The Nonlinear Deformation Analysis Of Crane Combined Boom System Outside The Luffing Plane

With the construction scale of contemporary engineering projects getting higher and higher,the crane with only one boom can no longer meet the needs of construction tasks.Cranes with a combined boom system are very popular and gradually occupy the market.The increase of the number of arm frames makes the length-slender-ratio of the whole system larger and larger,and the design and application of lattice section makes the arm frame more and more soft,which brings the trouble of the nonlinear analysis of arm frame to the designers.Especially,the second-order effect of small displacement becomes more and more significant when the combined boom is subjected to the transverse and longitudinal loads at the same time.Therefore,how to accurately solve the nonlinear deformation problem of the combined boom system of the large flexibility crane outside the variable amplitude plane is a major research direction in the field of construction machinery.The previous analysis of the nonlinear theoretical problem of crane boom system mostly stays at the level of ideal linear theory,and the nonlinear theoretical analysis is often carried out only on a single boom,and the nonlinear problem of the whole system of the combined boom is rarely explored.This will leave a certain error for the subsequent design and manufacture of the crane combined boom system,and even more potential risks for the future actual construction work.The finite element method is often used in the analysis and calculation of lattice truss arm system.The modeling process is tedious and the final result is a numerical solution with errors.In order to solve this kind of difficult problem,the aim of this paper is to find a method which can solve the nonlinear problem of the combined boom system more quickly and accurately.First of all,in order to make a better nonlinear analysis of the lattice composite boom,the complex composite truss boom is simplified to the composite solid web boom model by using the equivalent method of moment of inertia section.This method does not change the overall size of the arm,which makes a good foundation for the efficient introduction of second-order effect.At the same time,the differential equation of flexural line used in solving the nonlinear deformation problem of composite arm is derived in detail.In the study of out of plane nonlinear deformation of composite boom system,the simplified composite beam column is taken as the research object.Firstly,the special case of composite stepped columns with variable cross-section is selected.When it is subjected to the load in and out of the variable amplitude plane,the second-order effect is taken into account to establish the second-order deflection curve differential equation,and the analytical solution of the non-linear lateral displacement outside the plane of each column end is obtained by substituting the boundary condition and the connection relationship solution,and the non-linear strength analysis is carried out.ANSYS software is used to verify that the derivation process and results are correct.Compared with the simplified method of solving the nonlinear deformation of composite structure with equivalent load moving down which is commonly used in engineering,it shows that the method adopted in this paper is more accurate.In addition,the nonlinear deformation and strength of the composite beam outside the variable amplitude plane without torsion are analyzed.The out of plane nonlinear deformation of the simplified model of composite boom is calculated considering the coupling of bending and torsion.The second-order differential equation of deflection curve of each beam column is established and solved.The more accurate expression of out of plane nonlinear lateral displacement at the end of each beam column is obtained.The correctness of the derivation is verified by ANSYS software.The influence of torsion on out of plane nonlinear deformation is explored.The calculated expression of lateral displacement of composite beam considering the coupling of bending and torsion is degenerated,and the nonlinear deformation of different structures is obtained.Based on the principle of equal stability before and after simplification,the boom part of tower crane with complex structure is simplified as inclined beam column structure.The feasibility of the simplified method is verified by ANSYS software.Finally,when the internal parameters,such as height,width and elevation,are changed,the influence of nonlinear deformation outside the luffing plane of the combined boom is analyzed.