Studies On Stiffness Optimization Theory And Pretensioning Technology Of Long-Span Cable-Net Structures

Cable-net structure is a typical cable structure and is widely used in large-span roof structures for landmark buildings.In this paper,based on an engineering project of a large-span cable-net roof structure,studies on stiffness optimization theory and pretensioning technology of this type of structure are carried out.The main work and conclusions are as follows:(1)The analytical expressions of the elastic stiffness and geometric stiffness matrix of the cable-net structure were derived.The approximate incremental relationship between the axial stiffness and force density of the element and the structural displacement were also derived with constant external loads,and the analytical expressions of the sensitivity matrix were given.(2)For the constraint condition of multi-point displacements of cable-net under constant loads,a numerical strategy for optimizing structural stiffness was put forward by means of the eigenspace of sensitivity matrix.was adopted as an illustrative example.Using this method,structural stiffness of a saddle-shaped cable net with trapezoidal plane was optimized to satisfy the limit of the pre-set displacement field under a given load,which verified the effectiveness of the stiffness optimization method.(3)The stiffness optimization method proposed in this paper was used to optimize the stiffness of the cable-net roof structure project.The calculation results showed that the pre-tension level of the structure could be greatly reduced by increasing the sectional area of some members while maintaining the original stiffness of the structure,thereby significantly reducing the burden on the surrounding support structure.This method provides a new idea for the stiffness design of cable-net structure.(4)Using the idea of inverse analysis,the internal force and deformation characteristics of this long-span cable-net roof structure during the pretensioning process were analyzed.It was pointed out that the large deformation of the truss would cause some of the curtain wall cables' axial force to exceed the initial design tension value,while the other part of curtain wall cables would appear slack.Therefore,it was necessary to carry out grading and batch pretensioning of the cable-net roof structure.(5)In order to meet the requirements of strength and overall stability during the pretensioning process,a set of construction schemes for pretensioning the curtain wall cables,roof stability cables and roof load cables was proposed.The safety and effectiveness of the construction scheme were verified by numerical simulation.