"Вестник МГСУ"

Foundations of laterally loaded single piles are widely used as part of power transmission lines, wind power stations, highway structures, etc. Ongoing pressure applied to a laterally loaded pile, particularly at the ground level, causes the soil deformation characterized by the bulging of the soil surface.
In the majority of cases, the deformation strength of a pile depends on the front-face soil resistance, Horizontal beams, ground caps or rigid plates are used to increase the pile resistance. An effective method of pressure reduction contemplates the use of a rigid round cap at the front-face or upper level of the soil.
In this paper, the authors analyse the data to examine how a round cap installed at the ground level impacts the bearing capacity of a single pile.
This research based on the methodology developed by the authors demonstrates that a laterally loaded pile, supported by a rigid cap at the ground level, is exposed to increased resistance due to the following factors, including the passive pressure along the cap side that creates an unloading effect for a horizontally-loaded pile. The cap acts as a vertical soil rebuff creating an additional resistance moment; the horizontal shear of the cap causes supplementary lateral resistance of a pile.
The following initial geometric and elastic material properties of the single pile are applied: total length = 5.0 meters (3.0 m above and 2.0 m below the ground surface); pile diameter = 40 centimeters; circle plates of various diameters = 60; 70; 80 and 100 cm and their thickness = 20 cm. A lateral load is applied at various heights, , of 0.2; 1.0; 2.0 and 3.0 meters above the ground level.
Elastic properties of the soil are assumed to be constant at each point below the surface of the ground, they are listed below: bulk modulus of soil E=20 MPa; Poisson's ratio μ=0,37; unit Weight γ=18,5 kN/m; cohesion =0,05 MPa; angle of internal friction φ=20°.
The data has proven that cap-covered piles are substantially more economical (over 40 %) in terms of materials consumption rate if compared to constant cross-section piles (cap-free or broadening piles), all other factors being equal.

Introduction. Reviewed the features of the work of the pile on Permian claystones with the help of numerical and field experiments, analytical calculations. Materials and methods. Numerical modeling was performed in the Plaxis 3D and Midas GTS NX software packages. Full-scale tests of driven piles are made in accordance with the requirements of GOST 20276-2012. The obtained results are compared with the results of analytical calculations according to SP 24.13330.2011. Results. The scientific novelty of the investigation consists in a comparative analysis of the results of numerical modeling of the interaction of a driving pile with claystones with the results of field tests and analytical calculations. Finite element analysis in software package Plaxis 3D using Hardening Soil model shows higher values of settlement (up to 6 times) in relation to stabilized settlement of full-scale pile tests. Calculations in the software package Midas GTS NX showed overestimated values of pile settlements in relation to full-scale pile tests (13-24 times). Analytical calculations in accordance with SP 24.13330.2011 also showed overestimated (up to 3 times) values of the maximum pile settlement in relation to the stabilized settlement during full-scale pile tests. Conclusions. The calculations by the finite element method in the package Plaxis 3D and Midas GTS NX, by the analytical method according to SP 24.13330.2011, show overestimated values of settlement in relation to the stabilized settlement of piles on claystones. Using the Linear-Elastic model for claystones in numerical calculations in Plaxis 3D provides a value close to the settlement of full-scale pile. However, the use of this model is not fully justified for claystones due to the presence of residual deformations and the nonlinear character of pile settlement during loading. Necessary to correct the existing numerical and analytical methods for calculating pile foundations on claystones. It is necessary to continue the work on the further generalization of the experience of arranging piles on weathered claystones in order to evaluate the long-term work of not only a single pile, but also a pile foundation.

The buildings made of monolithic reinforced concrete currently enjoy great popularity. Along with a great number of advantages of monolithic building, which are repeatedly listed in the works of many authors, there are many unexplored issues which require detailed consideration. The technological concrete joints are among them. The joints are inevitable in the process of construction of almost any monolithic building and their quality affects the reliability of buildings and structures. Despite regular use of the concept of cold joint and clear instructions in building standards on the technology of joint production, most organizations do not follow the correct technology of concreting the elements. As a result, the strength and stiffness characteristics of the construction deteriorate, because the linkage value of new concrete with the old one is significantly lower than in monolith. In order to conduct experimental studies the reinforced concrete beams of rectangular section were produced. As a result of testing, it was determined that the presence of a concrete joint significantly reduces the stiffness and carrying capacity of the structures. It is confirmed by the fact that the received deflections of solid beams without joint are significantly lower than the deflections of beams with cold joint. It also noted that the deflections of the beams manufactured following the normative technology are lower, than the deflections of the beams, manufactured with violation of the rules. Basing on the obtained results, it was concluded, that more detailed study of the work of a construction with cold joints in concrete is required. The reason for it is in the changing for the worse of the strength and stiffness characteristics of structural element, which is made produced with a joint, while in the process of real designing, the monolith buildings are calculated as solid monolithic, without joints.

The proposed calculation method is specific in terms of determining the carrying capacity of eccentrically compressed concrete elements, in contrast to the calculation by error method, as in the existing regulations, where in the result of the calculation is not known what is the limit load the eccentric compression element can withstand. The proposed calculation method, the publication of which is expected in the next issue of the "Vestnik MGSU" the above mentioned shortcomings of the existing calculation methods, as well as the shortcomings listed in this article are eliminated, which results in the higher convergence of theoretical and experimental results of eccentrically compressed concrete elements strength and hence a high reliability of their operation.

The author presents the results of calculations of eccentrically compressed elements in the ultimate limit state of bearing capacity, taking into account all possiblestresses in the longitudinal reinforcement from the R
_s to the R
_sc, caused by different values of eccentricity longitudinal force. The method of calculation is based on the simultaneous solution of the equilibrium equations of the longitudinal forces and internal forces with the equilibrium equations of bending moments in the ultimate limit state of the normal sections. Simultaneous solution of these equations, as well as additional equations, reflecting the stress-strain limit state elements, leads to the solution of a cubic equation with respect to height of uncracked concrete, or with respect to the carrying capacity. According to the author it is a significant advantage over the existing methods, in which the equilibrium equations using longitudinal forces obtained one value of the height, and the equilibrium equations of bending moments - another. Theoretical studies of the author, in this article and the reasons to calculate specific examples showed that a decrease in the eccentricity of the longitudinal force in the limiting state of eccentrically compressed concrete elements height uncracked concrete height increases, the tension in the longitudinal reinforcement area gradually (not abruptly) goes from a state of tension compression, and load-bearing capacity of elements it increases, which is also confirmed by the experimental results. Designed journalist calculations of eccentrically compressed elements for 4 cases of eccentric compression, instead of 2 - as set out in the regulations, fully cover the entire spectrum of possible cases of the stress-strain limit state elements that comply with the European standards for reinforced concrete, in particular Eurocode 2 (2003).

The article discusses the features of the stress state of the plate of capitalless girderless overlapping as a result of force of prestressed reinforcement, where the reinforcement used is high-strength reinforcement in flexible shell of "Monostrend" type. The peculiarity of specific design solution is a diagonal arrangement of prestressed reinforcement with heads fixed at the outer edges of the columns. The purpose of this arrangement of the prestressed reinforcement is deflection reduction of the central area of a plate and reduction of the width of cracks on the lower surface in the bay and on the upper surface of the support areas. The article shows the distribution of normal stresses of existing loads in the plane plate. The stress distribution over the thickness of the plate was assumed uniform. In order to establish design size of a section in diagonal direction it is possible to set the variables x and y and then calculate the coordinates of stress distribution curves in the concrete as a result of compression by prestress force. The authors offer diameter values of equal stresses in case of 4 and 8 K7O ropes. The method of calculating prestressing losses of concrete creep are offered.

The authors present features of the strength analysis of monolithic beamless floors, obtained using the limit equilibrium method. This method consists in the following procedure: a monolithic plate bends and breaks in the limit equilibrium under a uniformly distributed load. The influence of various combinations and dimensions of column sections on bending moments are considered. The influence of cross-sectional dimensions of columns on values of effective forces is analyzed in detail. The general equation to solve the strength problems of monolithic plates, having regular grids of columns exposed to continuous uniform loads, is derived and solved by the authors. This expression can be applied to calculate the span and support moments and to establish optimal reinforcement of plates. Results of calculations are presented in graphs that make it possible to derive interesting findings.

Precast-monolithic construction is becoming an increasingly popular form of housing. The wide distribution of this type of construction is explained by the possibility to successfully combine the advantages of precast and monolithic construction, at the same time reducing their disadvantages. Though there is a significant lack of data, including experimental data, for objective assessment of the stress-strain state of precast-monolithic floor structures. In order to investigate the structural reliability of the bolt joint of a bearer with a column in a precast-monolithic building a series of experimental investigations were carried out in the laboratory of testing the building structures of the Siberian Federal University.One of the main conclusions is that the bolt joint of a bearer with a column is characterized by sufficient rigidity, crack resistance and bearing capacity. The results of the given work have proved the data obtained in previously conducted investigations on a fragment of a precast-monolithic ceiling.

The paper presents calculations of the punching girderless monolithic slab with transverse reinforcement under the action of a concentrated force in accordance with the applicable regulations. The authors specify the circumstances that may limit the use of the certain sizes of spans of beamless floors. The influence of various factors on ensuring the strength of the joints of columns and ceiling is obserced, such as the class of the concrete slab thickness, the presence of transverse reinforcement. In this paper the calculations of the burst strength were performed for girderless slabs of the thickness 20, 21 , 22, 23, 24 and 25 cm of concrete classes B15, B20, B25, B30 and columns of square section with the side b = 30 cm. The cells of 5 × 5, 6 × 6, 7 × 7, 8 × 8, 9 × 9 m were analized. Bending moments were not taken into account. The utmost bursting effort for various classes of concrete slab thickness and the absence or presence of transverse reinforcement were discovered. The limiting uniformly distributed loads for plates with different grid of columns were calculated. It was found out that in case of the size of the cells up to 5 x 5 m inclusively, you can use all the above concrete classes and slab thicknesss. But in case of the cells of 9 x 9 m and more the use of overlap without capitals is problematic because of the impossibility to ensure the burst strength without special design solutions. Some of contemporary ways to expand the use of overlap without capitals are: the use of high-strength concretes, application of stiff reinforcement in the area of joint of stiff reinforcement, fiber reinforcement and the use of prestressed reinforcement.

The author considers the results of experimental studies of the influence of some factors on the sloping section bearing capacity. These factors are: the value of the relative distance from the support to the load line (shear span) depending on the quantity of transverse reinforcement and the shape of the cross section of the elements; the size of compression flange overhang in T-section beams; the prestress rate of the transverse reinforcement. The author specifies the types of fracture across sloping sections of T-section beams.

The principal objective of the research project is to identify the thickness of an advanced
composite adhesive material used as part of a glued connection of wooden surfaces. The active
ingredients of the proposed adhesive material include an epoxy matrix and a glass fiber fabric. The
author has analyzed the bearing capacity and deformability of the proposed connection in relation
to the thickness of the composite material. The author used the methodology of assessment of the
bearing capacity of wooden structures developed by professor Yu.M. Ivanov. For the purposes of
development of optimal parameters of the "QM Glued" connection, the author identified the optimal
ratio of b, or width of the surface of connected elements, and the thickness of the composite material:
t = 1/40 b.

Presently, offshore projects have moved to a new level. Advanced technologies are employed to develop those oil and gas deposits that were inaccessible in the past. SPAR and FPSO platforms are used to develop deposits at a depth of over 2,000 meters. Versatile technologies, including suction piles, represent a major factor of successful implementation of these projects.Renewable energy sources arouse more interest. Wind energy is a most ambitions area of research. Wind farms may be installed along the coastline or a shelf. Today many offshore projects are implemented using renewable energy sources. Presently, wind power generators represent sophisticated structures having blades with a diameter of up to 150 m. One of the main objectives is to have them strongly attached to the seabed. Suction piles are often used to solve this task. Suction piles minimize the work at sea, and they are used to install both fixed and floating platforms. The authors consider modern constructions used in similar projects and present the history of suction piles and their use in different offshore projects. The authors also analyze the most recent developments in the area of anchor design for suction piles.The area of research covered in the article is highly relevant. Anchors and foundations based on suction piles can be widely used to develop offshore projects in Russia.

The supports of a overhead wiring used in transport take up substantial loads both because of wires and constructions holding them and wind, dynamic and other extraordinary impacts. In case of using single-member piles a question about their stability appears. For this reason different sleepers constructions are used. In order to improve the bearing capacity of horizontally loaded single pile supports of the contact systems used in urban, road and rail transport, power lines, etc.., it is recommended to use sleepers as horizontally laid under the ground in the depth of support beams. The calculation methods for different support sleepers of different lengths and cross sections are not well investigated. The proposed calculation method allows determining the carrying capacity of horizontally loaded bearings with soil pieces of different structural dimensions and their location in the soil, which allows choosing the best option for cost and material consumption. The calculations offered by the authors prove the efficiency of sleepers use in order to increase the bearing capacity of horizontally loaded piles and the possibility to chose their size.

When a long pile is interacting with the soil, the combined force applied to the pile head is distributed among the side face and the pile toe inhomogeneously. The toe gets not more than 30 % from the general force, which doesn’t let using the reserves of the bearing capacity of relatively firm soil under the fifth pile. Account for the depth of the pile toe and the dead load of the soil allows increasing the bearing capacity of the soil under the pile toe and decrease the pile settlement in general. For the quantitative estimation of these factors it is necessary to solve the task on the interaction of the rigid long pile with the surrounding soil, which includes under the pile toe, which is absolutely rigid round stamp.The article presents the formulation and analytical solution to a quantification of the settlement of a circular foundation with the due account for its depth, basing on the development of P. Mindlin’s studies as well as the interactions between a long rigid pile and surrounding soils, including under pile toe.It is proposed to compare the estimated value of stresses under the heel of pile with the initial critical load for the round foundation to check the condition that the estinated value is less than the intial critical one.

The article deals with the questions of designing the foundations for the Oil Pumping Station-2 site of “Kuyumba — Tayshet” trunk oil pipeline. The problems of choice and grounds for technical solutions are considered basing on the results of complex thermo-technical calculations.
The construction territory of OPS-2 site of “Kuyumba — Tayshet” trunk oil pipeline is characterized by complex engineering and geocryological conditions:
1) presence of permafrost soil on 80 % of the site area;
2) absence of sufficiently widespread rocky soils under designed buildings and constructions;
3) transition of loamy grounds into yield during thawing.
The buildings and facilities are designed on the basis of pile foundation type with high rigid foundation grill. The piles’ diameter is 325 mm and 426 mm, the total length of piles is 9—12 m. The full designed vertical loading, transferred to the pile, is ranging from 10.6 to 50.4 tf.
According to the results of the calculations, in order to provide the necessary bearing capacity of piles, securing the perception of transmitted designed loadings, the equivalent temperature of the soil along the side surface of piles (Te) should not be higher than –0,5 °C. Taking into account that the soil temperatures on the projected site mainly range from –0.1 to –0.3 °C, in order to lower their temperatures to the calculated values ventilated underground areas are arranged under the buildings and facilities and seasonally active cooling devices (soil thermal stabilizers) are installed.
Assembly technique and construction of ventilated underground areas with application of soil thermal stabilizers were developed earlier while designing the pipeline system “Zapolyarye — Oil Pumping Station Purpe”.
For confirmation of the accepted decisions forecasting thermotechnical calculations were performed with the use of a special computer program TermoStab 67-87, which allows simulating the changes of temperature regimes of the permafrost in the process of construction and operation of the facility.
As a result of thermo-technical calculations, in case of operation of ventilated underground areas only, in the foundation of the facilities at the OPS-2 site (without the application of thermal stabilizers) a reduction in temperature of frozen soils is predicted, however, the required design temperatures, necessary for providing the bearing capacity of piles (–0,5 °C on their side surfaces and below), in one cold season cannot be achieved. For the areas of the distribution of the confluent type of the permafrost the necessary temperatures are achieved only by the 5th year of operation, and for the areas of distribution of non-confluent type of permafrost such temperatures are not achieved even by the 10th year of operation. A joint operation of the ventilated underground areas and soil thermal stabilization systems is conductive to the reduction of soil temperature of the buildings and facilities’ foundations up to the required values, which secure the load-bearing capacity of piles for one cold season.

Today the design and calculation of pile foundations in rocks is poorly considered in the national regulatory and technical literature. It should be also noted that the need of taking into consideration the mechanical properties of rocky soils often occurs when designing structures for various purposes. The Requirements SP 24.13330.2011 “Pile foundations” in Appendix B (recommended) set out the calculation methodology of the combined effect of a horizontal force and torque of a single pile. The pile in this methodology is substituted by beam on an elastic foundation and the surrounding soil may be regarded as a linear-elastic deformable medium characterized by a coefficient of subgrade reaction. The manual for the design of pile foundations contains two calculation methods of piles for the combined effect of horizontal forces and torque (basic and tabular methods), which are based on considering the subgrade reaction on the side of a pile. Also this guide provides the guidance on calculation of single piles in rock under lateral loading. At the same time uniaxial compressive strength of intact rock is used as the main characteristics for rock massive. In general, the methods outlined in the manual are extensive explanation of the design methods with the examples of calculation, which is the development of the paragraph of the construction norms SNIP , which are now replaced by the actualized SP. In the analysis of the foreign experience of the design of drilled shafts in rock, there are three main groups of calculation methods of laterally loaded drilled shafts in rock: 1. Analytical methods based on the theory of elasticity; 2. Joint deformation of piles and soil with taking into account the non-linear subgrade reaction of soil (the so-called “p-y method”); 3. Numerical methods (FEM and DEM), which are implemented in a variety of special software computer systems. Among the first group of methods the following ones should be distinguished: Carter and Kulhawy (1992) and Zhang (2000). The “p-y” method was studied by Reese (1997). Poulos and Davis (1980) obtained solutions for piles using numerical methods. Randolph (1981) made a parametrical study of drilled shafts socketed into continuous elastic rock mass. The analysis of domestic and foreign calculation methods shows that there are no methods, which can be effectively applied both at the preliminary and detailed stage of the project. The majority of them require obtaining specific data, such as the coefficient of subgrade reaction along the length of the shaft or p-y deformation curves for a reliable estimation of shaft behavior in each case . However, today the materials on rock mechanics are accumulated and systematized, allowing to accurately enough determine the mechanical characteristics of the rock mass with a limited number of input data. Furthermore, the numerical modeling methods, having significant development and upgrading recently, can replace time-consuming and expensive field-testing. It is also worth considering that the numerical simulation can be effectively used on the stage of detailed calculations. In this preliminary study for the project design the use of numerical methods can be combined with the method of experimental design that allows getting the desired response function depending on several factors. Guided by this approach, the author carried out the study of the numerical models of laterally loaded drilled shafts in rock. Using 3D modeling and experimental design method the behavior of shafts was described depending on various factors. After processing of the results it is possible to obtain the parametric dependencies and nomograms. In this study, the parameters and the limits of their changes were chosen. In order to carry out the numerical experiment the matrix of experimental design was created that allows within the varied factors to obtain a mathematical relationship (response function) of bearing capacity of the shaft from three selected factors. The experiments and calculations allowed obtaining the dependence of bearing capacity of shaft from the set parameters: The checking of the adequacy of the equation shows the convergence of 2...9 % and it was conducted on the models with intermediate features within a selected factor space. The further processing and systematization of the obtained results is currently conducted, as well as the construction of nomograms after obtaining of parametric equations. The results of this study may be used for the preliminary assessment of the bearing capacity and deformation of laterally loaded drilled shafts in rocks. Using this technique it is also possible to reduce the number of field tests and increase their efficiency, reduce material consumption and the amount of shaft installation works, without decreasing of safety of the building.

The article describes the results of a comprehensive survey of the bridge structure in Dubna. The survey was performed to determine the load capacity and maintainability of the bridge structures for the period prior to the repair, as well as to collect the information necessary to update the draft decision and the right strategy of major repairs. The growing needs of the city Dubna, which several times increased the operational loading of the bridge structures, and no major repairs since the construction, led to the need of restricting the traffic capacity of the only transportation artery. By the time of the survey in November 2011, contraflow over the bridge and the restricted traffic of more than 8 t was organized, which resulted in tense atmosphere in the city.The authors studied the historical data and design features of the supporting structures of the bridge. Particular attention was paid to the state of load-bearing structures of the bridge and their deformability. The strength characteristics were studied. The authors analyzed the results of calculations in order to determine the carrying capacity of the bridge structures with the test loads. It turned out that the carrying capacity of the bridge is sufficient for load accommodation. However, in accordance with the regulations, the bridge does not meet modern requirements for the travel width. It was recommended to maintain contraflow and to provide operational loads of the class H-10 (i.e. platoons with GVW of 10 t and the presence of a single vehicle in a platoon with GVW of 13 t) until the major repairs. After major repairs with restoration of bearings, waterproofing, water disposal system, replacing the bed, repair of the protective layer, it will be possible for single vehicles weighing up to 25 t to pass over the bridge.

Interaction between long piles and the adjacent soil has a spatial and temporal nature. This phenomenon is based on a set of non-linear and rheological properties of soils. Distribution of lateral forces between the surface and the pile toe is heavily dependent on the above properties. The process of formation of the stress-strain state around the pile can demonstrate decaying, constant or progressive velocity depending on the rheological processes in the soil that may be accompanied by hardening and softening processes at one and the same time. These processes may be caused by destruction and restoration of ties between clay soil particles, soil compaction and de-compaction. Predominance of the process of hardening leads to damping, while predominance of the process of softening causes progressive destruction. Description of this multi-component process depends on the rheological model of the soil. This research is based on the modified rheological model originally designed by Maxwell. The authors consider solutions to the problem of quantification of the stressstrain state of soil around the pile and their interaction. This research makes it possible to project motion patterns of long piles over the time and evaluate the limit of their long-term bearing capacity.

The paper is an overview of nationwide testing results demonstrated by pulse-discharge technology piles exposed to the vertical load under conditions of soft soils of Tunis coastal area. Bored cast-in=place piles are constructed through the employment of the pulse-discharge technology (PDT). In the construction norms of France, PDT piles are classified as bored piles, which are cast-in-place using a hollow stem auger; they are reinforced, and their diameter exceeds 25 centimeters. PDT piles are made through the application of high pressure to the surrounding soil in the course of concreting.Photos of testing facilities are provided in the paper. Graphs of cyclic and experi- mental load testing of piles, complying with the values of design loads for a 10-storey building under construction, are analyzed. The findings obtained by the authors have proven a considerable growth of the PDT pile bearing capacity in comparison with the analytical solutions obtained in accordance with Russian and French construction norms and regulations. It is pointed out that the results of pressuremeter testing can be reason- ably used in calculations as stated in the French norms. Negligible pile settlements and the high value of the bearing capacity of piles prove the expediency of employment of this technology in the course of construction of piles in the soft soils of the Tunis shoreline. It is concluded that further elaboration of the PDT pile calculation technique is required.

Accurate and adequate description of external influences and of the bearing capacity of the structural material requires the employment of the probability theory methods. In this regard, the characteristic that describes the probability of failure-free operation is required. The characteristic of reliability means that the maximum stress caused by the action of the load will not exceed the bearing capacity.
In this paper, the author presents a solution to the problem of calculation of structures, namely, the identification of reliability of pre-set design parameters, in particular, cross-sectional dimensions. If the load distribution pattern is available, employment of the regularities of distributed functions make it possible to find the pattern of distribution of maximum stresses over the structure.
Similarly, we can proceed to the design of structures of pre-set rigidity, reliability and stability in the case of regular load distribution. We consider the element of design (a monolithic concrete slab), maximum stress which depends linearly on load . Within a pre-set period of time, the probability will not exceed the values according to the Poisson law.
The analysis demonstrates that the variability of the bearing capacity produces a stronger effect on relative sizes of cross sections of a slab than the variability of loads. It is therefore particularly important to reduce the coefficient of variation of the load capacity. One of the methods contemplates the truncation of the bearing capacity distribution by pre-culling the construction material.