| With the railway bridge and highway bridge continuously developing toward the large-scale and long-span direction, large tower cranes have attracted increasingly widespread attentions as the effective construction equipments. However, there are many theoretical and practical problems in the structural design of the tower cranes, they need to be further studied and solved. Under the support of the national "twelfth five-year" science and technology support project(Grant No. 2011BAJ02B01-02), we have studied the structural stability problem, the structural limit bearing capacity of geometric nonlinearity problem, vibration isolation problem and moving load problem in the statically indeterminate structure of bar system of the tower crane. The aim of this work is to provide theoretical bases and useful references for the structural design of the tower crane so that we can improve the precision of the structural calculation and eliminate the potential safety hazard most in the design stage.Taking the statically indeterminate horizontal jib with double lifting points of the tower crane as the object of the research, we have studied the overall stability of the jib under non-conservative forces in the rotary plane. According to the force method, we derived the general analytic expression for the jib-tie forces considering the axial eccentricity. Based on the second order theory and the method of the differential equation, we derived the buckling characteristic equation of the jib under non-conservative forces in the rotary plane. Then, we verify the correctness and validity of this method through a simulation based on the nonlinear finite element method. The result obtained provides theoretical supports for the internal force calculation of the jib ties and the overall stability analysis under non-conservative forces in the rotary plane of the jib, and it is adopted by the newly revised national standard GB/T 13752-2016 Design Rules for Tower Cranes.With the attachment of the tower crane as the research object, we have studied the calculation method of the internal force and the influence of the member buckling on the bearing capacity of the whole structure. Based on the second order theory and the stiffness distribution method, the analytical expression of the reaction force for the elastic attachment is derived. By applying the method of the equilibrium equation, we derived the exact expression for the three-bar type attachment and the four-bar type attachment with a buckling member. According to calculation examples using the finite element method, the correctness and validity of this method is verified. We studied the inflence of the member buckling on the bearing capacity of the statically indeterminate attachment. The potential bearing capacity of the statically indeterminate attachment after member buckling is qualitatively analyzed, and the change of the structural stiffness before and after member buckling is also analyzed. The relevant research results about the attachment provide the theory basis for the further structural dynamic/static design and analysis.With the bar system of the tower structure as the research object, we have studied the analysis method of the limit bearing capacity considering the geometric nonlinearity and the member buckling. First of all, the mechanical behavior of the elastic buckling bar considering the large deformation of the geometrical nonlinearity is discussed. We propose the concept of the two-state elastic bar and establish the corresponding element. Then, in order to consider the influence of the member buckling, we modified the classic cylindrical arc-length method. According to the equilibrium path calculation results of the typical model in the literature, the correctness of the method in this paper is proved. Finally, the method was applied to the limit bearing capacity analysis of the tower bar system, the influence of the arrangements of web members on the tower bearing capacity is analyzed. To different type towers, we give the recommendation for the suitable arrangements of web members, the result provides a theoretical basis for the choice of the arrangements of web members.With the space frame structure of tower crane as the research object, the dynamic property of the periodic structure has been studied. Based on the theory of discrete Fourier transform, the Nyquist theorem and the variational method, we deduced the precise dynamic stiffness matrix of rod, beam, shaft and space beam-column element in the frequency domain. Then, the method was applied to the frequency response calculation of the space periodic frame structure. Compared with the traditional finite element method, the method in this work has the advantages of the lower system degree of freedom, the shorter calculation time and the high calculation precision. According to the analysis of the frequency response curve, we found that the overall vibration isolation performance of the structure is better when the geometric size of the substructure is larger, the material composition is more diverse, the property of the material is more different and the load is more uniform. The results in this work provide the beneficial reference for the vibration isolation design of the structural members in tower crane.Taking the horizontal jib with double lifting points of the tower crane as the object of the research, we have studied the moving load problem in the structure. Based on the Laplace transform theory and the variational method, the dynamic stiffness matrix of the rod element, the beam element and the plane beam-column element is derived in the Laplace domain. Based on the static Green’s function, the improved function for the moving load problem was deduced. According to the comparison with the analytical solution of the moving load problem in the simply supported beam, the correctness of the method in this paper is proved. Then, the method is applied to the moving load problem in the horizontal jib with double lifting points of the tower crane. Compared with the traditional finite element method, the calculation cost of the method in this paper is lower, the precision is higher, the commonality is stronger. the method in this work is particularly suited to solve the moving load problem of the statically indeterminate structure. The work in this paper provides a highly efficient new method for the solution of the moving load problem in the tower crane. |
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