Research on Automatic Layout and Optimization of Reinforced Crossed Cable Nets in Inflatable Membrane Structures

As a typical flexible structure， inflatable membranes require cable net reinforcement to ensure the stiffness and stability of the structure. However， in the design process of cable net reinforced membrane structures， the stiffening cable nets and membrane surface are usually simplified as direct connections， ignoring the problem of tight adhesion between cables and membranes. This simplified approach brings certain hidden dangers to the design safety of membrane structures. Studying the generation and optimization methods of inflatable membrane cable nets is crucial for solving the problem of cable slip and improving the stiffness and bearing capacity of membrane structures. Therefore， this paper proposes a cable segment generation method based on thermal stress finite element and an automatic cable net layout optimization method. The cable segment generation method utilizes the thermal stress finite element method to generate geodesic lines on the membrane surface. The cable segments arranged along the geodesic lines can fit more tightly with the membrane surface， thereby solving the cable-membrane slip problem and ensuring the safety and reliability of the structure. On the basis of the cable segment generation method， the membrane surface cable nets are arranged in an oblique form for load analysis of membrane structure cases. Two optimization layout methods， namely local cable net optimization layout and uniform layout， are proposed to address issues such as the need to adjust local spacing and uneven overall force distribution of the cable nets. Taking the rectangular plane long-span inflatable membrane structure as an example， the cable net layout and optimization methods were elaborated in detail， and different optimization schemes were compared.1） A stress performance analysis was conducted on the inflatable membrane structure （Scheme I） obtained by using the cable mesh arrangement method and the traditional cable net membrane structure， including the axial force distribution of the cable nets and the stress distribution on the membrane surface of both. 2） For Scheme I， local cable net optimization and a uniform layout were used to obtain Schemes Ⅱ and Ⅲ， and the differences and advantages in stress performance between the two schemes and Scheme I were analyzed. 3） Based on the advantages of two optimization layout methods， a combined optimization scheme featuring sparse intermediate cable nets and densely arranged edge cable nets was proposed on the basis of Schemes Ⅱ and Ⅲ to obtain Scheme Ⅳ. The various force indicators of the cable nets and membrane surfaces of the four schemes were statistically analyzed.
The research results indicated that：1） the maximum axial forces of the two cable nets were concentrated at the diagonal position of the cable nets， and the axial force of the cable segment in the traditional diagonal cable net was much greater than that in Scheme I， indicating that the proposed cable net layout method has made certain optimization and improvement compared to the traditional method； 2） the local optimization layout method effectively improved the situation of excessive local stress on the cable net， but its effects on the membrane surface stress and deformation were not significant； the uniform arrangement method improved the overall stress situation of the cable net， but it would increase the stress on local cable segments and membrane surfaces， and the effects on the membrane surface deformation were not significant； 3） the new optimized layout scheme simultaneously achieved the dual objectives of reducing the amount of steel used in the cable net and improving its stress situation， proving the feasibility of this optimization scheme.