Strength And Stability Analysis Of Typical Box Structure Of The BMU

The application of large area curtain wall in high-rise building has resulted in the BMU becoming the necessary equipment of high-rise building.Due to the late development of high-rise and super high-rise buildings in our country,the design and manufacture ability of the BMU in China has not been paid enough attention.There are a lot of unreasonable structure design in many building maintenance equipments that have been put into use.The design style is single,the material wastes seriously,the critical stress position is not paid enough attention,which cause safety accidents occur.In recent years,the development of China’s crane equipment is rapid and box type structure is used largely in crane equipment.The structural strength is large,the stress distribution is reasonable,the weight is light and it has the characteristics of bending and torsion resistance.But because the window box structure design lacks followed general theory and method of design,which lead to the existence of a large number of unreasonable structural design and large redundant weight and result in very large waste materials.This thesis is based on the purpose,through the statics analysis,dynamics analysis,structural simulation and combining with the theory of equal strength,a comprehensive study of the box structure of the main components about the performance of the design issues in the BMU is conducted.In order to check the safety of the BMU box structure in the strength and stability and provide guidance for the structure design of the BMU,This thesis studies the box structure in general condition and the special condition of slope transformation in the BMU.The following works are conducted.(1)Through the analysis of the working mode of the BMU,the function and main parameters of the box type structure in the main parts of the BMU system were classified.The research theory and method of stability and strength were collected and the utilization of virtual prototyping technology in stability and strength field was introduced.(2)The static analysis of box jib in the two general BMU condition was conducted with direct calculation method and finite element method and two analysis results based on the different methods were obtained.The impact of force to the box jib used in BUM was studied deeply.The most dangerous condition was selected based on the analysis of several special working conditions of gondola.The dynamic differential equations were established and dynamic load time-varying carve was plotted with MATLAB software.Considering time-varying dynamic load,the transient dynamics analysis of jib was conducted by finite element software and maximum stress was obtained under the most dangerous working condition.The inherent characteristics of box structure was combined with the force characteristics of BMU and under the condition of the same cross-sectional area,through the equal strength design theory was adopted,the regularity of box section parameters with the variation of the span was studied.(3)Based on the load analysis of column box structure,the differential equation of flexure deformation was established.The relation between the load on the column and flexure deformation was derived with Euler pressure bar theory.Torsional stress equation of column was established.Based on the Umanskii theory of the closed thin wall box,the result of transverse critical load were obtained.The buckling analysis of the column was investigated by the finite element method.According to the actual working conditions,torsional critical load factor、moment critical load factor、axial critical load factor、critical load factor under comprehensive force and buckling deformation distribution in different stress conditions were obtained.(4)This thesis made a further study on the strength and stability of the box structure in the special working condition of the slope exchanging.Based on the dynamic analysis software ADMAS,the dynamic process of the ramp climbing orbital BMU is simulated.The simulation result of the maximum stress in the box jib was extracted in order to check its strength.The maximum displacement of the front end and the center of mass in box jib were extracted in order to check overturning resistance of the whole machine.Based on the maximum cylinder thrust load and the actual working condition,the dynamics problem was transformed into a static problem.Cylinder thrust was loaded into the ANSYS finite element model.Then the linear buckling analysis of the underframe was conducted by ANSYS WORKBENCH software and the critical load factors of the first four order buckling modes and the buckling deformation distribution were obtained.In this paper,the strength and stability of the box structure are analyzed under the general BMU stress condition and under the special stress condition of the ramp climbing orbital BMU.On one hand checking methods of the strength and stability was provided to the BMU structure,on the other hand guidance was provided to the BMU box structure design before producing.