Space Truss Structures Research Articles

Effect of Member Length Uncertainty and Backlash on Deformation Accuracy for a High-Precision Space Truss Structure

Effect of Member Length Uncertainty and Backlash on Deformation Accuracy for a High-Precision Space Truss Structure

Dynamic Analysis of Multi-Layered Grid Space Structures

In the present study, an attempt has been made to understand the structural behavior of a two-way lattice grid space structure. Two-way lattice grid space structures are analyzed for dynamic earthquake loads such as time-history analysis by STAAD. Pro V8i software, using structural steel hollow tubular sections for a span of 30 m for 4.0 m height column and 3 storeys were considered for a total height of 12 m. Further the dynamic analysis such as displacements and modal analysis to find natural frequency and time period, were carried out for the eight different configurations and three different grid sizes of space truss structure.

The effect of Tube-in-Tube buckling-restrained device on performance of hybrid PFRP-Aluminium space truss structure

Due to low elastic modulus, overall buckling of slender pultruded fiber reinforced polymer (PFRP) strut is prone to occur. Hence, the Tube-in-Tube buckling restrained device (TTBRD) for PFRP tube was firstly proposed and detailly introduced. The structural effect of TTBRD was examined by compressive tests on hybrid PFRP space truss girder with and without TTBRDs. The results demonstrate that the structural bearing capacity and ductility have been greatly improved. To implement accurate structural calculation, preliminary finite element (FE) analyses were conducted at the component level. A single PFRP tube with TTBRD was separately modelled by three kinds of FE models, which adopt the concept of “surface-to-surface”, “line-to-surface” and “line-to-line” contact, respectively. The difference of the three kinds of FE models was compared and analysed. The appropriate FE models have been selected, and the behaviour of PFRP girder can then be well simulated. To further explore possible application, the verified FE model was used to simulate a large-scale 5 × 5 square-on-square space truss structure with different numbers of TTBRDs. It was demonstrated that the structural progressive buckling can be effectively prevented. Additionally, the TTBRD provides a good way for structural health monitoring of PFRP space truss structures.

Analytical Study on the Behaviour of Composite Space Truss Structures with Openings in a Concrete Slab

A space truss structural system is a three-dimensional arrangement of linear elements in a pyramid pattern forming a Double Layer Grid (DLG) system. Space trusses are an elegant and economical means of covering larger areas such as roof systems, in a wide variety of applications such as a stadium, aircraft-hanger, assembly hall, etc. The major problem encountered in using the space truss as a roofing system is the sudden failure of the whole structure due to critical buckling of the top chord member. Earlier research has shown that the optimal solution to overcome such a failure is by providing a small thickness of concrete slab over the space truss, so that the space truss with concrete slab (Composite Space Truss) will act as a floor system for the multi-storey building. For better ventilation and lighting in the building, the need for openings in the composite space truss is unavoidable; however, providing an opening in the concrete slab will reduce the load carrying capacity of the structure. The analysis of a composite space truss of size 30m x 30m with all possible locations of openings for four different support conditions was carried out using ANSYS in order to study the load - deflection behaviour. Further, the ductility factor and energy absorption capacity of the composite space truss with different locations of slab openings were compared.

Fuzzy PD hybrid control of low frequency vibration of annular antenna

The annular antenna is a typical large flexible space truss structure featured by small damping and low modal frequencies. The external disturbances, e.g. impulse load resulting from satellite attitude adjusting, may induce the low frequency large amplitude vibrations of annular antenna for a long time and thus reduce working precision and cause even its damage. The active control of vibration of annular antenna under impulse excitation is investigated in the paper. The voice coil actuator instead of piezoelectric stack actuator is used in order to meet the demand of large output displacement. The governing equation of active vibration control system is established by use of finite element method. The proportional differential (PD) control and fuzzy control algorithms are firstly studied in the active control. The results show that the fuzzy control exhibits worse control performance than PD control due to weak control function near structural equilibrium position. To circumvent the drawback of fuzzy control, a fuzzy PD hybrid control strategy is proposed which can combine the merits of both control methods. The simulated and experimental results show that the fuzzy PD hybrid control can yield the best control effect under impulse excitation comparing with the PD control and ordinary fuzzy control. The work provides a promising control way for active control of low frequency and large displacement vibration of annular antenna in satellite engineering.

An effective method for damage assessment based on limited measured locations in skeletal structures

This article proposes a new damage detection method using Modal Test Analysis Model and artificial neural networks. A challenge in damage detection problems is lack of measured degrees of freedom, as well as limitations of attached sensors. Modal Test Analysis Model has been used in order to estimate unmeasured degrees of freedom. An experimental cantilever beam was used to show Modal Test Analysis Model’s efficiency in estimation of unmeasured mode shapes. To solve the inverse problem of damage detection, mode shapes estimated by Modal Test Analysis Model were used as inputs, and characteristics of the damage served as outputs of the artificial neural network. The sensitivity analysis carried out for each example showing the performance of artificial neural network after mode shape expansion was efficiently improved. Three numerical examples for plane and space truss structures are considered, in order to verify effectiveness of the proposed method. Results demonstrate a high accuracy of Modal Test Analysis Model and artificial neural network for structural damage detection.

Bending strength and design methods of the 6082-T6 aluminum alloy beams with circular hollow sections

Circular hollow section (CHS) specimens are widely employed in long-span space structures, truss structures, and bridge structures; however, only a few experimental and numerical investigations on CHS aluminum alloy beams have been conducted in China. This paper presents a detailed experimental investigation on CHS beams made of 6082-T6 aluminum alloys. The effects of length and section slenderness on the ultimate strength and buckling behaviour were investigated. Seventeen extruded CHS specimens were subjected to four-point bending tests, with the diameter-to-thickness ratio (D/t) ranging from 16.4 to 29.1. The failure modes observed included overall buckling and the coupling of local and overall buckling. The initial geometric imperfections were measured prior to the bending tests. Subsequently, fine finite-element (FE) models were developed using the nonlinear analysis program ABAQUS and validated against the experimental results. An extensive parametric study involving 600 numerical results was performed to evaluate the effects of D/t, the section dimensions, and the slenderness ratio on the mechanical responses and bending strength of the CHS beams. The test results, together with the obtained FE analysis results, were utilised to assess the accuracy of the bending-strength provisions in the current design codes GB 50429 (China), Eurocode 9 (Europe), and AA-2015 (America), as well as optional design approaches, i.e. the direct strength method (DSM) and continuous strength method (CSM). The results indicated that all five design provisions provided conservative predictions of the ultimate moment capacities; the predicted results of DSM and CSM were more accurate than the three design specifications. The reliability levels of the bending-strength provisions were confirmed and compared using statistical parameters from the corresponding specifications.

An effective deep feedforward neural networks (DFNN) method for damage identification of truss structures using noisy incomplete modal data

Structural damage assessment is a challenging problem of study due to lack of information in data measurement and the difficulty of extracting noisy features from the structural responses. Therefore, this paper proposes an effective deep feedforward neural networks (DFNN) method for damage identification of truss structures based on noisy incomplete modal data. In the proposed approach, incomplete datasets are randomly generated by a reducing finite element (FE) model. Based on the collected data, the DFNN model is constructed to predict damage position and severity of structures. To obtain a better performance of the network, the new ReLu activation function and Adadelta algorithm are employed in this work. In addition, the state-of-the-art mini-batch and dropout techniques are adopted to speed up the training process and avoid the over-fitting issue in training networks. Various hyperparameters such as number of hidden units, layers and epoches are surveyed to built a good training model. In order to demonstrate the efficiency and stability of the proposed method, a 31-bar planar truss structure and a 52-bar dome-like space truss structure are investigated with various damage scenarios. Moreover, the performance of the DFNN method is not only illustrated with the noise free input data but also with noisy input data. Different noise levels of the input data are taken into account in this study. To accurately predict the damage location and severity of the structures, 10000 and 20000 data samples corresponding to the 31-bar planar truss and the 52-bar dome-like space truss are randomly created in term of quantity of damage members, damage locations and damage severity of the structures for training the DFNN models. The results predicted by the DFNN using incomplete modal data are compared with those of the complete and actual models. The obtained results indicate that the DFNN is a promising method in damage localization and quantification of civil engineering structures.

Passive vibration suppression of large space truss structures by viscous damping

Viscous damping methods are commonly employed to suppress the vibration due to their simple design, low cost, and stable damping performance. However, the harsh space environment makes the normal viscous dampers suspicious to various failures. This paper proposes a novel and robust design of viscous damper to provide high damping under low-frequency vibration disturbance in space. The characterisation of the damper at low-frequency and large displacement is first investigated by numerical analysis and then validated by experiments. Based on the results of the damper, this paper presents an optimal design strategy for the damping system of large space truss structures, which is critical for space mission because there is no sufficient damping in such space structures. The design is further optimised by weighted-sum that includes the damping characteristics of dampers and elastic flexibility of space truss structures. The effect of the damping system is demonstrated by the optimal design of a 60-bay truss structure. The results show that the damping ratios of the first three modes of the truss structure can be increased by over 10% with two viscous dampers. Comparisons between the structure with and without dampers demonstrate that significant vibration suppression at low-frequency bandwidth can be achieved satisfactorily.

Passive vibration suppression of large space truss structures by viscous damping

Viscous damping methods are commonly employed to suppress the vibration due to their simple design, low cost, and stable damping performance. However, the harsh space environment makes the normal viscous dampers suspicious to various failures. This paper proposes a novel and robust design of viscous damper to provide high damping under low-frequency vibration disturbance in space. The characterisation of the damper at low-frequency and large displacement is first investigated by numerical analysis and then validated by experiments. Based on the results of the damper, this paper presents an optimal design strategy for the damping system of large space truss structures, which is critical for space mission because there is no sufficient damping in such space structures. The design is further optimised by weighted-sum that includes the damping characteristics of dampers and elastic flexibility of space truss structures. The effect of the damping system is demonstrated by the optimal design of a 60-bay truss structure. The results show that the damping ratios of the first three modes of the truss structure can be increased by over 10% with two viscous dampers. Comparisons between the structure with and without dampers demonstrate that significant vibration suppression at low-frequency bandwidth can be achieved satisfactorily.

TRUSS STRUCTURE OPTIMIZATION BASED ON IMPROVED WOLF PACK ALGORITHM

Aiming at the optimization of truss structure, a wolf pack algorithm based on chaos and improved search strategy was proposed. The mathematical model of truss optimization was constructed, and the classical truss structure was optimized. The results were compared with those of other optimization algorithms. When selecting and updating the initial position of wolves, chaos idea was used to distribute the initial value evenly in the solution space; phase factor was introduced to optimize the formula of wolf detection; information interaction between wolves is increased and the number of runs is reduced. The numerical results show that the improved wolf pack algorithm has the characteristics of fewer parameters, simple programming, easy implementation, fast convergence speed, and can quickly find the optimal solution. It is suitable for the optimization design of the section size of space truss structures.

Equivalent Dynamic Model of the Space Antenna Truss with Initial Stress

The equivalent modeling approach is one of the key technologies in the design of vibration controllers motivated by the large flexible space truss structure applications. Based on the energy equivalence principle and the classical Timoshenko beam theory, this study establishes a new equivalent dynamic model for the space antenna truss with initial stress by the static condensation method. Compared with previous truss structures of the triangular prism reported in equivalent modeling, the space antenna truss has a more complicated configuration and more members. Meanwhile, this truss structure is in a self-stress state and the connection of the adjacent members is a rigid-jointed. The equivalent anisotropic Timoshenko beam model of the complex space antenna truss with a rigid joints is proposed for the spatial repeating element composed of the beam and cable members in the initial stress state and the joints. According to the kinematic assumptions, displacement expressions of the spatial repeating element are derived using the Taylor series expansion at the center of the spatial repeating element. Then, the stiffness and mass matrices of the equivalent beam model are obtained. The natural vibration characteristics of the equivalent beam model are proved to be in good agreement with those of the original space antenna truss, which indicates that the equivalent beam model has a satisfactory accuracy. As a result, the equivalent dynamic model may serve for the vibration control of the space antenna truss.

An Optimized Approach for Tracing Pre- and Post-Buckling Equilibrium Paths of Space Trusses

In this paper, a novel optimization-based method is proposed to analyze steel space truss structures undergoing large deformations. The geometric nonlinearity is considered using the total Lagrangian formulation. The nonlinear solution is obtained by introducing and minimizing an objective function subjected to the displacement-type constraints. The proposed approach can fully follow the equilibrium path of the geometrically nonlinear space truss structures not only before the limit point, but also after it, namely, including both the pre- and post-buckling paths. Moreover, a direct estimation of the buckling loads and their corresponding displacements is possible by using the method. Particularly, it has been shown that the equilibrium path of a structure with highly nonlinear behavior, multiple limit points, snap-through, and snap-back phenomena can be traced via the proposed algorithm. To demonstrate the accuracy, validity, and robustness of the proposed procedure, four benchmark truss examples are analyzed and the results compared with those by the modified arc-length method and those reported in the literature.

Vibration-based damage detection of planar and space trusses using differential evolution algorithm

In this study, an efficient damage detection technique using the differential evolution (DE) algorithm and vibration data is proposed to properly detect the locations and extents of multiple damages of truss structures. The general equilibrium equations in which the reaction forces at notes are taken into account are considered. The compatibility equations in terms of forces are presented using the singular value decomposition (SVD) technique and then the extended equations of motion are developed based on the force method. As an optimization algorithm, the differential evolution (DE) algorithm is utilized and the objective function for damage detection is based on vibration data such as natural frequencies and mode shapes. Three numerical examples for planar and space truss structures are considered to verify the effectiveness and practical applicability of the present study. The numerical results show that the proposed method based on DE and vibration data can provide a reliable tool on determining the locations and extents of multiple damages of truss structures when it compares with those obtained from the genetic algorithm.

Research on motion characteristics of space truss-crawling robot

For the future demands of unmanned assembly of orbital space truss structures, a new space truss-crawling robot based on biomimetic principles is proposed. The robot system mainly consists of multi-joint legs and an adhesive microstructure imitating a gecko. The kinematics analysis of a single leg and the system design are accomplished based on functional requirements and adaptivity analysis. The motion simulation model of the robot and the discrete element simulation model of the adhesion microstructure are established based upon this analysis. The simulation of the holding motion of a single leg is implemented based on the EDEM-ADAMS platform, and the feasibility of the scheme is demonstrated by analyzing the influence of adhesive microstructures comparatively. The related motion characteristics of the robot while crawling are obtained by co-simulation, and the influence law analysis is carried out by analyzing the interaction between not only the crawling infrastructure but also the crawling gait and motion characteristics. A crawling experiment in a simulated low-gravity environment is conducted to further verify the robot’s movement function, which will provide beneficial reference for practical applications of the robot in the future.

System-reliability-based design and topology optimization of structures under constraints on first-passage probability

For the purpose of reliability assessment of a structure subject to stochastic excitations, the probability of the occurrence of at least one failure event over a time interval, i.e. the first-passage probability, often needs to be evaluated. In this paper, a new method is proposed to incorporate constraints on the first-passage probability into reliability-based optimization of structural design or topology. For efficient evaluations of first-passage probability during the optimization, the failure event is described as a series system event consisting of instantaneous failure events defined at discrete time points. The probability of the series system event is then computed by use of a system reliability analysis method termed as the sequential compounding method. The adjoint sensitivity formulation is derived for calculating the parameter sensitivity of the first-passage probability to facilitate the use of efficient gradient-based optimization algorithms. The proposed method is successfully demonstrated by numerical examples of a space truss and building structures subjected to stochastic earthquake ground motions.

The lateral displacements analysis of space lattice beam with variable section based on the flexibility coefficients method

The space lattice beam is a complex statically indeterminate rod structure which, composed with several beams, is an important process for calculating the internal force and lateral stiffness in the design analysis. First, taking the single-chip truss structure with variable section as research object, each member’s force, lateral displacements and flexibility coefficients of the tapered truss with different arrangement in the form of webs are given. Finally, based on the flexibility coefficient of monolithic truss structure, considering it comprehensively with the effects of lateral stiffness caused by the chords and webs, the lateral displacement expressions are deduced for rectangular space truss structure. Result of analysis of examples show that the application of the method mentioned in this paper to calculate the lateral displacement of space lattice beam with variable section is correct and effective which can be used for practical engineering.

Stiffness and Damping Formulations for Jointed Deployable Space Truss Structure

In this paper, the dynamic behaviors of a elastic rod connected by a joint with clearance of deployable truss structures are investigated. A one-dimensional cantilever with joint support is examined in the deployable truss structure. These formulations consist of the nonlinear joint dynamic stiffness model and damping models are formulated and the dynamic characteristics of free-vibrating structures are estimated. The natural frequency transitions are investigated by considering the contact and noncontact conditions of the clearances, then the formulation of dynamic stiffness model is obtained. The friction models are mathematically formulated and simplified to make them easy to calculate. The impact damping models are formulated using the linear envelope of the time response and it can be negligible when the speed is small. The dynamic characteristics can be estimated by integrating these models and formulations using the energy loss factors. Experimental evaluations show the dynamic characteristics and demonstrate the validity of the formulations.

Modeling the creep behavior of GRFP truss structures with Positional Finite Element Method

Abstract This paper presents the development of a formulation, based on Positional Finite Element Method, to describe the viscoelastic mechanical behavior of space trusses. The numerical method used was chosen due to its efficiency in the applications concerning nonlinear numerical analyses. The formulation describes the positional variation over time under constant stress state (creep). The objective is to provide a way to quantify the creep behavior for space truss structures and thus contribute to the encouragement of GFRP usage in such structural components. Time-dependent behavior of such materials is one the most important factors for their use in design of structures, demanding studies about the deformations expected within the operational life of the structural systems. To perform this study, the proposed methodology considers a standard solid rheological model to describe stress-strain time-dependent law. This model is implemented in the formulation for quantify the total strain energy. The effects of the model parameters in the mechanical response of the structure with accentuated geometric nonlinearity were presented. In this analysis, it was possible to identify the influence of the elastic and the viscous moduli on the creep response. Model calibration was performed using test data obtained from literature and a GFRP transmission line tower cross-arm was simulated to predict the evolution of displacements under real operational loads. From the results, it was possible to observe a fast evolution of displacements due to the creep effect in the first 7,500 h. This increase was close to 0.6% in relation to the displacement obtained in the elastic behavior. The presented methodology provided a simple and efficient way to quantify the creep phenomenon in viscoelastic GFRP composites truss structures, as can be seen in the developed analyses.

Two-stage Optimization Based on Force Method for Damage Identification of Planar and Space Trusses

In this study, an efficient two-stage optimization procedure based on the force method is proposed to properly identify the sites and extents of multiple damages in the planar and space truss structures. In the first stage, the elements which have the higher probability of damages are selected by using the anti-optimization (AO) method and the weighed sum procedure. In the second stage, the genetic algorithm (GA) is performed to determine the actual damage sites and their extents based on the force method. The accuracy and effectiveness of the proposed method are proved through the planar and space truss structures. The results from the present study indicate that the combination of the first stage with the second one can provide a reliable tool to accurately and efficiently identify the multiple damages of truss structures.