Subject: economic and mathematical methods for forecast of the development of a city conducted for the purpose of more accurate determination of the need for land resources. Development of a city is related to development of construction branch which, in turn, reflects the state of economy. If construction process is conducted, the new enterprises emerge and taxes come to all types of budget from new urban areas, etc. Therefore, forecasting the need for land resources for construction of residential and nonresidential real estate needs to be carried out more qualitatively and carefully, applying various scientific methods. Research objectives: the study of the theoretical and methodological foundations of forecasting the use of land for city’s development and application of the model for forecasting the growth of the city’s territory to increase the economic efficiency of the municipal budget under conditions of the PRC legislation. Materials and methods: correlation-regression analysis, Markov chains, “gray” Markov chains. Results: on the basis of analysis of various economic-mathematical models, whose application is possible when forecasting the needs of cities in construction of buildings, plants and factories, comparison of several common prediction methods is carried out: correlation-regression analysis and “gray” model (GM (1,1)). Upgrade of the Markov chain model is proposed with allowance for uncertainty factors. On the basis of the dynamics of the Zhangqiu land growth, using the proposed “gray” Markov chains, a forecast was made and its statistical, mathematical and economic significance was confirmed, which makes it possible to propose the application of the proposed model to predict the growth of any cities, including the ones in the Russian Federation. Conclusions: practical application of the proposed mathematical method under conditions of uncertainty of long-term forecasts on the example of forecast of city’s needs in land resources will increase the accuracy and economic efficiency of creation of master plans.

Subject: the article is devoted to investigation of prestress losses and force distribution in the reinforcement of span reinforced concrete structures. As the long-term studies have shown, these quantities are very unstable, which should be taken into account in structures design. However, the existing normative documents take into account the possible deviations of losses and forces in prestressed reinforcement from their design values in a fairly general form. Since each of the types of losses, according to the formulas, depends on one or several random factors, they should be considered from a probabilistic point of view. Research objectives: determine the scattering of different losses and acting forces in the prestressed reinforcement to identify the factors affecting its value. Materials and methods: in this work, we used the normative technique of prestress losses calculation and characteristics of the variability of physical and mechanical properties of concrete and reinforcement, obtained from the previous studies. The distribution laws of investigated parameters were assumed to be normal (the Gaussian law). To calculate the coefficients of variation, the method of statistical testing (the Monte-Carlo method) and the linearization method (the Taylor series expansion) implemented in MATLAB software package were applied. Results: in the process of numerical experiment, the values of prestress losses and forces scatter in the reinforcement were obtained for all prestressing methods stipulated by the current design codes. It was established that both values depend significantly on the method of reinforcement tensioning, its type and class, and also on the diameter of wire. Moreover, many concomitant factors affect the variability of the above-mentioned characteristics such as the plant-manufacturer, stability of technological process, qualification of the service staff, etc. Conclusions: the obtained data is recommended to be used to determine the accurate values of strength, deformability and crack resistance of span reinforced concrete structures as well as in probabilistic calculations related to the assessment of their reliability by various limit states. In particular, the described technique was applied in calculating the reliability of bent prestressed elements from the viewpoint of strength of oblique sections.

Subject: a technique for optimizing parameters of the soft soil model with account for creep (soft Soil Creep model) using the PLAXIS 3D geotechnical software package is presented. The results of laboratory tests of soils are compared with the results of modeling in the software package, the process of optimizing the parameters obtained in the laboratory for use in software systems is described, and description of the process of testing the obtained parameters for adequacy (approximation to the behavior in the process of testing) is given. The obtained technique is relevant for application in geotechnical calculations. Research objectives: description of the technique for optimizing parameters of the soft soil model with creep taken into account using the PLAXIS 3D geotechnical software package; comparative analysis of the obtained results of laboratory tests of soils with simulation results in the software package. Materials and methods: when describing the technique for optimizing parameters of the soft soil model, taking into account the creep, numerical methods of solution were used. Laboratory studies of soils were carried out on certified equipment in accordance with the current set of regulations, and the numerical calculations were performed on a certified PLAXIS 3D software package. Results: the technique presented in the article on optimization of parameters of the soft soil model, taking into account the creep, allows us to estimate the degree of correctness of the soil massif behavior simulation in the software package relative to the behavior of the real soil in laboratory setup. This is necessary when this technique is used in geotechnical calculations, since it is very important for designers and analysists to know how well the soil behavior modeled with the software system can approximate the behavior of the soil during actual testing. Conclusions: the conducted comparative analysis and the proposed technique for optimizing parameters of the soft soil model with allowance for creep are obtained from the practical experience of works carried out for determining parameters of the described soil model and applying this model for geotechnical analysis of the stress-strain state of the bases of buildings and structures, being designed and under construction.

Subject: The existing testing methods and instruments (gas analyzer) used do not allow us to obtain the real characteristics of household furnaces to the full extent. This is due to the fact that the combustion of firewood in the furnace is a very unstable process and varies over time over a large range. Such an important parameter as the concentration of carbon monoxide in flue gases proves to be significantly underestimated, and the efficiency of the furnace is too high, which does not allow us to reliably estimate the characteristics of the furnaces and compare them. It requires a more detailed analysis of the firewood combustion process itself and the development of recommendations to improve the reliability of experimental results. Research objectives: investigation of available methods of testing household furnaces and development of recommendations for increasing the reliability of experimental results. Materials and methods: A detailed analysis of the combustion of firewood in the PDKSh-2.0 furnace was carried out. Results: The results of the study were used to develop recommendations for selecting a zone for measuring the characteristics of household furnaces and using a gas analyzer in conjunction with an anemometer to increase the accuracy of measurements and test quality. The proposed recommendations make it possible to obtain more real characteristics of firewood combustion in household furnace and significantly reduce the error in measuring concentration of carbon monoxide and also when measuring the efficiency of the furnaces. Conclusions: The results of the work can be recommended for use in the testing of household furnaces.

Subject: technological properties of self-compensating concrete mixtures with a fine-grained microfiller, represented by quartz flour. Objectives: to determine the quantitative parameters of the influence of the granulometric composition of quartz flour and its dosages on the workability and delamination of self-compacting concrete mixtures with a constant consumption of gauged water and various contents of the superplasticizing additive. Materials and methods: portland cement CЕМ II/A-S 42,5N was used in the work; natural pit sand of 0…5 mm fraction; crushed stone of fraction 5...20 mm; Silverbond quartz flour with an average particle size of 17 μm and 34 μm (grades 15 and 30, respectively); Superplasticizer based on polycarboxylate ester GLENIUM®115. The grain size composition of microfillers was investigated by laser diffractometry using the laser particle analyzer "Analysette 22" COMPACT in accordance with ISO 13320-1: 2009. The mobility of the cone flow diameter and the delamination of the concrete mixture were measured in accordance with GOST 10181. Results: it was researched the influence of quartz flour of various granulometric composition (with an average particle size of 17 μm and 34 μm), applied in dosages of 50, 100 and 150 kg/m3, on the technological properties of self-compacting concrete mixtures with different superplasticizer content (2, 4, 6 and 8 l/m3) and a constant flow of gauged water, as a result of which it has been established that the use of quartz flour of finer grinding provides higher values of SCC mobility under the condition of equal content of superplasticer and gauged water; when using a more coarse quartz flour, the growth of the dosage of the superplasticizer causes a more pronounced increase in the mobility of the concrete mixture; increasing the dosage of quartz flour allows to reduce the delamination of SCC. Conclusions: experimental studies have shown the effectiveness of the use of quartz flour for obtaining SCCs of various classes of workability (SF1 ... SF3) and resistance to delamination (SR1, SR2) and have established that the use of quartz flour D50 = 34 μm leads to insufficient optimization of the granulometric of the composition of the SCC and, as a consequence, stratification of the mixture with its low mobility, whereas the thinner fraction D50 = 17 μm, of the same type of microfiller, makes it possible to obtain resistant to the delamination of any SCC in for the workability due to varying dosages of both the microfiller and superplasticizer.

Subject: calculation of heat and moisture regimes of enclosing structures made of aerated concrete taking into account the transfer of liquid moisture, which is determined by the values of moisture transfer coefficients. The results of calculations of the thermal and moisture characteristics of walls made of aerated concrete, carried out with the use of generally accepted regulatory methods, require confirmation since a physically unacceptable result can be obtained. Research objectives: the goal of the study was to determine the effect of temperature dependence of the sorption isotherm and the moisture conductivity coefficient on the moisture transfer in the enclosing structures of aerated concrete. Materials and methods: numerical modeling of nonstationary heat and moisture transport processes in a flat homogeneous wall made of aerated concrete D400 for climatic conditions of Tomsk city was performed. The proposed model reflects the movement of moisture due to the gradient of partial pressure of water vapor for the entire range of values of relative humidity in air or moisture content in the material, and for large values of relative humidity - due to a gradient of moisture content. In the calculations, we took into account the dependence of sorption moisture not only on the relative humidity of air but also on its temperature. To determine the coefficient of moisture conductivity, we used an approximation formula constructed on the basis of known experimental data. Interpolation formulas are presented that reflect the change in temperature and humidity of the outside air in accordance with the data of the normative literature. Results: when carrying out special test calculations, it was established that moisture transfer through the inner surface of the wall is practically insensitive to the temperature dependence of the sorption isotherm and coefficient of moisture conductivity. The moisture flow through the outer surface is also not sensitive to the temperature dependencies of these parameters. However, the dependence calculated with allowance for the temperature in the sorption isotherm differs significantly from the dependence without taking temperature into account, and in addition, the position of a maximum of the average overall humidity is displaced from November to December. From the above analysis it follows that taking into account the temperature dependence of the coefficient of moisture conductivity does not lead to a significant change in the characteristics of moisture transfer, both at the stage of removal of construction-generated moisture and in the process of further operation. The temperature dependence of the sorption isotherm only affects the moisture content of the outer surface, but the discrepancy does not exceed 1 % in absolute value. Conclusions: the use of the sorption isotherm and the coefficient of moisture conductivity without taking into account their dependence on temperature is permissible for calculating the heat and moisture regime in homogeneous structures made of aerated concrete under conditions of sorption moistening or drying.

Subject: the research was carried out in the field of production of reinforced cellular concrete of autoclave hardening (aerated concrete). As initial data, we present joint experimental studies on selection of reinforcing material performed by the enterprises producing aerated concrete (town of Electrostal) and composite reinforcement (city of Pskov). Research objectives: the research task is reduced to selection of the material alternative to metal reinforcement, which will reduce the technological cycle of manufacturing of reinforced cellular concrete products, facilitate the structure’s weight reduction and increase the life cycle of the product. Materials and methods: we consider the use of composite reinforcement made with application of various hardeners (e.g., anhydride and aliphatic amine) that influence the behavior of the composite in a medium of autoclaved cellular concrete (ACC) (alkaline reaction medium, conditions of increased heat resistance). Results: the results of the performed studies showed the existence of the possibility of reinforcing element replacement in the production of autoclaved cellular aerated concrete. Conclusions: on the basis of the tests carried out, it was decided to continue laboratory studies for heat resistance of composite reinforcement with the use of amine hardener in a medium of autoclaved aerated concrete (AAC). It is also noted that this work was carried out for the first time, being valuable in improving the existing production technology of reinforced aerated concrete.

Subject: the article considers one of the possible solutions to the problem of choosing the optimal waterproofing system for underground parts of buildings and structures using logical-probabilistic method. Selection of reliable hydro insulation of underground structures is a complex multi-task, and for successful functioning of the insulation it is necessary to focus on the systematic approach upon its creation. When choosing a waterproofing system, it is necessary to solve a multi-task and account for the specifics and status of a specific object, hydrogeological conditions, the depth of the structures, acting loads, the quality of construction works, etc. Apriori neglect of these factors and the lack of a systematic approach in the selection of hydro insulation system lead to accelerated wear and failure of structures. During operation as the main stage of life cycle of the building, the waterproofing of underground load-bearing frames of constructions is exposed to several rather difficult conditions. Hence, to avoid frequent overhaul, they should be chosen with the increased operational properties. The irregular choice of the protective coating leads to the accelerated wear and failure of the design. Objective assessment of the right choice of protective materials for an underground waterproofing and also selection of the most reliable and long-lived materials, especially for the bases, is a relevant task. The scientific novelty of this work consists in theoretical justification and the proof of a possibility of objective assessment of the choice of long-lived protection of designs of an underground part of buildings with the use of a logical-probabilistic method. Criteria of operational assessment of optimum long-lived materials are established and also the model of a tree of failures for different types of original materials of organic and mineral structure is proposed: bituminous, bituminous and polymeric, elastomeric, thermoplastic, clay, cement. Research objectives: choose an effective and durable hydro insulation system for underground structures of buildings under certain conditions of their operation using mathematical models and tools. Materials and methods: the “wall-foundation plate” system is considered which includes waterproofing membrane, waterproofing key, a repair mix, fillet, foundation mat, cast in-situ reinforced concrete, drainage geocomposite. We have applied logical-probabilistic method, the idea of which is the description of possible ways of functioning of the system by means of mathematical logic and the determination of its operability with the help of probability theory. Results: logical-probabilistic method allows us to analyze alternative options for creating waterproofing system by means of description of the possible ways of functioning of the variants being analyzed with the help of mathematical logic and determine the probability of their operability, based on which the optimal system that meets the requirements can be selected. A lot of factors were considered including the specificity and a status of a specific facility, hydrogeological conditions, depth of structures, acting loads, the quality of construction and installation works, etc. Conclusions: for achievement of the goal of the research, a set of factors including specificity and a condition of a specific facility, hydrogeological conditions, depth of structures, acting loads, quality of installation and construction works, etc. was considered. Taking into account the specified factors and systematic approach when choosing the waterproofing system proved its effectiveness by use of a logical-probabilistic method as the most accurate and reliable mathematical method.

Subject: the “load”-“deformation” dependence and phases of the stress-strain state of claystones and sandstones. Research objectives: perform stamp and pressuremeter tests, analyze results of field tests and create recommendations for the design and calculation of foundations on claystones and sandstones. Materials and methods: in this article the field methods of testing of claystones and sandstones are considered. Stamp and pressuremeter tests were performed, the “load - settlement” dependence was obtained and phases of the stress-state for claystone and sandstone were identified. The design strength of the soil for the drill pile buried in claystones and sandstones by more than 0.5 m was determined. Results of field tests are processed by mathematical statistics methods in accordance with GOST 20522-2012. The obtained results are analyzed and compared with the previous results of tests on foundations. Results: the scientific novelty of this work consists in revealing the regularities in the formation of the stress-strain state in claystones and sandstones under the action of the load in various directions. The deformation mode and development of phases of the stress-strain state in claystones and sandstones differ significantly from modern clays and sands. In 58 % of the stamp tests, the loss of the bearing capacity of the base, composed of claystones and sandstones, was observed only after reaching the load of 3.0 MPa. In 19 % of the stamp tests, the deformations sharply increased already at the load level of 0.6…2.2 MPa, which is characteristic of less stable varieties of claystones and sandstones. In 23 % of the experiments, the vertical deformations of sandstones and claystones had a linear character for the entire “load”-“settlement” graph and the phase of soil bearing capacity loss was not achieved. A similar picture was observed when performing pressuremeter tests: the phase of bearing capacity loss was not achieved for claystones at a maximum horizontal pressure of 0.85 MPa and for sandstones - at a maximum horizontal pressure of 1.0 MPa, and the deformations of the soil were predominantly linear, which is typical for compaction phase and phase of local shears. Conclusions: claystones and sandstones have high values of design strength and can be a reliable low-compressible base for buildings and constructions with loads from 0.2 to 0.3 MPa. Calculations can be made using the theory of a linearly deformed soil when designing the foundations of buildings and constructions on claystones and sandstones. However, it should be taken into account that this observation is valid for one-time loading, since claystones and sandstones have residual deformations associated with the destruction of cementation bonds between soil particles. It is rational to use in calculations of foundations on claystones and sandstones the values of the strength parameters of the soil obtained in laboratory or field tests with soaking, taking into account the possible deterioration of the properties of these soils.

Subject: operation of concrete and reinforced concrete hydraulic structures on river systems and in the extended coastal zone of Vietnam takes place under the influence of aggressive environments, which significantly limits their service life. Therefore, the search for ways to solve the problem of increasing the durability and terms of maintenance-free operation of such facilities is very important. Previous studies have established the possibility of increasing the operational performance of hydraulic concrete (HC) by modifying their structure with complex additives that combine the water-reducing and densification effects. The possibility of increasing the quality of hydraulic concretes by using rice husk ash (RHA) as a finely dispersed mineral additive with high pozzolanic activity was also established. Research objectives: modification of the structure of hydraulic concrete; determination of the effect of an organo-mineral modifier consisting of RHA in combination with a superplasticizer on water resistance, chloride-ion permeability and strength of hydraulic concrete. Materials and methods: portland cement of type CEM II 42.5 N was used with the addition of rice husk ashes and a superplasticizer ACE 388 “Sure Tec” BASF. Quartz sand and limestone crushed stone were used as aggregates. Composition of the concrete mixture, compressive strength of concretes, water resistance and permeability of the concrete structure for chloride ions was calculated based on methods of Russian and international standards. Results: the use of an organo-mineral modifier consisting of a water-reducing superplasticizer ACE 388 and finely dispersed rice husk ash leads to a densification of the HC structure, which increases their water resistance and decreases the permeability for chloride ions. Conclusions: it was found that the introduction of the developed organo-mineral additive into the concrete mixture leads to densification of the concrete structure, contributes not only to the growth of compression strength at the age of 28 days by 32 % for HC-10, 23 % for HC-20 and 9 % for HC-30, but also to the increase of its water resistance by one or two marks. In addition, there is a significant decrease in the permeability for chloride ions of HC samples containing 10, 20 and 30 % RHA by mass of the binder, since the average value of electric charge that have passed through the samples made of HC-10, HC-20 and HC-30 were 305, 367.5 and 382.7 K respectively against 2562 K for control samples made of non-modified concrete without RHA. (The experimental results of measuring permeability for chloride ions were obtained according to standard ASTM C1202-12). Our study has confirmed the assumption that the introduction into the concrete mix of organo-mineral modifier consisting of a polycarboxylate superplasticiser and fine ash of rice husk, up to 90 % consisting of amorphous silica, will increase the density of hydraulic concrete structure, which will increase their strength, water resistance and reduce permeability for chloride ions.