Research On The Sudden Unloading Impact Coefficient Of The Horizontal Jib Tower Crane

Tower cranes which is a tall, heavy-duty large engineering machinery has been widely used in various industries, especially the construction industry. With the extensive application and increased demand for new engineering technologies and new materials in the field of mechanical engineering, tower crane structure toward largescale, high-speed and lightweight direction, a sharp increase in the use of tower cranes in the impact on the process, for the dynamic characteristics of tower cranes and study design of dynamic load factor and more attention, suddenly unloading the tower crane is more common structure for carrying one of the most serious conditions, the impact of the tower crane unloading of research has been sudden industry researchers crane direction of interest, great significance and value of the works. This article focuses on the dynamics of a horizontal jib tower crane unloading conditions by establishing reasonable suddenly unload dynamic model, carried out the research with different characteristics unloading condition tower structural dynamics, for the revision of the "Tower crane design Specification " sudden unloading impact factor and the practical application of how to reasonably consider unloading impact provide a theoretical basis.Firstly,this thesis made a dynamic model of the tower crane unloading conditions, according to the structure and operation characteristics of the tower crane, selecting appropriate generalized coordinates, to establish an appropriate scale kinetic equations. Based on the general dynamics equations, the equations of motion of the tower, the tower cap, boom, arm balance, rod and other components, and finally adopted the multi-body system dynamics, consider the constraint relationship between the various parts of the establishment with five free the entire tower crane system equations degrees.Secondly, this thesis made the ANSYS model of QT15 and QT810 type tower crane. Respectively ANSYS model and the proposed model was static analysis and dynamic analysis and comparison of the simulation results of the two methods proved correct model results presented herein, high computational efficiency; application of ANSYS model and the proposed model transient analysis, show that uninstall impact coefficient and amplitude, unloading conclusions have a relationship of quality, balance block quality, which is actually consistent with the project, but also further validate the results obtained by this method than the traditional method of using a single load factor formula is more realistic. Improved specification will suddenly unload coefficient provides a theoretical basis.Finally,the existing laboratory QT15 tower crane unloaded suddenly experimental study carried out conditions under main different amplitudes, tower cranes tower sudden changes in stress unloading conditions and experimental results, this paper compared the results of the thesis,ANSYS and " Specification" further evidence that this method better reflect the crane suddenly unloaded real shock situation.This paper systematically studied the most commonly used horizontal jib tower crane unloading conditions in sudden transient impulse response problem by establishing a rational dynamic model, obtained tower crane unloading conditions vibration, and then get a tower vibration stress when; and the use of finite element software ANSYS simulation results and the actual results of the tower proposed method was validated. The conclusion will provide a more accurate theoretical guidance tower crane design, and provide a theoretical basis for the revision of the tower crane design specifications.