Nonlinear Stability Analysis Of Lattice Boom Structure Based On Geometric Defects

With the development of society,crawler crane is widely used.As the main load-bearing structure of crane,the boom is a kind of typical slender lattice structure.In order to ensure the safe use of the crane,the boom stability requirements in the design are higher and higher.The initial defects have certain influence on the stability of the structure,and it is inevitable that the excessive defects can reduce the ultimate load of the structure and affect the ultimate bearing capacity.Therefore,the simulation of the boom's defects is very important for the stability calculation of the boom.According to the statistics and arrangement of the initial geometric defects of the boom,the initial geometric defects of the boom can be divided into overall defects and local defects.Taking the boom of 750 t crawler crane as an example,the finite element modeling method of the boom with geometric defects is studied.The overall defect of boom is simulated by equivalent load method.The buckling mode selection order,scale coefficient and defect amplitude of the uniform defect mode method are redefined,and various possible local defects are simulated with the combination of buckling modes.Therefore,the finite element model of the boom with overall and local defects is built.Then,the calculation of dual nonlinear stability is carried out based the FEM of boom.Compared the limit loads of different FEM models with various defect forms,the FEM model with the most unfavorable defect form is found,which provides reference for the nonlinear stability calculation of the boom with geometric defects.By comparing the load displacement curve of the ideal boom model with that of the overall defect model and the displacement stress nephogram of the relevant time,the influence of the overall defect on the stability of the boom is analyzed.Then,taking the 91 m boom model as the research object,the limit loads of the ideal model and the most unfavorable defect model are calculated and the load displacement curves of the two models are drawn.The influence of the most unfavorable defects on the stability of the boom is analyzed by comparing the limit loads,load displacement curves and the displacement stress nephogram at the relevant time of the two models.Finally,the limit loads of the ideal boom model and the most unfavorable defect boom model with different elevation angles of the same boom length are calculated,and the influence of the most unfavorable defect on the stability of the boom is analyzed by comparing the limit loads of the two models at different elevation angles.