Инновационные процессы в исследовательской и образовательной деятел

A.S. Martirosyan

Perm National Research Polytechnic University

NUMERICAL MODELING OF DEFORMATION PROCESS FOR COLUMNS WITH RIGID REINFORCEMENT

In modern high-rise buildings the columns supporting the overlap are subjected to vertical load reaching 10,000 tons and more. Thus, random eccentricities should be taken into account. Rigid reinforcement of such columns is advisable along with flexible fitting to create a composite structure in this way. The paper investigates the influence of different computational models on deformation and failure process of a concrete column with rigid metal reinforcement in the increasing complexity of implementation for its further comparison with field testing of models having linear and nonlinear material properties, considering interaction of metal with concrete and including flexible fittings.

Key words: reinforcement, concrete, debonding, rigid reinforcement, flexible fittings.

Introduction

Lower floor columns of multi-storey high-rise buildings take up significant loads of 10 000–15 000 tons and sometimes more. Rigid reinforcement of columns is advisable along with flexible fitting to create a composite structure.

Consider the design of a high-rise building column on the ground floor which is 8.4m long. B80 class concrete column with square section of 1500*1500 mm is enhanced with both flexible reinforcement of 52 A500S steel grade rods which are 36 mm in diameter and rigid fittings of two I-beams arranged crosswise.

The paper is aimed to study the influence of computational models on deformation and failure processes of a reinforced concrete column with rigid metal fittings in terms of their further comparison with field testing. The column is subjected to a load P = 14970 tons applied eccentrically with the moments created Mx = My = 840 tm.

Mathematical statement of the boundary value problem is determined by equations of equilibrium, physical and geometrical correlations, boundary conditions. For numerical solution of the boundary value problem the finite element method and ANSYS software package [1] verified in the Russian Academy of Architecture and Construction Sciences were used.

In the research context there were compared 4 versions of computational models listed below in the order of implementation increasing complexity:

1.Model with linear properties of the materials based on rigid reinforcement (RR) and full contact between reinforcement and concrete;

2.The same model based on “metal – concrete” contact interaction;

3.The same model based on only concrete nonlinear properties (with cracking and crumbling options);

4.Non-linear model including extra flexible fitting (FF).

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1. Model with linear properties of materials

The boundary value problem with linear determining correlations was solved by means of a finite element method in the variational statement. Prelinear analysis can show the most dangerous sections of a computational model in which structural failure is possible.

For rigid reinforcement and concrete modeling tridimensional 8-node finite element SOLID45 was used.

In this model reinforcement and concrete bond in the contact area was assumed to be complete. Calculations showed that concrete stresses in some areas exceeded not only calculated but also normative values of an ultimate strength.

2. Nonlinear problem with contact interaction on a “metal – concrete” boundary

It is known that a bond of reinforcement with concrete provides monolithic behavior of reinforcement and concrete in a construction and allows a twocomponent reinforced concrete to act as a single material. Traditionally the bond is provided by a corrugation available on the surface of reinforcement that ensures resistance to wrinkling and concrete shear [2, 3]. There is no such a corrugation on rigid reinforcement. Therefore, the research is required to examine how specific external influence will not disrupt a monolithic behavior of a composite.

To do this the contact value problem of a “surface-to-surface” type was solved. That was a nonlinear analysis with a view of contact interaction variability (closing-opening), Coulomb sliding friction, possibility of destruction for the material in contact and other nonlinearities.

Engineers are mostly interested in stresses and the possibility of the material in contact to be destructed. They also care about deflections and forces which occur in the contact area.

Solution of the contact value problem proved the lack of debonding in the contact zone under the operating load conditions. (The possibility of concrete cracking was not considered).

3. Model based on concrete non-linear properties

Possibility of crack formation was investigated for the construction under study. For this purpose there was chosen the model oriented to the description of concrete elastic-brittle behavior which was developed by K.J. Willam and E.D. Warnke [4]. It implies that originally the material is isotropic and when it fails it gets orthotropic.

In the general case of a complex stress state for elastic-fragile material it can be assumed that failure occurs when stress intensity reaches a critical point [5].

Availability of some cracks does not mean the destruction of a structure.

When accumulating cracks can lead to the loss of a structure’s bearing capacity.

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This is not all of a sudden point but a result of the damage accumulated on different structural levels. Nonlinear analysis was performed by means of NewtonRaphson method using a complete procedure of NROPT, FULL and automatic step selection. In order to improve convergence under supercritical behavior asymmetric matrix storage scheme was applied.

As a result of the intensely deformed state calculation crack patterns in a concrete column and view of the deformed column have changed. The column does not lose its fundamental strength and equilibrium at this.

4. Model including extra flexible reinforcement

In addition to rigid reinforcement a real-time column construction includes flexible reinforcement in the form of vertical flexible rods and clamps. Flexible reinforcement was simulated as a layer of concrete with effective physical and mechanical characteristics.

Results of the solution to a nonlinear problem also proved availability of cracks in the concrete. However the cracks are concentrated only in the upper and lower zones of the column.

Results

Adjusted for a flexible reinforcement, stresses in concrete fall by ~ 3 % and in metal by ~ 5 % as compared to the calculations excluding flexible reinforcement.

Stresses obtained in concrete and reinforcement are lower than those calculated for the considered loading and given classes of concrete and reinforcement. Hence these calculations prove the required strength of the column section.

References

1.Басов К.А. ANSYS. Справочник пользователя. – М.: ДМК Пресс, 2005. – 640 с.

2.Попов Н.Н., Чарыев М. Железобетонные и каменные конструкции. – М.: Высшая школа, 1996. – 255 с.

3.Математическое моделирование процесса разрушения сцепления арматуры с бетоном. Ч. 1: Модели с учетом несплошности соединения / А.В. Бенин, А.С. Семенов, С.Г. Семенов, Б.Е. Мельников // Инженерностроительный журнал. – 2013. – № 5. – С. 88–144.

4.Willam K.J., Warnke E.D. Constitutive model for the triaxial behavior of concrete // Proceedings, International Association for Bridge and Structural Engineering. – 1975. – Vol. 19. – Р. 174.

5.Кашеварова Г.Г., Труфанов Н.А. Численное моделирование деформирования и разрушения системы «здание – фундамент – основание». – Екатеринбург–Пермь: Изд-во УрО РАН, 2005. – 225 с.

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A.V. Lunova

Perm National Research Polytechnic University

BIOGAS PRODUCTION FROM DAIRY WASTES

This paper deals with the utilization of biogas from milk plant wastes as an alternative energy source. The optimal conditions for the biogas production, the characteristics of wastewater at dairy plants, as well as environmental and economic benefits of anaerobic digestion are given.

Key words: biogas, methane, anaerobic digestion, wastewater, dairy industry.

The beginning of the XXI century is marked by the rapid growth of productive forces, which led to a sharp increase in the consumption of all forms of energy, especially fossil fuel energy, such as coal, oil and natural gas energy. At the same time, this situation intensified the trend towards the so-called alternative energy sources, which include biogas in addition to solar, groundwater and wind energy.

Biogas is a mixture of a methane and carbon dioxide (with an average ratio of СН4 : СО2 3:1) obtained as a result of the anaerobic (without air) fermentation of organic substances in special reactors – digesters [1].

The process of the anaerobic digestion is conventionally divided into three phases depending on the type of the process that occurs: hydrolysis (decomposition of macromolecular compounds (fats, proteins and carbohydrates) into low molecular weight substances), acidogenesis (formation of organic acids, hydrogen, ammonia, hydrogen sulfide and acetic acid) and methanogenesis (conversion of organic compounds to methane and carbon dioxide).

The optimal biogas production values are given in the Table.

Optimal biogas production values [3]

The main reaction of methane formation can be written as follows:

СО2 4Н2 СН 4 2Н2О.

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The average biogas yield is 0.15 m³ per 1 m³ of capacity and it largely depends on the initial raw material characteristics.

The scheme of a biogas installation is shown in Figure [4].

Fig. Scheme of a biogas installation

The biogas production allows us to solve a number of problems:

–to reduce the weight of organic substances by their biological degradation;

–to decrease anthropogenic load on the environment by reducing emissions of harmful organic compounds;

–to reduce the greenhouse effect by burning the biogas produced (methane conversion into carbon dioxide reduces the greenhouse effect by 5.5 times).

The availability of raw materials for its production is a significant advantage of this type of fuel.

The disadvantages include lower (by 30 %) calorific value in comparison with natural gas, higher capital costs and the need for guaranteed sales of the energy produced.

On average, 1,250 m³ of industrial waste and 250 m³ of whey, which are characterized by a high content of organic matter (COD 2,000–4,500 mg/l), fats and suspended particles, are produced at a dairy plant daily [4].

The analysis of the dairy wastewaters showed that the main problem of such wastes was a large amount of fat (100–200 mg/l), which covered the water

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plane, when entering natural water bodies, and made re-aeration and oxygen dissolution complicated, thereby creating danger for fish and the environment. Passing through the sewage network, fat particles adhered to the channel walls, glued the contamination together and reduced the flow section.

Thus, the utilization of fat-containing wastes and their rational use is an urgent problem, which can be solved by the anaerobic digestion accompanied by the production of biogas. For this purpose, wastes must be brought to the required parameters (moisture, ash content, pH level) and sent to a digester, where the substrate decomposes under the influence of acid and methanogenic bacteria and biogas releases.

This method allows us to decompose the concentrated wastewater at dairy and cheese plants into clean water, biogas with a methane content of 75–85 % and organic fertilizer. And with it, from 20 to 50 % of the company's needs in electricity can be covered by biogas, and the remaining part can cover the space or water heating expenses. A characteristic feature is the fact that the more the contamination is, the greater the amount of the emitted power supply is. The anaerobic technology also reduces the volume of tanks by approximately 5 times relative to the size of “classical” aerobic treatment plants [4].

The production of biogas is the most optimal direction of wastewater treatment development. It is a profitable and competitive technology, whose more detailed study and implementation will reduce energy consumption and save the environment.

References

1.Добрынина О.М., Калинина Е.В. Технологические аспекты получения биогаза // Вестник Перм. гос. техн. ун-та. Охрана окружающей среды, транспорт, безопасность жизнедеятельности. – 2010. – Вып. 2. – С. 33–41.

2.Герасименко В.Г. Биотехнология. – Киев: ИНКОС, 2006. – 647 с.

3.Баадер В., Доне Е., Бренндерфер М. Биогаз: теория и практика. –

М.: Колос, 1982. – 149 с.

4.Современная концепция возврата энергии с целью снижения эксплуатационных затрат и себестоимости продукции для молокозавода

[Электронный ресурс]. – URL: http://biologicheskaya-ochistka.enviro- chemie.ru/?p=444#more-444 (дата обращения: 13.02.2015).

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S. Monchenko, N. Slyusar

Perm National Research Polytechnic University

RESEARCH INTO PROPERTIES OF MSW LEACHATE BASED ON LABORATORY LANDFILL BIOREACTOR

The article presents factors that affect the rate of waste biodegradation processes. Landfill bioreactor modeled in the laboratory to study MSW biodegradation is described. The MSW biodegradation stage can be determined based on the leachate investigations.

Key words: landfill, bioreactor, MSW biodegradation, leachate.

Currently, waste disposal in landfills is the most common way of dealing with municipal solid waste (MSW). Functioning of the landfills is accompanied by the biogas and leachate formation [1]. Biogas, produced as a result of biochemical processes pollutes the air, and often leads to waste burning. The leachate pollutes soil and groundwater [2]. Therefore it is necessary to use the concept of landfill management according to which the MSW biodegradation should be accelerated and the negative impact of the landfill facility on the environment reduced. The concept makes it possible to actively manage the biological, chemical and physical processes in the landfill. The aim of the landfill bioreactor is to accelerate the biodegradation and stabilize the waste within a relatively short time. The concept implementation will give an opportunity to use the landfill gas potential as an alternative source of heat and electricity, and the leachate recycled to be used for keeping the waste humidity stable.

Fundamental factors capable of affecting the efficiency of biodegradation of MSW landfilled waste are shown in Table 1 [3].

Under laboratory conditions landfill bioreactor was modeled in order to study biodegradation processes in compliance with the main influencing factors (Figure).

Laboratory landfill bioreactor simulates and accelerates the MSW biodegradation by adjusting the necessary parameters of the waste, such as pH, humidity, and temperature.

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The pH increase proves existence of enzymolysis of acids formed in the acetogenic phase, which is also accompanied by a significant evolution of gases (methane, carbon dioxide, mercaptans, ammonia and others).

It is known that decomposition of the proteins, pectins and other nitrogencontaining compounds under anaerobic conditions form ammonium ions which pass completely into the leachate.

At the stage of active methanogenesis there occurs a significant reduction of organic substances in the waste, which results in the COD decrease.

Reduction in the amount of carbonate is due to the fact that during their decomposition, they pass into oxides.

To sum up, the MSW is under active methanogenesis. Research will be continued in order to study the processes of gas evolution.

References

1.Савичев А.С. Биореактор на месте свалки // Химия и жизнь. – 2005. – № 1. – С. 20–25.

2.Исследование свойств отходов разного срока захоронения / Ю.М. Загорская, Н.Н. Слюсарь, И.С. Глушанкова, Ю.В. Завизион // Транспорт. Транспортные сооружения. Логистика. – 2014. – № 1. – С. 40–50.

3.Глушанкова И.С. Очистка фильтрационных вод полигонов захоронения твердых бытовых отходов на различных этапах жизненного цикла: дис. … д-ра техн. наук. – Пермь, 2003.

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A.U. Melnikova

Perm State Academy of Art and Culture

CULTURAL TRANSFORMATION IN PRESENT-DAY

“LEISURE SOCIETY”

The paper deals with the study on how cultural transformation correlates with leisure activities in present-day “leisure society”. To prove the relevance of the “leisure society” concept for Russian community a supply and demand research of cultural services market in the city of Perm was undertaken. The results obtained showed up some partial inconsistency of the concept since people living in Perm are not determined to increase their leisure time willingly just because to do some leisure activity in any of its cultural form. Still, the relevance of a new “cultural consumer” notion which is appropriate to “leisure society” was proved.

Key words: сultural consumer, leisure time consumption, leisure society, cultural sphere, post-industrial society.

Introduction

Any state can develop effectively only when it ensures a sustainable development of its human potential. Social and cultural sphere as a component of this development determines the community welfare. Historically culture turned to be the tool of mental, ethical and artistic education. However, since the 70s of the 20th century there has been a lot of discussion in Europe about the changing role of culture. Culture begins to be regarded as a leisure activity and means of entertainment. The question arises as to how culture fits in with the development of post-industrial society. Can it be useful for the country’s economy and community development?

With the transition to a post-industrial society organization of leisure time has become an inherent value independent of labor activity. There has been a shift of community needs in the benefits of culture from humanistic values to material wealth, which resulted in new forms of leisure activity.

Since the 1960s there has been made a lot of research into division of labor and leisure time. In the 80-s the concept of ‘the selected time revolution’ was suggested. As the concept states, time cannot be formally divided into labor and leisure time. Everyone is free to choose the scope of labor and leisure time according to one’s biorhythms.

It was J. Dumazedier who started speaking about “leisure society”, a new phenomenon in leisure and cultural sphere. Leisure is not regarded as a mode of resting from labor activity any more. It has become part and parcel of human life, its “essential variable” [1].

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