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Tower cranes are one of the main tools for execution of reloading works during construction. Design of tower cranes is carried out in accordance with RD 22-166-86 “Construction of tower cranes. Rules of analysis”, according to which to ensure stability it is required not to exceed the overturning moment upper limit. The calculation of these moments is carried out with the use of empirical coefficients and quite time-consuming. Moreover, normative methodology only considers the static position of the crane and does not take into account the presence of dynamic transients due to crane functioning (lifting and swinging of the load, boom turning) and the presence of the dynamic external load (e.g. from wind for different orientations of the crane). This paper proposes a method of determining the stability coefficient of the crane based on acting reaction forces at the support points - the points of contact of wheels with the crane rail track, which allows us, at the design stage, to investigate stability of tower crane under variable external loads and operating conditions. Subject: the safety of tower cranes operation with regard to compliance with regulatory requirements of ensuring their stability both at the design stage and at the operational stage. Research objectives: increasing the safety of operation of tower cranes on the basis of improving methodology of their design to ensure static and dynamic stability. Materials and methods: analysis and synthesis of the regulatory framework and modern research works on provision of safe operation of tower cranes, the method of numerical simulation. Results: we proposed the formula for analysis of stability of tower cranes using the resulting reaction forces at the supports of the crane at the point of contact of the wheel with the rail track.

Subject: despite the accumulated experience in the construction of ground dams with anti-filtration elements from geosynthetic products, the response of geosynthetic products in the structure of ground dams have been little studied. It was not determined whether positive stretch values can arise in the polymeric anti-filtration elements and whether they can threaten integrity of anti-filtration elements. For this, studies of the stress-strain state are required. The recent results of investigations of the physico-mechanical properties of contacts of polymeric geomembranes with soils allow us to study the behavior of geosynthetic products in the structure of soil dams. One of the possible designs - a high ground seam with a zigzag geosynthetic diaphragm - has been studied here. Materials and methods: investigations of the stress-strain state of the seam were carried out using numerical simulation. Calculations were carried out for a wide range of physico-mechanical properties of the geomembrane and the contact of geomembrane with the soil. The modulus of linear deformation of the polymer material, the angle of internal friction, and the tangent stiffness of the contact were varied. Results: the results of studies of the analyzed seam designs have shown that, in the main, the stresses in the geomembrane are determined by the modulus of linear deformation of the polymer material. The higher the stiffness of geomembranes, the higher are the tensile stresses in them. The shear characteristics of the geomembrane-soil contact are also important. The lower the shear strength of the contact, the higher are the tensile stresses in the geomembrane. Conclusions: the most vulnerable point of the zigzag diaphragm is its upper anchors, because it is in them that the greatest tensile stresses occur. It is recommended to turn them to the bottom side. In the diaphragm of the considered structure, it is impossible to use a geomembrane made of polyethylene; it is necessary to use a geomembrane made of PVC.

Introduction. An approach to the application of finite element programs (FEM) ABAQUS/Standard and ABAQUS/Explicit with various equations of state of incompressible isotropic hyperelastic materials is presented when analyzing compressed and stretched shell elements of elastomers. Elastomers are commonly used in construction as well as in structural shell elements, in particular pipes of different cross sections. Materials and methods. Three FEM models for pipes with the same length and initial stiffness were created. Pipes with elliptical, square and triangular cross sections are considered. Three types of structural models of rubber-like material (elastomer) were used - with a polynomial elastic energy function in the form of the MV model and the standard models of Neo - Hooke and Mooney - Rivlin. In the FEM models of the analyzed pipes, not enter initial imperfections. Numerical modeling buckling of pipes was performed for two types of initial and boundary conditions - for quasistatic and dynamic problems. Results. It is shown that the type of buckling depends on the cross section of the pipe. Comparison of buckling solutions for simulated pipes with different structural models demonstrated a good correlation of the results. An approximate history of the deformation of an elliptical sample analyzed by ABAQUS/Standard, loaded by moving the boundary, is given. Conclusions. It has been established that the ABAQUS/Standard program allows the use of incompressible hyperelastic materials, the ABAQUS/Explicit program does not provide this possibility. This implies the need to set the parameters of the material associated with the spherical part of the stress tensor. The parameter should not be too small, otherwise it will lead to numerical errors. Solving problems on the stability of pipe models with different physical models give good correlations of results.

In the article the authors considered the technique of evaluating the performance of a grouting curtain basing on the analysis of mathematical forecasting and regular measurements of water temperature in the reservoir and in the rock mass behind the dam. The initial data for the solution of heat transfer problem are the rate of filtration, obtained from the solution of the stationary problem of filtration, and the experimental factor, generalizing thermophysical properties of rocks. For calculating the period of time from to the change of the water temperature in the reservoir till the change of water temperature at the reference point of the rock mass a computer program was designed, which allows defining the path and time of filtration from the reservoir to the reference point in the rock mass with the help of the reverse conversion on flow lines. The calculation was carried out from the point in question in the rock mass till the crossing paths of filtration with the bottom boundary of the reservoir. As an example, we present the results of computational studies of filtration and temperature regimes in the rock foundation of a concrete dam at the design work of the grouting curtain and in case of the presence of pervious area. The calculations were performed with a time step
dt = 2 days. At each time step, with account of water motion along the lines of the current through the rock mass, the previous position of the reference points in space has been determined, for which the value of the velocity vector of filtration field was corrected. In the first case, the motion of water from the reservoir was carried out in the circumvention of the grouting curtain. In the second case, the motion of water took place from the reservoir through the permeable portion of the grouting curtain. The change of the water temperature during its seepage from the water reservoir through permeable area of grouting curtain because of conductive heat transmission in all the checkpoints in permeable area of grouting curtain is 0.5-1.0 °C at measurement accuracy of water temperature 0.1 °C. Thereby, by measuring the changes of water temperature in the reservoir and in the rock mass behind the grouting curtain as a result of alternative calculations using the developed method we can calculate the position and size of a possible permeable area.

Introduction. Presented the approach to studies of the impact of a rockfill dam staged construction on the reinforced concrete face SSS. Experience in construction of reinforced concrete face rockfill dams (CFRD) shows that at perception of hydrostatic pressure the integrity of the seepage-control element may be broken. By the results of mathematical modeling it was revealed that the tensile stresses appearing in the face concrete may exceed concrete design tensile strength. The causes of appearing tensile stresses are bending deformations and the face longitudinal extension. The urgent issue is selection of the way of improving the stress-strain state (SSS) of the face to provide its safe operation as a seepage-control element. Materials and methods. The studies were conducted on the example of a 100 m high dam with the aid of numerical modeling. Two cases were considered: in the first case the dam was constructed in one stage, in the other in two stages. Rockfill is considered as a lineally deformed material, but computations were conducted for a wide range of the soil linear deformation modulus: from 60 to 480 МPа. Steel reinforcement was considered in the face. Results. Longitudinal stresses in a reinforced concrete face were compared for two cases of the dam staged construction. Analysis was fulfilled with determination of the longitudinal force and bending moment appearing in the face. The obtained maximum values of tensile longitudinal stresses in the face were compared for two cases. Conclusion. It was revealed that construction and loading of the dam by stages on the whole is favorable for the face stress-strain state. The second-stage dam weight transfers to the first-stage face the compressive longitudinal force, which permits decreasing tensile stresses in it. Bending moments in the face vary insignificantly and even may increase to some extent by value. Nevertheless, at dam construction and reservoir filling in 2 stages the maximum values of tensile stresses in the face concrete decrease, therefore, such construction sequence contributes to enhancing safety of the dam seepage-control element.

Introduction. Deals with the results of studying effectiveness of arranging transverse joints in the face as the means of regulation of its stress-strain state. At present reinforced concrete faces are constructed without being cut height-wise and transverse joints may be arranged only at the end of the dam construction stages. This is validated by the fact that experience in construction of flexible (discontinuous) faces has not demonstrated the required level of safety of this structural design. However, in the dams of the up-to-date structural designs, maintaining the face integrity is not guaranteed: cracks appeared in reinforced concrete faces at a number of high dams. Formation of cracks in faces should be attributed to presence of tensile stresses, whose values exceed concrete tensile strength. To prevent seal failure of the seepage-control element it is feasible to provide arrangement of the transverse joint in the face section where tensile stresses may be expected. Materials and methods. The studies were conducted on the example of a 100 m high dam with the aid of numerical modeling. Rockfill was considered as a lineally deformed material, but computations were conducted for a wide range of the soil linear deformation modulus: from 60 to 480 МPа. Steel reinforcement was considered in the face. Transverse joints were modelled with the aid of contact finite elements. Results. By the results of numerical modeling the tensile stresses appear in the uncut face due to bending deformations and deformations of longitudinal extension. The most hazardous is the face lower section. At this section the longitudinal tensile force and considerable moment are acting. Transverse joints are feasible to be arranged in this particular section of the face. Conclusion. It was revealed that the main positive effect of the transverse joint arrangement is in decreasing the value of longitudinal tensile force perceived by the face. Impact of the transverse joint on bending moments has a local effect and covers the section of the limited length. Moreover, at arranging joints the values of bending moments may increase. We may recommend arrangement of a transverse joint in the face which is parallel to the perimeter joints only in the face lower part which is subject to longitudinal deformation.

The authors analyze the Hardening Soil Model possibilities for describing the soil behavior under the load, using numerical simulation of the stabilometric tests for varied density sand.According to the study, the assumption that dilatancy angle stays constant is correct only for the dense soil. On the other hand, for the loose or medium density soil this assumption is unacceptable. For the loose and medium density sands, the calculation error in volumetric strain analysis may exceed 50 %.In order to assess the adequacy of soil behavior description in the calculations using the model of "Hardening Soil" numerical simulations were performed using Plaxis triaxial testing of soil. In deviatoric loading the loose soil consolidants, the dilatancy development in the sand of average density has an alternating pattern, the dense sand deconsolodates. The values parameters of the model "Hardening Soil" were determined by the results of experimental data obtained in the AO «NIIES» in triaxial tests the «Liuberetskii» sand and on the recommendations of the program Plaxis. As the results of numerical studies, the soil model "Hardening Soil" describes quite well the development of volumetric strain with the full compressing the soil and the development of shear deformations in the deviatoric loading.In the case of deviatoric loading the relationship between the centerline and the volume deformation is essentially non-linear (Fig. 3a), in contrast to the theoretical assumption of constancy of the angle of dilatancy. In the dense sand at the approach to the limiting value the increment of volume strain (by absolute value) increases, and in the loose sand decreases.

The interaction process of a power plant building with the soil base is studied basing on mathematical modeling of the construction process of Kambarata-2 HPP, taking into account the excavation of foundation pit, the concreting schedule of the building construction, the HPP units putting into operation and territory planning. Mathematical modeling of stress-strain state of the system “power plant - soil base” in the process of construction was performed by using the computer program “Zemlya” (the Earth), which implements the method of finite elements. Such a behavior of soil was described using elastoplastic soil model, the parameters of which were determined from the results of the triaxial tests. As shown by the results of the research, the continuous change of settlement, slope, deflection and torsion of the bottom plate and accordingly change of stressed-strained state of power plant are noted during the construction process. The installed HPP construction schedule, starting from the construction of the first block and the adjacent mounting platform, is leading to the formation of initial roll of bottom plate to the path of the mounting pad. In the process of further construction of powerhouse, up to the 29th phase of construction (out of 40), a steady increase in its subsidence (maximum values of about 4.5 cm) is noted. Filling of foundation pit hollows and territorial planning of the construction area lead to drastic situation. In this case, as a territory planning points exceeded the relief, the plastic deformation in the soil evolves, resulting in significant subsidence of the bottom plate under the first block (up to 7.4 cm). As a result, the additional subsidence of the soil of bottom plate edges lead to the large vertical movement in relation to its central part and it is bent around the X axis, resulting in a large horizontal tensile stress values of Sz (up to 2.17 MPa) in the constructive elements of the upper part of the powerhouse. At the same time, the calculations performed on the assumption of instantaneous power plant construction forecast only a uniform slope of bottom plate in the direction of the headwater and do not allow us to track the process of stress-strain state of the power plant for adequate reinforcement of its elements.

This article considers some aspects and common problems associated with the organization of parallel calculations in the problems of hydrodynamics. As an example the authors consider the calculation problem of the velocity field in the area of river and sea water mixing and the simulation of sedimentation of terrigenous material.

The present paper is concerned with the method, research objective and the results of numerical simulation of change of stress-strain behaviour of soil masses when constructing underground complex. In order to get consistent results of forecast, all major factors affecting the results of design studies have been taken into account, including spatial performance of soil mass, enclosure structure and an adjacent context area, phasing of construction, site investigation, initial stress-strain behaviour of soil mass and elasto-plastic strain of soils. The authors give assessment of influence of pit excavation and subsequent construction on a context adjacent area and construction of an underground railroad. Results of the studies show that the proposed construction of an underground complex on the Tverskaya Zastava square would not have a significant impact on the surrounding buildings and subway structures. The spreading of the subsidence crater around the excavating pit is projected by 30...80 m. The ground lift directly below the bottom of the excavation pit in the places of metro stations and transport tunnels will be about 0.1 cm.

Subject: the algorithms and software for numerical analysis of flow-measuring structures in open channels are considered. The actual accuracy of measurements and range of application of such structures are limited by the conditions of preliminary experimental studies. The empirical formulas given in literature are in most cases insufficient for correct estimate of the metrological characteristics reliability and the applicability limits of hydrometric structures. Research objectives: development of software package for the analysis of hydrometric structures which ensures an increase of measurement results reliability and expansion of the range of flow measurements in open channels of water management systems. Materials and methods: based on trial calculations, we have identified and analyzed the shortcomings of the known general software packages for fluid flow analysis in terms of calculation of water discharge characteristics of hydrometric structures. We have developed the numerical algorithms and modules of a specialized software package for analysis of hydrometric structures without the drawbacks inherent to universal software products. Results: the computer software package for analysis of hydrometric structures based on the numerical solution of the Navier-Stokes equations in a three-dimensional formulation was created and tested on several types of flow-measuring structures. For increasing accuracy of discharge calculation, the new program module for generation of the grid with hexoidal cells was developed. The individual boundary and initial conditions for different structures are prescribed depending on free-flow or variable backwater regime. All calculation procedures, from the input of initial data to the output of results of the analysis in text or graphical form, are performed automatically, without participation of the user. As an example, the software testing was performed on the Crump weir calculation and the results of the test are given. Conclusions: according to the test results, the error in calculating the discharge characteristics doesn’t exceed 2…4 % depending on the type of hydrometric structure, which meets the requirements of technological and commercial water accounting. Thus, the developed software package can be used to increase the accuracy and expand the range of measurements of existing hydrometric structures, develop new types of water accounting facilities and study in depth their operation under non-standard conditions.

ABSTRACT Introduction. The article considers results of research of reinforced-concrete face stress-deformation state depending on availability of the reinforcement. At some ultra-high reinforced-concrete faced rockfill dams (CFRD) the transversal (horizontal) cracks were developed in the seepage-control element. It is supposed that the cause of the crack formation is high values of tensile stresses. In this connection, opinions are expressed about the necessity of strengthening the face reinforcement. However, in accordance with the experience gained, in real dams the reinforcement, as a rule, is arranged in one row with reinforcement percentage 0.35 to 0.5 %. The urgent issue of CFRD studies is assessment of impact of the concrete face strengthened reinforcement on enhancement of its reliability. Materials and methods. The studies were conducted for different variants of rock fill deformation properties on the example of 100 m high rockfill dam. The reinforced concrete face was adopted to be wide (1 m thick). The reinforcement was adopted to be two-row one, with reinforcement percentage of 1.5 %. The study was conducted using the finite element method. The reinforcement was simulated using bar finite elements. Results. To reveal the role of reinforcement, analyses of the stress-deformation state were conducted for two cases. In one case it was assumed that reinforcement is absent and in the other case consideration was made for the face with steel reinforcement. Stresses in concrete and steel reinforcement were analysed. Stresses acting along the upstream slope were considered. Conclusions. It was revealed that due to the reinforcement of steel-bar reinforced concrete face it was impossible to provide decrease of tensile stresses in the face concrete down to the permissible level. Reinforcement may play a significant role in the face stress-deformation state only at the moment of forming transversal cracks in the face concrete, but such a case is inadmissible.