M.I. Kazakevitch
Chaos in aeroelastic systems
Dnepropetrovsk National V.Lazaryan University of Railway Transport
Abstract. It’s well-reasoned that chaotic oscillations exist in non-linear determined systems of any origin as an unpredictable regime of their dynamic behaviour. This unpredictability as the chaos feature is first of all conditioned by the initial conditions. By the example of the interaction between a wind flow and a tandem of cylinders there was investigated a character of streamline, a mechanism of the onset and possible regimes of aero-elastic oscillations depending on such initial conditions as a flow velocity, a flow slant (a relative arrangement of both cylinders as to the flow direction), a proper frequency of the cylinders oscillations. There is shown a chaotic nature of a number of the aero-elastic instability phenomena by the example of galloping.
Keywords: non-linear determined system, cylinder tandem, aero-elastic phenomena, chaotic oscillations.
S.F. Pichugin
Estimation of steel structure elements reliability
Poltava National Technical University named in honor of Yuri Kondratyuk
Abstract. There are considered alternate estimations of steel element reliability. The method proposed takes account the time factor. Loads and a carrying capacity reserve of structures are given in the form of random processes, absolute maxima of the random processes, random sequences of independent overloads, a discrete representation and extremes. New probability parameters are introduced to combine loads presented in different stochastic techniques. Recommendations to calculate the elements reliability are formulated in the form of the successive algorithms.
Keywords: structure reliability, random loads, probability load models, load combinations.
A.Ya. Martynyuk, A.A. Nilov, M.V. Laznyuk
T elements and thin cross-corrugated web
PEM Ukraine Ltd., Zeman Group Kyiv National University of Construction and Architecture State Research Institute of the Automated Systems in Construction
Abstract. There are discussed the problems of designing and producing double-T steel structures with a thin corrugated web. There are considered engineering problems of welding thin webs and girdles, flanges and ribs made of thick sheet steel. It is noted that the problem of welded seams of corrugated webs as thick as 2…3 mm and thick girdles and bearing ribs or flanges which in practice can be as thick as 30-40 mm remains unsolved in the terms of the home normative documents. The main aim of this article is to discuss and substantiate a possibility of using double-T structures with a corrugated web of welded seams different from those approved in Ukraine when producing structures. There is analyzed a technology of producing such structures. Factory-welded connections of the elements of such structures are suggested to be done by the technological instructions developed and approbated both in Ukraine and abroad. The reliability of such connections has been proved by numerous tests and researches as well as by the lasting experience of their use in construction.
Keywords: welded double-T profile, thin corrugated web, web-flange welded connection.
A.I. Davidenko, V.V. Stoyanov
How to increase crack resistance of a crane way girder near a crack with a coal-plastic joint by mathematical modeling
State Research Institute of Building Constructions Odessa State Academy of Building and Architecture
Abstract. The article is devoted to the investigation of crack resistance of a crane way girder near a crack with a coal-plastic joint by mathematical modeling. This modeling makes it possible to find out the stress rate coefficient at an apex of crack and to compare it with a critical meaning of the rate coefficient to estimate crack stability of structures with defects both at the stage of designing and to extend a crane way girder operation life under attaching carbon fibres. A crack modeling is being done in the computing complex “Lira Windows” with the help of super-elements.
Keywords: crack, crack resistance, super-element, carbon linen, crane way girder.
M.V. Gogol’
Design and calculation of rational combined metal structures
National University «Lvov Polіtekhnіka»
Abstract. On the basis of a generalized practice of controlling efforts in metal structures there is shown that calculation is the most rational method of controlling in the process of designing. This method requires no additional financial costs. As emphasized, the problem of calculating building structures, including combined ones, should initially considered as the problem of their rational design. There was developed a generalized mathematical model of calculating combined structures on the base of an energy approach, a deformed state of the rigidity of a girder being taken into account. There is given an essence of calculation: on the base of a system decomposition method the system is divided into two subsystems, the main and auxiliary ones. Then, with the help of the system synthesis one can calculate its stress-strained state. There is given an algorithm of controlling a system stress-strained state, an efficiency of such a control and cases of introducing such rational structures are shown.
Keywords: model, method, combined structures, equi-stress, rational design, control, efficiency.
A.M. Boldyrev, A.A.Sventikov
Application of methods of parametric optimization in studying suspended structures with a variable design scheme
Voronezh State Architecture and Civil Engineering University
Abstract. There is considered the problem of searching optimum physical and geometrical layout parameters of suspended spatial coverings. The problem is formulated as a multi-parameter one-criterion, nonlinear one of an implicit kind. The basis of the local search is the Hook-Jivce method. The global search is done by the method of sampling points. An estimation of the stress-strain state is accomplished with the use of a finite-element algorithm, a design scheme variability being taken into consideration. Using cross flexible strings There have been obtained the areas of the rational layout values of the suspended spatial coverings.
Keywords: suspended covering, parameter, criterion, search.
Yu.G. Peretyat’ko
Transverse-longitudinal bending of welded columns in terms of an elastic behavior of flange welds
Kharkiv State Technical University of Civil Engineering and Architecture
Abstract. Using a design model of a 3-layer compound rod with elastic-ductile constraints the problem of determining a deflected mode of an H-shape transverse-longitudinal bended column with ductile flange welds was theoretically solved in a linear form. With help of the solution obtained there was also determined a critical value of a longitudinal force compressing the column. To illustrate the situation, the problem was solved for a cantilever 6 meter welded column made of steel С245 of a double-T cross section with flanges of 120×10 mm and a web 250×6 mm. Throat of flange welds is equal to 6 mm. The column is stressed by compressing force Р at its top end and by a uniformly distributed load of a permanent intensity 0.3kN/m. While solving this problems the following was studied: an influence of a deformed scheme on the elements of a column stress-strain state; an influence of a deflection rate of flange welds on the value of a critical force; the character of distribution and values of shearing and transversal loads occurring in welds under different values of the compressive force including its values close to a critical one. An estimation of those welds strength was done.
Keywords: welded columns, transverse-longitudinal bending, compound rod, stress-strain state, elastic compliance of welds, deformed scheme.
S.І. Bilyk
Methods of controlling spatial stability of steel columns with a variable web height from a bending moment cross-section
Kyiv National University of Construction and Architecture
Abstract. There are given analytical researches carried out on the base of V.Z.Vlasov’s theory of thin-wall rods to analyze a spatial stability of frame and column elements of the I-shaped cross-section under a longitudinal force and bending moment. There was obtained a system of differential equations which describes a spatial operation of a variable cross-section elastic rod under a bending moment. There is suggested an approximate solution of the system of differential equations when approximating a cross-section inertia moment and sectorial cross-section inertia moment by a parabolic dependence. There have been developed methods of controlling stability of a double-T column of a variable cross-section from the plane of a bending moment effect. There are shown peculiarities of a methodological approach of controlling a spatial stability of fixed section columns adopted in the normative documents.
Keywords: steel frame, columns, I-shaped cross-section with a variable web height, buckling resistance of columns, stress-strain condition, optimum structure, rational design.
I.S. Kholopov
An optimum design of rod metal structures using modular form
Samara State University of Architecture and Civil Engineering
Abstract. There are given principles of the formation of optimization models, of the acceptance of a quality criterion, of the development of the set of constraints for an optimum design of steel rod structures. A general statement of the problem of an optimum design of steel skeletons and spatial frame structures under a computer-aided design is considered. There is formulated a mathematical optimum model with the use of modular forms (MF) and out-forms (OF) of the volume. There are considered and illustrated properties of the МF and АF formed convex hyper-surfaces. An algorithm of an optimum assortment of cross sections for steel rod elements is put forward.There are given specific solutions of the problem of an optimum design of steel frames for power plants, metal structural coverings (both (flat and billowed) obtained on the base of using a suggested mathematical model of optimization. There are also presented the results of calculations and an optimum design of steel frames and structures.
Keywords: modular form, volume out-forms, optimum design, goal function.
E.V. Gorokhov, V.F. Muschanov, V.R. Kasimov, Ya.V. Nazim, S.G. Kuznetsov, V.N. Vasylev
Monitoring of complex engineering systems
Donbas National Academy of Civil Engineering and Architecture
Abstract. The article is devoted to the peculiarities of monitoring of complex engineering systems in the form of unique designs of stationary coverings over stadium stands, power line towers, high buildings including those which are being erected within an existing housing. For stationary long-span coverings over stadium stands on the basis of various ideological approaches to the development of such systems (e.g., BSA «Luzhniki») there is suggested our own original monitoring scheme which comprises both current and long-term automated measurements of the stress-strain condition parameters, loads and effects in the “on-line” mode, the data of which are the basis for changing indices in the reliability of the operating facilities. For over-head power lines there are given the data on the developed system of monitoring ice-wind loads, the main feature of this system is an automated ice-wind meteo-post. There is also described a structure and operation principles of the improved ice-wind meteo-post which is now being implemented in the NEC «Ukrenergo». For high-rise buildings there are given the results of full-scale studies of wind loads performed with the use of the developed electronic complex, these studies were based on the program of drainage experiments of determining pressure factors.
Keywords: monitoring, covering over stadium stands, power line towers, high-rise buildings.