limiting the payload twisting. A nonlinear dynamic model of tower cranes carrying distributed-mass beams is described. Furthermore, an open-loop control method is proposed to reduce both the swing and twisting of the payloads during slewing motions. Simulations and experiments demonstrate the theoretical dynamic behavior of the model and validate the effectiveness of the proposed control method.