OPTIMIZATION OF TRUSS STRUCTURES WITH CHORDS OF STEP-VARIABLE CROSSSECTIONS MADE OF RECTANGULAR PIPES

2021 ◽  
Vol 295 (2) ◽  
pp. 53-61
Author(s):  
A.S. Marutyan ◽  
Keyword(s):  
Cross Sections ◽  
Welded Joints ◽  
Optimization Problems ◽  
Truss Structures ◽  
Technical Solution ◽  
Variable Cross ◽  
Load Bearing ◽  
Strength Tests ◽  
The Difference

The article describes the regularity of the optimization calculation of unification zones in relation to beam chords of step-variable cross-sections with the determination of their design coefficients. The rationality of the formation of these chords in truss structures made of rectangular pipes is shown due to the difference not in the heights of the sections, but in their thicknesses with welded joints on the longitudinal slits.The engineering method for calculating such joints, as well as their load-bearing capacity, has been tested by tensile strength tests of the samples.The universality of the technical solution of welded joints with slits ensures their use in structures made of tubular and rolled profiles, and it preserves the accepted layout of standardized trusses with assemblies and flanged connections. The significant reduction in structural material (steel) in standardized trusses made of bent-welded profiles was revealed when chords of uniform cross-sections were replaced with chords of step-variable cross-sections. The article also gives the comparative calculation of the design coefficients and the averaged coefficients of chord elements use when the lengths of the unification zones and the belt panels coincide. Sufficient correctness of the approximate calculation method for solving optimization problems and variant design of load-bearing structures is confirmed.

Destruction of C2H4O2 isomers in ice-phase by X-rays: Implication on the abundance of acetic acid and methyl formate in the interstellar medium

2017 ◽  
Vol 13 (S332) ◽  
pp. 418-424
Author(s):  
Marina G. Rachid ◽  
K. Faquine ◽  
S. Pilling
Keyword(s):  
Acetic Acid ◽  
Cross Sections ◽  
Methyl Formate ◽  
X Rays ◽  
Formation Cross Section ◽  
X Ray ◽  
Synchrotron Light ◽  
The Difference ◽  
Astrophysical Ices

AbstractC2H4O2 isomers, methyl formate (HCOOCH3), acetic acid (CH3COOH) and glycoaldehyde (HOCH2CHO), have been detected in a lot of sources in ISM. However, their abundances are very different, with methyl formate much more abundant than the other two isomers. This fact may be related to the different destruction by ionizing radiation of these molecules. The goal of this work is experimentally study the photodissociation processes of methyl formate and acetic acid ices when exposed to broadband soft X-ray from 6 up to 2000 eV. The experiments were performed coupled to the SGM beamline in the Brazilian Synchrotron Light Source (LNLS/CNPEM) at Campinas, Brazil. The simulated astrophysical ices (12K) were monitored throughout the experiment using infrared vibrational spectroscopy. The analysis of processed ices allowed the determination of the effective destruction cross sections of the parent molecules as well as the effective formation cross section of daughter molecular species. The relative abundance between acetic acid and methyl formate (NCH3COOH/NHCOOCH3) in different astronomical scenarios and their column density evolution in the presence of X-rays were calculated and our results suggests that such radiation field can be one of the factors that explain the difference in the isomers C2H4O2 abundances. We also quantified the daugther species after the establishment of a chemical equilibrium in the samples.

On Differences of Statically and Dynamically Determined Elastic Modules of Materials Like Trabecular Bone

2007 ◽  
Author(s):  
D. H. Besdo ◽  
S. Besdo
Keyword(s):  
Trabecular Bone ◽  
Cross Sections ◽  
Step Function ◽  
Shear Mode ◽  
Variable Cross ◽  
Half Cycle ◽  
Longitudinal Waves ◽  
Ultrasonic Methods ◽  
Elastic Modules

The linear elastic material law which is usually applied in simulations of bone behavior reads σij = Cijkl εkl. It contains up to 21 independent constants. In most applications only nine constants (orthotropic behavior) are used. The determination of these constants is troublesome. The most applied experimental method is based on ultrasonic wave propagation. As it is often recognized the elastic modules measured by this method differ significantly from those found by static testing. Whereas Young’s modules differ slightly only, the determination of shear modules by ultrasonic methods is extremely doubtful, especially in trabecular bone. To find reasons for this effect, wave propagations are simulated by Finite-Element-techniques. This is done for artificial structures and also for realistic models of trabecular bone based one μCT-data. It can be recognized that in structured media always three types of waves propagate through the material with different speeds. Unfortunately the shear wave which is to be measured is the slowest one. Even if no longitudinal waves disturb the measurements, at least bending waves appear and pretend some kind of shear mode. The different orientations of the trabeculae can cause longitudinal waves when shear waves are applied. The stimulation of the ultrasound is at first simulated as a half cycle or as a step function only. The realistic waves are superimpositions of several of such motions. Such a relatively simple simulation makes possible to distinguish the three wave types mentioned above. The superimpositions complicate the motion extremely. Also reflection, damping and variable cross sections make it almost impossible to identify the modules, especially the shear modules, in a certain manner.

Contact and Bending Strength Tests of Ceramics: What is the Difference?

2009 ◽  
Vol 409 ◽  
pp. 185-192
Author(s):  
Lucia Hegedűsová ◽  
Alexandra Kovalčíková ◽  
Monika Kašiarová ◽  
Ján Dusza
Keyword(s):  
Bending Strength ◽  
Ceramic Materials ◽  
Contact Test ◽  
Four Point Bending ◽  
Sic Ceramic ◽  
Bending Mode ◽  
Strength Tests ◽  
The Difference

The paper deals with the determination of the characteristic strength and the Weibull modulus m of Si3N4 and SiC ceramic materials using conventional four-point bending and unconventional contact tests between opposite rollers and opposite spheres. Ceramographic and fractographic methods were used for the characterization of strength degrading defects represented by processing flaws and by cracks of different types arising during the loading. The processing flaws influenced the Weibull parameters mainly in the bending mode, and the strength and its scatter in contact modes was influenced by lateral, median and contact end cracks, originated during the contact test using rollers, and by cone cracks originated during the contact test using spheres.

scholarly journals Stability of Thin-Walled Beams with Lateral Continuous Restraint

2015 ◽  
Vol 15 (1) ◽  
pp. 1-10 ◽  
Author(s):  
Ivan Balázs ◽  
Jindřich Melcher
Keyword(s):  
Critical Load ◽  
Cross Sections ◽  
Building Industry ◽  
Lateral Torsional Buckling ◽  
Torsional Buckling ◽  
Load Bearing ◽  
Buckling Resistance ◽  
Resistance Assessment ◽  
Thin Walled

Abstract Metal beams of thin-walled cross-sections have been widely used in building industry as members of load-bearing structures. Their resistance is usually limited by lateral torsional buckling. It can be increased in case a beam is laterally supported by members of cladding or ceiling construction. The paper deals with possibilities of determination of critical load of thin-walled beams with lateral continuous restraint which is crucial for beam buckling resistance assessment

scholarly journals Effect of Addition of Alccofine on the Compressive Strength of Cement Mortar Cubes

2021 ◽  
Vol 5 (2) ◽  
pp. 155-170
Author(s):  
Balamuralikrishnan R. ◽  
Saravanan J.
Keyword(s):  
Compressive Strength ◽  
Cement Mortar ◽  
River Sand ◽  
Mix Proportion ◽  
Strength Tests ◽  
The Difference ◽  
Glass Wastes ◽  
Cement Strength ◽  
Modern Era

In the modern era, many research works are going on throughout the world for finding suitable cementitious material for the replacement of cement since it causes environmental pollution. In this order Fly ash, Silica fume, GGBS, Metakaolin, Micro materials, Quartz powder, etc. are tried out for replacing partially or fully the cement in concrete. A new ultrafine material called Alccofine (AF) which is manufactured from glass wastes is tried out for replacing partially in this research. Compressive strength is one of the important properties of cement. Strength tests are not made on neat cement paste because of difficulties of excessive shrinkage and subsequent cracking of neat cement. Cement mortar of 1:3 mix proportion is used to cast the cubes having an area of 50 cm2 are used for the determination of compressive strength of cement as per IS: 4031-1988 (Part-6). The graded Indian Standard sand (Ennore Sand -ES) confirming to IS: 650-1991 is used for preparing the cubes. In the same mix proportion, the same size cubes are cast with the River Sand (RS) to study the difference of the compressive strength between the Indian standard sand and river sand. Ordinary Portland cement (OPC) and Portland Pozzolana Cements (PPC) are used. The present study is the influence of Alccofine on cement mortar cubes by replacing the cement by Alccofine with various proportions like 5%, 10%, 15%, 20% were cast and tested in the laboratory as per Indian Standard 4301-1988 (Part-6) and the results were analysed and presented in the form of charts and graphs. It is observed that the early age strength is obtained for all the combinations but 10 percent of Alccofine yields more strength than other dosages. Doi: 10.28991/esj-2021-01265 Full Text: PDF

scholarly journals PECULIARITIES OF EVALUATION OF METHODS OF DETERMINATION OF CHARACTERISTICS OF FIRE RESISTANCE OF BUILDING STRUCTURES

2020 ◽  
Vol 1 (2) ◽  
pp. 29-40
Author(s):  
S Novak ◽  
M Novak ◽  
O Bedratiuk
Keyword(s):  
Fire Resistance ◽  
Fire Protection ◽  
Steel Structures ◽  
Bearing Steel ◽  
Building Structures ◽  
Load Bearing ◽  
Methods Of Determination ◽  
Wide Range ◽  
The Difference

The results of the study aimed at further improvement and development of procedures for evaluating methods of determining the fire resistance characteristics of building structures are presented. The features of estimation of methods of determination of characteristics of fire resistance of building structures are determined. It is established that for the validation of experimental-calculation methods intended to determine the thickness of fire protection of building structures, which ensures their fire resistance in a wide range of parameters of these structures, it is impossible to use samples of structures with certain properties due to their inability to create. A procedure for such validation using a computational experiment method is proposed. In this procedure, accurate (conditional) temperature data for steel column specimens are determined by solving a direct one-dimensional non-stationary thermal conductivity problem. The validity of the proposed validation procedure by its application for the experimental calculation method, designed to determine the thickness of fire protection materials for load-bearing steel structures (columns and beams), has been established. It is established that the overwhelming number of calculated values of the thickness of the fire protection materials, determined by this method, exceeds its true values, which indicates the acceptability of the obtained results in terms of providing fire resistance of load-bearing steel structures. It is established that the difference between the calculated and actual values of the thickness of the fire protection materials can reach a considerable value (twice or more).The direction of further researches which are focused on revealing of influence of thermophysical properties of fire protection materials and stress-deformed state of samples of steel structures during the test on the accuracy of the method. This will identify more appropriate procedures for evaluating the method and processing the experimental data with increased accuracy.

scholarly journals OPTIMIZATION OF TREE STRUCTURES WITH HALF-DRAWER GRIDS

2020 ◽  
pp. 39-50
Author(s):  
А. С. Марутян
Keyword(s):  
Bearing Capacity ◽  
Communication Systems ◽  
Truss Structure ◽  
Truss Structures ◽  
Technical Solution ◽  
Rectangular Section ◽  
Tree Structures ◽  
Load Bearing ◽  
Different Shapes ◽  
Necessary And Sufficient

Приведено новое техническое решение в виде дополнительных стержней I-образной, Y-образной, Ψ-образной формы в полураскосных решетках для стержневых (ферменных) конструкций. Показана эффективность их применения в фермах, у которых грузовыми являются не только верхние (сжатые) пояса, но также и нижние (растянутые). Повышена степень унификации ферменной конструкции из гнутосварных профилей (профильных труб) прямоугольного сечения за счет повторного использования в верхнем поясе расчетного сечения, принятого для нижнего пояса. При этом ресурсы несущей способности разнятся между ними в пределах 3-4-процентного порога, что обеспечивает необходимую и достаточную равнопрочность обоих поясов при их унификации. Соединительные узлы верхнего пояса с дополнительными полураскосами разных очертаний позволяют опереть на них определенное количество прогонов с уменьшенными размерами грузовых площадей. Увеличение общего количества прогонов приводит к их облегчению, что представляет собой весьма важный фактор для несущих конструкций, рассчитанных на особые нагрузки и воздействия, а также для объектов повышенной ответственности. Выявлена перспективность применения нового технического решения в составе несущих и связевых систем различных зданий и сооружений. A new technical solution is presented in the form of additional I-shaped, Y-shaped, Ψ-shaped rods in half-diagonal lattices for rod (truss) structures. The effectiveness of their use in farms is shown, in which not only the upper (compressed) belts, but also the lower (extended) ones, are cargo. The degree of unification of the truss structure from bent welded profiles (profile pipes) of a rectangular section due to the reuse in the upper zone of the design section adopted for the lower belt is increased. At the same time, the resources of the bearing capacity differ between them within a 3… 4 percent threshold, which ensures the necessary and sufficient equal strength of both zones when unifying them. The connecting nodes of the upper belt with additional half-braces of different shapes allow to support a certain number of runs with reduced sizes of cargo areas. An increase in the total number of runs leads to their facilitation, which is a very important factor for load-bearing structures designed for special loads and impacts, as well as for objects of increased responsibility. The prospects of applying a new technical solution as a part of the bearing and communication systems of various buildings and structures are revealed.

A selective genetic algorithm for multiobjective optimization of cross sections in 3D trussed structures based on a spatial sensitivity analysis

2016 ◽  
Vol 12 (2) ◽  
pp. 423-435 ◽  
Author(s):  
Javier Luis Mroginski ◽  
Pablo Alejandro Beneyto ◽  
Guillermo J Gutierrez ◽  
Ariel Di Rado
Keyword(s):  
Genetic Algorithm ◽  
Sensitivity Analysis ◽  
Multiobjective Optimization ◽  
Convergence Rate ◽  
Cross Sections ◽  
Optimization Problems ◽  
Search Space ◽  
Truss Structures ◽  
Internal Stresses ◽  
Content Type

Purpose – There are many problems in civil or mechanical engineering related to structural design. In such a case, the solution techniques which lead to deterministic results are no longer valid due to the heuristic nature of design problems. The purpose of this paper is to propose a computational tool based on genetic algorithms, applied to the optimal design of cross-sections (solid tubes) of 3D truss structures. Design/methodology/approach – The main feature of this genetic algorithm approach is the introduction of a selective-smart method developed in order to improve the convergence rate of large optimization problems. This selective genetic algorithm is based on a preliminary sensitivity analysis performed over each variable, in order to reduce the search space of the evolutionary process. In order to account for the optimization of the total weight, the displacement (of a specific section) and the internal stresses distribution of the structure a multiobjective optimization function was proposed. Findings – The numerical results presented in this paper show a significant improvement in the convergence rate as well as an important reduction in the relative error, compared to the exact solution. Originality/value – The variables sensitivity analysis put forward in this approach introduces a significant improvement in the convergence rate of the genetic algorithm proposed in this paper.

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