Reinforcement Rods Research Articles

Анализ напряженно-деформированного состояния узловых соединений высотных зданий при учете климатических воздействий

Purpose: to analyze the design solutions of the junctions of floors with external walls in buildings erected using monolithic technology. To identify defects and damages that occur on facades and overlaps with perforations for thermal pads during construction and operation. To investigate by numerical methods the stress-strain state of the overlap disk at the junction with the outer wall, taking into account temperature influences. Materials and methods: the standard version of the nodal connection of a monolithic building of various storeys is considered. The fragment of the junction joint of the overlap disk with the wall was modeled in the Ansys and SCAD software complexes. The model consisted of an anisotropic material — concrete and reinforcement rods included in it. The behavior of the stress-strain state under various temperature influences was studied. Results: numerically, taking into account geometric parameters and temperature loads, the patterns affecting the nature of changes in the values of normal stresses in the characteristic sections of the perforated plate are revealed and the existing types of design solutions are evaluated. The locations of stress concentration zones and their impact on performance are determined. Practical significance: it is shown that the most dangerous cross-section in perforated discs of overlaps takes place at the key joints. It is determined that vulnerability in such compounds is caused by the influence of alternating cyclic temperatures. Patterns leading to an increase in normal stresses at stress concentration sites have been established. Fundamentally new design solutions have been proposed, protected by utility model patents, which allow to reduce stress values and thereby ensure higher performance in monolithic buildings, including high-rise ones.

Geometric modeling of blast waves reflected from the cylindrical surface of a sineusidal profile

A method is proposed for geometric modeling of a family of blast wave fronts reflected from a cylindrical surface of a sinusoidal profile. The model of “optical” reflection is adopted as a basis, when for each incident virtual explosive “ray” the angle of reflection is equal to the angle of incidence. To illustrate the graphic-analytical approach, a test model of the formation of a family of reflected wave fronts for a cylindrical parabolic surface has been developed. A cylindrical surface of a sinusoidal profile obtained by bending a rectangular metal sheet by longitudinal forces is considered. Geometric models of a family of blast wave fronts reflected from a cylindrical surface of a sinusoidal profile are described. Maple has been compiled – programs for visualizing models of a family of blast wave fronts reflected from a cylindrical surface. Conducted studies of sinusoidal cylindrical reflectors designed to demonstrate the effect of multiplying the effects of shock blast waves directed towards the fire zone. For their practical use, it is necessary to find the bending parameters of the cylinder such that the virtual beams of the “point” explosive are transformed into a system of beams that are close to parallel in the fire zone. As a result of the research, the parameters of bending of a metal rectangular sheet by longitudinal forces were calculated, and the coordinates of the location of the “point” explosive substance were determined. It is taken into account that cylindrical reflectors with a sinusoidal profile can be manufactured at the site of their use. To do this, a rectangular sheet of metal must be bent by longitudinal forces and the bend must be fixed by welding reinforcement rods. The research carried out is aimed at developing the technology of extinguishing forest fires with directed explosions.

Comparing the efficiency of strengthening timber beams reinforced with carbon composite rods and plates

This study reports the results of experiments comparing the effect of structural reinforcement for timber beams strengthened with different carbon composite materials. Samples of one series were strengthened by gluing a carbon fiber plate from the outside to the face of the beam. The samples of the other series were strengthened by laterally gluing two carbon fiber rods inside the beam. According to the bending research program, the ultimate loads and deflections were determined for both series. As a result of the analysis of the results and comparison with unreinforced samples from the control series, the effect of beam reinforcement and the model of their destruction were determined. Studies have shown that the effect of external reinforcement with a plate was 86.7 % according to the criterion of full failure load, 20.5 % according to the criterion of ultimate load, 13.4 % according to the criterion of ultimate deflection. The effect of rod reinforcement was 48.6 %, 18.6 %, and 4.1 %, respectively. The theoretical analysis of the results showed a convergence of up to 8.2 % with the experimental results. External reinforcement with a plate compared to lateral gluing of rods showed better results due to the placement of the plate in the zone of maximum tensile stresses. This arrangement more effectively limited the spread of ultimate stresses and the development of cracks. The reinforcement parameters of the samples (materials, placement, percentage of reinforcement) were selected under the condition of the same theoretically predicted bearing capacity after reinforcement. However, comparative experimental studies have revealed differences in the processes of deformation and destruction of reinforced beams. The results will contribute to making rational project decisions and for choosing a relevant technique of strengthening timber beams with carbon composite materials

Flexural Performance Study of Basalt-Fiber-Reinforced Polymer Bar Basalt-Fiber-Reinforced Concrete Beams

The utilization of Fiber-Reinforced Polymer (FRP) rods to strengthen concrete beam structures can enhance their ultimate load-carrying capacity and mitigate steel reinforcement corrosion damage. However, a prominent issue with BFRP (Basalt FRP) rod reinforcement in flexural members is its lack of yielding behavior, which can lead to catastrophic brittle failure without any preventive measures. Therefore, this study aims to enhance the ductility of concrete by introducing a specific quantity of basalt fiber, thereby reducing the hazards associated with the brittle failure of this composite structure. This experiment focuses on two main variables: the inclusion rate of basalt fiber and the type of longitudinal reinforcement and conducts four-point static bending tests on four BFRP bar BFRC (Basalt-Fiber-Reinforced Concrete) beams. Results showed that the inclusion of fibers resulted in a delayed initiation of vertical cracks and a reduction in the severity of beam failure, thereby enhancing structural safety and reliability. When the basalt fiber inclusion rate was 0.2%, the cracking load and ultimate load of the beam increased by 18.42% and 8.27%, respectively. Furthermore, compared to traditional RC beams, BFRP bar BFRC beams showed a 58.27% increase in ultimate load capacity. A cracking moment calculation model for BFRP beams is proposed and subsequently validated through the utilization of existing experimental data.

ИССЛЕДОВАНИЕ НАПРЯЖЕННО-ДЕФОРМИРОВАННОГО СОСТОЯНИЯ ПЕРЕМЫЧЕК ГАЗОБЕТОННЫХ СОСТАВНЫХ

In this paper, the authors study the stress-strain state of composite jumpers made of aerated concrete blocks with steel reinforcement rods and external composite reinforcement when working in bending. Rod reinforcement of jumpers is carried out by inserting steel reinforcing bars into the body of aerated concrete in the longitudinal and transverse directions. Composite reinforcement is performed with carbon fiber tapes in the stretched edge of the element over the entire width, as well as parts of tapes on the flange sides of the aerated concrete block at the vertical seam or in the center of the element. The test results are assessed by comparing the strength of the normal section and the deformability of aerated concrete bending jumpers, the effectiveness of gluing carbon fiber tapes and aerated concrete, and the optimal use of various types of reinforcement. It has been established that external composite reinforcement at a load of up to 60% of the breaking load reduces the deformability of aerated concrete bending elements due to an increase in flexural rigidity, and at a load of more than 60% due to a change in the design scheme. Jumpers with rod reinforcement have a brittle nature of destruction, while those with external composite reinforcement fail plastically. In general, the load-bearing capacity of composite aerated concrete jumpers reinforced with external composite reinforcement is sufficient to withstand operational loads

Rigidity of partially concreted steel beams and steelreinforced floors

The use of steel-reinforced (composite) floor structures with partially concreted steel beams and prefabricated flooring elements is an effective solution in terms of reducing the material consumption and increasing the structural rigidity. The experimental results of partially concreted composite beams and beams as part of full-size ceilings are studied and analyzed herein. It is shown that the stiffness graph of simple steel-reinforced concrete beams of any shape can be divided into 3 stages: an initial stiffness drop, normal operation, and transition to the limit state with subsequent destruction. The boundaries of these stages are identified for each beam type. The stiffness of the combined cross-section of the partially concreted beam with the rod reinforcement is calculated using well-known formulas from regulatory documents. The element rigidity without rod reinforcement is determined with the decreasing coefficient. Tests of full-size ceilings with partially concreted beams and prefabricated floors confirm the possibility of using standard formulas for the stiffness calculation. However, the width of the compressed concrete flange should be taken into account by less than 3 times than for monolithic slab. The destruction of bending composite structure is accompanied by plastic deformation in flanges of I-beam, destruction of compressed concrete and steel–concrete interaction. However, it does not lead to zeroing of its rigidity. When residual stiffness reaches the ultimate strength state, it is at least 60–70 % of its normative value. This rigidity can be used for the progressive collapse analysis of buildings.

Application of a Nonlinear Deformation Model to the Analysis of Complete Moment-Curvature Diagrams of Reinforced Concrete Elements with Reinforcement A500

This article suggests a calculation procedure for the parameters of complete moment-curvature deformation diagrams with a down leg that can be used for the calculations of the multistorey monolithic building frameworks taking into account the specifics of reinforced concrete. To construct complete deformation diagrams for bending elements, a non-linear deformation model is used that is based on using the physical diagrams of the concrete and reinforcements to calculate the inner moments of cross-sections at all loading stages via balance and strain compatibility equations. Using this model, the authors researched complete moment-curvature deformation diagrams for the elements with different percentages of longitudinal tensile reinforcement that changes the bending properties of the structure. We used grade А500 steel as the reinforcement. The parameters of the tensile reinforcement diagram were determined in the tension testing of samples with constant deformation rates. The performed computer tests to calculate the moment-curvature diagram parameters for reinforced concrete beams reinforced with grade А500 efficiency rods and conventional grade A400 reinforcement rods with different longitudinal reinforcement congestion rates helped the authors assess the bending properties of the elements under conditions approaching their destruction and determine their efficient use in the calculations of building frameworks taking into account the redistribution of forces.

USE OF MAGNETIC NON-DESTRUCTIVE TESTING TO EVALUATE THICKNESS OF CONCRETE PROTECTIVE LAYER FOR ENCLOSING AND BEARING STRUCTURES AT NPP

Introduction. This article discusses methods and means of controlling the diameter and position of reinforcement and the thickness of the concrete protective layer, along with the contemporary techniques and devices for diagnostic and non-destructive testing of concrete. A comparative analysis of the applicability of contemporary devices was carried out.Aim. In this work, magnetic non-destructive testing was used to assess the thickness of the concrete protective layer, along with establishing the location of the upper row of rod reinforcement and embedded parts. Based on analyzing the interaction between the electromagnetic field of the sensor and the electromagnetic field of eddy currents induced by the source coil of the sensor in rebar, this method allows the diameter of the latter to be approximately estimated at an unknown protective layer.Materials and methods. As an example, the thickness of the concrete protective layer of enclosing structures (walls, floors) at power unit № 1 at the Kalinin Nuclear Power Plant (NPP) was measured using the POISK-2.6 device.Results. The analysis of design and as-built drawings for buildings and structures of the main facility of power unit № 1 at the Kalinin NPP was carried out. The state of passive fire protection equipment at the power unit (fire doors, cable penetration seals, and ventilation fire dampers) was evaluated. The actual thickness of the concrete protective layer and the location of the reinforcement of concrete elements at the facilities of the Kalinin NPP power unit were measured as per GOST 22904-93 using electromagnetic NDT. The applicability of the magnetic NDT for determining the thickness of the concrete protective layer was shown during the inspection of building structures.Conclusions. During the inspection of the facilities, it was established that the average thicknesses of the concrete protective layer, including the thickness of the reinforcement, range from 38 to 85 mm, with the diameter of the reinforcement of 12–20 mm. During the measurements, the applicability of the method was shown; it was also confirmed that the examined structures exhibit fire endurance of at least 90 minutes, which meets the requirements of regulatory documents.

Инновационное армирование фундамента резервуара

The article considers the causes of defects and accidents of reservoirs, identifies the problems of uneven precipitation of the foundation. The analysis of the perception of external loads of the reinforced concrete structure is carried out, the disadvantages of horizontal reinforcement are revealed. A scheme of combined reinforcement of reinforced concrete consisting of horizontal and curved reinforcement rods is proposed, and an analysis of economic efficiency in the operation of a tank with an innovative scheme of reinforcement of the foundation is also carried out.

Analytical calculation of bending elements with basalt fiber and glass composite rod reinforcement under short-term dynamic loading

During the construction and operation of buildings and structures, in addition to static loads, short-term dynamic impacts may occur on building structures and their elements caused by explosions, accidents, etc. As a result, damage or destruction of structures may occur, which leads to possible loss of life and significant material losses. Taking into account the influence of such impacts on the load-bearing capacity of building structures is relevant. A significant number of works by domestic and foreign authors are devoted to methods for calculating bending reinforced concrete elements under static and short-term dynamic loading. In the overwhelming majority, bendable concrete elements with steel rod and/or fiber reinforcement are considered as the object of research. The issues of predicting and assessing the stress-strain state of bending concrete elements reinforced with glass-composite reinforcement and/or basalt fiber under short-term dynamic loading have not been sufficiently studied. The current building codes consider calculations of such elements only under the action of static loads.

Peculiarities of the condition of the foundation slab of the pumped storage power plant water intake

The authors present the results of the analysis of field observations of the condition of the base slab of the water intake structure of hydroelectric power plant (including the stresses in the reinforcement in the areas of intersection with the vertical joints and the width of the opening of these joints). The aim of the study is to control the condition of the reinforced concrete structure of the foundation slab of the water inlet of the hydroelectric power plant, as well as to develop measures to strengthen the bottom section of the foundation slab in the areas of vertical interblock joints. In order to control the stress and strain of the base plate of the water intake of hydroelectric power plant, string control and measuring equipment was installed: on reinforcement rods - reinforcement dynamometers PSAS, on vertical interblock joints - displacement sensors PLPS. The field observations of the stress state of the reinforcement of the base slab of the water intake structure of hydroelectric power station showed that high values of tensile stresses, exceeding the design resistance of A500C class reinforcement (435 MPa), occurred in the reinforcement rods (directed along the flow), crossing the lower vertical interblock joints. There was also fixed the width of opening of the vertical interblock joint, reaching 1.28 mm. There was a necessity to strengthen the lower section of the foundation slab of the water intake structure of hydroelectric pumped storage power plant. For this purpose, inclined reinforcing bars (anchors) crossing the lower vertical interblock joints were installed. The outlet sections of the buttresses of the slab of the downstream section of the inlet to the downstream parapet were increased.

Comparative study of finite element methods of calculation of ribbed reinforced concrete floors

The paper presents the results of a comparative study of several finite element models of ribbed reinforced concrete solid floors. Using the example of a solid slab with infrequent ribs arranged along a grid of columns, three models frequently used in computational practice are analyzed. Those models include both rods and thin-walled elements. In the first model, the plate and its ribs are considered separately, within the framework of the decomposition scheme of the structure. The second model contains plate finite elements and the rod finite elements of the ribs connected to each other. The third model consists entirely of thin-walled finite elements that model both the plate and the floor ribs. The ribbed floor is also considered in the formulation of the problem within the framework of the theory of elasticity. The floor is represented in the form of rigidly connected solid bodies of ribs and plates. Reinforcement rods inside the concrete massive are included in the model as separate solid bodies. This model serves as a benchmark for assessing the accuracy of the obtained results. Its calculation is performed in the FEM application Ansys. The paper compares the results of calculations performed using various models. A conclusion is made about the accuracy of the obtained results. A significant difference between the proposed work and similar studies devoted to the selection of the best design schemes of ribbed slab of floor is the consideration of the influence of reinforcement on the behavior of the structure.

Characterizing the bond properties of automatically placed helical reinforcement in 3D printed concrete

The incompatibility of 3D concrete printing (3DCP) with conventional reinforcement methods is well known. Recently, solutions have suggested the insertion of helical reinforcement rods through a screwing motion into the freshly printed material. The current study focuses on the bond properties of such reinforcement and its relation to placement time relative to the 3D printed concrete age, of which until now hardly any data exists. Confined pull-out tests and micro-computed tomography (μCT) scans were performed to characterize the time-dependent bond properties for automatically placed screw-type reinforcement in 3D printed concrete in the range of 0–200 min after material deposition. An experimental program was carried out using a gantry type 3D concrete printer and a robotic hand with the Automated Screwing Device to automate the reinforcement placement process. In total 200 specimens were produced and tested in pull-out. μCT scans were done on the specimens to quantify air content in the vicinity of the reinforcement, for every other time stamp. Two different screw geometries were used. A high mechanical interlock was achieved resulting in a high bond strength in confined pull-out tests. It was concluded from the confined pull-out tests that the pull-out performance is not influenced significantly by the time of application after mortar deposition in a time frame of up to 200 min. This firmly positions automatically applied helical reinforcement as a viable method to reinforce 3DCP structures.

THE DETERMINATION OF PARAMETERS OF COMBINED REINFORCEMENT OF STRETCHED AND BENDING REINFORCED CONCRETE ELEMENTS WITH THE SPECIFIC CRACK RESISTANCE

Recently, there has been an increase in the use of reinforced concrete structures withcombined reinforcement in construction, which makes it possible to increase the resistance of suchstructures to deformation and cracking. Dispersed reinforced concrete was used to cover roads, flooring in industrial buildings, the manufacture of curbs and more. For the construction of publicand industrial buildings, the use of combined reinforced structures has not been widely used, as noperfect method of their calculation has been developed.Combined reinforcement structures include concrete structures that are reinforced with steelrods and steel fiber, which is randomly arranged in the mass of concrete. The strength of reinforcedconcrete depends on such factors as: the strength of concrete, reinforcement with rod reinforcement,the type of fiber and its characteristics, the volume of fiber per unit volume of concrete, the size ofthe cross section of the elements. These factors affect the tensile strength of reinforced concrete bothdirectly and by their interaction. Therefore, determining the effective parameters of dispersedconcrete reinforcement is a complex multivariate task, its solution is proposed to be achieved byperforming mathematically planned experiments.When choosing the parameters of dispersed reinforcement of centrally stretched and bendingreinforced concrete elements (lower truss belt, arch tightening, cylindrical tank wall, beams, slabs),it is advisable to choose the strength of concrete fck, fiber length lf and volume dispersion coefficient.The optimal choice of values of these parameters is proposed to be performed using quadraticregression equations, which are based on the results of three-factor three-level mathematicallyplanned experiments, which are based on the matrix of the Box-Behnken plan.The obtained mathematical models make it possible to analyze the influence of dispersereinforcement parameters on crack formation forces in combined reinforced concrete elements andto determine their optimal values. The use of combined reinforcement allows increasing the crackresistance of reinforced concrete elements in two or more times.

СИЛОВОЕ СОПРОТИВЛЕНИЕ ЖЕЛЕЗОБЕТОННЫХ КАРКАСОВ МНОГОЭТАЖНЫХ ЗДАНИЙ С КОСВЕННЫМ АРМИРОВАНИЕМ В ЗАПРЕДЕЛЬНЫХ СОСТОЯНИЯХ

The results of studies of monolithic reinforced concrete frames of multi-storey buildings and reinforced concrete frames simulating fragments of such frames in over-extreme limit states caused by special actions are presented. Two options for reinforcing the beams of the frames are considered: with double reinforcement, which ensures the operation of the beam when the force flows in the frame and, accordingly, the sign of the moment change; option with double reinforcement and installation of additional indirect reinforcement in the support zones of the beams for the entire height of the section. Primary and secondary design models were built using volumetric finite elements for concrete and reinforcement rods. The obtained design parameters of deformations, crack patterns and frame failure patterns for all options are compared with each other and with the results of testing physical models of these structures. To assess the effect of mixed reinforcement on the limiting deformations of compressed concrete in over-extreme limit states, based on the theory of plasticity of concrete and reinforced concrete G.A. Geniyeva, deformation dependencies are constructed for a typical reinforced concrete element reinforced with rods in one direction and meshes in the other two under uniaxial compression and volumetric deformation. It has been established that the use of indirect reinforcement in combination with double longitudinal reinforcement in bending elements under static-dynamic loading conditions significantly increases the ultimate deformation of the compressed zone. This reinforcement option can working way to protect monolithic reinforced concrete frames of multi-storey buildings from progressive collapse under special actions.

Experimental behaviour of FRP reinforced concrete structural elements

Reinforced concrete structures form a major part of the Engineering infrastructures of all developed countries and their integrity over long periods of service is of vital economic importance. However, there are a number of factors that can endanger the serviceability of reinforced concrete structures. These factors result in high maintenance costs (or) the early replacement of structures. The most widespread problem of premature deterioration is caused by deterioration of steel reinforcement. Corrosion induced deterioration of steel reinforcement in concrete has increasingly become a major problem use of non-metallic reinforcement such as GFRP (Glass Fibre Reinforced Polymer) rebars helps to rise the mechanical characteristics of concrete structure as it does not corrode. The GFRP rebars look like steel with similar, properties such as high tensile strength and bond characteristics. The key aim of this project is to replace the steel reinforcement by using GFRP rebars in concrete structural elements and to find the load carrying capacity etc., and comparing with the test results of the experiment carried out on the same size of beams with use of GFRP and tor steel as reinforcement. Reinforcement rod 8 mm size 3 at bottom and 2 at top is placed with stirrup spacing of 100 mm c/c. Load applied in 3 Kn variation and 7 cycles of load was applied. Load carrying capacity was good at 0.1 % GFRP addition.

Раціональне використання несучої здатності сталевих профільованих листів незнімної опалубки сталезалізобетонних перекриттів

Building structures effective design should ensure uniform strength of all building load-bearing elements. Steel-reinforced concrete structures are made both during new construction and during the reconstruction of buildings or structures by a successful combination of steel, mainly rod elements, and monolithic concrete. Quite often, in order to increase the manufacturability of such floors installing and reduce the construction time, a monolithic reinforced concrete slab is arranged on a fixed formwork made of profiled flooring. To include a profiled sheet in compatible work with a monolithic slab, anchoring means are provided: protrusions on the sheets surface, rod reinforcement, etc. However, due to the usually equal pitch of the profiled sheets (steel beams) supports, they are unevenly stressed. On the basis of the conducted theoretical analysis, 6 slabs 6 m long, 1.06 m wide and 0.53 m made of K35-0.5 steel profiled flooring were designed, manufactured and tested according to a continuous three-span scheme, as a fixed formwork for monolithic steel-reinforced concrete floors. The samples were loaded with bricks. To measure deflections during sample loading, watch-type indicators with a division value of 0.01 mm were used. To measure strain electro tensile resistors were used. An analysis of supports installation variable step influence, as one of the methods of these floors load-bearing capacity use level balancing was carried out. It has been experimentally confirmed that when equalizing the values of the span or support bending moments (at the same time, the support moments are twice as large as the span), as well as deflections, the lengths of the extreme spans should be 25% less than the central spans.

BIM Structural Project Applied in A Case Study: Interoperability Analyses, Reinforcement Detailing Drawings and Quantity Take-off

Background: The Building Information Modelling (BIM) methodology has been acquiring, worldwide, a growing acceptance in all sectors of the Construction industry, and the study intends to contribute to its implementation within the structural design. The fundamental concept of BIM is based on the generation of a centralized virtual model with all information concerning different specialties. This is supported in efficient interoperability, but within the structural design, this aspect is difficult to achieve completely, as currently, the interoperability of this system is still inefficient. Introduction: This study intends to analyze the degree of interoperability verified in the development of all the processes (modelling, transposition, structural analyses and reinforcement detailing) involved in a structural design using BIM tools. Methods: A structural project concerning a study case was performed in order to identify benefits and limitations, based on the consistency analysis of the transposed data between systems, Revit and Robot, in all steps required in a BIM process. This text describes the stages of modelling, checking the suitability of the analytical model, its transference to the analysis tool in order to proceed with the structural calculations and detailing drawings and, finally, the transfer of drawings to the main BIM model. Results: The limitations verified in the last stage were partially surpassed with complementary work enabling the automatic transfer of drawings and quantities of materials. In addition, the study explores new capacities of BIM, namely, the extraction of information allowing the presentation of specific drawings and maps of the geometry of the reinforcement rods. Conclusion: This study identifies a working strategy that leads to an appropriate use of BIM software contributing to the optimization of labor in a structural office.

Experimental-theoretical studies of hydrotechnical angular-type retaining walls

Relevance. Retaining walls are common structures that are part of waterworks. They have the characteristic features of hydraulic structures, such as large dimensions, low percentages of reinforcement (up to 1.0%), horizontal interblock joints. The listed features determine the nature of the work and the stress-strain state of the retaining walls. The main loads on the rear faces of the retaining walls are loads from the action of the backfill soil. The incomplete consideration of the design features and the nature of the loads action in the design of a number of retaining walls that are in the stage of long-term operation has caused the need to strengthen them. One of the reinforcement methods was to install reinforcement rods in drilled inclined holes in the zones of horizontal interblock joints. It was necessary to conduct experimental studies of reinforced concrete retaining walls under the action of various loads, in particular conside- ring the reinforcement by inclined rods. The aim of the experimental research was to study the effect of variable load on the stress-strain state of these structures, among others with due regard to inclined reinforcement installed in the zones of horizontal interblock joints. When solving the set tasks, proven experimental methods of researching reinforced concrete structures of hydrotechnical structures were used. Results. Experimental data from the study of models of retaining walls, including those with reinforcement by inclined reinforcement, at different locations of the resultant load on rear faces of models were obtained. An experimental substantiation of the reinforcement of reinforced concrete structures of retaining walls with an inclined reinforcement crossing horizontal construction joints has been carried out.

A Study on the Adhesion in the Interfacial Transition Zone Between Glass Fibre Reinforced Rebar and the Cement Matrix

This study is aimed at increasing the adhesion of the fibre-reinforced polymer rods to the binder in the cement-based composites in order to eliminate the problem of rod slippage under loading and broaden the application of composite reinforcement in the construction industry. It is assumed that the better adhesion of reinforcement rod to the cement matrix can be provided by increasing the cement stone structural density, and, in particular, by compacting the structure of the hydration products formed on the surface the fibre-reinforced polymer reinforcement rod. Such increase in strength and density can be achieved by adding nanodispersed additives such as metakaolin, the dispersion of carbon black and Peneco Nano Stachema primer into the composition of the cement matrix. Additional adhesion of the cement matrix to the reinforcement is ensured by coating it with the primer, which seals the structure of the cement matrix located in the interfacial transition zone between the reinforcing bar and the cement stone. Experimental study proved that the proposed approach allows the formation of a strong and dense structure in the interfacial transition zone between the cement matrix and the fibre-reinforced polymer reinforcement rod surface. The introduction of metakaolin and a dispersion of technical soot led to an increase in the adhesion strength of fibre-reinforced polymer rod with a cement matrix by 27% and 29%, respectively. The IR spectral analysis and DTA analysis results showed that the mineralogy and morphology of the hydration products was changed due to the addition of the modifying additives, thus improving the adhesion characteristics and corrosion resistance of fibre- reinforced polymer in the cement-based composites.