Research And Analysis On Dynamic Characteristic Of Flat-top Tower Crane

Flat-top tower cranes are mainly used in construction industry and are important equipment for hoisting and transporting cargoes.In the working process of the flat-top tower crane,the frequent starting and braking of mechanism cause vibration of the structures and swing of the cargoes.The alternating load caused by the structure vibration and the cargo swing easily lead to fatigue damage of the structure and reduced the service life of the cranes.Therefore,studying mechanism of the structure vibration and the cargo swing have important theoretical significance and engineering application value for improving the working efficiency,safety and reliability of the flat-top tower cranes.In this paper,we set up models of the vibration system based on the elementary beam bending vibration theory and the Lagrange motion equation for the flat-top tower crane and carried out simulation and experiment.The main study are as follows:(1)According to the structure characteristics of the flat-top tower crane,the lattice jib structure was equivalent to the solid structure by the equivalent inertia moment method.And equivalent inertia moment of the three-limb lattice structure was calculated by using of the equivalent slenderness ratio formula.(2)For the case of no cargo swing,the characteristics of mechanism motion were studied under the condition of lifting,translation and rotating.The vibration differential equations of cargo-jib coupled vibration system,under the condition of lifting,translation and rotating,were deduced by the elementary beam bending vibration theory and the Lagrange motion equation.Effect laws of the dynamic parameters,such as motion acceleration of each mechanism,the cargo mass and distance between the trolley and rotary center of the jib,on the jib vibration were simulated and analyzed.The simulation results show that vibration amplitude and period of the jib increase with increasing of the cargo mass and the distance between the trolley and the jib rotary center under the condition of lifting,translation androtating.The amplitude of the jib vibration also increases as the mechanism motion acceleration increases.(3)For the case of cargo swing,the characteristics of mechanism motion and cargo swing under the condition of translation and rotating were studied.The vibration differential equations of cargo-trolley-jib coupled vibration system under the condition of translation and rotating were deduced by using of Lagrange motion equation.Effect laws of the motions acceleration of each mechanism,the cargo mass,the distance between the trolley and the jib rotary center and the lifting rope length on the jib vibration and the cargo swing were simulated and analyzed.The simulation results show that the amplitude and the period of the jib vibration and the maximum angle of the cargo swing increase as the mechanism motion acceleration increases,the amplitude and period of the jib vibration increase with increase of the cargo mass and the distance between the trolley and the jib rotary center,the cargo swing period decreases as lifting rope length increases.(4)The test system for measuring mechanism motion,structure vibration and cargo swing was set up on the QTZ5613 flat-top tower crane.The measurement plans of mechanism motion,structure vibration and cargo swing were developed for the crane.The test error source and the simulation error source were analyzed by comparing the test data with the simulation data,which verified correctness of theoretical deduction and simulation results.The experimental research also provided experimental data for further study of the coupled mechanism between the whole structural vibration and the cargo swing for flat-top tower cranes.