APPLICATION OF THE APPROACH TO CREATE AN INFORMATION CONSTRUCTION MODEL AT THE PRE-DESIGN STAGE OF INVESTMENT AND CONSTRUCTION PROJECTS

At the present stage of development of the construction industry, steps to improve the efficiency of investment and construction projects can no longer be considered outside the context of construction information modeling technologies. Today, one of the main criteria for optimizing work on investment and construction projects is to reduce the time spent searching, working out and agreeing on spatial, financial, and temporal information about the construction object, therefore, the issue of the correct organization of information modeling of a construction site is quite relevant. In most cases, the design assignment is drawn up in the form given in Appendix B DBN A 2.2-2-2014 and is formal in nature. The presence of a design assignment, drawn up using the tools proposed below, reflects the thoroughness of the customer's elaboration of an investment and construction project, and reduces the risks of its implementation. The proposed methodology is based on three components of counter design, such as disaggregation, aggregation, and decomposition, from which its name – DAD –approach comes from. Allocation of structural elements in the structure of a building by disaggregation (analysis of alternative options) allows to create its model in the form of a hierarchical structure consisting of detailed and mutually synchronized parts - the configuration of the building. In accordance with the configuration of the construction site, hierarchical numbering is further reflected at all stages of design and in all its sections, incl. stamps of drawings and local estimates. This creates a unified system of interconnection and control of project sections. The creation of a construction site configuration in the form of a tree model with hierarchically numbered elements at the pre-design stage allows it to be applied at subsequent stages of the life cycle of a construction object in information modeling technologies. The use of the DAD – approach in counter-design is intended to increase the efficiency of the implementation of investment and construction projects.

NUMERICAL MODELING OF THE DISTRIBUTION OF SNOW LOAD ON A HYPERBOLIC PARABOLOID. THEORETICAL BASIS

The paper discusses the choice of a method for studying the distribution of snow loads on a biconcave roof of a hyperbolic paraboloid and its theoretical justification. It is noted that the numerical modeling of the aerodynamic characteristics of buildings and structures is a difficult and resource-intensive task due to the design features of building objects, which, as a rule, have a complex geometric shape, as well as due to a complex unsteady flow resulting from their flow around them. In addition, the task becomes more complicated due to the interference of vortex structures between different objects. Overcoming these objective difficulties became possible with the advent of modern specialized software systems, primarily ANSYS Fluent. Opportunities have appeared for accurate modeling with verification of the results obtained, which implies the use of an effective, well-tested mathematical apparatus. To implement the theory of two-phase flow, two methods based on numerical modeling are mainly used: the Euler-Lagrange method and the Euler-Euler method. The second method is used in the work. Comparative analysis, which investigates two-phase flow around different structures using different turbulence models (including RSM model, SST k-ω model, k-ε model and k-kl-ω model), shows that the k-kl-ω model is the best fit with experiment. ANSYS Fluent supports four multiphase models, i.e. VOF model, Mixture model, Wet Steam and Euler model. Compared to the other three models, the Mixture model provides better stability and lower computational costs, while the Euler model provides better accuracy, but at a higher computational cost . With a rather complex geometry and flow conditions, the use of the RANS approach does not lead to reliable simulation results. Moreover, unsteady turbulent flows cannot be reproduced. In real situations, landslides, saltations, and the suspended state of snow particles are closely related to the real effects of microbursts and bursts present at the surface of the boundary layer. Therefore, in further research, it is advisable to apply alternative approaches to RANS, which include Direct Numerical Simulation (DNS), Large Eddy Simulation (LES), and the hybrid RANS-LES approach to turbulence modeling, which combine efficiency LES techniques in tear-off free zones and the cost-effectiveness of RANS in near-wall areas.

CARRYING CAPACITY OF DAMAGED REINFORCED CONCRETE TWO-TUBE COLUMNS

The article presents the results of experimental and theoretical studies of the work, the parameters of the stress-strain state and the methodology for calculating the residual bearing capacity of reinforced concrete I-section columns damaged during operation and combat operations. The analysis of the literature on this subject made it possible to study the main factors affecting the residual bearing capacity, namely: the depth of damage; the angle of inclination of the damage front; relative eccentricity of application of external compressive force. A three-factor three-level experimental design has been developed. The conducted field tests of prototypes of damaged reinforced concrete columns made it possible to determine the parameters of the stress-strain state of damaged elements and their actual residual bearing capacity. On the basis of the performed experimental-statistical modeling, the main factors influencing the residual bearing capacity of damaged elements have been established. The prerequisites for calculating damaged reinforced concrete I-beams are proposed and equilibrium equations are drawn up. The proposals set out in the article are based on the main provisions of the current norms and expand the effect of their use. The analysis of influence of various factors on bearing capacity of the damaged I-beam reinforced concrete columns is carried out. It was found that the columns can withstand a maximum destructive load of 1738 kN at an angle of inclination of the damage front of 60о and in the absence of relative eccentricity. And the least destructive load columns can withstand in the absence of the angle of the damage front, and the relative eccentricity will be 1/8 of the applied load. On the basis of the conducted researches the technique of definition of reliably substantiated residual bearing capacity of reinforced concrete compressed elements of a T-profile profile damaged in the course of operation is developed. This makes it possible to determine the possibility of further trouble-free operation of structures or the need for their reinforcement or reconstruction.

BOILER PLANTS AND THE ENVIRONMENT PROTECTION FROM INDUSTRY HARMFUL EFFECTS

At present, environmental problems have become aggravated. The production process has a negative impact on the natural environment. It accumulates these harmful secondary effects. The degree of their harmful effects is increasing rapidly. The natural environment, taking into account its self-healing, undergoes dangerous, irreversible changes in its state. Now it is possible to talk only about slowing down this process. The ability to slow down and then stop the increase in the harmful impact on the natural environment is the essence of the nature conservation activities of humanity. It is necessary to move from a strategy of using the natural environment to a strategy of parity interaction with it. The problem was discussed at the Kyoto and Paris conferences of global importance. Among the branches of production, the most dangerous for the natural environment is energy. Its harmful effect is complex. Defending against it is a complex environmental issue. The adopted energy saving program actively contributes to solving the problem of saving the natural environment from degradation and death. The most environmentally aggressive element of power plants is solid fuel boiler plants. Reducing the intensity of their impact is the main direction of activities to protect the natural environment. The most difficult technical object is considered the power unit of a large thermal power plant. The most difficult part is the boiler plant. The most difficult element is the steam boiler. The level of environmental friendliness of the boiler is highly dependent on the degree of its wear. The problem of updating the fleet of boilers is of current importance. The general line of improving the environmental friendliness of production should be considered an increase in the level of environmental friendliness of power plants, especially those using fossil fuels, and a decrease in their emissions of carbon dioxide and heat. It is necessary to improve boiler installations, to increase their efficiency level, and the quality of their management. It is important to ensure the modernization of worn-out boiler installations based on their complete or partial renewal. In the formation of the power engineering of the future, the socio-psychological position of humanity must be radically changed.

LOAD-BEARING CAPACITY ANALYSIS FOR STRUCTURAL COLD-FORMED MEMBERS SUBJECTED TO CENTRAL COMPRESSION

The main purpose of the research was a deep analysis and verification of the consistency and completeness of the design code relating to calculation of load-bearing structural members made from cold-formed profiles. The work has been done in close connection with the implementation on the territory of Ukraine of this design code. The article has discussed and investigated the load-bearing capacity of structural members made of cold-formed profiles subjected to the action of central compression. A system of constraints has been presented, in which the strength and buckling constraints for thin-walled cold-formed column members are formulated, taking into account their possible post-buckling behavior, namely, the ability to resist external loads and effects even after the occurrence of the local buckling and/or distortional buckling phenomenon. The performed load-bearing capacity investigation has shown that for the mono-symmetric cold-formed profiles, the flexural-torsional buckling is determinative. For such cold-formed profiles, the effect of the overall dimensions ratio (flange width to web height) on the load-bearing capacity of cold-formed profiles has been estimated. It has been shown that for the same cross-sectional area the load-bearing capacity of a column structural member made from cold-formed profile and subjected to axial compression can be significantly increased by assigning an optimal ratio of flange width to web height. The paper also has presented the results of the load-bearing capacities for the structural cold-formed members subjected to central compression, calculated according to the design standard DSTU-N B EN 1993-1-3: 2012 and according to the design code DBN V.2.6-198: 2014. It has been shown that in some cases the difference in the assessment of the load-bearing capacity for such structural cold-formed members reached 25%. A comparison of the load-bearing capacities for the action of the central compression has been made for structural cold-formed members made from a C-shaped profile and with a composite section of two C-shaped profiles. It has been shown that the load-bearing capacity of the structural cold-formed member of the composite section exceeds the load-bearing capacity of the member with single C-shaped profile by more than 3 times, while cross-section areas of these structural members differ only doubly.

KINETICS OF RHEOLOGICAL CHARACTERISTICS OF FOAM CONCRETE MIXTURE

The results of experimental studies are presented, the purpose of which was to study the influence of variable formulation and technological factors on the rheological characteristics of the foam concrete mixture, in particular, the structural strength. This is preceded by an analysis of the process of structure formation of cellular concrete. As a result, it is shown that the properties of cellular concrete are determined by the nature of the distribution of the solid component. The structure of the solid phase is formed at the earliest stages of the formation of cellular products and depends on the rheological characteristics of the mortar and cellular mixture. In the technology of cellular concrete, it is important to synchronize the processes of pore formation and the growth of plastic (structural) strength, which is also associated with a change in the rheological properties of the mixture. Using the methods of mathematical statistics, the influence of the content of the filler in the mixture with cement, the content of the complex additive, and the effect of mechanical chemical activation on the kinetics of the plastic strength of the foam concrete mixture were studied. The kinetic dependences of the plastic strength of the foam concrete mixture in the range of 6 ... 24 hours from the moment of manufacture have been constructed. Each of the 15 curves is maximized by a 3rd-degree polynomial. Based on the obtained dependences, they are differentiated between the first and second derivatives. As a result, the equations of the speed and intensity (acceleration) of the plastic strength of the foam concrete mixture were obtained. According to the results of the previous experiment, carried out according to a three-factor plan, a 4-factor plan was synthesized, in which the aging period of the foam concrete mixture was taken as the fourth factor. The calculated theoretical values of the characteristics of the structural strength of the foam concrete mixture were entered into the matrix. As a result, mathematical models of plastic strength, speed, and intensity of plastic strength of the foam concrete mixture were calculated and the influence of variable factors studied on the isosurfaces of these properties was visualized. The analysis of these dependencies made it possible to determine the characteristic recipe and technological conditions for obtaining a foam concrete mixture with the required values of plastic strength.

STUDY OF SPATIAL PROBLEMS OF DYNAMIC STABILITY OF REINFORCED CONCRETE FRAMES

The article proposes a method for constructing areas of dynamic instability of reinforced concrete frames in the space of parameters (frequency and amplitude) of seismic and operational dynamic impacts that cause the appearance of longitudinal forces in the bars of structures, which periodically change in time and lead to an unlimited increase in amplitudes of transverse vibrations when the values of these parameters are in the areas of instability. The proposed method is demonstrated by a specific example, which considers the spatial problem of dynamic stability of a П-shaped frame with two concentrated masses located on it, which are under the action of vertical periodic forces. These forces create periodic longitudinal forces in the vertical rods of the frame. Areas of dynamic instability of the frame are constructed. From the point of view of human activity, fluctuations can be both beneficial and harmful. We can observe vibrations of various buildings, structures, bridges, which cause additional stresses and deformations of these structures, have a harmful effect on their safe functioning. Too intense fluctuations lead to serious consequences. This leads to the destruction of individual elements of the structure and, as a result, to accidents. The most destructive effect of vibrations is observed during earthquakes and explosions. The study of vibrations is of great practical importance. This avoids the unwanted effects of fluctuations by limiting their level. Only on the basis of a deep study of various types of vibrations can important practical problems of the dynamics of structures be solved. Solving dynamics problems is a complex problem. In contrast to static calculation, when studying oscillations, one has to take into account an additional factor – time. The dynamic design of structures provides them with bearing capacity under the combined action of static and dynamic loads. A construction will be considered as a system with an infinite number of elementary masses distributed over it with an infinitely large number of dynamic degrees of freedom.

EVALUATION OF FIRE-PROTECTIVE ABILITY OF NEWLY CREATED FIRE-PROTECTIVE COATINGS OF STEEL STRUCTURES

The results of the development of fire-retardant substances based on domestic materials to increase the fire resistance of fire-retardant steel structures are presented. New compositions of fire-retardant substances on the basis of domestic materials capable of swelling are developed. A series of experimental studies to determine the heating temperature of fire-resistant steel structures. For this purpose, samples of reduced size in the form of a steel plate with a flame retardant applied to the heating surface were used. Fire tests of fire-retardant steel plates coated with the developed fire-retardant substance forming a coating on the protected surface, in the conditions of their tests on the standard temperature of the fire using the installation to determine the fire-retardant ability of fire-retardant coatings. The results of experimental determination of temperature from an unheated surface of steel plates with a fire-retardant covering in the conditions of fire influence at a standard temperature mode of a fire are analyzed. Based on the obtained data (temperature in the furnace and from the unheated surface of steel plates with fire protection system) the solution of the inverse problems of thermal conductivity found thermophysical characteristics of fire protection coating (thermal conductivity and specific volume), which can be used for thermal calculation heating of fire-retardant steel structures at arbitrary fire temperatures. The thermophysical characteristics of the formed fire-retardant coating are substantiated to find the characteristics of the fire-retardant ability of the newly created fire-retardant coating and to ensure the fire resistance of fire-retardant steel structures. The efficiency of the developed fire-retardant coating for protection of steel structures is proved.

USE OF EXPERIENCE IN CONSTRUCTION OF MONOLITHIC CEMENT-CONCRETE PAVEMENT OF THE AIRPORT «ODESSA» IN THE DEVELOPMENT OF A NEW NATIONAL STANDARD FOR THE AIRFIELD DESIGN

Inspection of the monolithic cement-concrete pavement of the «Odessa» airport runway was carried out. Visual inspection of the runway surface, taxiways and apron for defects has been performed. The condition of the runway pavement was assessed as "excellent", destruction category I. In addition, strength tests of the rigid concrete pavement upper layer were carried out using non-destructive testing methods and core testing. The obtained strength characteristics correspond to the design requirements; the concrete has a grade of at least C32/40. Based on the processed data and own scientific developments, proposals were drawn up for a new standard (instead of SNyP 2.05.08-85 "Aérodromy") regarding the requirements for materials, concrete mixtures and concretes based on them for the runways construction in Ukraine. Modern requirements for monolithic cement-concrete airfield pavements require an extension of their service life up to 40 years. To ensure such indicators of serviceability, in addition to high strength indicators, it is imperative to ensure the rigid pavements durability using high-performance modified concretes. The proposals indicate the cement type, aggregates and chemical admixtures that can be used in the manufacture of concrete for airfield pavements. The requirements for the concrete and concrete mixture properties, the process of concrete curing are also presented. Taking into account the modern superplasticizers and the requirements for the workability of concrete mixtures for the construction of monolithic cement-concrete airfield pavements, the maximum W/C should be in the range of 0.3-0.35. To increase the flexural strength and crack resistance, it is desirable to use dispersed concrete reinforcement. To ensure the service life and satisfactory operational condition of the runway pavements, it is necessary to conduct an annual inspection for the timely identification and correction of arising defects.

THE INFLUENCE OF HYDROPHOBIC COATING ON THE EFFICIENCY OF FIRE PROTECTION OF TEXTILE MATERIALS

The analysis of fire-retardant materials for fabrics is carried out and it is established that the paucity of data for explanation and description of the process of fire protection, neglect of elastic coatings, leads to ignition of fabric structures under the action of flame. The development of reliable methods for studying the conditions of fire protection of fabrics leads to the creation of new types of fire protective materials. Therefore, it becomes necessary to determine the conditions for the formation of a barrier both for high temperatures and for leaching in the presence of precipitation and to establish a mechanism for inhibition of these processes. In this regard, full-scale tests were carried out and it was found out that when the flame is applied to untreated model samples of tent elements made of canvas fabric, the surface ignites and spreads the flame, which leads to their complete combustion within 105...120 s, instead, the model The fire-resistant sample of tent elements did not catch fire when ignited with a gasoline-based substance, and the flame did not spread. In this case, the final combustion was recorded for 3 c and the swelling of the protective coating reached 3...5 mm, and the surface was charred on an area of about 80% from the inside. When tested for fire retardant efficiency for a fire-resistant sample treated with a water repellent (5 % solution of GDJ-94), a decrease in efficiency and carbonization of the material was recorded, which amounted to 100%, and for a fire-resistant sample treated with a water repellent (5 % solution), a decrease in efficiency was recorded due to the combustion of paraffin and local burnout of the material, and carbonization was 100 %. Obviously, such a mechanism of influence of the fire-retardant coating is the factor regulating the process, which preserves the integrity of the object. Thus, there is reason to argue about the possibility of targeted regulation of the processes of fire protection of the fabric by applying coatings capable of forming a protective layer on the surface of the material, which inhibits the rate of heat penetration.