| Since the beginning of the new century,our country’s economic development has become more and more rapid.Meanwhile our country’s national infrastructure market is getting bigger and bigger,and the demand for crawler cranes in national infrastructure is increasing.Due to the fierce competition between domestic and foreign brands on a global scale,especially the design and manufacturing technology of large crawler cranes are concentrated in a few large enterprises,which also makes crawler cranes become the focus of attention of scholars.However,the existing theory holds that the stiffness of the web member is smaller than that of the chord member,and the restraining effect of the web member on the chord member is not strong at the node where the chord member and web member intersect.In order to simplify the calculation,it is generally considered that the node is approximately equal to the hinge point.The calculated length is equal to the geometric length between the nodes of the chord member.In the actual production situation,the chord member and the web member of the truss boom are generally connected by welding.The welded connection is a rigid connection,which makes the web member generate a force that resists the bending of the chord member when the jib is loaded.The flexural deformation of the rod has a certain limiting effect,not just the role of connecting the chord member,so that the structural performance cannot be fully exerted.Therefore,on the basis of previous research,this paper establishes the theoretical calculation model of the top section of the cross-type and point-to-point variable-section lattice boom by Timoshenko’s elastic stability theory,analyzes the force at each point,and establishes the balance equations of each point.Equations are used to establish the stable equilibrium equations of the boom section.And the critical load of the variable-section boom section is re-solved under the consideration of the limitation of the web member on the chord member.The main work of this paper is as follows:(1)According to Timoshenko’s elastic stability theory,the theoretical calculation models of cross-type and point-to-point variable cross-section of the top section of truss boom are established respectively.The force at each point in the mechanical model is analyzed,the bending moment and rotation angle are balanced at each point.Equilibrium stability equations of the models are established respectively.Bring in the actual parameters of the boom section,and using Matlab software to assist the calculation,the theoretical calculation of the critical load of the boom section in the calculation is solved.(2)The finite element model of the top section of the cross-type and point-to-point variable-section truss boom is established by finite element software,and the buckling analysis is carried out.The theoretical calculation and simulation results are compared to verify the correctness of the theory in this paper.(3)The theory of this paper is further verified by changing the parameters of the boom,mainly by changing the inclination angle of the web rod and the size of the chord member to compare and verify,and explore the influence law of different influencing factors on the critical load of the variable-section boom. |
