D.G.Zelentsov, O.A.Radul
Research on the development of stress in corroding plates with a circular cut-out
The Ukrainian State University of Chemical Engineering
Abstract. There is offered a solution of the problem of durability of a planar stressed corroding plate weakened with a circular cut-out. A general case of a corrosion interaction when corrosion rate depends on mechanical stresses is considered. The process of a plate deformation in a corrosive medium is modeled both by numerical solution of a Cauchy problem for the systems of differential equations describing the process of accumulating geometrical damages in structure components and by the finite elements method. To solve the Cauchy problem a special algorithm is used. This algorithm is based on the application of the analytical formula which defines a relationship between initial and finite values of a reduced stress at a point, the corrosive medium parameters, an initial thickness and time. Junctions of a finite-element mesh which in this case has a non-uniform spacing are used as these points. There is offered an adapted triangular finite element of a variable thickness with 12 degrees of freedom which provides the second order of approximation of a thickness function. Problems of a mode of deformation and durability are solved within a plane problem of the theory of elasticity. Results of the numerical experiment are given.
Keywords: planar-stressed plate, corrosive wear, stress concentrator, mode of deformation, durability, finite element of a variable thickness.
Yc.V. Gorokhov, Ya.V. Nazim, N.S. Smirnova, M.V. Bus’ko
Restoration of operating capacity of tower structure near-mast zone
Donbas National Academy of Civil Engineering and Architecture
Abstract. The article is devoted to problems of increasing service performance of power supply structures under restoration. The basic method of increasing the reliability level of power supply objects is an up-to-date elimination of defects in the going structures. The authors have analyzed damages within the near-mast zone of high power transmission towers, outdoor switchgear gantries, and column bases for electrical equipment. Having analyzed the results of examining bearing structures, there were suggested candidates of strengthening structure bases, highs and lows of the given solutions being given in comparison with other methods. The suggested methods being used, it allows to solve a number of problems, in particular, to save money in comparison with a structure replacement and/or in comparison with the costs caused by power cut, and it also allows to make strengthening and repair without any complex mechanization means of a structure discharge. But a decision of either to use or not to use the strengthening technique should be separately made in every case taking into account reasonable financial and maintenance expenses and potentials. The methods of strengthening suggested in the article require the development of a new approach to the problem of restoration repairs and criteria of the adequacy of technical decisions taken.
Keywords: power supply structures, defects and damages, strengthening.
O.G. Arkhipov, O.V. Zinchenko, D.O. Kovalyov, R.G. Zaika
Estimation of degradation of steel equipment at oil-refining and chemical enterprises
East-Ukrainian National V.I. Dal’ University, Technological Institute
Abstract. This work has been executed within the complex program of the NAN of Ukraine “Problems of a resource and safety of operation, structures, buildings and machines (RESURS)”. The urgency of the subject-matter is conditioned by a lot of equipment and apparatuses which has been long used in oil-refining and chemical industries under a corrosive medium. A large part of this equipment has its scheduled resource exhausted or is about to it. The purpose of this research was to find out ways to estimate degrees of steels 09G2S and 20 degradation after a continuous service at oil-refining and chemical enterprises. The task of the work is determination of electrochemical descriptions sensitive to degradation changes of a metal and tendencies in their change. While researching there were used standard methods which are used at electrochemical and metalоgraphic experiments.
Keywords: electrochemical corrosion, degrade steel, initial steel, potential of corrosion, metallography, chloride sodium.
N.G. Saigak, K.F. Zhadanova, P.V. Kokoshuev
Estimation of the in-service reliability of steel structures of an industrial building frame regarding non-uniform deformations of subsidence soil
Zaporizhzhya State Engineering Academy LTD “Nastroy”
Abstract. Industrial building multi-span steel frame deflected mode regarding a subsidence soil non-uniform deformations is examined. The analysis was carried out to estimate the JSC “Zaporozhtransformator” assembly department No.1 steel structures in-service reliability. The results of the structures examination performed in 2006 are analyzed. For a temperature block of a building as big as 138.0×108.0 m vertical column displacements were determined and the surface characterizing a subsidence soil deformation was built. Using the PC SCAD a complex of computations comprising a computation of a plane frame for dead, snow, wind and crane loads and a temperature block spatial computation for the ground base subsidence were carried out. Computation results show ground base deformations are the very factor specifying a steel frame deflected mode. Besides, a substantial factor effecting a multi-span roof state is a continuous nature of steel trusses operation. The analysis carried out allows to draw a conclusion of the model adequacy to frame actual operation under non-uniform ground base deformations.
Keywords: steel frame, deformed base, subsidence soil, analysis model, in-service reliability.
V.N. Vasylev, I.M. Garanzha
Peculiarities plotting a design finite-element model of polyhedral bent bays in the computer system SCAD Office
The Donbas National Academy of Civil Engineering and Architecture
Abstract. The purpose of the article is to analyze an influence of the given kinds of computation (analytical, linear and nonlinear) on the IDC for various levels of a design digitization scheme. There is considered a reasonability of using the finite-element method (FEM) implemented in the software-computer system SCAD to design structures on the base of many-sided bent bays at the stage of pre-computation or at the initial theoretical researches. There is described a principle of choosing Fes to design a model. Besides there is given an algorithm of determining an optimal design scheme МBR. In the conclusion there are analyzed the results of calculating the mode of a structure deformation (MSD) depending on the level of the digitization model and a calculation type, the main conclusions are given too.
Keywords: more-sided bent bays, mode of deformation, finite-element method, optimum design scheme, digitization, method of calculation.
V.N. Vasylev, Y.I. Dozorenko
Deformation-free cutting of a hot$rolled beam with a perforated web
The Donbas National Academy of Civil Engineering and Architecture
Abstract. This article is devoted to issues of designing and efficiency of using perforated beams. It includes the following parts: relevance of the topic, design features, technology of manufacturing perforated beams, operational peculiarities of perforated beams, conclusions. Information on estimating operational and cost efficiency of using perforated beams in construction is provided; recommendations on the best ratio of geometrical dimensions of beam perforations are given. Technology of manufacturing perforated beams is considered. The focus is on the impact of heating temperature on inner stresses and their redistribution in the process of manufacturing. There is given a formula to determine a desired temperature for flanges heating, there are also shown diagrams of a perforated beam inner stresses after a rearrangement of forces as a function of a flange temperature heating and its zigzag shape cutting. There is given a scheme of a hot-rolled I-beam redistribution with the help of gas burners, peculiarities of ready-made structures, its internal stressed state being presented as well. This work aims at a further study of a stressed state of perforated beams, minimization of working hours and costs keeping in mind the technology of their manufacture.
Keywords: perforated beam, stressed state, stratum layer, redistribution, shape, beams of inflexibility, residual stresses.
V.N. Kuschenko
Basic Principles of Building Structures Protection
The Donbas National Academy of Civil Engineering and Architecture
Abstract. The article is about the up-to-date state of the problem – building structures protection. Having analyzed the literature data, we have considered the main constituents of the methodology of determining building structures protection. There have been fixed the following main principles of building structures protection: improvement of analytical methods of specifying loads, actions and design mathematical models of structures (the principle of design scheme specification); a choice of structural schemes excluding a possibility of an avalanche-like damage of a structural system under breaking one or some elements (the principle of a structural system survivorship); a choice of rational structural forms providing a good quality of assembly works and technical maintenance (the principle of a structural form rationality); control of materials and civil and erection works (the principle of quality control); operating conditions control in the process of operation (the principle of technical supervision); an artificial decrease of loads if there are observed features of a dangerous state (the principle of load limitation); defense of structures of attacks (the principle of structure protection); enhancement and reconstruction of structures at their damage in operation (the principle of recovery).
Keywords: methodology, building structures, failures, survivability, safety.