Method of Experimental Research of New Construction of Beams from Glued Wood with Combined Reinforcement

Structures of glued wood have significant advantages in comparison with structures made of metal or reinforced concrete (less mass, better resistance to the action of chemically aggressive environments, high fire resistance, aesthetic attractiveness, eco-friendliness). However, at the same time, scientists are looking for new ways to improve the characteristics of such wood. We also proposed a new construction of combined reinforcement of glued beams in which the steel bar reinforcement of the periodic profile was arranged in the grooves of the compressed zone, and in the stretched zone reinforcement was carried out with the external composite tape made of carbon fiber. This combination increases both rigidity and bearing capacity of the elements that we are testing from glued wood for work on transverse bending. The method of experimental research on the transverse bend of a new construction of glued beam beams with combined reinforcement was developed. The proposed method fully allows us to examine and experimentally investigate the stress-strain state under load of glued beams from combined reinforcement at different stages of their work.

Influence of the percentage of reinforcement by unstressed rebar on the deformability of pre-stressed RC beams

This article presents the materials of deformability studies of pre-stressed steel-concrete beams reinforced with a package of reinforcement with different ratio of tape and rebar in the pure bending moment zone. The aim of the research was determination of the reinforcement percentage influence, for pre-stressed reinforced concrete beams reinforced with a package of reinforcement on their deformability. Also, the aim was to evaluate the effectiveness of using pre-stressed rebar in combined reinforcement. The practical significance of the experimental research is to study the deformability in pre-stressed bending elements with external tape and rebar reinforcement, taking into account the influence of different ratios of reinforcement areas within the combined reinforcement and development of proposals for such structures` calculation and design. The scientific novelty of the research is in obtaining the deformability characteristics of reinforced concrete beams reinforced with a package of reinforcement (tape and steel bars with periodic profile) with different ratios in the case of static loads` action.

EXPERIMENTAL STUDIES OF THE FATIGUE STRENGTH OF A500 CLASS REINFORCEMENT WITH VARIOUS TYPES OF PERIODIC PROFILE

The article presents the results of studies of the fatigue strength of A500 class reinforcement by GOST 34028-2016 with various types of periodic profile. The data on the results of previously conducted experimental studies of the fatigue strength of various types of reinforcement are generalized and systematized, and the main factors affecting fatigue are established. Experimental data on strength and deformation characteristics under static and high-cycle loads of A500C class reinforcement with various types of periodic profile have been obtained. Based on the research results, proposals were made to improve the characteristics of the reinforcement and the periodic profile to increase its resistance to repeated cyclic loads and to amend the current regulatory documents. Вестник НИЦ «Строительство» • 3(30)2021 101 Ключевые слова: Арматура, периодический профиль арма- туры, предел выносливости, усталостная прочность

Serrated Chip Formation Induced Periodic Distribution of Morphological and Physical Characteristics in Machined Surface During High-Speed Machining of Ti6Al4V

Difficult-to-cut materials are widely used in aerospace and other industries. Titanium alloys are the most popular ones among them due to their high strength-to-weight ratio and high temperature resistance. However, in high-speed machining, the alloys are prone to produce serrated chips, which have a serious influence on surface integrity. In this study, a coupled Eulerian–Lagrangian method is used to simulate the orthogonal cutting of Ti6Al4V due to its advantages of avoiding element distortion and improving the data extraction efficiency. The internal relationship between serrated chip formation and periodic profile of machined surfaces is analyzed by the simulation results and experimental data which are obtained by optical microscope and white light interferometer. Furthermore, thermal–mechanical loads on machined surfaces are reconstructed based on the simulation results, and a coupled finite element and cellular automata approach is used to describe the dynamic recrystallization process within the area of the machined surface during the formation of a single serration. According to the results, the periodic fluctuation of cutting forces is attributed to the serrated chip formation phenomenon, which then leads to the periodic profile of machined surfaces. The period is about 60–70 µm, and its amplitude decreases with the increase of cutting speeds. Moreover, the loads on machined surfaces also show the same period due to serrated chip formation. As a result, the grain refinement layer thickness (about 2 ∼ 5 µm) in machined surfaces is related to the surface temperature and exhibits the same periodic characteristics along the cutting direction.

ABOUT CONDITIONS OF RECEIVING HIGH-STRENGTH COLD-DEFORMED REINFORCEMENT WITH USING OF NON-DRIVING ROLLING STAND

The energy-power parameters of applying a periodic profile to a remaking bars are determined. For the considered sizes of calibers, the maximum value of the forces acting on the rollers, as well as the values of the required pulling force, are established. The influence of the depth of dents of the profile on the bearing capacity of high-strength reinforcing steel is studied. It was experimentally established that after applying the profile and stabilization, the loss of the bearing cross section of reinforcing steel by 5.0 % is compensated by an increase in Rm and R0.2. The proposed methodological approach based on the modeling of the technological process and the assessment of the complex of its parameters allows you to design equipment for profiling the remaking bars, integrated into the common line of the stabilization section together with the pulling device.

Research of non-metal composite basalt reinforcement of periodic profile and prospects of its use

Introduction. The results of research of physical and mechanical characteristics of non-metallic composite basalt reinforcement obtained by researchers, in particular, the shear strength of basalt reinforcement, coupling of basalt reinforcement to concrete, leaching of basalt fiber, durability of structures reinforced with non-metallic composite basalt reinforcement.Problem Statement. In the road industry, the main part of the costs for repair and restoration of reinforced concrete structures of bridges and overpasses is associated with corrosion of metal reinforcement. The use of non-metallic armature is a promising fundamental solution to this problem. Technical characteristics allow to apply basalt armature for road construction, at strengthening of bridges, for enclosing designs, in the designs which are exposed to aggressive environments.The effect of the use of basalt reinforcement is obtained, in particular, from reducing the cost of construction through the use of reinforcement of smaller diameter (hereinafter Ø) compared to metal while providing the necessary strength characteristics, reducing the weight of structures with such reinforcement. Also, due to the absence of certain types of corrosion of the armature during operation, the durability of the structure increases, reduce or eliminate certain types of repair work.However, the use of non-metallic composite basalt reinforcement of periodic profile, made of basalt fibers, designed for reinforcement of concrete structures of transport structures, is constrained by the lack of a sufficient number of research results of the characteristics of such reinforcement. On the basis of such researches it will be necessary, further, to make changes in norms on designing, standards on test methods, etc.Purpose. Investigate the armature of one of the main manufacturers, which were manufactured at the time of the study in Ukraine. Determine the geometric dimensions, mass, color, temporary resistance, elongation after rupture of the basalt reinforcement of the periodic profile with a diameter of 6 mm, 10 mm. To process the results of tests of physical and mechanical characteristics of non-metallic composite basalt reinforcement of periodic profile with a diameter of 6 mm, 10 mm, analysis of test results. Develop, based on the conclusions of the analysis of test results, proposals for the requirements for non-metallic composite basalt reinforcement for public transport structures.Materials and methods. Experimental studies of physical and mechanical characteristics of basalt reinforcement of periodic profile type A, nominal diameter 6 mm, 10 mm, manufactured according to TU U V.2.7-25.2-34323267-001, in particular, the curvature of the bar, surface quality, color of reinforcement, inner diameter reinforcement, temporary resistance, elongation after breaking.Results. As a result of researches it is established that curvature of a bar, quality of a surface, color of armature correspond to TU U V.2.7-25.2-34323267-001. The inner diameter of the valve, for individualbars, exceeds the permissible deviations within 0.3 mm in accordance with TU U V.2.7-25.2-34323267-001, DSTU B V.2.7-312:2016. However, as a result of the analysis of the obtained mechanical characteristics it was found that such deviations do not significantly affect the values of the mechanical characteristics of the tested samples (they are not less than necessary).However, in the future, when using basalt reinforcement, it is necessary to check such reinforcement for compliance with the requirements of DSTU B B.2.7-312:2016 and compliance must be ensured.Determined for basalt reinforcement temporary resistance, elongation after breaking, respectively: for Ø 6 mm ― 1 105 MPa and 2,13 %; for Ø 10 mm ― 1 068 MPa and 2,10 %.Conclusions1. Analysis of research on non-metallic composite reinforcement has shown that in recent years, scientists have paid considerable attention to reinforcement, as they see the prospect of its widespread use in the future. Studies of basalt reinforcement have shown that it has high strength, low density, has sufficient resistance to alkaline environment.2. As a result of researches of armature with a diameter of 6 mm and 10 mm it is established that curvature of a bar, quality of a surface, color of armature correspond to TU U V.2.7-25.2-34323267-001, DSTU B V.2.7-312:2016. The inner diameter of the valve, for individual bars, exceeds the permissible deviations within 0.3 mm (according to TU U V.2.7-25.2-34323267-001 and DSTU B B.2.7-312:2016). However, as a result of the analysis of the obtained mechanical characteristics it was found that such deviations do not significantly affect the values of the mechanical characteristics of the tested samples (they are not less than necessary). However, in the future, when using basalt reinforcement, it is necessary to check such reinforcement for compliance with the requirements of DSTU B V.2.7-312:2016 and compliance must be ensured.3. Defined for basalt reinforcement temporary resistance, elongation after breaking, respectively: for Ø 6 mm ― 1105 MPa and 2,13 %; for Ø 10 mm ― 1068 MPa and 2,10 %.4. The strain corresponding to the maximum static tensile load (Pmax) before the failure of basalt reinforcement samples was set when testing the reinforcement sample Ø 6 mm and is near 1153 MPa, which corresponds to the tensile strength of high-strength steel reinforcement class A-1000. The relative elongation of the basalt reinforcement δ is in the range from 2,0 % to 2,3 %, and is proportional to the δof the reinforcement A-1000, which is equal to 2,0 %.5. The results of tests for static loads show high performance characteristics of basalt reinforcement Ø 6 mm and Ø 10 mm, which is a prerequisite for the use of the tested reinforcement in the construction of transport facilities.Keywords:reinforcement, basalt, basaltoplastic, test, diameter, research, bridge, periodic profile, size, series, transport structure, characteristic.

Deformation steel rods periodic profile with operational damages

Introduction. In the transverse and longitudinal sections of the rods with a periodic profile, there are layers with different structural and phase states, physical and mechanical characteristics, stress state and resistance to external influences. The appearance of plastic deformations in the bases of the depressions and other defects of a periodic profile during stre­tching of the rods leads to a decrease in the resistance to corrosion damage due to the occurrence of galvanic pairs between inhomogeneous sections of the rod. This makes the computational and experimental studies of the deformed state of such rods under tension urgent. Materials and methods. The finite element modeling of the deformation process during the elastic-plastic work of steel was carried out using the ANSYS software complex and solid models of the rods under study. Experimental tests of the samples were carried out using an R-50 tensile testing machine with the recording of a load-elongation diagram in accordance with the requirements of GOST 1497. The process of deformation of the samples was displayed by photographic recording. After the destruction of the samples, the geometric dimensions (lengths, changes in cross-sections) were measured, the typical types of samples and their fragments, and fractures were photographed. Results. On experimental and finite-element models, it was found that during elastic-plastic deformation of steel rods in dangerous sections, a change in the angle of inclination of the banks of periodic protrusions (undercuts) affects the volume of plastically deformable material at the base of the undercuts. Such an analysis of the models in the limiting state has shown that the volume of the plastically deformed material is significantly reduced at the angles of the protrusions at their bases with the axis of the rod close to 900. The calculation established that the plastically deformed area at the base of sharp undercuts is more than a hundred times smaller than the corresponding volume at the base of the gently sloping undercuts. In samples with a group of protrusions, constraint of plastic deformations at the base occurs only for protrusions, the width of which is comparable to the diameter of the rod in weakened sections. The greatest development of equivalent plastic deformations is observed at the base between narrow projections. Damage to the outer layers of quasi-composite rods with a periodic profile causes significant changes in the stress-strain state of the rods under tension. Conclusions. The finite element modeling of the tensile work of steel rods with a periodic profile with a quasi-composite structure is a complex multifactorial problem. Plastic deformations develop in the depressions of the periodic profile. At the same time, undeformed areas remain in the metal of the protrusions. These zones have different potentials and between them the occurrence of internal galvanic currents is possible, leading to the acceleration of corrosion processes.

Grips for testing of chemical (adhesive) anchors with periodic profile rebar

Современные приборы для испытаний на «вырыв» не комплектуются специальными захватами для связей и арматуры периодического профиля. Предложен новый тип захвата для испытаний муфта-захват. Проведены лабораторные испытания химических анкеров с арматурой периодического профиля с применением новых типов захватов (муфт-захватов). Выполнен сравнительный анализ полученных результатов испытаний анкеров с применением четырех типов захватов. Сформулированы предложения по применению захватов при проведении натурных испытаний на объекте и в лабораторных условиях.

Influence of mechanical correction on the geometric and mechanical properties of cold-formed periodic profile fittings

The article describes the process of mechanical correction of cold-formed fittings produced in coils on industrial rightsized cutting machines of rotary and roller types. The main qualitative characteristics of the reinforcement are given, such as: ultimate tensile strength, offset yield stress, the ratio of ultimate tensile strength offset yield stress, conditional yield strength, total elongation at maximum load and the relative area of crumpling. To assess the effect of mechanical correction on the properties of cold-formed periodic profile fittings, statistical data is used for testing samples of fittings produced in coils and straightened before manual testing and samples of the same fittings transferred from consumer companies after mechanical correction on right-sized rotary type cut machines.Tensile testing of samples was performed on testing machines in the laboratory of physical and mechanical tests No. 3 of the OJSC «BSW – Management Company of the Holding «BMC» in accordance with the requirements of ISO 15630-1:2010 «Steel for concrete reinforcement and pre-stressing. Test method. Part 1. Reinforcing rods, wire rod and wire» and ISO 6892:2016 «Metal Materials. Tensile test. Part 1. Method of test at ambient room temperature».

Deformability of Glued Laminated Beams with Combined Reinforcement

Wood is one of the most popular renewable natural materials. Nowadays, raw wood is hardly ever used in the construction industry. It has been substituted by glued laminated wood that is processed with the use of high-tech methods, thus eliminating the principal flaws and defects of the natural material. The deformability of glued laminated beams with combined reinforcement has been studied, under which the steel reinforcement of the periodic profile was placed in the dappings of the upper compressed zone, while ribbon-reinforced composite was glued to the bottom of the stretched zone. The graphical charts for the layer change of the deformations of wood, steel, and composite reinforcement from the beginning of the loading application to the moment of destruction are presented.