The Research On The Influence Of The Cable With Bending Stiffness On The Cable-strut Structure In The Tow-lifting Phase

Cable-strut tensile structure is composed of cables and struts.It has the advantages of large span,light weight and rapid construction speed.And it is one of the development trends of large-span spatial structures in China.The cable is generally considered as flexible member with only tensile loads and no flexural loads when the cable-strut tensile structure is being designed and analyzed.In fact,the cable has a certain bending stiffness because it is made of steel wire.For the forming state of cable-strut tensile structure,there is little effect on the results when the cable is considered as flexible member because of the application of prestressing force.However,in the initial phase of tow-lifting,the hypothesis will have a certain impact on the results.The present calculation methods of cable-strut tensile structure do not take into account the bending stiffness and the initial bending of the cable.In order to analyze the structural motion and overall geometric stability during the construction process accurately,it is necessary to consider the bending stiffness and the initial bending of the cable.This paper introduces the wire rope,parallel wire bundle,spiral strand,steel rod and power cord detailedly according to the classification of cable.At the same time,it summarizes the research status of the bending stiffness and the initial bending of the cable and the construction methods of cable-strut tensile structure in the world.On this basis,the basic theory of mechanics of the cable is reviewed.And the theory of form-finding analysis for static equilibrium state of cable-strut structure based on the nonlinear dynamic finite element method is introduced in detail.The cable model is established to study the bending stiffness of the cable under tensionless condition by the finite element software ANSYS.The results show that for the parallel wire bundle without the twist angle,in the pure bending state,its deformation conforms to the plane-section assumption after limiting the deformation of its end section.Therefore,its bending stiffness is basically a fixed value.For the cable with the twist angle,the bending stiffness decreases with the increase of length L.And the change of the bending stiffness is not obvious when L>λ,and the bending stiffness is basically stable when L≥2λ.At the same time,the bending stiffness of the cable increases with the increase of lay length.In the last,the bending stiffness of the cable increases with the increase of the friction coefficient between the wires in the cable.And the increase is not obvious when the friction coefficient reaches a certain value.Then,for the open beam and closed beam in pure bending state,this paper proposes the method of establishing the initial bending strain and the method of line-expanding analysis of open beam and cicle-expanding analysis of closed beam.The program is compiled with the parameterized language of APDL based on the ANSYS platform.And the program has been fixed and proved to be correct by some examples.The program can be applied in the cable-strut tensile structure.And it is the foundation for the follow-up accurate studies.On the basis of the above research,this paper combined with the engineering example,the cable dome of WUXI Science and Technology Exchange Center,to compare the conventional analysis method with the study in this paper.The results show that,in the initial phase of tow-lifting,the ability of resistance to deformation of structures is enhanced when the bending stiffness and the initial bending are considered.And the new study is closer to the actual situation because some cables have the out-of-plane displacement.And the influence on the cable with small length and low stress is greater than the cable with large length ang high stress.With the application of prestressing force,the disparity is significantly reduced.And there is no difference in the forming state.And the overall geometric stability of the structures is better when the bending stiffness and the initial bending are considered.Therefore,the analysis of the structural motion and overall geometric stability is more accurate when the bending stiffness and the initial bending are considered.And the new study is proved to be correct because the results is the same with the traditional methods when the prestressing force is full applied.At the end of this paper,the main research contents and research results are summarized systematically,and some problems and further research directions are put forward.