Cable-net Structure Research Articles

Development and engineering application of fiber bragg grating intelligent cable in large-span hyperbolic parabolic spatial cable network

In order to accurately control the prestress force of cables in long-span cable net structures, a new type of fiber Bragg grating (FBG) intelligent cable was developed. The FBG sensor was directly encapsulated inside the cable, and the sensing performance of the intelligent cable was verified by the cyclic tensile tests. The results show that the sensitivity coefficients of FBG monitoring are basically consistent, and the linearity deviation of the fiber Bragg grating is less than 4.67 %. Based on a real project Shunde Desheng Sports Center, a 114 m long-span saddle-shaped cable net structure model was established using finite element analysis, and the distribution and correlation of internal forces of cables in different tension stages were calculated and compared with the actual monitoring results of intelligent cables. The analysis results indicate that the force changes of intelligent cables is basically consistent with the value of finite element simulation. According to the data of long-term intelligent cable monitoring, the change of cable force caused by the temperature deformation of the steel ring beam is much greater than the influence of the temperature rise and fall of the cable itself on the cable force. Intelligent cables can provide a reference for cable force monitoring of long-span cable net structures.

Analysis of Construction Process and Configuration Automatic Monitoring for the Spoke-Type Single-Layer Cable Net Structure

Analysis of Construction Process and Configuration Automatic Monitoring for the Spoke-Type Single-Layer Cable Net Structure

Automated geometric reconstruction and cable force inference for cable-net structures using 3D point clouds

Laser scanning provides an efficient solution to digital twin construction in civil engineering. The complexity and redundancy of large-scale point clouds substantially prolong the labor-intensive model reconstruction process. This paper presents an automated and high-precision geometric reconstruction approach for cable-net structures with a complete workflow from raw points to the extraction of cable shapes and forces. The strategy involves the extraction of coordinates of key cable regions through the characterization of cable geometry and local registration methods, followed by the computation of cable forces and shapes using segmented catenary theory and nonlinear optimization. The approach is validated with a single-curvature cable-net structure, with the accuracy of cable shapes within ±5 mm and errors in cable forces <5%. The method contributes to health monitoring and rapid reconstruction of cable-net structures. The precise geometry and forces will facilitate the creation of the mechanical models reflecting the physical authenticity of structures.

Pre-tension design and research of cable net structure for space modular deployable antenna

Modular deployable antennas represent an ideal structural form for the development of large-aperture antennas because of their flexibility, adaptability, and high versatility. To enhance the surface accuracy of the antenna after deployment, a comprehensive pre-tension design method that considers truss deformation and tension uniformity is proposed. First, the configuration design of the antenna cable net is constructed, and the mathematical models for cable length under surface accuracy requirements and boundary nodes are established considering catenary effects. Second, the distribution patterns of cable net structure nodes and segments are analyzed, leading to the creation of node coordinate matrices and cable net connection matrices. A basic model for cable net pre-tension design is developed based on the fundamental principles of force density. Furthermore, a multi-objective optimization of cable net pre-tension is performed using a genetic algorithm, considering truss structure deformation and tension uniformity as dual factors. Finally, the developed model is applied to design a single-module cable net structure, and numerical simulation is used for validation. Research results show that the overall surface form error is 0.32 mm, and the maximum tension ratio of cable net on the front cable net surface is 1.54, whereas the maximum tension ratio of tension ties is 2.28, thereby meeting the design requirements. Numerical simulation shows that the maximum deformation of the cable net structure is 0.16 mm, validating the correctness of the model. This research can provide valuable insights and references for the pre-tension design and research of cable net structures in other antennas.

Surface accuracy prediction method for mesh reflector antenna considering uncertainty factors in manufacturing process

The cable-net structure of mesh reflector antenna meets the requirement of surface accuracy by optimizing the shape and tension. However, in the process of manufacturing and assembly, there are inevitable random errors and structure gravity, which lead to the displacement of the nodes in surface, the surface accuracy of the antenna decreases after fabrication eventually. It is challenging to analyze the uncertainty factors and the effects on the surface accuracy. Therefore, this paper analyzes the uncertainty factors of the antenna during fabrication and proposes a method to predict the surface accuracy of the antenna after manufacturing and assembly. Firstly, based on the equilibrium equation of the cable-net structure, the mechanism of node displacement induced by uncertainty factors leading to the reduction of surface accuracy is analyzed. Secondly, based on the structure characteristics and manufacturing conditions of the antenna, the uncertainty factors including cable-net manufacturing and assembly errors, cable-truss assembly errors and gravity are analyzed qualitatively and quantitatively, the distributions of the uncertainty factors are given. Thirdly, based on Monte Carlo method, the mean and interval of the surface accuracy of different dimension parameters are predicted, the empirical prediction formulas of the surface accuracy mean and interval are fitted. Finally, the accuracy and effectiveness of the proposed formulas are verified by several numerical simulations and surface accuracy measurement experiments. The prediction method can effectively guide the design and craft of large-aperture mesh reflector antenna.

Wind-induced responses for cable net structures considering punching rate of reflecting panels

The datum surface of the active reflector of the Five-hundred-meter Aperture Spherical radio Telescope (FAST) is a spherical crown with a radius of 300 m and an aperture of 500 m. The reflector is supported on a cable net structure. Due to its sensitivity to wind loads, it is imperative to investigate its aerodynamic characteristics and wind-induced vibration response. This paper explores the aerodynamic characteristics of the reflecting panel through computational fluid dynamics (CFD). Compared with the nonporous panel, the drag coefficient of the reflecting panel with a punching rate of approximately 50% increases by approximately 51%, and the main reason is that the resistance changes little, but the projected area decreases by 50%. On this basis, the calculation method of the aerodynamic coefficient of the reflecting panel under arbitrary wind direction angle is established. Then, the simulation model of the active reflector system is established, and the wind-induced vibration response is analyzed under different wind speed conditions. The displacement and stress responses of the cable net structure, ring beams, and lattice columns are studied, and the gust response factors (GRFs) are calculated. The results show that the wind load has a very strong effect on the nodal displacement and column bottom stress but has little effect on the stress of the cable net structure; the displacement GRFs of the cable net structure, ring beams, and lattice columns increase with increasing wind speed, of which the simulated results can provide a reference for the design of similar projects.

Design and Analysis of Cable Net Structure for Modular Hexagonal Prism Deployable Antenna

Design and Analysis of Cable Net Structure for Modular Hexagonal Prism Deployable Antenna

The modified force density method for form-finding of cable net structure

Form-finding is crucial for the design of typical cable net structures. Based on the original basic force density method, a modified force density method utilizing the concept of relation matrix is proposed in this paper. The modified method realizes the establishment of a clear correspondence between members and nodes of cable net structures. On the basis of the relation matrix, the find function is introduced, and the calculation formula of the modified branch-node matrix is derived. Meanwhile, the corresponding analysis steps and calculation process are given. The modified method is verified by the analysis of representative structural forms. The results show that for the saddle-shaped orthogonal cable net structure, the outcomes obtained from the modified force density method highly agree with the theoretical values, providing preliminary verification of the method's effectiveness. For single-layer spoke cable net structures, the relative error between the results calculated by the modified force density method and the numerical solution is approximately 5 %. The results of both methods are relatively consistent, and the relative error varies in relation to the ratio of inner ring cable force density to radial cable force density. For circular single-layer crossed cable net structure without inner ring, the results of the modified force density method are very close to the numerical solution. The maximum relative error between the two is 6.95 %, and the accuracy is higher than that of the nonlinear finite element method. The outcome of this research demonstrates the accuracy of the modified force density method and its effective application in the form-finding of actual cable net structures.

Error Influence Simulation of the 500 m Aperture Spherical Radio Telescope Cable-Net Structure Based on Random Combinations

The reflector of a Chinese 500 m aperture spherical radio telescope is supported by a giant cable-net structure. In the actual operation process, active displacement observation is realized by connecting the actuators with the control cables to adjust the cable net, which requires high manufacturing and installation accuracy. In this study, an error sensitivity computing method based on a normal distribution is adopted to perform single-error computing and multi-error coupling computing and to investigate the effect of the length error of all the cables, tensioning force error of active surface cables, and installation error of external nodes on the cable force. The results show that the length error of the surface cables and the installation error of the external nodes are the main factors affecting the cable force, while the length error of the control cables is a secondary factor. The coupling effect of multiple errors is not the linear superposition of each error’s influence; therefore, all the error factors should be comprehensively considered for coupling computing to determine the control index. Through multi-error coupling computing, it is determined that the length error limits of the surface cables and control cables are ±1.5 mm and ±20 mm, respectively, the tensioning force error limit of the active surface cables is ±10%, and the installation error limit of the external nodes is ±50 mm.

Methods and Applications of Safety Control for Cable Net Structure Considering Spatiotemporal Changes

The construction of cable net structures is intricate, and the construction process itself is laborious. Conventional safety control measures during the construction of cable net structures involve monitoring cable forces and deformations at specific moments during the construction steps. However, these measures do not guarantee adequate safety assurance. This paper proposes a method for the safety control of cable net structures, considering spatiotemporal changes, based on the concept of digital twins. This method enables real-time monitoring and control of the cable net construction process onsite, facilitating a comparative analysis between the mechanical and geometric information of the construction site and the real-time finite element simulation results. Such an approach ensures safety control throughout the construction process. Firstly, a twin model framework for safety control is established. Then, the methods for spatiotemporal representation, data collection, and processing at the construction site are analyzed. Finally, the proposed method is validated through its application to the Xiaotian Cultural and Sports Park project. The results demonstrate that this method can achieve real-time monitoring and control of cable net structure construction.

On the Plane Geometry Design Method of the Loop-free Hyperbolic Single-layer Cable Structures

The plane geometry design of the cable-net structure is the basis for the form-finding and structural design. The loop-free single-layer cable-net structure is a new cable-net scheme, but due to its special and complex shape, it is difficult to determine its plane geometry according to architectural requirements. In this paper, the moving support node method is proposed, which can quickly get the plane geometry of a loop-free single-layer cable-net structure. The form-finding is proceeded based on the existing small elastic modulus method. There are two constraints when using the moving support node method. One is that the projection of all cables is straight line, and the other is that the distance between the two cables of each support node and the inner boundary of the target is equal. The aim is to minimize the sum of the distances from all cables to the inner boundary of the target. Using the plane geometry control parameters and the plane coordinates of the support nodes as decision variables, the plane geometry closest to the target inner and outer boundaries is get through optimization analysis. According to the derivation of the formula, the plane projection shape of a loop-free single-layer cable-net structure is mainly related to three parameters, including the number of supports, the difference between the node numbers of the supports at both ends of each cable, and the target curve equations of the inner and outer boundaries. Finally, taking the roof structure of Linyi Olympic Stadium as an instance, the feasibility of the plane geometry design method of the loop-free single-layer cable-net structures based on the moving support node method is verified.

A new source finding and tracking analysis approach for the active reflector of five-hundred-meter aperture spherical telescope

The FAST (Five-hundred-meter Aperture Spherical Telescope) is the world’s largest single-aperture radio telescope. During operation, FAST needs to follow the observed celestial body to adjust displacements, which can be divided into two processes: the source finding and tracking. In this paper, a new numerical method based on Vector Form Intrinsic Finite Element (VFIFE) is proposed to simulate the source finding and tracking process for FAST’s active reflector. The basic principle of static equilibrium and calculation flow of the sourcing and tracking analysis is proposed, and the finite element program is compiled to analyze the displacement process of the reflector cable-net structure. Then, six typical test conditions are selected to simulate the sourcing and tracking displacement process. The obtained final form in the equilibrium state adheres to the target configuration, demonstrating the applicability of the suggested approach and the correctness of calculation findings. In addition, the change in the actuator length and the structural force distribution can be simultaneously derived. These values serve as a vital theoretical foundation for FAST’s practical operation and regulation.

Pretension design of a flexible support cable net structure with high node position precision

Pretension design of a flexible support cable net structure with high node position precision

Shape Adjustment and Experimental Study of a Shape Memory Cable (SMC) Structure.

Large deployable cable net antennas have attracted extensive attention worldwide because of their simple structure and high storage ratio. The cable net structure is affected by long exposure in a harsh space environment during satellite operation, resulting in large thermal deformation and stress relaxation, which leads to a degradation of antenna performance. To address the thermal deformation of the cable net structure, a shape memory cable (SMC) net structure model was proposed with surface accuracy as the research objective. Specifically, we aimed to utilize its phase transition characteristics to adjust the thermal deformation of cable net structure and improve its surface accuracy. A shape memory cable net structure model with a diameter of 2.2 m was built, and a normal temperature experiment and high- and low-temperature experiments were carried out. High- and low-temperature test refers to environmental simulation testing of shape memory cable net structures under high- and low-temperature conditions. This was done to determine whether the adjustment method for surface accuracy meets the requirements. The results showed that the shape memory alloy wire has a relatively stable ability to adjust the surface accuracy of the cable net structure at room temperature. During temperature cycling, the thermal deformation of the shape memory cable net structure is slight, and the surface accuracy is good. Compared with ordinary cable net structures, the shape memory cable net structure has improved surface accuracy by 44.4% and 45.2% at high and low temperatures, respectively. This proved the effectiveness of the method for adjusting surface accuracy. These experimental results offer guiding significance for engineering applications.

Effect of Clamp Deletion on Static Behavior and Dynamic Characteristics of Loop-Free Cable Net Structures

The loop-free single-layer hyperbolic cable net structure (LSHCS) is a new tensile cable structure for buildings, and it can overcome the disadvantages of key elements and the high tension in tensile cable structures with loop cables. The imperfection of the LSHCS is that cable clamps near the inside boundary are redundant. In this paper, the static behavior and dynamic characteristics of thirty-one schemes in five levels of deleting cable clamps are carried out with ANSYS software and Midas/Gen software. The results show that SE1/1, SE2/1, SE3/1, and SE4/1 are the best cable clamp deleting schemes for their respective levels. Displacements are the most sensitive to deleting cable clamps, the natural vibration period comes in second, and tensions are not sensitive with the growth rates of 6.09%, 5.11%, 15.97%, and 19.28% in the best scheme of each level. It is concluded that schemes involving the virtual rings of cable clamps closest to the inside boundary cause the smallest effect on static behavior and dynamic characteristics. Deleting the cable clamps affects the structural stiffness significantly, but the bearing capacity is not seriously affected. It turns out that removing redundant cable clamps in the dense part of the LSHCS is feasible.

A numerical strategy for relieving pretension of cable net structures by exchanging stiffness components

Cable net structures are generally highly tensioned to resist the deformation induced by external loads, while the peripheral structural members are heavily burdened to balance the pretension. A numerical strategy is proposed to relieve the pretension without changing the structural geometry and deformation by exchanging the stiffness components, i.e., the structural elastic stiffness and geometrical stiffness. Based on the eigen-decomposition of the tangent stiffness matrix, the stiffness resistance to the deformation generated by a dominant load is quantified for any direction of eigenvector. The key structural stiffness is therefore defined and characterized by those eigenvalues and their corresponding eigenvectors with significant stiffness resistances. The contributions to the key structural stiffness are evaluated for the structural elastic stiffness and geometrical stiffness, respectively, and whether the decrease in key structural stiffness due to the pretension reduction can be compensated with the elastic stiffness by changing the cross-sectional areas of cables is analyzed. Then, the variations in isolated or closely spaced eigenvalues and their corresponding eigenvectors are estimated based on the first-order perturbation analysis of the tangent stiffness matrix. The underdetermined system of linear equations between the adjustments of the cross-sectional areas of cables and the expected variation in the key structural stiffness is established, and its least squares solution is employed to minimize the rehabilitation cost of the key structural stiffness. The proposed numerical strategy is applied to rehabilitate the key structural stiffness of an illustrative saddle-shaped cable net structure, whose pretension is proportionally decreased to different levels, by adjusting the cross-sectional areas of cables, and its accuracy and validity are verified. The applicability of the numerical strategy is also discussed in terms of the contribution coefficient of elastic stiffness to the key structural stiffness and the magnitude of pretension reduction.

Effect of Construction Errors in Cable Forces of Single-Story Orthogonal Cable Network Structures Based on GA-BPNN

The construction process of cable net structure is complicated, which leads to the strong randomness of construction errors. The safety state of the cable net structure is very sensitive to construction errors. Obtaining the coupling relationship between construction errors and cable force response efficiently and accurately is critical to developing the construction technique of cable structures. This paper proposed an analysis method based on a genetic algorithm optimized back propagation neural network (GA-BPNN) to judge the influence of construction error on the cable force of single-layer orthogonal cable network structures. Taking the speed skating stadium of the 2022 Winter Olympic Games as the research object, this paper analyzed the structure form of the venue. According to the characteristics of cable network structure and GA-BPNN calculation, the principle of construction error analysis was put forward. The influence of construction errors of load-bearing cables and stable cables on cable force response was analyzed. The influence degree of different component errors on structural cable forces was obtained, and the most unfavorable key components were obtained. For the key components, the influence trend of different construction errors on cable force was analyzed, and the fitting formula was given. Driven by GA-BPNN, it can realize the analysis of structural and mechanical responses under the action of multi-type, multi-component, and multi-combination construction errors. The results show that the research method efficiently and accurately obtains the performance law of structural cable force under the influence of construction error, effectively predicts the influencing factors of the structural safety risk, and effectively avoids structural safety accidents caused by construction error. The construction errors analysis method based on GA-BPNN proposed in this paper can provide a reference for similar structural analysis and application.

Three-dimensional laser scanning for large-scale as-built surveying of 2022 Beijing Winter Olympic Speed Skating Stadium: A case study

The latest 3D laser scanning technology is implemented in a practical project—2022 Beijing Winter Olympic Speed Skating Stadium—to investigate its effectiveness on the large-scale as-built surveying of civil infrastructures. The laser scanning was used for measuring the vertical deformation of flexible orthotropic cable net roof structure and for assessing the installation tolerance of curved glass curtain wall system. It was observed that 66% of clamps in the flexible roof structure showed vertical deviations within the range of ±5 mm and 94% of clamps showed deviations within ±10 mm. Additionally, about 60% of the vertical joints in transparent glass curtain wall showed deviations within the range of ±10 mm and the overall median deviation was only 2 mm. Given the complex structural form of the cable net roof structure and the glass curtain wall system, 3D laser scanning demonstrated unparalleled efficiency as compared to the conventional measuring methods.

Evolution of Modeling for Lightweight Structures: Creating the Munich Olympic Stadium Roof (1967–72)

The experimental structural qualities of the Munich Olympic Stadium roof compelled formative innovations in modeling techniques responsive to those conditions. The novel use of large-scale physical models allowed the team to navigate the complicated nature of generative form-finding for lightweight structures by balancing the various parameters of forms and forces. Although physical modeling was initially beneficial, it became obsolete as refinement and confirmation became requisite. The cable-net structure exceeded conventional capacity for analysis, which drove the engineers to evolve their confirmative modeling methods. Instead of abandoning the parametric logic of these physical models, the design team embraced this approach and applied their complementary interdisciplinary expertise to create two groundbreaking computational modeling techniques that are still in use today. Their modeling techniques exceeded their mandate for simple confirmation and evolved into the first generative and optimizing parametric modeling options for lightweight structures. The findings will show how the evolving use of these models and the collaborative complications that ensued situate contemporary challenges of experimental design, technology, and practice.

Optimization design of surface accuracy of SMC structure driven by space thermal radiation

The cable-net structure of large peripheral truss deployable antenna is radiated by the sun and planets for a long period of time, resulting in large thermal deformation and mechanical relaxation, which degrades the service performance of the antenna. In this paper, an optimal control strategy for surface accuracy of shape memory cable-net (SMC) structure under space thermal radiation is proposed. First, the shape memory alloy (SMA) is introduced and integrated with the cable-net structure. The SMC structure with shape memory effect (SME) has the capability to transform the space thermal radiation into a favorable factor for on-orbit adjustment of surface accuracy, in order to realize the on-orbit shape preservation of cable-net antenna in space environment. Then, the space temperature field of cable-net structure is calculated. Finally, the cable-net structure with a diameter of 2 m is simulated, and the influence of the diameter of SMA wire, slope for the relation between the critical stress of phase transformation and inverse phase transformation and temperature on surface accuracy are analyzed. It shows that the implantation of SMA can greatly improve the surface accuracy of cable-net structure in a single thermal cycle.