•The impact of individual member failure on the cable network antenna is studied.•A sensitivity-based member importance prediction method is proposed.•The condition of cable slack is considered in ...the member importance prediction.•A failure response analysis approach is proposed based on the VFIFE method.
Cable network antennas are likely to experience damage from the extreme space environment. This will deteriorate the antennas’ performance and even lead to the scrapping of antennas. To date, effective means for on-orbit maintenance of cable network antennas are lacking. Therefore, it is necessary to investigate the influence of each member failure on the antenna and find the most important ones before launching. But the method of exhaustion to analyze each member failure response is inefficient. Hence, we propose an importance prediction method for finding the key members of the antenna based on the sensitivity analysis. The sensitivity analyses with respect to the failure member are carried out, in which the condition of cable slack caused by member failure is considered. The node displacement sensitivity is used to predict the member importance. After that, based on the vector form intrinsic finite element method, a response analysis method for the incomplete antenna after member failure is proposed. The proposed method can accurately capture the transient response of the antenna and effectively avoid the non-convergence problem caused by slack cables. A numerical example is provided, and the most important members are predicted, which should be given special concern in the design stage.
Combining external dampers and cross-ties into a hybrid system to control bridge stay cable vibrations can address deficiencies associated with these two commonly used vibration control solutions ...while retaining their respective merits. Despite successful implementation of this strategy on a few cable-stayed bridges, behavior of such a structural system is still not fully understood. In the current study, an analytical model of a hybrid system consisting of two parallel taut cables interconnected by a transverse linear flexible cross-tie, with one cable also equipped with a transverse linear viscous damper close to one end support, is developed. The proposed model is validated by an experimental work in the literature and an independent numerical simulation. A parametric study is conducted to comprehend the impact of main design parameters on the performance of a hybrid system in terms of the in-plane frequency, the damping and the degree of mode localization of the system's fundamental mode. In addition, the concept of isoquant curve is applied not only to appreciate the effect of simultaneous variation in main design parameters on the modal behavior of a hybrid system, but also to identify the optimal ranges of these parameters to achieve the required cable vibration control effect.
•Proposed an analytical model for hybrid systems used in cable vibration control.•Increase cross-tie flexibility or spacing towards damper maximizes damper effect.•Cross-tie flexibility has opposite effect on indicators of system performance.•Isoquant curves are applied to identify optimum ranges of system parameters.
Cross-ties have proven their efficacy in mitigating vibrations in bridge stay cables. Several factors, such as cross-tie malfunctions due to slackening or snapping, as well as the utilization of ...high-energy dissipative materials, can introduce nonlinear restoring forces in the cross-ties. While previous studies have investigated the influence of the former on cable network dynamics, the evaluation of the impact of nonlinear cross-tie materials remains unexplored. In this current research, an existing analytical model of a two-shallow-flexible-cable network has been extended to incorporate the cross-tie material nonlinearity in the formulation. The harmonic balance method (HBM) is employed to determine the equivalent linear stiffness of the cross-ties. The dynamic response of a cable network containing nonlinear cross-ties is approximated by comparing it to an equivalent linear system. Additionally, the study delves into the effects of the cable vibration amplitude, cross-tie material properties, installation location, and the length ratio between constituent cables on both the fundamental frequency of the cable network and the equivalent linear stiffness of the cross-ties. The findings reveal that the presence of cross-tie nonlinearity significantly influences the in-plane modal response of the cable network. Not only the frequencies of all the modes are reduced, but the formation of local modes is delayed to a high order. In contrast to an earlier finding based on a linear cross-tie assumption, with nonlinearity present, moving a cross-tie towards the mid-span of a cable would not enhance the in-plane stiffness of the network. Moreover, the impact of the length ratio on the network in-plane stiffness and frequency is contingent on its combined effect on the cross-tie axial stiffness and the lateral stiffness of neighboring cables.
The use of a cross-tie is one of the effective countermeasures to suppress the undesired stay cable vibrations. It has been successfully applied on different cable-stayed bridges but the mechanics ...behind the cross-tie are not fully understood. Most of the studies dedicated to understand the dynamic behavior of the cable network assumed the main cables as taut cables. This assumption is acceptable on small to medium-sized cable-stayed bridges, however, in case of long span bridges, this assumption is unjustified. Therefore, in the current study, the in-plane modal behavior of a cable network is explored by considering the cable sag. An analytical approach is used to develop the characteristic equation of a basic sagged cable network. The in-plane modal behavior of the sagged cable network is compared with the taut cable network and also with the single sagged cable. The role of different system parameters, mainly the cross-tie stiffness and the cable sag, is explored to understand the in-plane modal behavior of a sagged cable network. During the parametric study, a comparison is also drawn with the conventional taut cable network and an in-depth discussion is made to discuss the role of different system parameters.
The article presents theoretical foundations of designing the components of an aircraft onboard cable network, proposed as a methodology for solving the problems of designing onboard equipment. The ...composition of the initial and developed technical documentation for the aircraft onboard cable network is determined. The article also shows the relationship between the stages of designing the onboard cable network and the stages of designing the aircraft. The formulation of the general task of creating the components of an onboard cable network is presented as a number of particular subtasks of a lower level of complexity. The method for solving the problem is based on a number of transformations performed with the original documentation in order to develop technical documentation for the introduction of the onboard system into the complex of onboard equipment. A number of successive transformations of the proposed bundle model using the apparatus of topology and multiset theory made it possible to form a model of the components of the onboard cable network of an aircraft that gives a detailed view of its future design. The proposed scientific approach to the design of aircraft onboard cable network components created the prerequisites for minimizing the heuristic component in the process of designing aircraft onboard cable network components.
Considering the cable sag as well as the impacts of cables’ dynamic axial forces on the transverse forces, this paper makes an effort to propose a generalized method for studying in-plane free ...vibration of the cable network attached with multiple rigid cross-ties. First, the vibration equations of the suspended cables are established and solved by separation-of-variables method. Then, the system is divided into several substructures, which are reassembled according to transfer matrix method (TMM). Using the boundary conditions, the characteristic equation of the system is yielded. In this way, the basic theory for solving the eigenproblem of a general cable network attached with rigid cross-ties is derived. Four examples are given to illustrate the applicability of the current method, and their frequencies and mode shapes are acquired by a developed calculating program. Meanwhile, a finite element model (FEM) is also established. It is found that the results are in a good agreement with those obtained by FEM, which verifies the validity and correctness of the method in this paper.
ABSTRACT
Most of the existing analytical solutions to the vibration of cable networks interconnected by cross-ties are developed based on string theory, where the effect of cable bending rigidity on ...cable vibration is ignored. However, the bending rigidity of cables strongly influences the natural frequencies and vibration mode shapes of short and stout cables and long cables at higher modes. Hence, this paper considers cable bending rigidity to form a closed-form solution that can be used in determining the natural frequencies and mode shapes of cable networks. The analytical solution of the cable network model with hinged-end boundary conditions is derived. It can be combined with other existing techniques to analyze the dynamic behaviors of a two-cable network with partly fixed supports. The analytical solution derived from this paper can be degenerated to the same solution without considering the cable bending rigidity in previous studies. The accuracy of this analytical solution considering cable bending rigidity is verified by finite element analysis. The effects of bending rigidity on the vibration frequencies and modes of the cable network with inclined and flexible cross-link are investigated in detail. This analytical solution can be applied to backward analysis to identify the cable tension of a two-cable network with partly fixed supports.
Geometric approximation errors of periodically distributed surface facets of cable-network reflector antennas can result in grating lobes undesired in some space missions. As the surface is shaped by ...the tensioned flexible cable-network structure, the electromagnetic (EM) and structural parameters are highly correlated, and the well-designed surface obtained only concerning the EM performance may not be shaped by the tension-only cable network with specified cable-tension constraints. To address the problem, this study proposes an integrated structural-EM optimization method to enable low grating lobe cable-network antenna design. In this method, force densities of the cables, which can determine both the cable tensions and surface node positions that decide the boundary conditions of the EM field, are selected as the design variables. An adaptive objective/constraint function is proposed, which enables the grating lobe level (GLL) to be minimized with constrained cable tensions, antenna gain, and first sidelobe level (SLL) in a simultaneous, feasible and relatively fast way. To demonstrate the feasibility and effectiveness of the proposed method, it was implemented on a 12 m-diameter cable-network antenna. The results indicate that the grating lobes are greatly degraded and the achieved surface can be formed by well tensioned cables.
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