Space Truss Structures Research Articles

Experimental and numerical study on static performance of ship lock sector gates

A sector gate is a fundamental type of lock gate. It is designed as a large cantilevered, rotatable space truss structure capable of withstanding bidirectional hydraulic pressures and operating under dynamic water conditions. This makes it prevalent in medium- and large-scale navigation locks. This research examines the structural behavior of a ship lock sector gate using one in-situ test and two numerical models. The sector gate, with an 11.72-m span, consists of a panel beam system, space truss system, boundary column, and floating box. An in-situ test was conducted to obtain the stress and deformation of key components of the sector gate under positive hydraulic head difference conditions during regular operation. A finite element model was established, verified, and a model updating framework incorporating sensitivity analysis based on the Hooke-Jeeves direct search method was established. The updated model was employed to perform an in-depth examination of the gate's mechanical characteristics under extreme conditions of both positive and negative hydraulic head. The findings suggest that the most crucial region is situated at the intersection of the boundary column and the bottom struts. The stress and displacement responses of the components exhibit a positive correlation with water depth, with the struts and truss chords experiencing significant stress. The entire gate demonstrates twisting along the longitudinal axis of the lock chamber, which negatively impacts its ability to seal effectively. These findings provide valuable insights for the design of sector gates, contributing to the safe operation of gates and efficient navigation of waterways.

Fuelless On-Orbit Assembly of a Large Space Truss Structure Using Repulsion of the Service Spacecraft by Robotic Manipulators

A servicing spacecraft motion control approach for the problem of on-orbit truss structure assembly is developed in this paper. It is considered that a cargo container with a rod set and servicing spacecraft are in orbit initially. The assembly procedure is based on spacecraft free-flight motion between the structure’s specified points. The spacecraft is equipped with two robotic manipulators capable of attaching to the structure and holding rods. In addition, the spacecraft can repulse from the structure with a given relative velocity using a manipulator, so the spacecraft and the structure receive impulses. The repulsion velocity vector is calculated in order to reach the structure target point to deliver and install the rod into the truss structure, or to reach the cargo container and take a rod. The problem of searching the repulsion velocity is formulated as an optimization problem with constraints, taking into account the limited value of the repulsion velocity, collision avoidance with structure, restrictions on the angular velocity and translational motion of the structure in the orbital reference frame. This problem is solved numerically with an initial guess vector obtained analytically for simplified motion cases. The application of the proposed control scheme to the assembly of a truss-based antenna is demonstrated. It is shown that the servicing spacecraft is successfully transferred between the structure points by means of manipulator repulsion. Main features and limitations of the assembly problem using a spacecraft with two manipulators are discussed.

Vibration-based methods for local damage identification of breathing cracks in truss-like structures

A vibration-based local damage identification method is proposed for truss-like structures with breathing cracks. Firstly, a bilinear model is established to represent the characteristics of breathing cracks, and the features of such cracks are detected through reciprocity and homogeneity tests on structural input-output signals. Since the crack is influenced by tensional and compressive forces on truss members, only one damage factor is required to quantify the stiffness reduction of each member. Subsequently, a dynamic equilibrium equation concerning the damage factor is constructed to identify the new load term. The integral equation method, which relies on the virtual work principle, is employed to obtain the displacement responses and loads under all tensile conditions. Finally, the mean value of cumulative damage coefficients for each truss member can be derived as their corresponding damage factor. Numerical examples involving a plane truss structure and a truss offshore platform are utilised to illustrate the effectiveness of this damage identification method. The results demonstrate exceptional precision and efficiency in accurately identifying various damages in truss structures under different excitations and signal-to-noise ratios. A actual space truss structure confirm that this damage identification method exhibits high-level precision in identifying single-member damages as well as multi-member damages with breathing cracks locally.

Identification of closely spaced modes in space truss structures as base for the determination of member normal forces

Identification of closely spaced modes in space truss structures as base for the determination of member normal forces

Damage detection in space truss structures using a third-level approach

Monitoring civil engineering infrastructure is crucial to ensuring that the structures can continue to function properly. An important aspect of this assessment is detecting structural damage. This study proposed a method that combined static loading techniques and modal parameters to establish a third level of damage detection. Specifically, the damage locating vector (DLV) was used as the static technique, and mode shapes, along with Modal Assurance Criteria (MAC), were integrated with the Firefly Algorithm (FA) to define the damage percentage. The objective of this method is to determine the location of the damaged members in space truss structures and accurately estimate the reduction in stiffness of the damaged members. DLV was used to show the location of damaged members, while the Modal Assurance Criteria – Firefly Algorithm (MAC-FA) was used to predict the stiffness loss in structural elements. This combined approach improved the DLV method, which could only identify potentially damaged parts. The fundamental concept behind MAC-FA was the relationship between the predicted mode shape and the mode shape of the structure, represented by the MAC value. This method was used to investigate damage detection in two space truss structures. The results demonstrated that the proposed method could identify damaged elements and quantify the loss of stiffness in space truss structures.

Equivalent modeling of LSTS and frequency calculation based on dynamic stiffness method

Large space truss structures (LSTS) are quickly becoming a vital type of space structure due to the fast expansion of the outer space field. The equivalent modeling approach has recently attracted the attention of researchers and engineers due to the finite element method’s limitations. In order to solve the equivalent beam model (EBM) in terms of frequency, the Wittrick-Williams algorithm based on dynamic stiffness matrix and the equivalent modeling procedure of large space truss structure are introduced in this study. The frequencies obtained by the equivalent model are good agreement with that obtaied by the finite element model, demonstrating the efficiency of the frequency solution method and equivalent modeling.

Reduced-order modeling and solution method for nonlinear frequency response analysis of large space truss structures

Reduced-order modeling and solution method for nonlinear frequency response analysis of large space truss structures

Shape and sizing optimisation of space truss structures using a new cooperative coevolutionary-based algorithm

Optimising the shape and size of large-scale truss frames is challenging because there is a nonlinear interaction between cross-sectional and nodal coordinate forces of structures. Meanwhile, combining the shape and bar size variables creates a multi-modal search space with dynamic constraints, making an expensive optimisation engineering problem. Besides, most of the real truss problems are large-scale, and optimisation algorithms are faced with the issue of scalability by increasing the size of the problem. This paper proposed a novel Cooperative Coevolutionary marine predators algorithm combined with a greedy search (CCMPA-GS) for truss optimisation on shape and sizing. The proposed algorithm used the divide-and-conquer technique to optimise the shape and size separately. Therefore, in each iteration, the CCMPA-GS focuses on shape optimisation initially and then switches to the size of bars and tries to find the best cooperative combination of the solutions in the current population using a context vector (CV). A greedy search is embedded in the following to fix the remaining violations from the structure's stress and displacement. This novel alternative optimisation strategy (CCMPA-GS) compared with 13 established genetic, evolutionary, swarm, and memetic meta-heuristic optimisation algorithms. The comparison is based on optimising two large-scale truss structures consisting of 260-bar and 314-bar configurations. Experimental results demonstrate that the proposed CCMPA-GS method consistently outperforms the other meta-heuristic methods, delivering optimal designs for the 314-bar and 260-bar truss structures that are superior by 52 % and 63.4 %, respectively. This signifies a substantial enhancement in optimisation performance, highlighting the potential of CCMPA-GS as a powerful alternative in the field of structural optimisation.

Continuum Modeling and Boundary Control of a Satellite with a Large Space Truss Structure

Due to its advantages of easy deployment and high stiffness-to-mass ratio, the utilization of truss structures for constructing large satellites presents an appealing solution for modern space missions, including Earth observation and astronomy. However, the dimensions of the traditional finite element model for a satellite with a large space truss structure become exceedingly large as the structure’s size increases. The control system design process based on the finite element model is complex and time-consuming. This paper employs the continuum modeling method to represent the truss structure as a continuous entity. The bending vibrations of the truss structure are encapsulated by a simplified partial differential equation (PDE), as opposed to the more intricate traditional finite element model. Simultaneously, the satellite’s attitude motion is characterized by an ordinary differential equation (ODE). Building upon this coupled PDE-ODE model, a boundary control law that only requires sensors/actuators at the boundary is formulated to effectively mitigate structural vibrations and regulate the satellite’s attitude. The exponential stability of this closed-loop system is scrutinized using Lyapunov’s direct method. The simulation results affirm that the continuum modeling method is indeed well-suited for satellites endowed with substantial truss structures, and the proposed boundary law proves to be highly effective in both attitude tracking and vibration suppression.

Dynamic Analysis of a Large Deployable Space Truss Structure Considering Semi-Rigid Joints

Joints are widely used in large deployable structures but show semi-rigidity due to performance degradation and some nonlinear factors affecting the structure’s dynamic characteristics. This paper investigates the influence of semi-rigid joints on the characteristics of deployable structures in orbit. A virtual connection element of three DOFs is proposed to model the semi-rigid joints. The governing equations of semi-rigid joints are established and integrated into the dynamic equation of the structures. A series of numerical experiments are carried out to validate the proposed model’s accuracy and efficiency, and the deployable truss structures’ static and dynamic responses are analyzed. The results show that semi-rigid joints exacerbate the effects of an in-orbit microvibration on the stability of deployable truss structures. Semi-rigid joints lower the dominant frequencies of structures, leading to a ‘closely-spaced-frequencies’ phenomenon and altering the dynamic responses significantly. The effects of semi-rigid joints on deployable truss structures are long-term and can be used to establish a relationship model between structural performance and service life. Nonlinear effects vary with the external load and depend on the structures’ instantaneous status. These results indicate that semi-rigid joints significantly influence the characteristics of deployable structures, which must be considered in the design and analysis of high-precision in-orbit deployable structures.

Vibration control for large space truss structure assembly using a distributed adaptive neural network approach

The vibration suppression problem of the large space truss structure during on-orbit assembly process is investigated in this paper, and a distributed adaptive neural network control approach is proposed to solve this problem. The dynamic modeling process of large space truss structure assembly is firstly developed. It can be used to describe the dynamic characteristics of the incrementally increasing space structure. To achieve the vibration suppression during on-orbit assembly, a distributed control approach is then proposed. The controller is designed for each assembly substructure, and a coordination term is added into the controller to reduce the interactions between the assembled substructures, and the distributed control system is therefore formed along with the assembly proceeds. The distributed controller is then redesigned using neural networks, to compensate the effect of the modeling uncertainties and the system parameter variation in the assembly process. It also could be noted that the dependence of controller design on dynamic models is then reduced. The simulation results demonstrate that the vibration is effectively suppressed, and the dynamic performance of the closed-loop system is improved. The controller designed based on the proposed dynamic model has good expansibility, and the control system also has robustness to external disturbance, and good fault tolerance when controller fails.

An improved equivalent beam model of large periodic beam-like space truss structures

Space truss structures are essential components for space-based remote sensing loads with high spatial and temporal resolutions. To achieve high-precision vibration control, an accurate and efficient dynamics model is essential. In addition to the current equivalent beam model (EBM) based on the classical continuum theory, an improved equivalent beam model (IEBM) is proposed that considers the impact of the distinction between trusses and beams on torsional and shear deformations, as well as the impact of shear deformation on flexural rigidity. According to the displacement expressions of spatial beams, torsional, shear, and bending correction coefficients are introduced to derive expressions of strain energy and kinetic energy. The energy equivalence principle is then utilized to calculate the elasticity and inertia matrices, and dynamics equations are established using the finite element method. Subsequently, an IEBM is constructed by employing the particle swarm optimization approach to determine the correction coefficients with the truss natural frequency as the optimization target. The natural vibration characteristics of the structure are estimated for various material properties. Compared with the full-scale finite element model, the EBM reaches a maximum error of 80% for a low modulus of elasticity, while the maximum error of the IEBM is less than 2% for any given parameters, indicating its superior accuracy to the EBM.

Space truss construction modeling based on on-orbit assembly motion feature

More space truss construction has been planned to develop and utilize space resources. These trusses are designed in the way of large-scale, complex, modular, and on-orbit assembly. To meet the upcoming challenge of large-scale space infrastructure construction, it is necessary to study space truss automation design and robotic construction. This paper proposes an ordinal finite screw adjacency matrix model (OFSAMM), focusing on the relationship between assembly motions, to express and compute a space truss structure. In this model, a space truss is abstracted as a set of ordered assembly motions, each of which is recorded as a finite screw as the basic element of the truss and its assembly. The operation of truss transformation is also derived under this model. Therefore, the truss configuration, the assembly sequence, the truss sub-assembly, the truss components, and the on-orbit assembly task can be expressed and calculated in a unified model, which is calculated and stores the truss topology and assembly with the minimum storage cost. At the end of this paper, we introduce how to synthesize and optimize space truss design through two cases. The study will help to improve design efficiency. Furthermore, it provides a theoretical basis for the automatic construction of space truss structures, especially in the next stage.

Modal identification of structures with a dynamic behaviour characterised by global and local modes at close frequencies

Identification of modal parameters of a space frame structure is a complex assignment due to a large number of degrees of freedom, close natural frequencies, and different vibrating mechanisms. Research has been carried out on the modal identification of rather simple truss structures. So far, less attention has been given to complex three-dimensional truss structures. This work develops a vibration-based methodology for determining modal information of three-dimensional space truss structures. The method uses a relatively complex space truss structure for its verification. Numerical modelling of the system gives modal information about the expected vibration behaviour. The identification process involves closely spaced modes that are characterised by local and global vibration mechanisms. To distinguish between local and global vibrations of the system, modal strain energies are used as an indicator. The experimental validation, which incorporated a modal analysis employing the stochastic subspace identification method, has confirmed that considering relatively high model orders is required to identify specific mode shapes. Especially in the case of the determination of local deformation modes of space truss members, higher model orders have to be taken into account than in the modal identification of most other types of structures.

Equivalent continuum modeling method for transient response analysis of large space truss structures with nonlinear elastic joints

Equivalent continuum modeling method for transient response analysis of large space truss structures with nonlinear elastic joints

Damage identification of large-scale space truss structures based on stiffness separation method

Optimization-based damage identification of large-scale space truss structures is challenging because with increasing degrees of freedom for the structures, the objective function becomes complex that is difficult to converge. To solve this issue, this study introduces a stiffness separation method for damage identification of large-scale space truss structures based on static response. The separate method splits the global stiffness matrix into the required sub-stiffness matrices, thereby significantly simplifying the objective function for damage identification. Two types of space truss structures are used to verify the accuracy and effectiveness of the proposed method. The results show that the proposed method reduces the number of iteration steps required to search for optimal values.

Equivalent Beam Model and Improved Structure Design of Large Space Antenna Truss With Geometric Nonlinearity

AbstractThis paper proposes a extend linear equivalent method that can extend the linear equivalent micropolar beam model to the nonlinear equivalent micropolar beam model to analyze nonlinear vibration for large space truss structure, and also proposes a lattice enhancement method to improve the cantilever truss for the buckling problem that exists in space cantilever truss structures. The nonlinear equivalent model is obtained by introducing a corotating coordinate system into the linear equivalent beam model. Since the instability of the fixed root end of the cantilever truss is the main reason for buckling, the method of strengthening the longeron of the truss lattice by lattice is proposed. The accuracy of the equivalent geometric nonlinear model and the effectiveness of the improved cantilever truss structure are verified by four numerical simulation examples. The methods proposed in this paper provide some reference for studying the dynamics analysis of large space trusses and the design of structures.

Effect of the MHS on Earthquake Response of Space Truss Structures under Horizontal Earthquake Motion

Space truss structures are commonly used in long-span roof structures. Recently, middle-hung scoreboards (MHS), a kind of large-scale display device flexibly suspended in the center of the roof, have been widely used in gymnasiums. However, the effect of the MHS on dynamic characteristics and earthquake response of space truss structures needs to be investigated. In this paper, the effect on the MHS under horizontal earthquake motion is studied. The simplified model, where the MHS is simplified to four fixed masses on a structure, and the flexibly suspended model are established with Abaqus software, and the earthquake response is analyzed by the time-history method with the dynamic explicit method. The influence laws of the wire extent and the MHS weight are discussed. Compared with the simplified model, the nodal acceleration and the axial force rise up to 2.123 times and 1.575 times, respectively, in the flexibly suspended model, indicating that the amplification effect of the MHS acts significantly under horizontal earthquake motion. It turns out that the earthquake response of a space truss structure could be underestimated if a simplified model is used. The crest acceleration of both top chord nodes and bottom chords nodes are greatly influenced by the MHS weight but little affected by the wire extent. The influence laws of the MHS weight and the wire extent on crest axial forces of structural members are very complicated. The central regions of both the top chords and the bottom chords are the most affected regions, and the boundary regions parallel to the direction of the earthquake motion are the least affected regions. It is suggested that the envelope value under the conditions of different wire extent and MHS weight are used for structural design.

Influence of Center-Hung Scoreboard on Seismic Response of Space Truss Structure under Vertical Earthquake

Influence of Center-Hung Scoreboard on Seismic Response of Space Truss Structure under Vertical Earthquake

Adaptive search space decomposition method for pre- and post-buckling analyses of space truss structures

The paper proposes a novel adaptive search space decomposition method and a novel gradient-free optimization-based formulation for the pre- and post-buckling analyses of space truss structures. Space trusses are often employed in structural engineering to build large steel constructions, such as bridges and domes, whose structural response is characterized by large displacements. Therefore, these structures are vulnerable to progressive collapses due to local or global buckling effects, leading to sudden failures. The method proposed in this paper allows the analysis of the load-equilibrium path of truss structures to permanent and variable loading, including stable and unstable equilibrium stages and explicitly considering geometric nonlinearities. The goal of this work is to determine these equilibrium stages via optimization of the Lagrangian kinematic parameters of the system, determining the global equilibrium. However, this optimization problem is non-trivial due to the undefined parameter domain and the sensitivity and interaction among the Lagrangian parameters. Therefore, we propose to formulate this problem as a nonlinear, multimodal, unconstrained, continuous optimization problem and develop a novel adaptive search space decomposition method, which progressively and adaptively re-defines the search domain (hypersphere) to evaluate the equilibrium of the system using a gradient-free optimization algorithm. We tackle three benchmark problems and evaluate a medium-sized test representing a real structural problem in this paper. The results are compared to those available in the literature regarding displacement–load curves and deformed configurations. The accuracy and robustness of the adopted methodology show a high potential for gradient-free algorithms to analyze space truss structures.