Large Truss Research Articles

Application and Prospect of Analysis of Structures Based on Finite Element Method

The structural requirements of buildings are becoming more stringent and sophisticated as a result of the quick advancement of science and technology. Due to the limitations of the traditional structural mechanical analysis methods, the calculation results often have large deviations from the actual, and therefore cannot simulate the structural forces and displacements in a more realistic way. The emergence of the finite element method (FEM) makes these complex and irregular problems can be solved well. This paper analyzes the specific applications of FEM and its effectiveness on three typical space structures, namely, space trusses, foundation pits, and steel buildings. The results show that in the analysis of large trusses, the three-dimensional nonlinear finite element analysis using relevant analysis software has good accuracy in displacement calculation, seismic simulation, static force analysis, and structural optimization simulation. In the application of foundation pits, this method can also well simulate the force and deformation characteristics of soil under different working conditions. In steel structure, this method can be applied to steel design, steel slip, and steel top plate force analysis. By discussing the finite element method and related software applications, this paper expects to provide ideas for the analysis of some complex problems in the civil engineering industry and to provide some predictions and suggestions for further advancements.

Design and Mechanical Characterisation of a Large Truss Structure for Continuous Manufacturing in Space.

In this paper, large space structures are essential components of significant equipment in orbits, such as megawatt-class solar power plants and long baseline interferometry. However, to realize the in-space fabrication of such megastructures, the primary consideration is the continuous fabrication of the structure. In this paper, we propose and design a structural form that differs from the minimum constituent unit shape of conventional truss structures by using an efficient winding and weaving method to construct truss structures. The continuously buildable one-dimensional truss’s structural design and mechanical properties are investigated. The parameters affecting the fundamental frequency of the truss structure are analyzed through modeling, simulation and experimental verification of the continuously buildable 1D truss. It is concluded that this configuration truss can be built continuously in space. The most influential factors on the fundamental truss frequency are the truss section spacing, the total truss length and the truss-specific stiffness. The simulated and theoretical values of the truss’s static stiffness and vibration frequency have minor errors, which provide a basis for the configuration design for the continuous manufacturing of large truss structures in space.

Parametric sub-structuring models of large space truss structures for structure/control co-design

Modern and future high precision pointing space missions face increasingly high challenges related to the widespread use of large flexible structures. The development of new modeling tools which are able to account for the multidisciplinary nature of this problem becomes extremely relevant in order to meet both structure and control performance criteria. This paper proposes a novel methodology to analytically model large truss structures in a sub-structuring framework. A three dimensional unit cube element has been designed and validated with a Finite Element commercial software. This model is composed by multiple two-dimensional sub-mechanisms assembled using block-diagram models. This constitutes the building block for constructing complex truss structures by repetitions of the element. The accurate vibration description of the system and its minimal representation, as well as the possibility of accounting for parametric uncertainties in its mechanical parameters, make it an appropriate tool to perform robust Structure/Control co-design. In order to demonstrate the strengths of the proposed approach, a structure/control co-design study case is proposed and solved using structured robust H∞-synthesis. The objective is to optimize the pointing performances of an antenna, minimizing the perturbations coming from the Solar Array Driving Mechanisms (SADM) of two solar panels, performing active control by means of multiple Proof Mass Actuators (PMA), and simultaneously reduce the mass of the truss-structure which connects the antenna to the main spacecraft body.

Comparison of Wind Load on Standard Steel Truss Bridge Based on Indonesian Bridge Loading Codes

The truss bridge is a type of bridge that is widely used in Indonesia because of its practicality and can be constructed in short period of time. The relatively light weight of the truss bridge structure also facilitates the transportation of superstructure materials to bridge locations located in remote areas. The dimensions of the large truss bridge and the relatively light weight cause the figure bridge to be vulnerable to wind loads. Meanwhile, the bridge loading regulations including wind load is continuing to change. Previous design code BMS 1992 and SNI T 02 2005 has been superseded with SNI 1725 2016. One of the main changes to the loading regulations is related to the magnitude and how wind loads are calculated and applied to the bridge structure. This study will compare the magnitude of the wind load in the previous loading regulations in Indonesia with the latest regulations and also with wind loading according to AASHTO on steel truss bridges. A 60-class standard steel truss bridge from the Ministry of Public Works which is used for Case Study. The results showed that there was a significant increase in wind loading by applying SNI 1725 2016 loading regulations

Integral terminal sliding-mode robust vibration control of large space intelligent truss structures using a disturbance observer

This study aims to develop an advanced integral terminal sliding-mode robust control method using a disturbance observer (DO) to suppress the forced vibration of a large space intelligent truss structure (LSITS). First, the dynamics of the electromechanical coupling of the piezoelectric stack actuator and the LSITS, based on finite element and Lagrangian methods, are established. Subsequently, to constrict the vibration of the structure, a novel integral terminal sliding-mode control (ITSMC) law for the DO is used to estimate the parameter perturbation of the LSITS based on a continuous external disturbance. Simulation results show that, under a forced vibration and compared with the ITSMC system without a DO, the displacement amplitude of the ITSMC system with the DO is effectively reduced. In the case where the model parameters of the LSITS deviate by ±50%, and an unknown continuous external disturbance exists, the control system with the DO can adequately attenuate the structural vibration and realize robust control. Concurrently, the voltage of the employed piezoelectric stack actuator is reduced, and voltage jitter is alleviated.

A net-shape forming process of Ti–6Al–4V sphere joints

ABSTRACT Near-net shape forming of the hollow sphere joints (60 mm in diameter) used in large space truss structure of spacecraft was realised by powder injection molding and diffusion bonding. For metal injection molding (MIM) process, two binder systems based on polyoxymethylene (POM) and paraffin wax (PW) are comparatively studied. The powder loading, power law index, viscous flow activation energy and integrated rheological factors of feedstock were systematically studied. Except powder loading, The feedstock based on POM system has a smaller strain and temperature sensitivity (n = 0.368, E = 17.95 kJ mol−1) and better rheological properties (α = 6.3). The lowest interstitials contents of as-sintered samples are 0.05 wt-% for C, 0.28 wt-% for O and 0.046 wt-% for N, which meet the Grade 5 PM (Ti–6Al–4V) specifications according to ASTM B988-13. The tensile strength and ductility reach 978 MPa and 6.3%, respectively, after 1300 °C sintering and capsule-free hot isostatic pressing (HIP).

Experimental seismic behavior of double skin composite wall with steel truss

This paper describes an experimental study to investigate the seismic behavior of double skin composite walls (DSCWs) with steel truss. Based on the results of seven specimens tested at full-scale, the influence of aspect ratio, axial compression ratio, and truss spacing to thickness ratio on the seismic behavior of DSCW with steel truss are considered. The failure mode, load-displacement relationship, strength, ductility, stiffness, energy dissipation capacity, and shear deformation were analyzed. The results showed that the aspect ratio had the most significant influence on the failure mode and seismic behavior of the specimen. For specimens with an aspect ratio of 2.0, shear compression failure dominates, while for specimens with an aspect ratio over 2.0, flexure shear failure dominates. The strength and initial stiffness decreased with the increase of aspect ratio, but the ductility and energy dissipation became better with the increase of aspect ratio. The axial compression had a little positive effect on the strength, but the specimen with a smaller axial compression ratio had better ductility and energy dissipation. The large truss spacing to thickness ratio weakened the external restraint effect of the steel truss on the steel plates, leading to premature buckling and failure of the specimen.

Reanalysis of 2D and 3D truss structures considering simultaneous variations in topology, geometry and size

Approximate reanalysis methods provide effective processes to achieve structural approximate responses without solving the complete set of modified implicit analysis equations. This paper presents methods for carrying out approximate reanalysis of 2D and 3D trusses. Apparently, for the first time, the simultaneous modifications in topology, geometry and size of the structures are taken into account. Three numerical methods, namely, combined approximation, rational approximation and Sherman–Morrison–Woodbury approximation (SMWA), are analyzed and compared for this purpose. The flowchart corresponding to each scheme is presented. Design variables considered are nodal coordinates and cross sectional properties. Moreover, an arrival with bounds between zero and arbitrary amounts includes the variations of the variables. Unlike most works, large trusses with many members are analyzed as numerical examples. Based on obtained outcomes in the several instances, a comparison is conducted between the three schemes and benefits and drawbacks of each method are thoroughly discussed.

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.

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.

Improved vibration attenuation performance of large hoop truss structures via a hybrid control algorithm

This paper proposed a hybrid control algorithm to further enhance the attenuation of the free-decay vibration of a large hoop truss structure by designing a fuzzy logic controller to adaptively tune the feedback gain factors of the PD controller. The basic principle of the tuning rule is that the gains of the PD controller are appropriately increased with the reduction of vibration amplitude, resulting in large active damping in the active vibration control (AVC) system. The hybrid controller was utilized to suppress the first-order modal vibration of a large truss structure and a space antenna. The experimental results demonstrated that the decay time of the truss structure and the space antenna was significantly reduced when using the hybrid control algorithm in comparison with using the PD control algorithm only. The reduction percentage of the decay time was increased to 77.14% in the test truss structure and 65.28% in the space antenna for the hybrid control algorithm, compared to 42.9% and 16.73%, respectively, for the PD control algorithm. Moreover, the vibration attenuation performance of the current hybrid control algorithm was better than that of the unique fuzzy logic control. The hybrid control algorithm enables the corresponding actuators to provide more damping effects on the overall AVC.

A Two-Step Method for Damage Identification and Quantification in Large Trusses via Wavelet Transform and Optimization Algorithm

This paper suggests a two-step approach for damage prognosis in long trusses in which the first step deals with locating probable damages by wavelet transform (WT) and static deflection derived from modal data with the intention of declining the subsequent inverse problem variables. And in the second step, optimization based model updating method applying Artificial Bee Colony (ABC) algorithm will be employed to quantify the predicted damages within an inverse problem. Interestingly, it is indicated that the two-step method greatly aids in declining the number of variables of the model updating process resulting in more precise results and far less computational effort. Moreover, the method is found considerably effective especially for damage prognosis of large trusses. In this regard, two numerical examples including noisy data are contemplated to assess the efficacy of the method for real practical problems. Furthermore, the validity of the second step results is investigated applying other optimizers namely Invasive Weed Optimization (IWO) and Particle Swarm Optimization (PSO).

Response Control of a High-Rise Television Tower under Seismic Excitations by Friction Dampers

High-rise television towers are prone to external wind and earthquake-induced oscillations in severe environments. To avoid excessive vibration under strong earthquakes, a large television tower requires certain measures to abate its dynamic responses. Friction dampers are simple and low-cost solutions for realizing the response control of television towers. In this study, response mitigation and performance assessment are conducted on a large-scale television tower with friction dampers under strong earthquakes. A 3D finite element static model of the high-rise television tower is first established, and then a 2D lumped mass dynamic model is developed. The mechanical model for the friction dampers is presented with the axial stiffness considered. The equations of motion of the damper–tower system under seismic excitations are then determined. The control force transformation, displacement increment transformation, and numerical integration of the coupled damper–tower system’s equations of motion are defined on the basis of the two aforementioned models. Finally, the seismic responses of a high-rise television tower system constructed in China are taken as an example to investigate the validity of the proposed control approach using the friction dampers. The results demonstrate that the implementation of friction dampers with optimal parameters in a large truss tower can substantially suppress the structural seismic responses in terms of peak responses and vibrant energy.

An improved interval finite element method based on the element-by-element technique for large truss system and plane problems

The interval finite element method based on the element-by-element technique is proved to be a rigorous and efficient method for considering interval uncertainties. The structural internal force of the same accuracy as the interval response displacement can be obtained by combining the variational method and the Lagrange multiplier method. However, the increase of the Lagrange multiplier reduces the efficiency of solving the equation, especially for a large truss system. In addition, the method is mostly used to analyse truss system, and the applications in plane problems are still rare. In this article, an improved method involving modification of the Lagrange multiplier interval equations is proposed to calculate interval displacements and interval internal forces at the same time. In this proposed method, the increase of the unknown Lagrange interval does not affect the solution of the equations. For plane problems, a new method for solving the stress interval of the element is proposed. This proposed method can effectively reduce the expansion of the stress interval of the element. Finally, the correctness and rationality of the proposed method are verified by numerical examples.

Improved GWO algorithm for optimal design of truss structures

In this article, an improved grey wolf optimizer (IGWO) algorithm is developed for optimal design of truss structures. Grey wolf optimizer (GWO) is a recently proposed algorithm for optimization, which is herein improved to handle structural optimization in an efficient manner. In this work, performance of the GWO in structural optimization is also investigated. A few tunable parameters are defined to provide proper adaptability for the algorithm and to optimize the structures using fewer structural analyses, while obtaining finer solutions. Hence, in addition to reduce the computational efforts, better solutions are obtained as it is shown by several benchmark examples, where both GWO and IGWO are employed for the optimization. Mathematical functions as well as various design examples from small to large truss structures with different search spaces are examined to demonstrate the ability and efficiency of the present improved version in comparison to its standard version.

Use of wavelets for damage diagnostics in truss structures

PurposeWavelets are being increasingly used for damage diagnostics. The purpose of this paper is to present an algorithm that uses the wavelet transform for detecting mixed-mode, also known as combined mode, cracks in large truss structures.Design/methodology/approachThe mixed-mode crack is modeled by superposing two damage modes, and this model is combined with a finite element model of the truss. The natural modes of the truss are processed through the wavelet transform and then used to determine the damage location. The influence of multiple parameters such as truss geometry, crack geometry, number of truss members, orientation of truss members, etc. is investigated as part of the study.FindingsThe proposed damage detection algorithm is found to be successful in detecting single mode as well as mixed-mode cracks even in the presence of significant end effects, and even when a relatively coarse sampling of natural modes is used. Results from multiple simulations that involve three commonly used truss structures are presented. A correlation between damage severity and the magnitude of wavelet coefficients is observed.Originality/valueThe proposed algorithm is found to be successful in accurately detecting damage, but direct determination of damage severity is found to be challenging.

Research Review on the Manufacturing Technology of Large-span Spatial Pipe Truss Structures of the Tongling Stadium

Aiming at the large cantilever triangle spatial pipe truss structure system of Tngling stadium, from the perspective of component processing technology, studying of machining technology for complex steel structure components, combining the new steel tube with existing commonly used hydraulic press, the smaller investment in equipment will meet the production requirements. In view of the small curvature angle bend, proposing the more straight pipe shrimp tube instead of the circular arc segment has solved the intersecting node production problems of the two small Angle steel pipes. In this paper, the results for complex pipe truss structure was processed for the future similar structure construction with popularization and application value.

Contribution to the knowledge of wide span wooden roofing in Bologna area

This paper deals with the analysis of some examples of large wooden trusses in important churches of Bologna carried out through a survey campaign conducted with a laser scanner. This study helped to develop a wider methodology for instrumental survey, aiming to derive a series of significant information: average deviations of the structures compared to theoretical models, deformations of the elements through time, instability, material state of conservation, structural behaviour both locally and globally. All results highlighted the knowledge that the structural design of these wooden roofing is strictly related to their dimensions and assembly, the understanding of which is functional on any restoration intervention.

Experimental and analytical investigations on a large floor truss pinned connection

The pinned connection method was used to connect the large-span floor truss to the steel column in Zoucheng International Conference Center project, which played a quite important role to achieve the in-plane rotation and transfer heavy loads directly. Four specimens were tested experimentally to investigate the monotonic and cyclic behavior of this connection method, including two independent pinned connections and two assembled truss connections. The load–displacement curves, deformation development, failure mode, ductility, and energy dissipation capacity were discussed in detail. Besides, the nonlinear multi-scale finite element models of the pinned and truss connections were established. The numerical simulations not only captured the global behavior and local limit states observed in tests but also revealed valuable new information that could not be directly obtained from the tests. The experimental and numerical results showed that both the pinned and truss connections had good ductility, load transfer ability, and ideal rotation capacity with large safety margin, indicating these constructions could be used as references for similar projects.

Multi-modal vibration control of truss bridges with tuned mass dampers under general loading

Applications of tuned mass damper (TMD) systems for bridge structures are observed for mitigation of problem related to excessive vibration induced by either wind loading or vehicle loading, where dominant modes usually in one direction (commonly vertical) are taken into account. Considering modes dominant in one direction may not be considered as a robust practice while any bridge structure is having dominant modes along both the transverse and vertical directions and the same bridge structure is subjected to loading along both the directions. In the present study, an approach for simultaneous control of major horizontal, vertical and torsional modes is presented targeting robust vibration control under general loading condition. A strategy using modal frequency response function (FRF) is proposed based on the traditional mode-wise control approach. The proposed modal FRF based approach is applied to an existing important large truss bridge (Saraighat Bridge) to carry out an analytical design of TMD system considering general loading conditions. The designed TMD system is found to demonstrate good performance under various white-noise based general loading conditions.