Space Truss Structures Research Articles

Description and Regulation of Drilling Completion Fluid Cake Structure

In the process of oil and gas well drilling and completion, under the action of positive pressure gradient or self-absorption, drilling and completion fluid solid phase particles block the reservoir pore and form the filter cake. The filter cake plays a vital role in reservoir protection, and is closely related to the oil and gas well productivity from cake formation to remove. The filter cake is always expected to be thin, tough, with low permeability and easy to remove. Many scholars made a lot of research from the filter cake layer structure, space truss structure, pore structure and the structure of fractal structure of filter cake. However, the researches on the structure of the filter cake are mainly conducted qualitatively at home and abroad, while the quantitative research progress is slow. At the same time, the research on the relationship between the filter cake structure and its performance is also relatively weak. In recent years, with the wide application of horizontal wells, it has called widespread attention on how to effectively remove filter cake in order to improve the oil and gas well production capacity at home and abroad. The widely-used filter cake removal technology mainly includes natural clear, mechanical removal, chemical removal and biological removal technology currently. Among them, the biological removal technology is developed in recent years as a new type of filter cake removal technology. With the further development of mud cake removal technology and downhole filter cake removing circumstance with increasing complexity, a single filter cake removal technology cannot completely meet the requirements. The filter cake removal technology is developing in the direction of the composite to clear, in order to obtain ideal filter cake removal effect.

Torsional behavior of a hybrid FRP-aluminum space truss bridge: Experimental and numerical study

A novel lightweight hybrid fiber-reinforced polymer (FRP) – aluminum space truss structure that consists of two triangular deck-truss beams has been designed for rapid emergency bridging system. This paper reports a large-scale pure torsion test on a cantilever full-scale specimen to evaluate the detailed linear-elastic torsional behavior and the load-carrying mechanism of the hybrid twin-trackway spatial structure. Additionally, a structural computational finite element model (FEM) was constructed and validated against the experiments. To fully understand the load-carrying mechanism obtained from the experiments, numerical analyses were performed by equivalently converting the torsion reaction of the hybrid twin-trackway structure to the bending and torsion of its twin triangular deck-truss beams. The results indicate that the experimental structure exhibits a good and specific torsional response, which can be well described by FEM. The unidirectional pultruded FRP profiles are mainly subjected to axial forces and are thus appropriate for application to this unique twin-trackway space truss, unlike in the case of the alone single-trackway triangular beam under torsion. The vertical bending of the twin triangular deck-truss beams play a key role in the behavior of load-carrying of the entire bridge, unlike in the case of the conventional torsional calculation method for the separated box beam. In the initial design, the torsional calculation of such a novel bridge can be carried out using the flexural analytical and numerical models of the triangular deck-truss beam.

Analysis of the progressive collapse of space truss structures during earthquakes based on a physical theory hysteretic model

This study develops a force–displacement hysteresis model (computer program) for a bar element based on a physical theory model. The model is capable of capturing complex physical phenomena of member, such as yielding under tension, non-elastic buckling under compression, growth effect and degradation of buckling capacity due to the Bauschinger effect. The proposed element model is validated by comparing the simulation results with previous experimental results and is applied to the dynamic analysis of space truss structures. The explicit dynamic analysis method is adopted for solving the nonlinear equations of motion. Furthermore, a case study of a three-layer space truss structure is conducted. The reliability of the proposed algorithm and the need to develop the bar element are verified by comparing the results obtained using the proposed method and the ANSYS finite element analysis software package. Moreover, several fracture criteria for bar elements are defined and are used to analyse the progressive collapse of a space truss structure under seismic loading. The analytical results demonstrate that the selection of the fracture criterion for the bar members significantly affects the calculation of the collapse of the space truss structure under seismic loading. The strut buckling/softening-based fracture criterion can be used to relatively accurately evaluate the collapse resistance of a space truss structure under seismic loading. Finally, the collapse mode of a power transmission tower model under seismic loading is simulated. The simulation results are then compared with the collapse mode of a power transmission tower with a similar structure that collapsed during the Wenchuan earthquake. The simulation results agree closely with the observations, thereby verifying the reliability of the proposed algorithm.

Sequence planning for human and robot cooperative assembly of large space truss structures

PurposeIn the future, large space truss structures will be likely to require on-orbit assembly. One of the several proposed methods includes cooperative assembly performed by pressure-suited astronauts during extravehicular activity (EVA) and space robots. An intelligent planning method was presented to generate optimal assembly tasks.Design/methodology/approachFirstly, the inherent hierarchical nature of truss structures allows assembly sequences to be considered from strut level and structural volume element (SVE) level. Then, a serial assembly strategy in human-robot environment was applied. Furthermore, a two-level planning algorithm was presented. At the first-level planning, one ant colony algorithm for assembly sequence planning was improved to adopt assembly direction and time as heuristic information and did not consider assembly tasks. And, at the second-level planning, another novel colony algorithm for assembly task planning mainly considered results of the first-level planning, human-robot interactive information, serial assembly strategy and assembly task distributions.FindingsThe proposed two-level planning algorithm is very effective for solving the human and robot cooperative assembly of large space truss structures.Research limitations/implicationsIn this paper, the case study is based on the following assumptions: each tetrahedron is assembled by two astronauts; each pentahedron is assembled by three astronauts.Practical implicationsA case illustrates the results of the two-level planning. From this case study, because of geometrical symmetry nature of large space truss structures, the optimal assembly sequences are not only one.Originality/valueThe improved ant colony algorithm can deal with the assembly sequence and task planning in human-robot environment more effectively.

Application of lightweight materials in structure concept design of large-scale solar energy unmanned aerial vehicle

Carbon fiber composites and film materials can be effectively used in light aircraft structures, especially for solar unmanned aerial vehicles. The use of light materials can reduce the weight of the aircraft, but also can effectively improve the aircraft's strength and stiffness. The structure of the large aspect ratio solar energy UAV was analyzed in detail, taking Solar-impulse solar aircraft as an example. The solar energy UAV has a wing aspect ratio greater than 20, and the detailed digital model of the wing structure including beam, ribs and skin was built, also the Finite Element Method was applied to analyze the static and dynamic performance of the structure. The upper skin of the wing is covered with silicon solar cells, while the lower skin is light and transparent film. The single beam truss form of carbon fiber lightweight material is used in the wing structure. The wing beam is a box beam with rectangular cross sections. The box beam connected the front parts and after parts of the ribs together. The fuselage of the aircraft was built by space truss structure. According to the static and dynamic analysis with Finite Element method, it was found that the aircraft has a small wingtip deflection relative to the wingspan in the level flight state. The first natural frequency of the wing structure is pretty low, which is closed to the gust load.

Optimum design and vibration control of a space structure with the hybrid semi-active control devices

Based on the super elastic properties of the shape memory alloy (SMA) and the inverse piezoelectric effect of piezoelectric (PZT) ceramics, a kind of hybrid semi-active control device was designed and made, its mechanical properties test was done under different frequency and different voltage. The local search ability of genetic algorithm is poor, which would fall into the defect of prematurity easily. A kind of adaptive immune memory cloning algorithm(AIMCA) was proposed based on the simulation of clone selection and immune memory process. It can adjust the mutation probability and clone scale adaptively through the way of introducing memory cell and antibody incentive degrees. And performance indicator based on the modal controllable degree was taken as antigen-antibody affinity function, the optimization analysis of damper layout in a space truss structure was done. The structural seismic response was analyzed by applying the neural network prediction model and T-S fuzzy logic. Results show that SMA and PZT friction composite damper has a good energy dissipation capacity and stable performance, the bigger voltage, the better energy dissipation ability. Compared with genetic algorithm, the adaptive immune memory clone algorithm overcomes the problem of prematurity effectively. Besides, it has stronger global searching ability, better population diversity and faster convergence speed, makes the damper has a better arrangement position in structural dampers optimization leading to the better damping effect.

Dynamic Analysis of Crane Boom System based on Positional FEM

The dynamic characteristics under modifying-amplitude of the crawler crane boom system are simulated by positional FEM. Based on the stress characteristics of space truss structure, the simplified FEM model for boom system is established by simulating the main jib of the boom with variable cross-section beam element and three-node beam element; the dynamic response time history of the boom system under modifyingamplitude is derived; these provide crucial theories for the design and analysis of hoisting machinery.

Interval analysis based robust truss optimization with continuous and discrete variables using mix-coded genetic algorithm

The problem of optimizing truss structures in the presence of uncertain parameters considering both continuous and discrete design variables is studied. An interval analysis based robust optimization method combined with the improved genetic algorithm is proposed for solving the problem. Uncertain parameters are assumed to be bounded in specified intervals. The natural interval extensions are employed to obtain explicitly a conservative approximation of the upper and lower bounds of the structural response, and hereby the bounds of the objective function and the constraint function. This way the uncertainty design may be performed in a very efficient manner in comparison with the probabilistic analysis based method. A mix-coded genetic algorithm (GA), where the discrete variables are coded with binary numbers while the continuous variables are coded with real numbers, is developed to deal with simultaneously the continuous and discrete design variables of the optimization model. An improved differences control strategy is proposed to avoid the GA getting stuck in local optima. Several numerical examples concerning the optimization of plane and space truss structures with continuous, discrete or mixed design variables are presented to validate the method developed in the present paper. Monte Carlo simulation shows that the interval analysis based optimization method gives much more robust designs in comparison with the deterministic optimization method.

A method of curvature mode difference and wavelet transform to damage detection on space grid structure

A method combined curvature mode difference and wavelet transformation was used to determine the damage location of space gird structure. This method considered the curvature mode difference of pre and post damage as the wavelet transform analysis signal. Moreover, these signals were analyzed by wavelet transform using wavelet function db3. As the wavelet transform coefficient occur sudden change, the damage locations of links will be obtained. In this paper, square pyramid space grid structure, orthogonal space truss structure, three way latticed grid and honeycomb triangular pyramid grid structure will be analyzed using this method to identify single damage and multi-damage location. The solutions from numerical simulations show that this method can take effective identification of single damage location and multi-damage location of square pyramid space grid structure by the first mode condition. And this method has versatility to detect damages from different space grid structures.

Research on the Vibration Control Algorithms for Large Space Truss Structure Based on Precise Integration Method

In this paper, vibration control algorithms for a large space truss structure are investigated. First, a precise integration method is used to solve the differential equation such that the validity and efficiency of the algorithm are guaranteed. Second, on the basis of the discrete algebraic equation combined with the decentralized control theory, the solving method of the control force based on the linear quadratic (LQ) optimal control theory is improved. Third, a new control method, the eigenvalue control method, is proposed in this paper, and its relationship with the LQ optimal control method is discussed. Finally, these two control methods are applied to the structure to analyze the effectiveness of vibration suppression. The simulation results show that the proposed algorithms can quickly suppress the vibration of a large space truss structure.

Simplified design method and seismic performance of space trusses with consideration of the influence of the stiffness of their lower supporting columns

Static and dynamic force performance of two types of space truss structures i.e. square pyramid space truss (SPST) and diagonal on square pyramid space truss (DSPST), are studied to determine the effect of stiffness of their lower supporting members. A simplified model for the supporting columns and the equivalent spring mass system are presented. Furthermore, the feasibility of the simplified model is demonstrated through theoretical analysis and examples of comparative analysis of the simplified model with the entire model. Meanwhile, from the elastic analysis under frequently occurring earthquakes and elasto-plastic analysis under seldom occurring earthquakes subjected to TAFT and EL-Centro seismic oscillation it is shown that the simplified method can be encompassed in the results from the normal model. It also showed good agreement between the two methods, as well as greatly improved the computational efficiency. This study verified that the dynamic effect of the supporting structures was under considered in space truss design in the past. The method proposed in the paper has important significance for other space truss structures.

Experimental studies on behaviour of bolted ball-cylinder joints under axial force

Due to excellent advantages such as better illuminative effects, considerable material savings and ease and rapidness of construction, the bolted ball-cylinder joint which is a new type joint system has been proposed in space truss structures. In order to reveal more information and understanding on the behaviour of bolted ball-cylinder joints, full-scale experiments on eight bolted ball-cylinder joint specimens were conducted. Five joint specimens were subjected to axial compressive force, while another three joint specimens were subjected to axial tensile force. The parameters investigated herein were the outside diameter of hollow cylinders, the height of hollow cylinders, the thickness of hollow cylinders, ribbed stiffener and axial force. These joint specimens were collapsed by excessive deformation of hollow cylinders, punching damage of hollow cylinders, evulsion of bolts, and weld cracking. The strain distributions on the hollow cylinder opening were mainly controlled by bending moments. To improve the ultimate bearing capacity and axial stiffness of bolted ball-cylinder joints, two effective measures were developed: (1) the thickness of the hollow cylinder needed to be thicker; (2) the ribbed stiffener should be adopted. In addition, the axial stiffness of bolted ball-cylinder joints exhibited significant non-linear characteristics.

A new approach to deal with sensor errors in structural controls with MR damper

As commonly known, sensor errors and faulty signals may potentially lead structures in vibration to catastrophic failures. This paper presents a new approach to deal with sensor errors/faults in vibration control of structures by using the Fault detection and isolation (FDI) technique. To demonstrate the effectiveness of the approach, a space truss structure with semi-active devices such as Magneto-Rheological (MR) damper is used as an example. To address the problem, a Linear Matrix Inequality (LMI) based fixed-order H FDI filter is introduced and designed. Modeling errors are treated as uncertainties in the FDI filter design to verify the robustness of the proposed FDI filter. Furthermore, an innovative Fuzzy Fault Tolerant Controller (FFTC) has been developed for this space truss structure model to preserve the pre-specified performance in the presence of sensor errors or faults. Simulation results have demonstrated that the proposed FDI filter is capable of detecting and isolating sensor errors/faults and actuator faults e.g., accelerometers and MR dampers, and the proposed FFTC can maintain the structural vibration suppression in faulty conditions.

Microvibration suppression of space truss structures using viscoelastic dampers with design parameter optimization

This paper addresses the microvibration suppression problem for space truss structures by using viscoelastic dampers (VEDs). Based on the principle of virtual work, a finite element dynamic model of a spacecraft consisting of a reaction wheels assembly (RWA), a truss support structure, VEDs, and an optic camera is built. The angular displacement response function of the structure at the camera optic axis excited by the RWA disturbance forces is obtained. Then an optimization model is built in which an improved average pointing stability metric is adopted as the objective function, and the placement, number, and design parameters of VEDs are considered as optimal variables. To solve the presented discrete–continuous optimization problem, a new hybrid algorithm that has combined the advantage of the differential evolution (DE) algorithm and the simulated annealing (SA) algorithm is presented. Simulation results demonstrate that the present method can find the optimal solution faster than DE. Finally, the disturbance forces data of the RWA are measured by experiment, and were used as the system input to simulate the pointing stability of the optic camera in three cases: without VEDs, with VEDs (initial parameters), and with VEDs (optimal parameters). The results indicate that VEDs with optimized parameters can significantly improve the pointing stability of the optic camera.

Application of multistage homotopy perturbation method to the nonlinear space truss model

The purpose of this study is to investigate the applicability of multistage homotopy perturbation method (MHPM) to space truss structures composed of discrete members in order to obtain an analytical solution. For this research purpose, a nonlinear dynamic governing equation of the space truss structures was formulated in consideration of geometrical nonlinearity, and homotopy equations were derived using a formulated differential equation. The result of carrying out a dynamic analysis on a single-free-node model and a double-free-nodes model were compared with the classical homotopy perturbation method and the 4th order Runge-Kutta method (RK4), and it was found that the dynamic response by MHPM concurred with the numerical results. Additionally, the pattern of the response and attractor in the phase space could delineate the dynamic snapping properties of the space truss structures under excitations, and the attraction of the model in consideration of damping reflected well the convergence and asymptotic stable.

Analytical testing and evaluation of truss typed structures for tunnel maintenance

The goal of this study is to present numerical modeling and analytical testing in order to evaluate an innovative space truss typed temporary structure, which is used to maintenance and repair of road tunnels. The present space truss structure has merits to use UL-700 high strength steel tube as members and to carry out maintenance and repair works of road tunnels without blocking cars and transportations. Numerical modeling and analytical testing of the space truss are investigated by using commercial engineering software, i.e., ABAQUS 6.5-1, and then it is verified that the truss structure has both structural safety and effective function for maintenances and repairs of road tunnels.

Estimation of internal forces in cladding support components due to wind-induced overall behaviors of long-span roof structure

Wind-induced internal forces in cladding support components of a long-span roof structure depend on local behaviors caused by local wind loads and wind-induced overall behaviors of the main structural frame. Based on the pioneering work of Ding and Tamura (2013); Ding et al. (2012), a new method is proposed to estimate internal forces in cladding support components due to wind-induced overall behaviors directly. A detailed investigation on the contributions of wind-induced overall and local behaviors for internal forces in cladding support components of a space truss structure is performed. The results demonstrate that the bending moments and shear forces in cladding support components are dominated by local wind loads acting on the corresponding tributary areas, and the axial forces are caused by the overall displacements of the main structural frame. Considering only the local behavior will underestimate the axial forces in cladding support components significantly, which may lead to buckling failure.

Damage Identification of Space Truss Structure Based on Strain Modal and Wavelet Transform

Based on the characteristics of space truss structures, the concept of modal strain energy is introduced and square difference in elemental modal strain is presented. Through the square difference in elemental modal strain and wavelet transform, this paper presents a method for space truss structure damage recognition. The structural damage index is presented with the change of wavelet coefficients. Numerical simulation results show that: this method is effective to locate the single, multiple damages and light, severe damage with the first mode information. The preliminary tries for damage extent identification were made by the wavelet coefficients.

Damage Identification of Truss Structures Based on Force Method

AbstractAn computationally efficient damage identification technique for the planar and space truss structures is presented based on the force method and the micro genetic algorithm. For this purpose, the general equilibrium equations and the kinematic relations in which the reaction forces and the displacements at nodes are take into account, respectively, are formulated. The compatibility equations in terms of forces are explicitly presented using the singular value decomposition (SVD) technique. Then governing equations with unknown reaction forces and initial elongations are derived. Next, the micro genetic algorithm (MGA) is used to properly identify the site and extent of multiple damage cases in truss structures. In order to verify the accuracy and the superiority of the proposed damage detection technique, the numerical solutions are presented for the planar and space truss models. The numerical results indicate that the combination of the force method and the MGA can provide a reliable tool to accurately and efficiently identify the multiple damages of the truss structures.

Preliminary Research on Connecting Strategy between Back-Up Structure and Alidade for 110-m QitTai Radio Telescope

The QTT (QiTai 110m radio telescope) antenna, with large aperture and high main-reflector surface precision, whose connecting strategy between back-up structure and alidade was investigated. In order to make the reflector surface deformation coordinated, the connecting strategies of “umbrella supporting”, “space truss” and “double gear” structure were constructed and analyzed based on FEM (finite element method). The results show that “double gear supporting” is superior to “space truss structure”, and the latter is better than “umbrella supporting”, while in the “umbrella supporting structure”, the smaller cone angle is good for reflector deformation coordination. These structures are easy to achieve antenna structure “homology” design.