Review of Research in the Field Study of the Stress-Strain State of Concrete-Filled Structures

The paper presents an analytical review of the literature, which reflects the results of national and foreign scientific researches aimed to studying the features of the composition and dosage of components of self compacting concrete as one of the most promising aggregate for modern composite structures. In addition, the results of numerical and experimental researches of stress-strain state of composite structures (concrete-filled tubes) under the influence of various power factors, have been considered. The description and features of existing analytical methods for the determination of the bearing capacity of the considered structures under compression and bendings, have been given. The analysis of deformation model of confined concrete in a composition of the composite structure, as well as non-linear models of steel works with their distinctive features, has been carried out. The main approaches to the finite element modeling of composite structures have been determined

Rational modeling of a wind unit tower taken into account of the features of its dynamic characteristics

Nowadays the level of development of finite element (FE) calculation systems allows us to count on the maximum level of design solutions quality, provided that is created an adequate and at the same time simple design model, which directly determines the level of accuracy of the results obtained when determining the parameters of the stress-strain state, as well as dynamic characteristics of buildings and structures. It is fundamentally necessary for the designer to know the degree of influence of various factors to the creation of a finite element design model on the dynamic response of the design object. There is no doubt the relevance of the problem of identifying the features of modeling tower-type structures, which will simplify the work of an engineer and at the same time reach a qualitatively new level in making design decisions. The purpose of this work is a comprehensive assessment of the influence of the features of creating a design model to the resulting parameter - the frequency behavior of a tubular tower for wind turbines which is the most popular at wind parks in Russia over the past two decades. For numerical research was used the domestic design complex SCAD Office. To create calculation models and perform a comparative analysis of the resulting parameters of tubular towers were used FE types 41, 42, 44, and 50. When determining the influence of the finite element type calculations were made for a cylindrical tower with fixed parameters, taking into account changes in the type and size of the FE. In the calculations the evaluating factors were: changing in the main and equivalent stresses, as well as the change in the frequency of the first form of own oscillations. When comparing the values of the main and equivalent stresses, the plate of the third row from the base was taken as the calculated one

Stress-strain state experimental researches of the lattice support pole sections for overhead power transmission line 110 kV

An article compares the theoretical and experimental researches of joint work of steel tower type supports' fragments of overhead power transmission lines (OHPL) 110 kV. Attention is focused to high voltage supports operated on the Ukraine territory. Is described a spending principle of static experimental researches for flat trusses on the developed specialized experimental installation, allowing to investigate the joint work of overhead lines supports' fragments. Are presented the technique and results of the flat support model calculation in the "SCAD" software package. Are presented calculation numerical results of the experimental installation together with a testing model. Are determinated experimental values of stresses in lattice elements and also horizontal and vertical displacements of braces holding on nodes. During the displacements determining is analyzed the joint work of the lattice elements of the experimental samples, is taken into account the supporting effect of the extended braces

Stress-strain state experimental researches of the lattice support pole sections for overhead power transmission line 110 kV

An article compares the theoretical and experimental researches of joint work of steel tower type supports' fragments of overhead power transmission lines (OHPL) 110 kV. Attention is focused to high voltage supports operated on the Ukraine territory. Is described a spending principle of static experimental researches for flat trusses on the developed specialized experimental installation, allowing to investigate the joint work of overhead lines supports' fragments. Are presented the technique and results of the flat support model calculation in the "SCAD" software package. Are presented calculation numerical results of the experimental installation together with a testing model. Are determinated experimental values of stresses in lattice elements and also horizontal and vertical displacements of braces holding on nodes. During the displacements determining is analyzed the joint work of the lattice elements of the experimental samples, is taken into account the supporting effect of the extended braces

Numerical analysis of axial compressed multifaceted concrete-filled tube elements

The object of study is multifaceted steel concrete- filled poles. The subject of research is the bearing capacity and parameters of the stress-strain state of multifaceted steel concrete- filled poles. The purpose of the research is to numerically study the features of the operation of multifaceted concrete-filled structures under axial compression. Are discussed the features of creating a computational finite element model of such structures in ANSYS APDL. Analytical methods are described for determining the parameters of the nonlinearity of the materials used, as well as the physical and mechanical characteristics of concrete operating under compression conditions. On specific examples the change in the bearing capacity for the object of study under various conditions of materials adhesion (friction coefficient μ varied within 0.1...0.6 with step 0.1). Is analyzed the "unified" analytical method for determining the bearing capacity of steel multifaceted concrete-filled structures, indicating the degree of variability of ultimate compressive load depending on the variation in the number of faces and thickness of the metal wall of the multifaceted model. The considered features of creating a computational model in the ANSYS APDL finite element analysis system, using various laws of deformation of steel and concrete, made it possible to determine the qualitative and quantitative levels of variability of their bearing capacity, which in combination will allow designers of such structures to reach a qualitatively new level when creating structures based on pipe concrete elements

Experimental researches of elastomeric materials to stabilize the oscillation of power grid structures

This paper proposes a new type of insulator, has both insulating and damping properties to improve the operational reliability of overhead power lines' structures (OHPL). In order to assess an effectiveness of the new insulator's design have made laboratory tests of a insulator model with different types of elastomer seals, differed of the rubber marks and the type of reinforcement. An experiment consist of two stages: at the first stage an object of study has been exposed to cyclical vibration, at the second – the impact of an impulsively load. Results of the research showed, that the most effective are the elastomeric gasket with a minimum rigidity characteristics without reinforcement. Using insulators with such dampers allows to reduce the first maximum impulse to a support by an average of 20% and reduce the frequency and amplitude characteristics of the system. Based on this was developed a new type of elastomer reinforcing with steel sheet elements in the form of a truncated cone

Experimental research of dynamic vibration damping for rigid busbar structures

Introduction: in the case when flexible structures interact with the wind flow, various phenomena of aerodynamic instability may arise. Typical representatives of such phenomena are vortex wind excitation of cylindrical structures, galloping of poorly streamlined structures with a square, rectangular or rhomboid cross-section, etc. The article highlights some basic ways of damping vibrations of rigid busbar structures. Materials and methods: the method of dynamic vibration damping consists in attaching additional devices to the vibration protection object to change its vibration state. The work of dynamic dampers is based on the formation of force effects transmitted to the object. It differs from another method of vibration reduction, characterized by the imposition of additional kinematic connections on the object such as fixing its particular points. Results: a mathematical model of the plate dynamic damper operation with a point load is presented. To determine the optimal parameters of dynamic vibration dampers, their calculation was performed, taking into account the joint action of the rigid busbar and the damper. Experimental research of the conjoint work of a rigid busbar with a plate dynamic damper is carried out. Conclusions: the effective application of plate dynamic dampers with a point load has been confirmed both outside and inside the tube busbar. Is proposed the special plate vibration damper. This allows to increase the logarithmic decrement of oscillations by 3-3.5 times and reduce the amplitude of oscillations of rigid busbar structures in the resonant mode by 12 time

Software package for analysis and design of overhead power transmission line structures

The article describes an algorithm for calculating wires and cables implemented by determining the loads on the supports, taking into account the compatibility of deformations of structural elements of an overhead power line (overhead line), atmospheric conditions and the profile of the route for all possible modes of operation of overhead lines. Wires and cables are exposed to the load from their own weight, as well as additional impacts in the form of horizontal wind load and the weight of icy deposits. Using the reduced equation of state of the wire (lightning-proof cable), the amount of tension in the operational state is determined if the voltages in the initial state and the values of loads and temperatures are known. It is revealed that for small spans, the voltage value is greatly influenced by temperature, and for large spans by load, which means there must be such a boundary (critical) span value at which the influence of temperature and load on the voltage value will be the same. As a result, software has been developed to solve the problem of determining the stress-strain state of wires and cables and collecting loads on overhead line supports. The developed calculation subsystems can function independently or be included in the software package as components written in the algorithmic language FORTRAN. In contrast to the traditional calculation, emergency loads for anchor-corner supports are determined not only in the ice regime, but also at minimum and average operating temperatures. The calculation in the software package allows us to consider the alternate breakage of all phases of wires and cables in both the left and right spans

The stress state analysis of lattice tower support for 330 kV overhead line using the “USL” software package

In conditions of market economy, overhead power transmission line (OPTL) support structures must be low-cost and of guaranteed quality, the manufacture of which will require a minimum amount of steel. Therefore, it is necessary to improve overhead line supports, which is possible by clarifying the forces in the support elements and when designing using numerical methods. In this article, a mode of deformation of a corner dead-end support of OPTL is analysed, which is considered a spatially multiple indeterminate open system with flexible joints. Attention is given to the basic problems that can occur in setting initial parameters and constructing design models for such structures. There are a number of problems connected with a refined specification of internal longitudinal stresses in the components of an OPTL structure. In designing, the joint operation of the lattice components of the support spatial pattern model is analysed, and the inclusion of stiffening diaphragms and diagonal element members in the operation on all four faces is taken into account. On the basis of the design and the extension of the results, the internal forces obtained and the ones specified in the components of the pattern OPTL support on the similar values of loads were thoroughly compared. When calculating the spatial model of an anchor-corner support as a result of the joint work of lattice elements, a decrease in internal forces in the elements of the spatial model is observed on average by 6.8%, compared to the forces determined in a typical overhead line support from the same load values. It has been established that it is quite acceptable to calculate overhead line lattice structures in the USL software package since the error in determining the forces in the rods is within 2% and the computer time consumption is less than in other software packages