ABSTRACT Introduction. The subject of the study is the kinematic variability and deformations of a planar statically-determinate elastic truss with a horizontal bolt, lateral supporting trusses and a cross-shaped grid under the action of various types of static loads. The structure has three movable supports and one fixed support. Objectives - derivation of formulas giving the dependence of the deflection of the structure in the middle of the span and the displacement of one of the three movable supports from the dimensions, load and number of panels; analysis of the kinematic variability and derivation of the analytical dependence of the forces in the rods of the middle of the span from the number of panels. Materials and methods. Forces in the rods of the truss are calculated in symbolic form by cutting out nodes using the Maple symbolic and numeric computational environment. In order to calculate the deflection, the Maxwell - Mohr formula was used. Calculation formulas for the deflection and displacement of the support were derived using the induction method based on the results of analytical calculations of a number of trusses with a different number of panels in the crossbar and lateral support trusses. The special operators of the genfunc package for managing the rational generating functions of the Maple system were used to identify and solve the recurrence equations satisfied by the sequences of coefficients of the formulas for deflection and forces. It is assumed that all the rods of the truss have the same rigidity. Results. Several variants of loads on the truss are considered. A combination of panel numbers is found in which the truss becomes kinematically variable. The phenomenon is confirmed by the corresponding scheme of possible velocities. All required dependences have a polynomial form by the number of panels. The curves of the dependence of the deflection on the number of panels and on the height of the truss are constructed in order to illustrate the analytical solutions. Conclusions. The proposed scheme of a statically determinate truss is regular, allowing a fairly simple analytic solution of the deflection problem. The curves of the identified dependencies have significant areas of abrupt changes, which can be used in problems of optimising the design by weight and rigidity.

Introduction. The approach to the creation of the methodological foundations of the innovative system of industrial and household waste management is presented. This will allow to implement the world principles of handling them: prevention of education, resource saving, minimization of burial volumes , energy production, including in industrial, civil, road construction, reconstruction and repair, as well as in the production of building materials. Materials and methods. The most common approach to conducting a scientific research is the analysis of regulatory legal acts, standards, methods, guidelines, project and regulatory documentation in the field of waste management, published data and materials of scientific domestic and foreign studies on this topic. The scientific study used the methods of factor, comparative analysis, expert assessment of indicators. Results. Scientifically based proposals have been formed in the field of sectoral strategic planning for the formation of a waste management system and secondary material resources, implemented during the development of the Industry Development Strategy for the Treatment, Disposal and Disposal of Production and Consumption Wastes for the Period until 2030, approved by the Government of the Russian Federation of January 25, 2018 No. 84-r. Conclusions. In of civil engineering, the proposed scientific and practical proposals for strategic sectoral planning of the waste-processing industry for the period up to 2030, the creation of an economic, organizational, managerial and legal mechanism for solving the problem of waste management and secondary material resources should be used in the formation of the regulatory framework and planning of promising measures for handling with waste secondary material resources in the framework of the development of the construction complex, construction materials.

Introduction. The question of increasing the efficiency of investment and construction projects in the life cycle of facilities on the basis of modern engineering schemes becomes of particular relevance during periods of economic crisis. A formalised description of a solution to this problem is proposed on the basis of an engineering scheme for the construction Life Cycle Contract (LCC) model. The engineering scheme model for the organisation of the construction Life Cycle Contract considers the distribution of limited material, technical and labour resources, depending on the class of importance of work performed and the cost of compensation for the negative impact of random factors. Materials and methods. The methodical approach consisted of analysis and comparison of organisational structures of investment and construction activity, analysis of theory, practice and ways of improving the efficiency of modern engineering schemes for organising construction projects, methods of logical-semantic and simulation modelling and the published work of Russian and foreign scientists on the topic under study. Results. The process of implementing investment and construction projects for Life Cycle Contracts is presented in the form of a model of the engineering scheme of the organisation of construction activity. In this model, important procedures for selecting options for organisational and technological solutions, as well as the assessment and allocation of resources for the work to be performed, are set out. The coefficient of importance for each type of work is determined by a mathematical method based on the method of nested scalar convolutions, based on Bohr’s principle of complementarity and Gödel's incompleteness theorem, as well as by means of expert estimates on the normalised reversed scale. Conclusions. An evaluation of the necessity for introducing complex engineering support to investment and construction projects throughout the life cycle is given with the maximum responsibility of the organiser of a construction project to the client under conditions of the greatest concentration of managerial powers. When the results of interaction between participants in the investment and construction process are predicted in various changing conditions, the practical use of the provisions proposed in the article makes it possible to adopt adequate management decisions that increase the efficiency not only of planning but also implementing construction projects. The results of the study can be applied in the development of recommendations for the formation of a new evaluation and regulatory framework, allowing indicators of the duration and cost of construction projects to be forecast considering the negative impact of random factors.

Introduction. The paper presents theoretical and experimental studies of the improvement of the structure of lightweight concrete, which provides the maximum value of the attenuation of the amplitude of external air temperature fluctuations during the passage of heat flow through the walls and the reduction of thermal conductivity, the results of the 3-factor experiment on determining the rational structure of claydite concrete and the methods for their processing. To determine the purposeful structure of the composition of lightweight concrete and its thermal conductivity, a complex of research works was carried out at the Central Research Institute for Housing, applied to lightweight concrete for exterior walls. The main optimization criterion was the maximum reduction in thermal conductivity while providing the necessary strength, durability and waterproofness. The purpose of this work is theoretical research and experimental substantiation of methods for improving the structure of lightweight concrete used for a hot climate with improved functional performance. Materials and methods. As material a claydite gravel with bulk density p = 400 kg/m3 of Lianozovsky plant (Moscow) was used, at a ratio of 40 % of the fraction 5-10 mm and 60 % of the fraction 10-20 mm and a Portland cement of the brand “400” of the Voskresensky plant, not plasticized. The water flow rate was varied for 10 seconds, to ensure the mixture to be vibropacked.As a foam generating agent and plasticizer, the “Saponified wood resin” (SDO) was used in a 5 % aqueous solution. The methods were adopted in accordance with the Recommendation on the technology of factory production and quality control of lightweight concrete and large-panel constructions of residential buildings. M. CNIIEP dwelling, 1980. In the department of the lightweight concrete application at CNIIEP of dwelling, a method for the purposeful formation of the structure and composition of lightweight concrete, which provides a set of physic-technical, technological and technical-economic requirements, was developed. Results. Calculations are reduced to obtaining mathematical models of dependence of strength R, density ρ, thermai conductivity λ and other indicators of concrete characteristics from initial factors in the form of regression equations. Based on the equations obtained, it was possible to determine the expedient composition of lightweight concrete, which, in combination with the operational characteristics, provides comparable results of the technical and economic characteristics of a single-layer structure from the projected type of lightweight concrete. Conclusions. 1. An improved composition of the structural and heat insulating lightweight concrete for the load-bearing part of the structure, providing its high thermal stability by chemical additives and low consumption of porous sand, was developed. An algorithm for selecting its composition on computer is made. 2. The conducted researches in the field of design of external enclosing structures for hot climate conditions have shown that: single-layer exterior wall constructions with massiveness of D ≤ 4 provide minimum allowable values of heat flux attenuation and temperature fluctuation amplitude on the inner wall surface.

ABSTRACT Introduction. The article reports on new research into improved reverse osmosis techniques and their expanded application in wastewater treatment practice. The results of experiments aimed at determining the operational characteristics of membrane facilities that treat wastewater are presented. A new method utilising reverse osmosis to decrease concentrate effluents is proposed. Flow diagrams and mass balance equations are used to demonstrate the principles underlying the new techniques. Objectives - development of reverse osmosis techniques as a novel tool for improving and modifying existing biological wastewater treatment schemes; economic evaluation of advantages in combining reverse osmosis with biological treatment processes in wastewater treatment applications; development of the required operational modes for membrane units used to treat wastewater. Materials and methods. A state-of-the-art review describes examples of the application of reverse osmosis in current wastewater treatment practices. Results of experimental research providing data for determining membrane operational parameters are presented. Analysis of results and their discussion are presented. Results. A new membrane technique that provides high product water quality and utilisation of concentrate effluents, as well as efficient removal of ammonia from reject water following sludge dewatering, is proposed. The presented results confirm the economic advantages and efficiencies of reverse osmosis applications in wastewater treatment facilities. Conclusions. The conducted investigations confirmed the high efficiency of the reverse osmosis membrane in removing all major impurities contained in wastewater following sludge digestion and during biological treatment. The use of membrane techniques thus provides efficient and reliable operation of wastewater treatment facilities. Reverse osmosis concentrate effluent can be utilised by blending with sludge or used in fertiliser production.

Introduction. One of the most significant environmental problems facing the Vietnamese city of Hanoi is anthropogenic pollution of surface water, especially in the To Lich river system. Currently, these rivers accept large quantities of wastewater from urban areas and industrial zones, which effluents are not treated prior to discharge into water bodies. The results of the study show that surface water in Hanoi has been contaminated by direct discharge of domestic and industrial wastewater. Considered the To Lich river system, including the To Lich, Lu, Set and Kim Nguu rivers, which receive sewage pollution from urban areas, industrial zones and other sources. Materials and methods. The most common approach to improving the situation is to identify sources of syrface water pollution and assess the quality of To Lich river and its tributaries in order to develop and propose effective and synchronous solurion for the management of water safety and quality in the water bodies of Hanoi city. The water samples were preserved and analysed in the laboratory of Environmental Analysis in accordance with standard Vietnamese methods. For this purpose, analytic apparatus, including Shimadzu AAS 6800 atomic absorption spectrophotometre (Japan), UV-VIS spectrometre, as well as a number of common laboratory instruments and equipment, are used. Results. The results of the study show that surface water in Hanoi has been contaminated by direct discharge of domestic and industrial wastewater. For many years, the rivers have been covered with rubbish, with the water turning black in colour and having an unpleasant smell. The primary cause of the pollution is drainage from many surrounding households discharging waste water directly into the rivers. Conclusions. In order to restore the aqueous ecosystems of Hanoi city, it is necessary to conduct continuous environmental monitoring of changes in the state of water bodies and develop effective and timely solutions for the management of safety and quality of water in the waterways of Hanoi.

Introduction. Presented the approach to studying impact of foaming agent process solution shelf life on the surface activity and fire-extinguishing efficiency of foams. One of the most important problems in construction is to ensure fire safety of construction objects. Fires arising at industrial facilities and construction sites are always catastrophic, both for the economy and for the environment. Storage facilities and tanks in which various types of materials and substances, often toxic and fire-hazardous, can be stored are of particular danger. Addresses the problem of oil product warehouse premises and tank farms fire safety using foam extinguishing system. The problem consists in reduction of foaming agent concentration in the process solution during long-term storage. Concentration reduction is expressed in a surface activity decrease and in violation of spreading coefficient structure, namely, by an increase in surface and interfacial tension. Consequently, the use of foaming agent process solution for extinguishing fire at oil product warehouse premises and tank farms that is not capable of providing required foam expansion ratio and spreading coefficient for successful subsurface suppression of oil products flame. Materials and methods. Four brands of fluorinated foaming agents are tested according to the methods described in GOST R 50588-2012 “Foaming agents for fire extinguishing. General technical requirements and testing methods” and GOST R 53280.2-2010 “Automatic fire extinguishing units. Fire extinguishing agents. Part 2. Foaming agents for subsurface suppression of oil and oil products fires in tanks. General technical requirements and testing methods”. Results. The studies have shown that foam quality determining fire extinguishing capacity of foam extinguishing system changes over foaming agent process solution shelf life and depends on spreading coefficient structure, which is characterized by surface and interfacial tension values for foaming agent process solution. Conclusions. The process solutions made from modern (biologically soft) fluorinated foaming agents decrease in their surface activity over time and become unsuitable for oil products subsurface suppression. To maintain efficiency of the foam extinguishing system used to ensure fire safety of oil product warehouse premises and tank farms, age of the process solution in the circulating pipeline system should not exceed one day.

Introduction. Presented the approach to the create a filtration model of the base of the hydroelectric system, built by mathematical and statistical generalization of the results of mass filtration testing of the rock mass. In the proposed filtration model, the rock base is divided into several engineering-geological design elements with different permeability. Materials and methods. The most common approach to build the model is determine the points of the array hydraulic pumping and injection of water into the well, as well as by calculation, when the filtration coefficient of the array is calculated on the parameters of cracks. Results. One of the advantages of the proposed form of the filtration model of the rocky foundation of the hydroelectric complex is the form and method of its construction by means of mathematical and statistical generalization of the results of mass filtration testing of the rock massif. Conclusions. In of civil engineering the filtration model of the base of the hydraulic unit can be built on the results of the poson filtration testing of drilling wells at certain points of the rock mass. The difficult task of dividing the base massif into zones with different water permeability is solved on the basis of a geological-genetic approach in combination with mathematical and statistical analysis. The practical significance of this filtration model is that it can be used to design reliable hydraulic structures while ensuring stability and minimizing filtration losses.

Introduction. An approach to the development of a method for assessing the fatigue strength of an offshore high-strength steel pipeline has been presented. The effect of fatigue caused by cyclic loads has been well studied, the combined destructive effect of fatigue and corrosion has not been studied enough, although it has unexpected consequences and significantly reduces the life of the structure. The synergistic effect of both fatigue and corrosion acting simultaneously makes it difficult to determine the exact interaction between the two, but it is safe to assume that the corrosion fatigue is more than just a simple superposition of the two negative effects. While we can improve the fatigue strength of a material through heat treatment and alloying, if the material is in a corrosive environment the advantage gained can easily be completely neutralized, as the corrosive mechanism in play usually dictates the endurance limit in such a case. In fact, the difference in fatigue strength is most noticeable at lower stress values. Materials and methods. The most common approaches are based on mathematical models for assessing the durability of structures under low-cycle loading. The work was carried out with reference to existing and future offshore projects. Results. One of the advantages of the proposals developed are the requirements for testing the fatigue strength of offshore subsea pipelines of high-strength steel with a longitudinally oriented defect. The Load of the offshore pipeline is 0.766 % of the operating load, excluding accidental loads. These requirements are submitted for consideration to the Russian Maritime register of Shipping. Conclusions. In of civil engineering, ensuring the reliability of offshore subsea pipelines of high-strength steel with a longitudinally oriented defect under low-cycle loading is an urgent problem and is of theoretical and practical interest. The results were obtained by combining the calculated and - the empirical approach according to the method for assessing low-cycle fatigue of the offshore pipeline structure. Calculations show the need to monitor the state of the structures of the offshore underwater pipeline.

Introduction. An approach to the study of the hydraulic flow regime behind the end section is presented in order to determine the possibility of ensuring uniform distribution of speeds across the width of the outflow channel and safe coupling of the outgoing flow to the lower pool. The four variants of designs of the ending portion of the pressure tubular spillways with a vertical flow outlet are considered, following constructions: a disk reflector, a flat horizontal sector reflector, a flat slanted sector reflector and a curved sector reflector. Materials and methods. The most common approach to the comparison of structures were made according to the following parameters: the length of the stream’s flight, the width of the jet, the form of flow spreading, the uniformity of the distribution of specific water flow, clash of the jet on the slopes of the channel. The diameter of the conduit on the model is d = 3.4 cm, the cost of Q = 0.67...2.44 l/s, pressure head H = 35...60 cm. For comparison of the chosen design with similar geometric parameters: the relative radiuses of the sectors of the reflector R/d = 3.0 and relative diameter of the disk-reflector D/d = 3.0. Results. The lengths of the jet departure are determined for disk and flat sector in the relative height range of t/d from 0.5 to 1.0, for slanted and curved sectors-from 0 to 1.0. The planned outlines of the jet are determined, the uniformity of the distribution of specific water discharge is estimated, the analysis of the hydraulic regime of the presented end portions is carried out. Conclusions. In of civil engineering the revealed advantages and disadvantages of the considered end portions allow to recommend it for use taking into account the peculiarities of the hydraulic regimes arising at the same time. The greatest length of the jet departure has a curved sector-reflector, and the smallest - a flat horizontal sector-reflector. Lowest unit costs are achieved with a disc reflector, the largest in the flat horizontal sector-reflector.