REGULATION OF GUYED MAST STRESSES

2009 ◽  
Vol 1 (2) ◽  
pp. 65-72 ◽  
Author(s):  
Donatas Jatulis ◽  
Algirdas Juozapaitis
Keyword(s):  
Numerical Experiment ◽  
Cross Section ◽  
Cross Sections ◽  
Mobile Communications ◽  
Bending Moment ◽  
Physical Parameters ◽  
Bending Moments ◽  
Rational Distribution ◽  
Guyed Mast ◽  
Prestressed Structures

Development of mobile communications and their networks in Lithuania produced an essential influence on high telecommunications structures design activities. In its turn it has stimulates their research and innovations of such structural systems. One of the most efficient systems of telecommunication structures is guyed mast. It should be indicated that the behaviour of prestressed structures systems has been thoroughly examined in many investigations. But recently the increase of economical efficiency of guyed masts becomes undoubtedly actual. The development of such structures in many cases is directed to the selection in the mast elements scheme and their cross-sections. It should be underlined that geometric and physical parameters have a decisive moment on prestressed structures. An exact parameters choice allows to obtain in the mast rational distribution of bending moments, predetermining a project solution closely connected with the mass criteria. The diagram of bending moment’s distribution in guyed mast is considered rational when negative and positive moment values are absolutely equal. In the present research, analytical expressions for rational bending moments determining are presented. Above mentioned non-linear expressions estimate an influence of axial force for the bending moments. When solving the task of rational bending moments in a guyed mast, it is necessary to select suitable (i.e. rational) guyed mast bending spans. In the article is described the calculations of the guys fastening altitudes when guy level number is known. It should be noted that it is necessary to use the way of gradual approximation. The sequence of calculations is interrupted, when the sum of guyed mast spans corresponds to the exactness selected. The decisive part in mast behaviour is played by guys. The main parameters of them are pretension and cross-section area. In the article the equations are presented for determining the above-mentioned parameters. It should be stressed that after making uniform stresses of the guys on the different level of each of them it is possible to minimise some steel quantities. In the article a numerical experiment is presented for determining the technical-economical effectiveness of stress regulation. For the analysis, a standard three edged lattice guyed mast with cross-section parameters was selected in a usual way. By the suggested beam composition methods the design of the shaft was performed, and the results obtained were compared to a standard guyed mast shaft. For determining the stresses of beam elements Robot Millennium software was used; its reliability was demonstrated by earlier investigations. The results of numerical experiment that the maximal bending moment of composed guyed mast is three times less than that of a standard maximal one. An applied regulation of stresses has allowed to lessen much of the cross-section of guy rope. By applying the suggested methods it was possible to diminish the steel expenditure of shaft by more than 30%.

A shear center demonstration model using 3D-printing

2021 ◽  
pp. 030641902110574
Author(s):  
Lawrence N Virgin
Keyword(s):  
3D Printing ◽  
Cross Section ◽  
Cross Sections ◽  
Principal Axis ◽  
Practical Importance ◽  
Bending Moment ◽  
Shear Center ◽  
Cross Sectional ◽  
Thin Walls ◽  
Section Profile

Locating the shear, or flexural, center of non-symmetric cross-sectional beams is a key element in the teaching of structural mechanics. That is, establishing the point on the plane of the cross-section where an applied load, generating a bending moment about a principal axis, results in uni-directional deflection, and no twisting. For example, in aerospace structures it is particularly important to assess the propensity of an airfoil section profile to resist bending and torsion under the action of aerodynamic forces. Cross-sections made of thin-walls, whether of open or closed form are of special practical importance and form the basis of the material in this paper. The advent of 3D-printing allows the development of tactile demonstration models based on non-trivial geometry and direct observation.

scholarly journals Premature destruction of two-span RC beams exposed to high temperature caused by a redistribution of shear forces

2016 ◽  
Vol 23 (4) ◽  
pp. 431-439 ◽  
Author(s):  
Robert KOWALSKI ◽  
Michał GŁOWACKI ◽  
Marian ABRAMOWICZ
Keyword(s):  
High Temperature ◽  
Cross Sections ◽  
Bending Moment ◽  
Middle Part ◽  
Transverse Reinforcement ◽  
Shear Load ◽  
Bending Moments ◽  
Rc Beams ◽  
Shear Forces ◽  
Load Bearing Capacity

When multi-span RC elements are exposed to fire one usually observes a yielding of span cross-sections while a safety reserve of support cross-sections is still significant. Due to this phenomenon a redistribution of bending moments occurs and the values of sagging moment in span cross-sections decrease while the values of hogging moment in support cross-sections increase. This paper shows the results of tests conducted on two-span RC beams in a situation when only one span has been exposed to high temperature from the bottom. The beams were 12×16 cm in their cross-section. The length of the span was 165 cm. The load has been applied by two forces put on each span. The beams were made of C25/30 concrete with siliceous aggregate. As a result of significant stiffness decrease of the heated span, redistribution of shear forces and bending moment occurs. Due to this redistribution the tested beams were prematurely damaged due to exhaust of the shear load bearing capacity in the middle part of the beam span where there was no transverse reinforcement.

Analysis of shear lag in cylindrical tubes of arbitrary cross section

1983 ◽  
Vol 389 (1797) ◽  
pp. 259-277
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Bending Moment ◽  
General Purpose ◽  
Simple Eigenvalue ◽  
Arbitrary Cross Section ◽  
Longitudinal Distribution ◽  
Shear Lag ◽  
Cylindrical Tubes ◽  
Polynomial Distribution

A very general analysis is given of the phenomenon of shear lag in thin-walled cylindrical tubes, with single-cell cross sections of arbitrary shape, containing any number of concentrated longitudinal booms that carry direct stress only, and subjected to any longitudinal distribution of bending moment and torque. Two equations relating the distributions of direct and shearing stresses on the cross section are derived for the most general case where the tube is non-uniform because of an arbitrary longitudinal variation of wall thicknesses and boom areas. These equa­tions, which are remarkably simple in view of their generality, incor­porate all the requirements of equilibrium and compatibility and provide corrections to the stresses, curvature and twist calculated from the engineers’ theory of bending and torsion. They also govern the distri­bution of stresses arising from the application of self-equilibrating systems of tractions to the end cross sections. Exact solutions are ob­tained for the case of a uniform, but otherwise arbitrary, cross section under any polynomial distribution of bending moment and torque, and it is shown how conditions at the end cross sections can be satisfied with the aid of solutions of a simple eigenvalue problem. The equations are in a particularly ideal form for incorporating into a general purpose com­puter program for the automatic numerical solution of any problem of this type.

scholarly journals NUMERICAL INVESTIGATION OF THE ELASTIC-PLASTIC LINEAR HARDENING STRESS-STRAIN STATE OF THE FRAME ELEMENT CROSS-SECTION

2016 ◽  
Vol 8 (3) ◽  
pp. 94-100
Author(s):  
Andrius Grigusevičius ◽  
Gediminas Blaževičius
Keyword(s):  
Cross Section ◽  
Axial Force ◽  
Cross Sections ◽  
Rectangular Cross Section ◽  
Bending Moment ◽  
Software Environment ◽  
Stress Strain ◽  
Hardening Material ◽  
Frame Element ◽  
Nonlinear Stress

The aim of this paper is to present a solution algorithm for determining the frame element crosssection carrying capacity, defined by combined effect of bending moment and axial force. The distributions of stresses and strains inside a cross-section made of linearly hardening material are analysed. General nonlinear stress-strain dependencies are composed. All relations are formed for rectangular cross-section for all possible cases of combinations of axial force and bending moment. To this end, five different stress-strain states are investigated and four limit axial force values are defined in the present research. The nonlinear problem is solved in MATLAB mathematical software environment. Stress-strain states in the cross-sections are investigated in detail and graphically analysed for two numerical experiments.

scholarly journals IV. On the practical solution of the most general problems in continuous beams

1879 ◽  
Vol 29 (196-199) ◽  
pp. 493-505
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
General Problem ◽  
Bending Moment ◽  
Moment Of Inertia ◽  
Shearing Stress ◽  
Practical Solution ◽  
Continuous Beams ◽  
The Moment

1. It is not necessary to enter into the question of the advisability of employing continuous girders in bridges with spans of less than 200 feet, but it is generally conceded that the increased economy due to the employment of continuous girders in longer spans more than counterbalances the well-known practical objections to continuity. Hence the practical solution of the general problem—given the conditions at the ends of a continuous girder, the spans, the moment of inertia of all cross sections, and the loading, to find the bending moment and shearing stress in every cross-section, is not unworthy of our attention.

scholarly journals TO QUESTION OF COMBINED SYSTEMS RATIONALIZATION

2019 ◽  
pp. 97-103
Author(s):  
S. D. SINCHUK
Keyword(s):  
Cross Sections ◽  
Bending Moment ◽  
Variable Number ◽  
Bending Moments ◽  
New Approach ◽  
Present Solution ◽  
Combined Structure ◽  
Optimal Values ◽  
The Cross ◽  
Effective Design

Purpose. Developing a new approach to the rationalization of the combined structure, taking into account constructive, technological, operational and economic requirements. Methodology. The bending moment adjustment method representations to achieve the goal, based on the properties of the thrust-systems, namely: in the combination beam construction cost material defining elements are experiencing stress state of compression with a bend; in cells operating at the bending compression, reducing the size of the cross section largely determined by the decrease of the bending moment; bending moments increase from the support to the middle of the span. Originality. On the basis of calculations using the methodology set forth above, the algorithm of optimal design of truss beams under the influence of permanent and temporary load. The present solution allows to obtain an effective design combined with a variable number of racks, depending on the required span length, corresponding to the received optimality criterion. Practical value. The use of this approach and the optimization algorithm based on the use of the design features of truss beams and requires minimization of bending moments, will significantly reduce the complexity of the calculation, as well as to find the optimal values of the cross sections for each case.

Single-electron detachment cross sections of Co− and Ir− in collision with Ar and an empirical formula for single-electron detachment cross sections of negative ions in collision with Ar

2013 ◽  
Vol 91 (2) ◽  
pp. 175-179 ◽  
Author(s):  
Zhixian Geng ◽  
Xue Bai ◽  
Baoren Wei ◽  
Xuemei Zhang
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Electron Affinity ◽  
Least Squares Method ◽  
Negative Ions ◽  
Single Electron ◽  
Clear Correlation ◽  
Physical Parameters ◽  
Electron Detachment ◽  
Empirical Formulas

The single-electron detachment (SED) cross sections for Co− and Ir− in collision with Ar in the energy region of 10–30 keV are obtained in our laboratory. As our previous paper reported, the SED cross sections have velocity and electron affinity dependency. Using the least-squares method, we analyze the available experimental data of SED cross sections for different negative ions in collision with Ar, and get empirical formulas for different sets of anionic projectiles. For most anionic projectiles, there is a clear correlation between increasing electron affinity and decreasing SED cross sections. Co and Ir, however, are an exception, and we discuss how other physical parameters can be taken into account in the search for general scaling rules for SED cross sections. As the incident velocity increases, the cross section dependence of the anion's electron affinity becomes weaker, and the relation between the SED cross sections and νp is supposed to be [Formula: see text].

Combined Bending and Compression of a Pressurized Circular Cylindrical Membrane Column

1965 ◽  
Vol 87 (3) ◽  
pp. 372-378
Author(s):  
W. E. Jahsman
Keyword(s):  
Compressive Strength ◽  
Cross Section ◽  
Compressive Load ◽  
Circular Cross Section ◽  
Bending Moment ◽  
Maximum Load ◽  
Bending Moments ◽  
Lateral Deflection ◽  
The Cross

Load-lateral deflection curves are developed for a pressurized tube of circular cross section under combined bending and compression. The tube walls are assumed to have negligible compressive strength so that wrinkling develops if the stress tends to become negative. It is found that for a given bending moment, the load increases monotonically with deflection until a maximum is reached beyond which the load decreases with increasing deflection. An interaction curve of the maximum load versus bending moment shows that the presence of only a small amount of bending significantly decreases the maximum compressive load below the classical Euler load. Conversely, for bending moments which produce almost complete wrinkling of the cross section, only very small amounts of compressive load can be supported.

scholarly journals Bending Resistance of Composite Sections with Nonductile Shear Connectors and Partial Shear Connection

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Svetlana M. Kostic ◽  
Biljana Deretic-Stojanovic
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Bending Moment ◽  
Nonlinear Material ◽  
Parameter Study ◽  
Shear Connectors ◽  
Shear Connection ◽  
The Cross ◽  
Section Analysis ◽  
Composite Steel

The paper presents the nonlinear section analysis for composite steel-concrete beams with different degrees of shear connection. The analysis is fiber based, i.e., integration over the cross section is performed numerically, and any uniaxial nonlinear material model can be assigned to the steel and concrete parts of the cross section or to the reinforcement bars. The analysis assumed full interaction between steel and concrete and therefore, is suitable for analysis of composite steel-concrete beam cross sections with nonductile shear connectors. Its accuracy is verified on few experimental results. The presented section analysis is used in the parameter study in order to evaluate different methods proposed by design codes for determining the bending moment resistance of composite cross sections with nonductile shear connectors and different degrees of shear connection. The following effects are considered: variation of concrete and steel material models, presence of slab reinforcement, and creep of concrete. Special attention is paid on two different constructional methods: propped and unpropped. The weaknesses of the simplified design method in determining bending moment resistance are identified and recommendations for practical design analysis are formulated.

On the Experimental Analysis of Temperature Influence on Stiffness of Reinforced Concrete Beams

2015 ◽  
Vol 6 (1) ◽  
pp. 49-58 ◽  
Author(s):  
Robert Kowalski ◽  
Michal Glowacki ◽  
Marian Abramowicz
Keyword(s):  
Reinforced Concrete ◽  
Cross Section ◽  
Cross Sections ◽  
Concrete Beams ◽  
Rectangular Cross Section ◽  
Thermal Strain ◽  
Bending Moment ◽  
Reinforced Concrete Beams ◽  
Stiffness Reduction ◽  
Tensile Zone

The paper presents results of experimental research whose main topic was determination of stiffness reduction in bent reinforced concrete beams in two cases: when only tensioned or only compressed zone was exposed to high temperature. Twenty four reinforced concrete beams with rectangular cross-section were prepared for the experiment. Eight groups of beams were prepared in total: 2 with reinforcement ratio - 0.44 and 1.13% x 2 levels of load - 50 or 70% of destructive force ensuring the constant value of bending moment in the centre part of heated beams x 2 static schemes. Three beams were used in each group. Significant cross-section stiffness reduction was observed in beams where the tensile zone was heated. This was due to considerable elongation of the bars where the steel load elongation summed up with the free thermal strain. In beams where the compressed zone was heated the stiffness reduction was observed only after the time where the tensile zone heated cross-sections were already destroyed.

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