Introduction. The article investigates the ways to optimise the design of a truss-to-column connection in a frame structure made of round tubes. A steel lattice frame with a span of 66 m has been studied. A spanning member of a frame in the form of a truss transmits loads to a frame column through a rigid truss-to-column connection. In such structures, the maximum bending moments are applied to a truss-to-column connection, thus the problem of regulating its geometry is one of the objectives to be solved within the optimal designing. The aim of this paper is to create the most rational design solution for such a connection.

Materials and Methods. In the lattice frames, depending on the chosen design, 5 to 7 members subject to compression stress converge at its inner side. The conventional variants of executing this connection would require using the heavy wall tubes which would result in the excess of material consumption. Within the research, modeling and calculation of various configurations of the truss-to-column connection were executed. The analysis of the calculation results revealed the shortcomings of the studied truss-to-column connection in a frame structure.

Results. As a result of the connection design optimisation, a new configuration was suggested, where the connection of a bottom chord was executed by a slotted gusset plate. Such a solution allows for the most complete use of the bearing capacity of the bottom chord cross section.

Discussion and Conclusion. As a result of the optimisation, the proposed design of a truss-to-column connection makes it possible to reduce the metal consumption while maintaining the relative simplicity of manufacture. At the same time, by reducing the local stresses, it is possible to achieve the greater strength and reliability of a truss-to-column connection. 

Introduction. Energy consumption and energy efficiency enhancement of buildings are among the most expedient objectives of the modern construction. Research is conducted on a wide range of issues within this field resulting in development of the efficient enclosure systems. One of the kind of such systems are the lightweight frame-sheathing enclosure walls, which allow enhancing the heat insulation of a building. The load-bearing members of such an enclosure are the light-gauge profiles encasing the low density heat-insulating material. In low-storey construction, the application of this technology allows using the steel profiles in both load-bearing and enclosure systems. In multi-storey buildings, the lightgauge steel structures (hereinafter referred to as LGS-structures) are used as the non-load-bearing enclosures — framesheathing walls. The present paper seeks to present the information about the new frame-sheathing wall systems (hereinafter referred to as FSW-systems) made using the LGS-structures, and possibilities for them to serve as the enclosures in construction of the multi-storey reinforced concrete frame buildings in the temperature, climatic and seismic conditions of Uzbekistan.

Materials and Methods. The systems under study are: a multilayer combined structural system consisting of a frame (skeleton frame) and materials for thermal /sound insulation; structures made of the roll-formed light-gauge galvanized steel profiles; frame-sheathing walls with the frames made of the roll-formed galvanized steel profiles; an external enclosure system of a building; a frame beam (channel profile) of the non-load-bearing structure; a horizontal member of the wall frame, which connects and closes up the vertical studs of the wall frame and serves to fasten the filling material and to transfer the loads to the vertical studs of the wall frame. The parameters of the exterior non-load-bearing walls have been studied by location, wall component composition, installation method and procedure. The classification of the exterior non-load-bearing wall connections to the members of the FSW building has been provided in the article. The classification by the exterior wall manufacturing method has been given.

Results. As a result of the study, the main advantages of the energy-saving frame-sheathing exterior walls have been identified. The durability of the exterior FSW-systems is ensured by:

1. Constructive solutions of the wall composition, the optimal layout of the thermal insulation, vapour barrier and wind protection inside the FSW cross section.
2. Sufficient corrosion protection of the roll-formed galvanized steel profiles, parts and connections.
3. Durability of each of the wall component in the exterior FSW-system.

The service life of the walls in a FSW building depends on the steel frame they are made of. In case of using the perforated profiles, the LGS-structures have a long service life, as well as low specific gravity.

Discussion and Conclusion. Upon the result of the work carried out, it has been acknowledged that due to the lack of research, even though the advantages of the FSW-systems are obvious, these systems are not widely used in the multistorey construction, including in Uzbekistan, because to be able to use the FSW-systems as the external enclosures (walls) of the multi-storey frame buildings, it is necessary to investigate and prove the expediency and possibility of using them in such a function. To do so, it is necessary to carry out the reliable modeling of a frame building with the exterior walls made of FSW-systems, taking into account spatial interaction between them under the impact of static and dynamic loads. 

Introduction. Due to intensified construction in the areas of loess subsiding soils, the issue of forecasting the evolvement of underflooding processes is becoming a relevant objective, since these processes can cause the emergency seepage, uneven groundwater surge, change of the soil stress-strain state  and, as a result, impossibility to operate the buildings or structures. Loess soils are attributed with the distinct anisotropic permeability. Subsidence and water infiltration take place in condition of incomplete water saturation. Emergence of the advanced computer technologies makes it possible to improve the mathematical modeling and develop the mathematical models by means of numerical computation, which reliably reflects the intra-soil processes. The article strives to improve a mathematical model of the moisture transfer problem in nonhomogeneous loess soils with anisotropic permeability, taking into account their structural features. 

Materials and Methods. The research includes:

• mechanical and mathematical modeling the infiltration and moisture transfer processes in loess subsiding soils, in which the percolation rate is determined according to Darcy's law; suction pressure, water permeability are the given functions of saturation;
• analysis of the physical and mechanical and structural properties of loess soils;
• study of the formulations and solutions of initial value and boundary value problems during presoaking the loess strata; – numerical experiments on the forecast of excavation pit presoaking; – comparing the results with the experimental data.

Results. It has been acknowledged that the existing calculation methodologies do not always reliably reflect the process of infiltration and moisture transfer in loess soils. An equation determining the moisture transfer was formulated. A mathematical model of the moisture transfer problem in nonhomogeneous media with anisotropic permeability was proposed, which took into account the structural properties of loess soils. The initial value and boundary value problems were solved by the iterative methods with linearization of the solution over sufficiently small time spans. For practical implementation of the theoretical solution, a flow chart of the program algorithm was developed, which included the calculation of the physical and mechanical properties of finite elements and the computational domain dimensions, as well as partitioning the computational domain into the units and triangular elements, determination of the permeability and diffusion coefficients, formation of the parameters of an equation according to the Krank-Nicholson scheme, solution of the system of equations by the compact elimination method and constructing  a vector of moisture. An algorithm for solving the axisymmetric problem of moisture transfer in condition of incomplete water saturation has been developed, which is characterised by stability of direct integration of the moisture transfer equation. The results of the numerical experiments and field tests on presoaking a circular-shaped excavation pit have been compared. The results of the numerical experiments have been presented in the curves of the volume moisture values in different periods of time. It has been found that the results of the solution are well cohered with the experimental data. 

Discussion and Conclusion. The results of the theoretical research of the problem of moisture transfer in unsaturated loess soils have justified the formulation and the finite element solution of the problem of moisture transfer in unsaturated media, without taking into account the stress-strain state. Based on the experimental data on test excavation pit presoaking, the calculation methodology was verified, and showed the coherence of calculated and experimental results. The proposed methodology is recommended for calculation of the second group of limit states — the deformations. 

Introduction. The bored сast-in-place piles are the type of piles most adjusted to specifics of the multistorey building construction. The article studies the existing methods of underreaming such piles as the main tool to minimise their diameter, length, and quantity, thus optimise and reduce the cost of foundation design and its subsequent construction. It is acknowledged that despite the diversity of these methods, the information about them is scattered, confusing, and sometimes contradictory, making it difficult to choose the optimal design solutions. To facilitate the choice, an application-oriented classification of the methods under study has been proposed aiming to specify the areas of rational implementation thereof.

Materials and Methods. The study took into account the data of the guidebooks on norms of production and estimate norms, the reference, normative and standard design documentation, as well as national practices and solutions proposed by the professional subcontracting organisations.  Upon analysis of the above materials, the information on the advantages, disadvantages and implementation area parameters of the existing methods of bored cast-in-place piles underreaming was systematised based on the internal and external factor criteria used for selecting the appropriate solutions in the competitive conditions of multistorey building construction. The competitiveness of three most advanced of such methods was investigated by a comprehensive (multi-criteria) evaluation method. 

Results. It was found that under general conditions that were studied, the most competitive among the selected methods was mainly the pulse-discharging treatment of a pile shaft and (or) pile base. The respective results were presented graphically in the form of the bar charts of unit labour costs and costs of underreaming by the studied method, as well as the radial bar charts showing the cumulative effect of these and other taken into account parameters on solving the set task of optimisation. 

Discussion and Conclusion. The reflections upon the efficiency of implementing the obtained results in the present-day designing have been further evolved, and the ways and circumstances of changing thereof depending on the project specification and local conditions of construction have been presented. On the whole, that allowed for specifying the areas of rational implementation of the studied methods and providing the recommendations on updating the relevant regulatory framework.

Introduction. The construction industry belongs to the branch of material production focused on research, design, construction and maintenance of buildings and structures. It can be divided into four main sectors: housing, construction of infrastructure, industrial construction and professional engineering. The aim of the present research is to identify the challenging issues and aspects in the construction industry of China.

Materials and Methods. The comparative analysis of the construction industry features and historical evolvement, as well as the analysis of the existing problems and trends in its development served a tool for solving the objective set forth.

Results. The conducted research made it possible to define the distinctive features of the Chinese construction industry and revealed its major problems. The article identified the most forward-looking trends in development of the construction industry.

Discussion and Conclusion. To overcome the problems existing in the construction industry of China, the main moves to encourage the development of the industry by investing funds into the technological research and findings have been identified, which lead to mutual benefit and global development taking into account the foreign experience.

Introduction. The thick-walled cylindrical shells are widely used in the hydraulic structures, protective structures of nuclear power plant reactors and missile system launchers. Due to the internal heat emission of concrete in massive monolithic structures, there is a high risk of early-age cracking. Computer modeling methods can be used to develop the preventive measures against it. Previously, modeling of temperature stresses within a construction process was carried out for the massive foundation slabs and walls, whereas the thick-walled cylindrical shells were not studied. The aim of the present work is to develop a methodology for calculating the temperature stresses during construction of the monolithic thick-walled cylindrical shells.

Materials and Methods. Stress calculations were made in a one-dimensional axisymmetric formulation. The dependence of the mechanical properties of concrete on the degree of its maturity was taken into account. The stress-strain state (hereinafter — SSS) calculation problem was reduced to a second-order differential equation relative to the radial stress, which was solved numerically by a finite difference method. The SSS calculation was preceded by the temperature field calculation, which was deemed independent from the stress state. The authors carried out the numerical solution in the MATLAB environment.

Results. At the first stage of testing, the developed methodology was compared with calculations made in the ANSYS software package under a time-constant modulus of elasticity of concrete that confirmed its reliability. Also, the calculation results, which took into account the dependence of the modulus of elasticity of concrete on degree of its maturity were presented. Moreover, compared to calculations under the time-constant mechanical properties of concrete, in the stress-strain state, the picture became radically different. 

Discussion and Conclusion. Calculations under a time-constant modulus of elasticity of concrete by means of the standard software packages, as opposed to the author’s methodology, leads to the overestimated circumferential stress values, and hinders calculation of the residual stresses. In the case of a time-constant modulus of elasticity of concrete, the temperature stresses are completely reversible.