Dynamic analysis of tower cranes

Tower cranes are widely used in the construction of high-rise buildings and the analysis of their dynamic behaviors is of both theoretical and practical significance. A parameterized super element formulation for modeling the multiple-pulley cables in a crane system is proposed based on the friction-free assumption between the cable and pulleys. The cable passages over intermediate pulleys are considered as new degrees-of-freedom in the proposed element model and equal tensions at different segments of a continuous cable are exactly achieved. Numerical results show that these cable passages have significant effect on both static tensions and dynamic properties of tower cranes and the proposed super element model provides more accurate and realistic results in dynamic analyses of the crane system. It is found that some modes are insensitive to the change of jib angle or bracings at crane mast, while others change drastically depending on the mode shapes. Picking up the payload from ground or payload accelerating/decelerating during lift operation will induce finite impulsive excitations and, therefore causes noticeable dynamic responses of the crane system.