Introduction.

Presently, the evaluation of underground railways in regional cities of Russia enjoys little attention in the research literature. We have assessed the relationship between passenger flows of underground railways in regional Russian cities and the number of residents within walking distance of the stations. This will allow understanding the potential development of underground railways and the future uses of existing networks towards a sustainable urban environment convenient for each resident.

Materials and methods.

The evaluation of the relationship was conducted retrospectively using the regression analysis method. The annual passenger flow of underground railways was chosen as a dependent variable, as it is less affected by random factors, compared to average daily variables. The living space of buildings within walking distance of underground railway stations was taken as an independent variable. Major social factors that may influence passenger flows were also taken into account.

Results.

For the period from the opening of the underground railway to the present day, the relationship between living spaces within walking distance of underground railway stations and passenger flows was identified for Ekaterinburg and Kazan. From 2005 to 2019, the relationship has been tracked for Novosibirsk with account taken of the effect of the benefit monetization reform and restrictive measures related to the COVID-19 pandemic. This dependence has not been identified for Samara and Nizhny Novgorod. The radii of walking distances from the stations, having the greatest impact on the passenger traffic, were identified for several cities.

Conclusions.

The residential function is not a universal factor determining passenger flows of underground railways in regional Russian cities. Social factors, affecting large segments of the population, such as monetization reforms, have a substantial effect. Further research is planned to evaluate other factors that influence passenger flows of underground railways in Samara and Nizhny Novgorod.

Introduction.

When a rockfill dam with a concrete face is constructed on the earth foundation, its seepage control facility is complemented by a cutoff wall and an apron. Together they represent a complicated integrated seepage control facility. The performance of an integrated seepage control facility gains relevance, which is proven by the experience in the operation of a number of dams, whose concrete faces and cutoff walls may be in the adverse stress state. Towards this end, the authors studied the stress-strain state (SSS) of an integrated seepage control facility.

Materials and methods.

The study was conducted at the Miaojiaba rockfill dam that has an integrated seepage control facility. This dam is 111 m high and 348 m long; its riverbed is about 45 m thick. Numerical modeling using the finite element method was performed to study the spatial SSS of this dam. Measurements of the dam displacements were taken to calibrate the finite element model.

Results.

The SSS of the dam was analyzed to develop two alternative structural designs of an integrated seepage control facility. As for the first design option, each element (the face, the cutoff wall, the apron) is made of concrete. The analysis of this option has shown that compressive and tensile stresses, arising in the cutoff wall, exceed the strength of concrete. Besides, the cutoff wall gets separated from the foundation. Within the framework of the second option, the cutoff wall is made of clay-cement concrete. According to the results of the analysis, this design option ensures the sufficient strength of all components of a seepage control facility.

Conclusions.

To ensure the strength of a seepage control facility that has a concrete face, a cutoff wall and a connecting apron, the cutoff wall and the apron should be made of less rigid materials.

Introduction.

The author addresses the choice of corporate general contractors participating in bidding for the construction of capital construction projects (CCP). The criteria evaluation pattern, employed by the customer pursuant to the effective legislation of the Russian Federation, is presented. The author has studied the criteria evaluation mechanism, applied to corporate general contractors in the course of implementation by the customer of the procurement procedure for the construction of facilities.

Materials and methods.

Legislative and subordinate acts, results of scientific research have been analyzed. The author has analyzed the process of tendering for public procurement contracts on the performance of work on the construction of capital construction facilities. Criteria evaluation problems, arising in the process of selecting general contractors, were identified. The benchmarking method was proposed to assess corporate general contractors.

Results.

Factors, influencing the quality of construction work, were presented. The author suggests consolidating them into a system of evaluation criteria and integrated into the “quality of construction work” criterion in the effective legislation. In addition, it is necessary to evaluate any procurement procedure for construction work using such parameters as “the qualification of the bidder”, “financial resources, equipment and other material resources of the organization”.

Conclusions.

Thanks to the proposed system of evaluation criteria, the mechanism of selecting general contractors will be more distinct, comprehensible and transparent. The system of criteria selection and evaluation, applicable to construction companies, should be simple and comprehensible not only by the customer, but also by the contractor. It is advisable to avoid using numerous mathematical formulas to calculate the rating of general contractors. Further relevant areas of research have been formulated, including the evaluation of qualitative components of assessment criteria applied to construction organizations and the issuance of their quantitative characteristic (weight significance) using the method of the full factorial experiment.

Introduction.

The authors present the results of pile continuity studies conducted using seismoacoustic defectoscopy. Tests were conducted in the Rostov region and Moscow. Reflectograms of tested piles, as well as the subsequent interpretation and confirmation of the design length and continuity of the pile shaft are provided.

Materials and methods.

The research results were obtained using Spektr 4.3, whose operating principle is based on the theory of elastic wave propagation. This device is used for the recording of the pile response to external impacts with the preset pulse parameters. The signal is recorded by means of an accelerometer sensor, connected to a special computer with the software for the digitization and interpretation of incoming information. Data processing results are presented in the form of computer graphic images (reflectograms), which show the pile length, continuity, damages (if any) and their location.

Results.

The dependence between soil homogeneity and signal purity has been identified. At the interface between two types of soils that are different in density, the sound wave was reflected and partially passed further, creating characteristic peaks of false defects. To eliminate false defects, studies of layered soils are necessary.

Conclusions.

The results confirm the effect of the soil homogeneity on signal purity. The higher the heterogeneity of the soil structure, the bigger the number of false peaks that the reflectogram demonstrates. A prerequisite for the correct interpretation of the results of pile continuity testing is the study of the geological section and preliminary instrumental identification of the ultrasound propagation velocity for each individual pile.

Introduction.

Steel-concrete structures are composite systems composed of steel beams and a reinforced concrete slab. The reliable transfer of shear forces between the beam and the slab is required for the structure to behave efficiently. Towards this end, anchoring devices are used to ensure a connection between the beam and the slab. The design of a steel-concrete beam, composed of a reinforced concrete slab and steel beams, having bent sections, is considered. The steel-concrete beam is a system of galvanized bent steel beams placed in parallel and partially embedded in the 90 mm thick concrete slab made of B25 concrete. Shear forces are transmitted due to adhesion between galvanized steel and concrete without anchoring devices or the additional treatment of the beam surface.

Materials and methods.

The samples, whose flat galvanized plate had been embedded in concrete, were tested to identify actual adhesion forces. Finite element models (FEM), developed using various software packages, were assessed. FEM parameters that ensured the accuracy, acceptable for practical use, were identified.

Results.

The strength of adhesion between the steel plate and concrete was experimentally identified for different options of its attachment to concrete. The mesh pattern was identified for the plate for the case when 3D finite elements were used.

Conclusions.

A steel-concrete beam with a span of 6-8 m, bent galvanized sections partially embedded in the reinforced concrete slab with a thickness of 90 mm was developed. The author experimentally identified the shear resistance of a galvanized steel plate embedded in concrete, which reached 0.248 to 0.415 MPa depending on how the surface of the steel plate embedded in concrete was prepared. Numerical models were tested using different computational packages designated for the calculation of steel-reinforced concrete beams. The author suggests FEM improvements on the basis of numerical calculation methods applied with due regard for the experimental data obtained during the testing of the full-scale structure.

Introduction.

The authors have formulated a system of equations to describe the liquid flowing in a self-contained pumping system (SPS) that has a centrifugal pump (CP). To solve the problem, it is necessary to take into account a change in static pressure, features of the hydraulic resistance of pipes, and the influence of temperature. The authors have shown that the flow under study has two similarity criteria in the case of a certain characteristic flow rate. The authors have also assessed their influence on the energy efficiency values of a basic hydraulic circuit.

Materials and methods.

The authors make a hydraulic analysis of an SPS that has pump 1K 50-32-125, whose characteristics are presented in the technical specification. A mathematical model, based on the Bernoulli equation for an unsteady flow, was developed to solve the problem.

Results.

The authors solve the non-steady problem of pumping liquid through the central heating system into the SPS if the liquid level is variable in the self-similar (quadratic) resistance range. For the case when Str = 0 and Str is the analogue of the Strouhal number, the authors find the analytical expression of pumping time for the pre-set amount of liquid and the value of criterion Θ (a dimensionless complex value linking the difference between the head in the central heating system and the initial static head in the event of zero supply, the steepness of the pressure characteristic and the hydraulic resistance of the circuit). The results of the hydraulic analysis of SPS that has pump 1K 50-32-125 and different pipeline diameters, technical parameters characteristic of self-contained water supply and sanitation systems are presented. Power consumption value E is identified for water pumping. This value is used to assess the energy efficiency of water supply and sewerage systems.

Conclusions.

The authors have found that the values of the similarity criterion Θ increase together with the pipeline diameter, while efficiency decreases and the energy consumption value improves. Under the conditions under consideration, it is advisable to focus on a change in the value of E rather than efficiency, when energy efficiency is assessed in the process of selecting equipment.

Introduction.

The article focuses on the relevance of the Life Cycle Assessment (LCA) method, used to quantify the environmental impact of a construction project at the design stage. LCA must be addressed in the process of designing buildings that will apply for green building certificates. The use of LCA software is an essential factor for obtaining LCA scores required for the majority of green building certificates.

Materials and methods.

The authors take advantage of various software packages, that make calculations and assess carbon emissions at each project stage. One of the software packages used by the authors is One Click LCA (2015).

Results.

The results of carbon emission calculations, made using One Click LCA (2015), are presented graphically in the form of carbon emission charts broken down by the life cycle stages (LCS); structural elements presented as comparative charts depending on different characteristics. The software allows assigning categories to buildings depending on their carbon emissions and impact parameters such as the Global warming potential (GWP), the Ozone Depletion Potential (ODP), the Acidification Potential (AP), the Eutrophication Potential (EP), depletion of non-renewable energy sources, etc.

Conclusions.

Software packages, used to assess life cycles of buildings, accelerate the calculation of carbon emissions, which can, in turn, streamline the selection of optimal engineering solutions for construction projects and minimize environmental impacts of buildings. It’s been found that accurate LCA calculations require comprehensive information about construction projects, including data on construction materials, energy and water consumption, as well as construction site operations. In the context of Russia, calculations are more problematic, since most manufacturers do not have construction materials databases, that contain information on carbon emissions. If manufacturers invest in the issuance of environmental product declarations (EPD), calculations of carbon emissions will be trustworthy.

Introduction.

An air conditioning system is the costliest engineering system in shopping and office centres. Buildings of this type have internal heat gains throughout the year. These heat gains are substantial because of the large number of people, the high level of artificial lighting, the availability of various items of equipment, and the heat gain from solar radiation. An air conditioning system known as ventilation cooling is of interest. It is not new; its energy assessment is quite high. The same system is under consideration, but it is evaluated from the economic perspective in the Moscow prices of 2021.

Materials and methods.

The problem is solved by applying a computational method to the case of a 35-storey office building in Moscow. Different values of the outdoor air temperature are studied to implement transition to ventilation cooling. Alternative options for the installation of dry coolers are compared, since they affect the length of routing of cooling circuits. Costs are calculated for all options under consideration.

Results.

Some results are presented as figures showing the costs of alternative air cooling systems.

Conclusions.

It is found that the location of dry coolers greatly affects the cost of pumping units. When comparing options 1 a, 1 b, and 1 c with the option that implies the installation of dry coolers on the building roof, the authors found that option 1 c is economically profitable at the 10 % discount. If options 2 a, 2 b, 2 c, are compared for the case when dry coolers are installed beside the building, option 2 c, that implies the transition from ventilation cooling to machine cooling at tn = 8 °C, is more economically profitable than option 2 b, when the transition occurs at tn = 5 °C, and option 2 a when the transition is triggered at tn = 0 °C.