INFORMATION RESOURCES FOR THE CONSTRUCTION SCIENCE
Pages 5-6
DOI: 10.22227/1997-0935.2016.4.5-6
Articles count - 15
Pages - 147
Pages 5-6
DOI: 10.22227/1997-0935.2016.4.5-6
Pages 7-16
Curtain wall systems are subjected to the influence of air flow, which is changing in its direction and speed. Such an influence gives rise to variable forces, which leads to fluctuating stresses in the structures of curtain wall systems. In case of fluctuating stresses the structural element is destroyed at lower loads, than in case of constant stresses. This fracture is called the fatigue. The fatigue fractures lead to drastic consequences because of their sudden emergence. The fracture mode of structural materials depends on the number of loading cycles. The authors state the notions of multicycle and low-cycle fatigue of materials. Some types of fatigue curves are offered. The authors hypothesize on the absence of horizontal areas of Wehler curve in case of plastic materials.
DOI: 10.22227/1997-0935.2016.4.7-16
Pages 17-26
The article deals with the solution for the stress-strain state of a multilayer composite beam with rectangular cross-section, which is bended by normally distributed load. The intermolecular interaction between layers is accomplished by the contact layer, in which the substances of adhesive and substrate are mixed. We consider the contact layer as a transversal anisotropic medium with such parameters that it can be represented as a set of short elastic rods, which are not connected to each other. For simplicity, we assume that the rods are normally oriented to the contact surface. The contact layer method allows us to solve the problem of determining the concentration of tangential stresses arising at the boundaries between the layers and the corner points, their changes, as well as to determine the physical properties of the contact layer basing on experimental data. Resolving the equations obtained in this article can be used for the solution of many problems of the theory of layered substances. These equations were derived from the fundamental laws of the theory of elasticity and generally accepted hypotheses of the theory of plates for the general case of the bending problem of a multilayer beam with any number of layers. The article deals with the example of the numerical solution of the problem of bending of a three-layer beam. On the basis of this solution the curves were obtained, which reflect the stress-strain state of one of the layers. All these curves have a narrow area of the edge effect. The edge effect is associated with a large gradient tangential stresses in the contact layer. The experimental data suggest that in this zone the destruction of the samples occurs. This fact allows us to say that the equations obtained in this article can be used to construct a theory of the strength layered beams under bending.
DOI: 10.22227/1997-0935.2016.4.17-26
Pages 27-35
The Cauchy problem of the Godunov - Sultangazin system of equations with periodic initial conditions is considered in the article. The Godunov - Sultangazin system of equations is a model problem of the kinetic theory of gases. It is a discrete kinetic model of one-dimensional gas consisting of identical monatomic molecules. The molecules can have one of three speeds. So, there are three groups of molecules. The molecules of the first two groups have the speeds equal in values and opposite in directions. The molecules of the third group have zero speed. The considered mathematical model has a number of properties of Boltzmann equation. This system of the equations is a quasi-linear system of partial differential equations. There is no analytic solution for this problem in the general case. So, numerical investigation of the Cauchy problem of the Godunov - Sultangazin system is very important. The finite-difference method of the first order is used for numerical investigation of the Cauchy problem of the Godunov - Sultangazin system of equations. The paper presents and discusses the results of numerical investigation of the Cauchy problem for the studied system solution with periodic initial condition. The dependence of the time of stabilization of the Cauchy problem solution of Godunov - Sultangazin system of equations from the decreasing parameter of system are obtained. The paper presents the dependence of time of energy exchange from the decreasing parameter. The solution stabilization to the equilibrium state is obtained. The stabilization time of Godunov - Sultangazin system solution is compared to the stabilization time of Carleman system solution in periodic case. The results of numerical investigation are in good agreement with the theoretical results obtained previously.
DOI: 10.22227/1997-0935.2016.4.27-35
Pages 36-51
When constructing large-span metal domes different methods of installation are used, which depend on geometry schemes of the frames and their construction solution. The frames of such domes consist of a lot of structures. During assembling large number of structures with different spatial orientation are joined together. Little differences of structures lead to distortion of their real geometric form compared to the design form. A computer analysis of the values of the initial forces due to force elimination of assembly errors of double-layer framed metal dome has been performed. The position errors of nodes of planar meridional ribs were considered in the annular directions at installation of the dome frame with temporary central support. The initial forces due to the connection of already assembled sectors of the dome with annular elements at different stages of the construction of the frame of the dome are investigated. For this purpose concentrated forces were applied to the nodes of the sectors to eliminate relative deviations of the connected ribs, and initial internal forces in the bars were registered. The values of the initial forces in the bars were compared to the values of the initial forces due to the dead load and design load. The results of the investigation are presented in the form of figures, schemes, diagrams, and tables. The conclusions are made on the influence of the initial forces on the stress-strain state of the dome frame.
DOI: 10.22227/1997-0935.2016.4.36-51
Pages 52-61
One of the consequences of the construction in the conditions of dense housing system is the development of underground part of buildings, which influences the surrounding buildings, changing the stress-strain state of soil masses and hydrogeological conditions of the construction site. The damming effect leads to local increase of hydrostatical pressure of ground waters on underground structures. The authors present a description of hydrogeological conditions of the construction site of underground construction and mathematical geofiltration model of the soil foundation. The results of numerical investigation of the change in the hydrogeological mode of the construction area in case of enveloping the foundation pit with the wall in the ground are considered. On the first stage the basic mathematical model was calibrated by variation of the values of geofiltration parameters of water-bearing sediments and water-resistant mass and the values of infiltration recharge. The validation criterion of the mathematical model was the good agreement of the modeled and real ground water levels obtained as a result of compilation of the existing geological and hydrogeological materials. The construction simulation was carried out in a multivariant formulation for the conditions of entirely impenetrable wall in the ground with the filtration coefficient 0.001 m/day.
DOI: 10.22227/1997-0935.2016.4.52-61
Pages 62-68
Lime-belite binder is obtained by low-temperature firing of natural marl, marling or sanding limestone and artificial lime-silica mixtures. The binder with calcium oxide also contains significant amounts of dicalcium silicate and some others materials, the composition and quantity of which depend on the chemical composition and firing temperature of the raw materials used. The authors investigated the kinetics of hydration structures and physicochemical properties of lime-based binders on the basis of belitic marl from Akburly and Porlytau. The formation of resistance is associated not only with the formation of the system of different types of structures - coagulation and crystallization, with the transition of the first to the second, but also with the different stages of formation of crystal structures. The possibility of using lime-belitic binders for the preparation of high-strength products of autoclave hardening is proved. The autoclaved binders used in the manufacture of sand-lime products are prepared with the use of mixtures consisting of 60...70 % lime-belite binder and 30...40 % ground quartz sand.
DOI: 10.22227/1997-0935.2016.4.62-68
Pages 69-75
The development of construction materials with increased operational properties is a priority direction of Russian modern structural material science. Dry mortars are among such materials. Various modifiers are added to the formulae of such mixes in order to control their structure formation and increase the operational properties. Previous investigations proved the efficiency of adding synthetic zeolites to the composition of dry mortars. The authors of the article have developed a formula of a dry mortar to be used as a tile adhesive for facades’ and inner walls’ facing. The authors evaluated the operational properties of tile adhesive layer based on dry cement mortar. The authors calculated the value of adhesive layer creep based on the developed dry cement mortar formula, which was spread over a vertical surface. The experimental data is presented in the article. The calculations and the experimental data proved that the adhesive layer based on dry cement mortar possesses a high creeping resistance.
DOI: 10.22227/1997-0935.2016.4.69-75
Pages 76-83
Concrete is a material very commonly used in modern construction, each year over 4 billion m3 of concrete is used around the world. In the recent years high-quality fine grain and other types of concrete allow giving the modern creation city buildings new architectural expressivity, meeting the requirements of the XXI century. The trend of using of these new types of concrete is also applied in the construction of tunnel systems and the subway. The fine-grained high performance concrete obtained by using a mixture of organo-mineral additives and fiber reinforcement, compares fovourably with ordinary fine-grained concrete, namely its bending and tensile strength is higher, it has good resistance to shock impacts and fatigue, as well as crack resistance, water resistance and resistance to erosion. So this type of fine-grained high performance concrete is suitable for the construction of subway tunnels and other special objects. When evaluating the concrete performance in underground rock layers subjected to complex mechanical forces, it is important to take into account the stress of metro upon departure and stopping at the stations. The article presents a new experimental method of determining the adhesion strength of fine-grained high performance concrete layer freshly poured on the surface of old concrete in the process of construction and repair of underground. The result of this method application showed that fine-grained high performance concrete is capable of skid resistance higher than 55 % compared to regular fine-grained concrete without additives.
DOI: 10.22227/1997-0935.2016.4.76-83
Pages 84-93
The speed of the human flow depends on its density. The free space in this flow depends not only on the number of people, but also on the area occupied by each of the people. The important parameter required for calculation of evacuation probability is the projected area of a human. The authors took ellipse as a shape of horizontal projected area of a human. The necessity of the dimensions for fire practice was first formulated in 1951. However, this was static dimensions. For evacuation software modeling the dynamic dimensions might be more appropriate. The paper discusses the experiments aimed to obtain static and dynamic dimensions of the pedestrians of various mobility groups. The obtained data should be used to increase the accuracy of evacuation process modeling and to rationing the escape routes and the sizes of exits.
DOI: 10.22227/1997-0935.2016.4.84-93
Pages 94-107
The scenario of a hydrodynamic accident of water flow over a crest of a soil dam is considered by the method of fault tree analysis, for which the basic reasons and controlled diagnostic indicators of an accident have been defined. Logical operators “AND”/”OR” were used for creation of a sequence of logically connected events, leading to an undesired event in the scenario of accident. The scenario of the accident was plotted in case of three basic reasons - an excessive settling of a dam crest, an excess flood, an inoperable spillway, taking into account the sequence of the events’ development and with observance of the necessary conditions leading to an accident. “Technical” reasons were observed in the present scenario, force majeure events were not considered. The provided scenario of the accident consists of two branches of events’ development: the left one that depends on an upstream level, and the right one that depends on settling of a dam crest. In each of the considered events an accident “the water spill over a crest of a soil dam” is possible only in case of execution of two different conditions at the same time, i.e. in case of an appropriate upstream level and the appropriate mark of a crest of a soil dam. The conditions of the accident are defined by diagnostic indices - the upstream level and settling of a dam crest, which at the same time are safety criteria of the hydraulic structure for soil dams. They allow defining the technical condition of the construction. Four possible technical conditions are suggested for the definition of technical statuses - normative, operable, limited operable, abnormal. Criteria of safety are the boundaries of the state: for loading and impact - it is the upstream level, for geometrical compliance of the construction - it is a dam crest mark.
DOI: 10.22227/1997-0935.2016.4.94-107
Pages 108-118
In the article the essence of outsourcing as a new form of employment relations is considered, its features are defined in comparison with traditional forms of employment, its advantages and disadvantages are given. The authors describe the reasons why companies resort to outsourcing, in particular, on the example of small business, illustrate the strategic importance of outsourcing. The practical application of outsourcing is becoming more widespread in the modern business. The scientific and actual role of outsourcing in the management of the enterprise has greatly increased, which is proved by the fact that today more than fifty per cent of current foreign companies apply data approach. Thus today in the Russian Federation outsourcing is at an early stage of formation and relates mainly to restructuring of business entities and development of the market of information technologies. The analysis allowed determining the provisional value of the outsourcers’ services. The basis of determining the cost of the services is the cost of maintenance of one unit of standard accounting service. The calculations show that for the investigated enterprise it is very advantageous to transfer a number of business process to outsourcing, and there is a need to carefully consider over the choice of an outsourcer in order to avoid the negative sides of the work under this type of agreements. When deciding about outsourcing, one needs to analyze the financial and organizational costs, while keeping the risks of associated with the work in terms of outsourcing in the analysis area.
DOI: 10.22227/1997-0935.2016.4.108-118
Pages 119-129
The article is devoted to the development of the main provisions of realtor business modeling. In the paper the development of notational complex is presented, which is involved in the design of the conceptual model, the formation of a reference model of real estate business and basic rules for the implementation of the model. In the construction of the proposed model important notational aspects are highlighted. Functional orientation of real estate business for rendering services reflects a functional approach to business modeling. In order to ensure the assessment of the offered services it is proposed to implement a nested model of the object. A reasonable functional approach using object-based elements allows optimizing the processes of business modeling and assessment of the results. The article discusses functional modeling of business, focusing on the results. Synchronizing the functional model with the models of business processes and sub-models of objects, in particular, the model of business result, contributes to the improvement of the notations tools. The article presents the adaptation of the template of the business model to the conditions of the realtor activity. The proposed reference model specifies the logical scheme of decomposition activity, which detaches economic, social and other values. The decomposition of services into functional groups with account for individual values and functional modules is presented: buying and selling real estate; mortgages and loans; rent of residential and commercial property; an independent evaluation of real estate; consultations concerning the issues of real estate transactions. In the focus of the results of business processes and performance standards of realtor organizations transitional notation to the evaluation system efficiency of business performance is developed. The simplest method of feedback for assessing customer satisfaction and, consequently, system efficiency is offered. This method can become the basis for the development of metrics processes, which are implemented to meet customers’ demands and achieve business objectives of a realtor organization.
DOI: 10.22227/1997-0935.2016.4.119-129
Pages 130-139
The authors determined the trends of sustainable development of the complex and the limitations obstructing them. The dynamics of investment and construction complex is considered as a self-organization process basing on information interchange, which allowed presenting a conceptual scheme and lifecycle of the changes in the system as a process of accumulation and dynamics of different innovations. The theoretical assumptions on the essence of the management process were proved thanks to empirical analysis of control system changes of investment and construction complex basing on the model of converging development spiral.
DOI: 10.22227/1997-0935.2016.4.130-139
Pages 140-147
Operational management of the construction is usually based on information analysis systems, which are aimed at the monitoring of working schedule and volumes as consistent with predicated schedules. The result of such systems’ operation is traditional information graphics (diagrams, charts, etc.), which provides idea on the current state of the construction site and deviations from the planned settings. The author considers the visualization technology of construction of objects using an image of the situation on the AutoCAD drawings, converted into an interactive format. The article focuses on imperfections of the existing technologies of information support of the managers. The creation of unified IT platform is offered on the basis of CAD for creating an integrated information storage and visualization of the environment using electronic drawings and diagrams. Using interactive methods it is possible to illustrate the condition of almost any part of the construction project using these drawings and diagrams. E-drawings contain the basic information resources - estimates, plans, sections, specifications, technology, construction, etc. necessary for the calculation of indicators. The author proved that implementation of visualization is most efficient in case of electronic drawings in 3D format.
DOI: 10.22227/1997-0935.2016.4.140-147