Truss Node Research Articles

Eccentric Compression Behavior of Truss-Reinforced Cross-Shaped Concrete-Filled Steel Tubular Columns.

In the paper, the eccentric compression behavior of the truss-reinforced cross-shaped concrete-filled steel tubular (CCFST) column is investigated. A total of eighteen CCFST columns were tested under eccentric compression, and the key test variables included the reinforced truss node spacing (s = 140 mm and 200 mm), slenderness ratio (λ = 9.2, 16.6, and 23.1), and eccentricity ratio (η = 0, 0.08, and 0.15). The failure mode, deformation characteristic, stress distribution, strain distribution at the mid-span of the steel tube, and the eccentric compression bearing capacity were assessed. The results show that due to the addition of reinforced truss, the steel plates near the mid-span of eccentrically compressed CCFST columns experienced multi-wave buckling rather than single-wave buckling after the peak load was reduced to 85%, and the failure mode of concrete also changed from single-section to multi-section collapse failure. Comparisons were made with the unstiffened specimen. The ductility coefficient of the stiffened specimen with eccentricity ratios of 0.08-0.15 and node spacings of 140 mm~200 mm increased by 70~83%, approaching that of the multi-cell specimens with an increasing steel ratio of 1.8%. In addition, by comparing the test results with the calculation results of four domestic and international design codes, it was found that the Chinese codes CECS159-2018 and GB50936-2014, and the Eurocode 4 (2004) can be better employed to predict the compression bearing capacity of truss-reinforced CCFST columns.

Mesh antenna cable net form finding optimization by an improved NSGA-II

The tension uniformity and surface accuracy of mesh antenna cable net are two well-accepted evaluation criteria for form finding. Traditional form finding techniques often rely on single-objective optimization and weighting factors. Although the Non-dominated Sorting Genetic Algorithm II (NSGA-II) can address the limitation, there are still challenges of wide distribution and insufficient precision of solutions. In the present work, a novel multi-objective optimization method based on an improved NSGA-II is introduced to conduct mesh antenna cable net form finding optimization. Based on the preference region (PR), a self-adaptive penalty function is proposed. The function is designed to steer the optimization process toward the PR, and enhancing the precision of the solutions. The extent of penalization for an individual solution depends on its positioning relative to the PR and is modified by a penalty coefficient that adapts dynamically to the population number within the PR. Additionally, a form finding method considering flexible frames is developed. The initial population for the flexible frame optimization is sourced from results of rigid frames, with the maximum truss node position error as the convergence criterion. Benchmark tests and case studies confirm that the improved NSGA-II enhances distributivity and convergence, while also providing form-finding results with higher surface accuracy and more uniform tension distribution.

Research on Economic Optimization Scheme of Pratt Truss Bridge

Economy is an important factor in bridge construction. The economic optimization of truss bridge is of great significance to improving the economic benefit of bridge construction. However, the safety and stability in bridge construction are often valued in traditional truss Bridges, and its economy is often ignored. The purpose of this paper is to study the economic optimization of Pratt truss bridge with 120 m span, 8m and node length of 6m, 10m and 12m respectively. The study of establishing two-dimensional model using structural mechanics solver shows that when the total length of the Pratt truss node is 12m, the total volume of the truss is the smallest, that is, the least materials are used, and the linear relationship between the bridge span and the node length is established to a certain extent. The results of this study provide an effective reference for the economic optimization of similar truss bridge structures.

Reliability analysis of planar steel trusses based on p-box models

Introduction. The development of probabilistic approaches to the assessment of mechanical safety of bearing structural elements is one of the most relevant areas of research in the construction industry. In this research, probabilistic methods are developed to perform the reliability analysis of steel truss elements using the p-box (probability box) approach. This approach ensures a more conservative (interval-based) reliability assessment made within the framework of attaining practical objectives of the reliability analysis of planar trusses and their elements. The truss is analyzed as a provisional sequential mechanical system (in the language of the theory of reliability) consisting of elements that represent reliability values for each individual bar and truss node in terms of all criteria of limit states.
 Materials and methods. The co-authors suggest using p-blocks consisting of two boundary distribution functions designated for modeling random variables in the mathematical models of limit states performed within the framework of the truss reliability analysis instead of independent true functions of the probability distribution of random variables. Boundary distribution functions produce a probability distribution domain in which a true distribution function of a random variable is located. However this function is unknown in advance due to the aleatory and epistemic uncertainty. The choice of a p-block for modeling a random variable will depend on the type and amount of statistical information about the random variable.
 Results. The probabilistic snow load model and the numerical simulation of tests of steel samples of truss rods are employed to show that p-box models are optimal for modeling random variables to solve numerous practical problems of the probabilistic assessment of reliability of structural elements. The proposed p-box snow load model is based on the Gumbel distribution. The mathematical model used to perform the reliability analysis of planar steel truss elements is proposed. The co-authors provide calculation formulas to assess the reliability of a truss element for different types of p-blocks used to describe random variables depending on the amount of statistical data available.
 Conclusions. The application of statistically unsubstantiated hypotheses for choosing the probability distribution law or assessing the parameters of the probability distribution of a random variable leads to erroneous assessments of the reliability of structural elements, including trusses. P-boxes ensure a more careful reliability assessment of a structural element, but at the same time this assessment is less informative, as it is presented in the form of an interval. A more accurate reliability interval requires interval-based assessments of distribution parameters or types of p-boxes applied to mathematical models of the limit state, which entails an increase in the economic and labor costs of the statistical data.

Compressive properties of the lattice structure with a new process

Abstract

Investigation of Stress State in Plane Truss Nodes

Stress state in a plane truss node was studied in two ways: numerically using the finite element method and experimentally using the photoelasticity method. The finite element method was used to calculate plane truss model. Photoelasticityor polarization-optical method was used to research stresses of piezo-optical materials. The picture of interference fringe patterns in the model of a plane truss was obtained by the method of photoelasticity. Stresses were calculated with their help. The purpose of the work was to compare both methods. Fields of maximum tangent stresses were obtained in the sample plane using both methods. This work is a continuation of [1]. So, we obtained picture of interference fringe patterns and isocline fields in the node of the farm model, using the photoelasticity method. The field of maximum tangent stresses in the truss node was obtained by the photoelasticity method. The stress fields in the truss node were obtained by the finite element method in the software package “SCAD”. A comparative analysis of the numerical and physical experiments results was carried out and it was found that the nature of the stress distribution in both numerical and physical experiments coincides.

Study of stresses in plane truss nodes

in this paper, the stress state in a plane truss node was studied in two ways: numerically using the finite element method and experimentally using the photoelasticity method. The finite element method was used to calculate plane truss model. Photoelasticity or polarization-optical method was used to research stresses of piezo-optical materials. The picture of interference fringe patterns in the model of a planetruss was obtained by the method of photoelasticity. Stresses were calculated with their help. The purpose of the work was compared with both methods. Fields of maximum tangent stresses were obtained in the sample plane using both methods.

Effect of geometrical parameters on the effective elastic modulus for an X-type lattice truss panel structure

Abstract The lattice truss panel structure (LTPS), which is a high strength material with high efficiency of heat transfer, has a good potential to be used as compact heat exchanger. The core of LTPS is a periodic porous structure, and the effective elastic modulus (EEM) will be different from the base material. It is essential to calculate the EEM for the design of this type of heat exchanger. This paper presents a study on the EEM of X-type LTPS by homogenization method, which has been verified by finite element method (FEM). It reveals that the effects of seven geometrical parameters of the X-type LTPS on EEM are not identical, and the relationship between the seven parameters and EEM has been established. Results calculated by homogenization method and FEM show a good agreement. The EEM decreases with the increase of truss length, stamping angle, shearing angle and node length, while it increases with the increase of truss width, truss thickness and face sheet thickness. Unlike the conventional foam material, there is no clear correlation between the EEM and the relative density, and a formula has been fitted to calculate the EEM of LTPS.

3D Modeling as Method for Construction and Analysis of Graphic Objects

The use of 3D modeling when constructing and analyzing perspective projections and shadows is considered. The creation of photorealistic image is shown. The perspective of the construction project and characterization of its image are given as an example. The authors consider the construction of a dynamic block as a means of graphical information storage and automation of geometric constructions. The example of the dynamic block construction at creating a truss node is demonstrated. The constructions are considered as applied to the Auto-CAD software. The paper is aimed at improving the graphic methods of architectural design and improving the educational process when training the Bachelor’s degree students majoring in construction.

Truss Joint with Positive Eccentricity Experimental Research

Abstract Due to the technological reasons in modern lightweight steel trusses, fabricated from cold-formed sections, positive eccentricities appear in the truss nodes what induce additional forces in the truss chords. To account for the real load-carrying capacity of truss node area the steel structure research in scale 1:1 were conducted. The experiments consisted of two parts: preliminary and proper one, when conclusions from the first part were applied. Carrying out preliminary studies helped to identify of the research station drawbacks and eliminate most of them, what ensure the appropriate research results. The initial numerical analysis were also conducted what was presented in the paper.

Graphical Methods for Designing Bolted Joints in Engineering Drawings

This article analyzes graphical methods for designing bolted joints in engineering drawings, presents design system of a truss node's with bolted connections. The creation methods of automated design system of a truss node's bolted joints are discovered with Unified Modeling Language. Graphical system can design steel plain truss node's bolted joints, form information tables of objects. The bars bolted connections near node sheet are calculated using programming object's bolted joints properties and methods. Drawing's graphical objects have additional data from which exchange of data between graphical system and information table of objects is executed. Example of truss node's bolted joints project with information table is presented. Creation problems of automated design system are discussed and conclusions are made.

Multi-Objective Optimization of Actuator Locations and Numbers for Piezoelectric Intelligent Trusses Based on Genetic Algorithm

The locations and number of actuators in piezoelectric truss is very important. The best number and locations of actuators can make truss node displacement minimum. Based on the function of truss node displacement, this paper analysis the axial force of every bar of intelligent truss, and deduced the piezoelectric truss node displacement, and optimized the location and number of truss using genetic algorithm (GA). The results of the example show that the proposed method is effective.

Experimental analysis of an original type of steel space truss node joint

In the paper is presented experimental analysis of an original type of node joint for a steel space truss. The joint sample was loaded by spatial set of forces that simulate real condition of the structure with eight balanced member forces (4 chord and 4 diagonal members), up to structure failure. It was realized in a specially designed test facility. Tested node joint samples were made in real scale, according to the model originated after FE analysis and optimization. Basic idea was to construct and test a node joint that can be made in average technology conditions, without special tools and requirements. Besides, results of a stress-strain FE analysis are presented and comparison of the two analyses is given for the most critical regions of the node joint. Values of measured and calculated strains across model samples and characteristic measuring points are presented.

Motion Planning of Kinematically Redundant Adaptive Truss. Use of Redundancy for Vibration Reduction.

The aim of the present study is to improve the dynamic behavior of an adaptive truss by considering the redundant kinematical degrees of freedom(DOFs). It is assumed that the truss follows the prescribed path in its workspace. The motion planning problem with respect to vibration is formulated in a discrete form with a criterion function based on the strain energy of the adaptive truss. It is also shown that the proposed approach is applicable to a real model of the adaptive truss which takes into account the nodal offset, as well as an ideal model which is based on the ideal truss node assumption. Simulation studies are carried out for both ideal and real models of the adaptive truss. The effectiveness of the proposed approach on the vibration reduction is demonstrated.

Parallel computing for analysis of variable geometry trusses

A fine-grained parallel algorithm is proposed to perform the integrated geometric/structural analysis of variable geometry trusses (VGTs) with complicated behaviors such as the interaction between the response of an actuator and a member force, and it is implemented to a multiple instruction stream/multiple data stream type parallel computer. One processor is assigned to one truss node, and each node moves synchronously or asynchronously so that its unbalanced nodal force vanishes. The effect of parallel processing is investigated, and the comparison of synchronous and asynchronous algorithms is performed from the viewpoints of processor efficiency, load balance, and interprocessor communications. The parallel integrated structural and geometric analyses of several VGTs are carried out to find the effectiveness of the proposed method.

Object-oriented approach to modeling and analysis of truss structures

Object-oriented structural and geometric analysis methods for truss structures are proposed. The methods are based on the iterative relaxation of nodal unbalanced forces by moving the nodes. The entities appeared in truss analysis are modeled as classes, and their class hierarchy is established. The knowledge about a truss node, a truss member, a material, and a sectional shape of the member are extracted and constructed as a knowledge base in an object-oriented manner. The object-oriented structural analysis is found to be valid for material and geometric nonlinearities, and the object-oriented geometric analysis where a kinematic problem is converted into a problem for a force equilibrium at the nodes is also found to be effective for determining the geometry of variable geometry trusses. The whole system is written in an object-oriented language, Smalltalk, and several results on structural and geometric analysis are presented. The speed of the computation is discussed along with the size of the structures and the over-relaxation factor. The extension of the knowledge base is also discussed.

Truss Structure Integrity Identification Using PZT Sensor-Actuator

This paper presents a frequency domain impedance-signature-based technique for health monitoring of an assembled truss structure. Unlike conventional modal analysis approaches, the technique uses piezoceramic (PZT) elements as integrated sensor-actuators for acquisition of signature pattern of the truss. The concept of the localization of sensing/actuation area for damage detection of an assembled structure is presented for the first time. Through a PZT patch bonded to a truss node and the measurement of its electric admittance, which is coupled with the mechanical impedance of the truss, the signature pattern of a truss is monitored. The admittance of a truss in question is compared with that of the original healthy truss. Statistic algorithm is then applied to extract a damage index of the truss based on the signature pattern difference. Experimental proof that over a selected band, the detection range of a bonded PZT sensor on a truss is highly constrained to its immediate neighborhood is presented. This characteristic allows accurate determination of the damage location in a complex real-world structure with a minimum mathematical modeling and numerical computation.