Truss Structure Model Research Articles

Research of methods for determining dynamic stress of the bars in the main structure of gantry crane installed on the cap of bridge pier to serve installation of Super-T girder

The article presents briefly findings in researching methods for determining dynamic stress of the bars in the main structure of gantry crane installed on the cap of bridge pier to install and launch SUPER-T girder. In order to study the dynamic stresses in the bars of the main truss structure of the gantry, the author first had to build a dynamic model, using Matlap software to solve the problem of dynamics with two cases cargo lowering combination combines braking and moving of gantry with cargo to find out the rules and values of dynamic cable tension, dynamic inertial force ( time-varying force), then consider these forces is the external force acting on the main truss structure model of the gantry, from which the author calculates the value of internal force and stress of each bar corresponding to the value of dynamic cable tension and corresponding dynamic inertia force. with two adverse working cases of the gantry. Using Matlap software to calculate the author has obtained a graph of internal force, stress changes over time of each bar in the main truss steel structure of the gantry. The findings of the research provided methods for determining the dynamic stress of the bars in the main structure of gantry crane, pointed out values and rules of change of the dynamic stress of the bars in the main structure of gantry crane. The findings of the research may be used to calculate fatigue, life-span of the main steel structures as well as other parts of the gantry crane

Structure Damage Identification Based on Information Entropy and Bayesian Fusion

When processing signals, information entropy theory and data fusion theory have their own advantages. The former can improve the sensitivity of signals, while the latter can superimpose multisource information to correct system deviations and obtain the best identification results. Therefore, we introduce two theories into structural damage identification to improve the reliability of damage identification. First, based on the modal strain energy damage identification index, combined with information entropy and data fusion theory, a fusion entropy index (FE) and an entropy weight fusion index (EWF) are constructed. Then, the simply supported beam and truss structure model are established for damage simulation, which verified that the FE index and EWF index can accurately locate the damage. The polynomial fitting method is used to identify the damage degree of the structure, and the identification results obtained are more accurate. Finally, a simple-supported steel beam model is established in the laboratory for verification and analysis. The results show that the proposed FE index and EWF index have high damage sensitivity, noise resistance, and robustness, and relatively speaking, EWF index damage recognition ability is better. The method proposed in this paper provides an empirical method for practical engineering application.

Using DNA to Control the Mechanical Response of Nanoparticle Superlattices.

Nanoparticle superlattice assembly has been proposed as an ideal means of programming material properties as a function of hierarchical organization of different building blocks. While many investigations have focused on electromagnetic, optical, and transport behaviors, nanoscale self-assembly via supramolecular interactions is also a potentially desirable method to program material mechanical behavior, as it allows the strength and three-dimensional organization of chemical bonds to be used as handles to manipulate how a material responds to external stress. DNA-grafted nanoparticles are a particularly promising building block for such hierarchically organized materials because of DNA's tunable and nucleobase sequence-specific complementary binding. Using nanoindentation, we show here that the programmability of oligonucleotide interactions allows the modulus of DNA-grafted nanoparticle superlattices to be easily tuned overly nearly 2 orders of magnitude. Additionally, we demonstrate that alterations to the supramolecular bond strength between particles can alter how a lattice deforms under applied mechanical force. As a result, the superlattices can be programmed either to reorganize their internal structures to dissipate mechanical energy or to completely recover their initial structure upon relaxation, independently of how the particles are arranged in 3D space. These behaviors are subsequently explained as a function of the hierarchical structure of the DNA-guided assemblies by using a simple truss-structure model. Altering the supramolecular DNA connections between particles therefore provides a simple and rational means of dictating different aspects of material mechanical response to produce tailorable properties that are not typically observed in conventional bulk materials. Ultimately, these studies enable control over the deformation behavior of future DNA-assembled nanomaterials and provide evidence that supramolecular chemistry is an effective tool in controlling the mechanical properties of nanomaterials as a function of their hierarchical design.

Magnetic Stress Sensing System for Nondestructive Stress Testing of Structural Steel and Steel Truss Components Based on Existing Magnetism.

To detect the stress of steel structures and members using the existing magnetism, a magnetic stress sensing system integrating a magnetic flux induction coil, a magnetic flux measurement device, a loaded device, and data acquisition software was developed. The magnetic coupling test research was carried out for different grades of structural building and bridge steel specimens to establish the magnetic stress flux mathematical model, and the fitting equation of the magnetic flux changes with the positions of different sections of specimens was analyzed. Furthermore, a practical formula for stress detection was obtained through the experiments. Meanwhile, on these bases, the typical steel truss structure model of a Bailey beam was designed and manufactured under different working conditions, nondestructive online stress testing was carried out, and the stress of the model structure and its members was measured by strain and magnetic flux tests to obtain the curves of the test results for the stress–strain and magnetic stress flux, respectively. The results of these two methods are in good agreement with each other. The stress of the steel truss model structure was analyzed and calculated using the finite element method. The results agreed well with the experimental results from the magnetic stress sensing system—the maximum error was about 5%, which meets the requirements of engineering applications.

Structural damage identification based on gray cloud rule generator algorithm

It is difficult for the traditional methods to identify uncertain damage problems caused by noise. Therefore, a gray cloud rule generator algorithm based on cloud model and modal strain energy is presented to solve the problems. Cloud model can simulate both randomness and fuzziness with fixed parameters. Therefore, it is applicable for the uncertain damage problems. First, modal strain energy and modal strain energy dissipation ratio index are introduced. Then, numerical characteristics of a cloud model are described and some cloud generators are analyzed. Finally, a gray cloud rule is proposed and the gray cloud rule generator algorithm based on the gray cloud rule generator and modal strain energy is developed. The interference of uncertain noise is reduced through a large number of cloud droplets. A two-dimensional truss structure model has been used to verify the effectiveness of the algorithm. The results indicate that the proposed gray cloud rule generator algorithm is applicable to identify the uncertain damage caused by noise, and the identification results of the proposed method are relatively better than those of modal strain energy dissipation ratio index.

Parameter selection for model updating based on the global sensitivity method

A new model-updating parameter selection method based on global sensitivity analysis is presented in this work. A specifically designed evaluation function is used for the probability that the sample fits the distribution of test data. In contrast to other parameter selection methods the test-data information is introduced to the parameter selection procedure. Global sensitivity analysis is performed and a set of composite indices for parameter selection is calculated. The parameters are selected based on the values of these composite indices. The method is validated using simulation data from a pin-jointed truss structure model. The cases of independent and correlated parameters are studied and the presented method is shown to be effective for both.

Parameter selection for model updating with global sensitivity analysis

Abstract The problem of selecting parameters for stochastic model updating is one that has been studied for decades, yet no method exists that guarantees the ‘correct’ choice. In this paper, a method is formulated based on global sensitivity analysis using a new evaluation function and a composite sensitivity index that discriminates explicitly between sets of parameters with correctly-modelled and erroneous statistics. The method is applied successfully to simulated data for a pin-jointed truss structure model in two studies, for the cases of independent and correlated parameters respectively. Finally, experimental validation of the method is carried out on a frame structure with uncertainty in the position of two masses. The statistics of mass positions are confirmed by the proposed method to be correctly modelled using a Kriging surrogate.

Global sensitivity analysis based on distance correlation for structural systems with multivariate output

Models with multivariate output are often used in practical structural systems. Multivariate global sensitivity analysis (GSA) plays an important role in quantifying the contribution of uncertainty in the model input to the output, which is quite useful for simplifying the models and improving the model performance. Many traditional global sensitivity indices can be considered as dependence measures of model input and output. However, these dependence measures can only measure the dependence between two scalar random variables. In this paper, the distance correlation, which can measure the dependence between random vectors, is utilized for multivariate GSA for structural systems with multivariate output. The distance correlation based sensitivity index not only considers the whole probability distribution of multivariate output but also can be easily estimated with only a single set of input–output samples. A numerical example is adopted at first. Then the distance correlation based sensitivity index is applied to a vibration problem in structural dynamics, a truss structure model and a wing box structure model. The results show that the distance correlation based sensitivity index has a higher robustness compared to the covariance-decomposition based sensitivity index.

Crack simulation and probability analysis using irregular truss structure modeling equivalent to a continuum structure

The problems related to agricultural structure engineering for crack simulation and reliability analysis are complicated because its variables contain wide ranges of mean and standard deviation. This paper describes an integrated model to perform crack simulation and reliability analysis of a continuum structure. The structure is assumed to be under a two-dimensional plane stress and the deformation is infinitesimal. A truss structure model that has the same behaviour as a continuum structure was developed using irregular triangle truss components where each element consists of two hinges with an axial degree of freedom at both of their ends. A Monte-Carlo simulation (MCS) was adopted for the reliability analysis. If the length of one side of the irregular triangle mesh is shorter than the thickness of the structure, the slenderness associated with compressive failure needs to be examined only for the short column. For that reason, the failure criterion suitable for the equivalent truss structure model was established by checking only axial stresses acting on truss members. Since nodes of the equivalent truss structure model for the structural analysis in this study consist of hinges, development of plastic hinges that occurred during crack propagation were not considered in this model. To simulate the development of crack, truss members over allowable stresses of tension or compression among truss members with the largest amount of stress at each completed structural analysis time step were sequentially removed. Since irregular triangle meshes have an uncertainty in themselves to compare with regular meshes, the equivalent truss structure model could describe crack propagation more realistically. The failure probabilities of structures under various loads and boundary conditions had good agreement with the analytical solutions directly solved from the limit state equations expressed in the form of moments. Keywords: crack simulation, probability analysis, irregular truss structure model, failure criteria, Monte Carlo simulation DOI: 10.3965/j.ijabe.20171001.2024 Citation: Choi W, Yoon S, Lee J. Crack simulation and probability analysis using irregular truss structure modeling equivalent to a continuum structure. Int J Agric & Biol Eng, 2017; 10(1): 234–247.

Damage Detection of Structures Subject to Nonlinear Effects of Changing Environmental Conditions

Damage detection of civil structures has been carried out by mainly analysing the vibration properties of the structures which change when damages occur. However, these properties are also affected by the changing environmental conditions the structures are face with, and these conditions usually produce nonlinear effects on the vibration properties. Hence, a method is proposed in this paper to analyse structures subjected to nonlinear effects of environmental conditions. The method first applies Principal Component Analysis (PCA) on a bank of damage sensitivity features, followed by applying Gaussian Mixture Model on the obtained first principal component scores to cluster the data into several linear regions. By creating a baseline for each linear region using two extreme and opposite environmental conditions, and adding new measurements to the baseline one at a time followed by applying PCA, damage detection can be achieved. The method is validated on a numerical truss structure model and on the Z24 Bridge. The results demonstrate the ability of the method to analyse structures under nonlinear environmental effects.

Optimal sensor placement methodology for uncertainty reduction in the assessment of structural condition

This paper introduces a novel approach for selecting sensor positions for uncertainty reduction in the assessment of structural condition, where the main difficulty is how to quantify the uncertainty. In order to tackle this problem, a condition index, which is a linear combination of the finite-element model parameters, is defined. By taking the multiplying coefficient equal to the vulnerability index corresponding to each model parameter, the linearized condition index is able to reflect the influence of local damage on the global damage condition. The uncertainty in the estimate of this linearized condition index can be readily quantified from the uncertainty in the updated model parameters. Bayesian finite-element model updating is applied for uncertainty quantification in the model parameters. The procedure of the proposed method is illustrated by designing the optimal sensor configuration for a truss structure model. The simulated damage and condition assessment of the truss structure shows that the proposed method is effective in reducing the uncertainty in the condition assessment. Furthermore, it is demonstrated that the proposed method is useful for a more important reason: it can reduce the uncertainty in the damage assessment of vulnerable substructure. Copyright © 2016 John Wiley & Sons, Ltd.

Regular truss structure model equivalent to continuum structure

It is difficult to solve the structural problems related to agricultural engineering, due to the wide ranges of the means of related variables and complex structural shapes. For these reasons, discrete models are required that are able to replace or simplify solid structure components used in traditional analysis methods. Therefore, the objective of this study was to develop a regular truss structure model that behaves the same way as a solid structure. It was assumed that if a unit element consists of truss elements with each hinge at the end of the element and the size of the element is infinitesimal, the stress distribution and displacement field will be constant throughout the domain of the unit element. Additionally, the behavior of the truss element was assumed to be in a linear state in a two-dimensional plane. The law of energy conservation, based on the theory of elasticity, was applied to determine the equilibrium conditions between discretized and solid elements. The restrictive condition that we obtained revealed that applications are limited to only ideal elastic materials with a Poisson’s ratio of 1 to 3. The volumetric ratio of the equivalent truss to the continuum structures was 3:1, regardless of the size or number of the mesh. To calculate the internal stress and strain of the unit element, the geometric relationships of each truss member, which has its own role against different stress directions, were used. The calculated von Misses stresses were used to verify this model. Stress concentrations, as explained based on Saint Venant’s principle, were also observed in the equivalent truss structure model. The main stress paths, indicating the areas where reinforcement bars should be placed, were successfully shown without the requirement that each element be transformed in the direction of principal stress; this was done by eliminating elements with only compressive and near-zero stresses. Keywords: structural analysis, regular mesh, equivalent truss structure model, discretized element, energy method DOI: 10.3965/j.ijabe.20150805.1742 Citation: Choi W, Lee J, Yoon S. Regular truss structure model equivalent to continuum structure. Int J Agric & Biol Eng, 2015; 8(5): 151－161.

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.

Deformation criterion of the prefracture state of truss-structure elements and an acoustic-emission resonance technique on their basis

The results of theoretical and experimental studies of the prefracture state of truss-structure elements with a cut determined by finite-element analysis of the resonance frequencies and modes of forced vibrations, which are associated with the time history of the acoustic-emission parameters, are given. The natural frequencies of plane vibration modes of a delta-shaped truss-structure element most sensitive to changes in the geometrical dimensions (the depth and angle of opening) of a cut are determined. A relationship between the angle of the cut opening and the value of displacements (accelerations) at the truss-structure model points adjacent to the cut is formulated. It is shown that the angle of the cut opening, calculated using this relationship, is completely a deformation criterion of the prefracture state of structures. The values of resonance frequencies of forced vibrations of structure elements at which the critical angle is reached and over which intense cracking begins are found.

Study on Spatial Stability of Mobile Bailey Truss Structure

Taking the southern approach bridge of Yudong Yangtze River Bridge as the research object,which applies the cast-in-place construction technology to continuous box girder on Bailey beams stent,the stent-reaction forces under different conditions of cast-in-place box girder are obtained through Dr 3.0 bridge finite element analysis software.Then Bailey truss structure model established by ANSYS 9.0 finite element analysis software is applied to check the spatial stability in the construction of Bailey truss structure.The relevant stability coefficients and the corresponding instability modes are obtained.Eventually,relevant recommendations to prevent such instability of Bailey stent are given.

Deformation analysis of timber-framed panel dome structure I: simulation of a dome model connected by elastic springs

This study develops an analytical method that enables the simulation of the deformation of timber-framed plywood panel dome structures, of which strength is largely governed by the rigidity of joints. A hybrid truss structure model was employed to analyze this structure. In this model, we aimed to incorporate the mechanical properties of bolted and nailed joints, which were employed to build the structures, although the present investigation focused on the deformation characteristics of a dome in which the panel elements were connected mutually by elastic springs. The results of the theoretical analysis are compared with those obtained by experiments. The simulated results were found to be in good agreement with the results of the experiments under similar loading conditions.

Continuum Modeling of an Innovative Space-Based Radar Antenna Truss

Many proposed inflatable designs for space applications consist of truss-like or lattice structures due to their simplicity of construction coupled with large stiffness to density ratios. An analytical approach is presented here in order to derive the governing partial differential equations of motion which are decoupled for bending and rotational coordinates of vibrations and applies this formulation to the truss structure model of an innovative space-based radar antenna. Kinetic and potential energy expressions are written in terms of nodal velocities and strain components of bar members within a repeating truss element. Hamilton’s principle is then employed to find the equations of motion for the system. The equations for bending are presented in their decoupled form in order to derive an equivalent Timoshenko beam model for the truss. Finally, the physical characteristics of the continuum model are written in terms of the material and geometrical properties of the original truss, which provide a simple tool for comparing dynamic characteristics of lattices with different properties. The natural frequencies are found for each of the bending coordinates of vibration and are compared to those of a standard finite-element method (FEM) solution, for the purpose of validation. The partial differential equations predictions of the natural frequencies for the truss are very close to the FEM. Finally the errors in the frequency estimations are found in terms of the wavelength of the traveling waves.

Application of hybrid compliance/force control to super long distance teleoperation

Japan-USA international joint research on 'Distributed space Telerobotics' has been undertaken in a scheme of AIST Specific International Joint Research Projects [1]. The space platform assembly experiment with an intelligent telerobotics system was demonstrated between the Electrotechnical Laboratory and the Jet Propulsion Laboratory. To overcome various telerobotics problems, especially the uncertainty of task environment, the robot manipulator at the remote site employed a compliance control and a force control system is available. This paper describes how the hybrid compliance/force control, developed by Kawasaki Heavy Industries, Ltd., is applied to assemble the truss structure model and shows the results of the experiments.