scholarly journals Stress-deformed state of proof areas of reinforced concrete beams

2021 ◽  
Vol 2 (92) ◽  
pp. 32
Author(s):  
Stepan Neutov ◽  
Zlata Holovata ◽  
Daria Kirichenko
Keyword(s):  
Concrete Beams ◽  
Experimental Studies ◽  
Breaking Load ◽  
Load Level ◽  
Reinforced Concrete Beams ◽  
Longitudinal Reinforcement ◽  
Shear Span ◽  
Long Acting ◽  
Inclined Cracks

Abstract. The results of experimental studies of the stress-strain state of the support sections of rein-forced concrete beams from some of the most signifi-cant factors are presented. It was found that during long-term loading such factors are the level of the initial loading; concrete class; the percentage of transverse reinforcement in the shear span; the per-centage of longitudinal reinforcement in the com-pressed zone; the percentage of longitudinal working reinforcement in the extended zone. With an increase in the class of concrete, the moment corresponding to the appearance of normal cracks and the shear force corresponding to the appearance of inclined cracks slightly increase, although they lag behind the growth of the class of concrete. The process of crack-ing in the investigated beams begins, as a rule, with the appearance of normal cracks in the zone of pure bending at a load level (0.15... 0.33) from breaking. Inclined cracks appeared somewhat later, at load levels close to 0.5 of breaking. With a relatively high percentage of longitudinal reinforcement, the first oblique cracks appeared in the middle of the beam height in the shear span. At load levels close to 0.7, the process of formation of new cracks practically stops, and already existing cracks open more inten-sively. During the period of exposure to a constant long-term load, the width of the opening of normal cracks increased on average by 1.2–1.5 times, and the width of the opening of inclined cracks increased by 2.5–3 times. In the process of loading before the destruction of previously long-loaded beams, the width of the opening of normal cracks remained practically unchanged, and the width of the opening of inclined cracks increased by 1.2–1.7 times, and the breaking load for beams loaded with a preliminary long-acting load of 0.85 from the breaking load in-creased by 13–15 % compared to short-term loading. The opening width of inclined cracks along the length was different, its maximum value was ob-served in the middle of the height of the section of the support sections of the beams.

scholarly journals ЭКСПЕРИМЕНТАЛЬНОЕ И ТЕОРЕТИЧЕСКОЕ ИССЛЕДОВАНИЕ НАПРЯЖЕННО-ДЕФОРМИРОВАННОГО СОСТОЯНИЯ И НЕСУЩЕЙ СПОСОБНОСТИ НАКЛОННЫХ СЕЧЕНИЙ ПОВРЕЖДЕННЫХ ЖЕЛЕЗОБЕТОННЫХ БАЛОК ПРЯМОУГОЛЬНОГО СЕЧЕНИЯ

2019 ◽  
Author(s):  
Ye. Klymenko ◽  
K. Polianskyi
Keyword(s):  
Bearing Capacity ◽  
Concrete Beams ◽  
Experimental Studies ◽  
Reinforced Concrete Beams ◽  
Transverse Reinforcement ◽  
Longitudinal Reinforcement ◽  
Concentrated Force ◽  
Shear Span ◽  
Materials Used ◽  
2D And 3D

В статье представлены результаты экспериментальных исследований несущей способности наклонных сечений железобетонных балок с повреждениями в сжатой зоне бетона в виде сколов. Испытано 16 однопролетных свободно опертых образцов с размерами 100х200х1200 мм и рабочим пролетом 1000 мм. Нагрузка приложена в виде сосредоточенной силы на расстоянии пролета среза 1d, 2d и 3d. Материалы, использованные для изготовления образцов бетон класса С25/30, рабочая продольная арматура класса А500С 18 мм, поперечная арматура в виде хомутов и сжатая продольная арматура класса А240С 6 мм. Искусственные повреждения закладывались у одной грани глубиной 0 мм, 50 мм и 100 мм, углом наклона 0, 30 и 60. Все экспериментальные образцы разрушены по наклонному сечению. В ходе теоретического анализа полученных данных определено, что такого вида повреждения ведут к снижению несущей способности и изменению напряженно деформированного состояния нейтральная ось наклоняется относительно действия силовой плоскости, предельные деформации бетона увеличиваются, а поперечной арматуры уменьшаются. Уменьшение величины пролета среза от 3d до 1d ведет к значительному увеличению несущей способности, уменьшению предельных деформаций бетона и поперечной арматуры. Проанализировано, что среди исследуемых факторов наибольшее влияние имеет пролет среза, глубина повреждения в меньшей степени, а угол наклона повреждения влияет наименьшим образом. Предложена усовершенствованная методика определения остаточной несущей способности наклонных сечений поврежденных прямоугольных балок, максимальная разница с экспериментальными данными составила 28,13 , коэффициент вариации составил 10,3 .The article reports on the results of the experimental studies to determine the residual bearing capacity of inclined sections of reinforced concrete beams with concrete damages in compressed zone. 16 single-span freely supported experimental samples with dimensions of 1002001200 mm and the working span is 1000 mm were tested. The acted load on the samples was applied as a concentrated force at a shear span of 1d, 2d and 3d. Materials used for make samples are concrete of grade C25/30, working longitudinal reinforcement of grade A500C 18 mm, constructive longitudinal reinforcement and transverse reinforcement in the form of vertical links 6 mm of grade А240С. Artificial damages was lied at one edge of a depth of 0 mm, 50 mm and 100 mm, and with a tilt angle of 0, 30 and 60. All experimental samples are destroyed in inclined section. During the theoretical analysis of the data obtained, it was determined that this type of damage leads to a decrease in the residual bearing capacity and a changes in the stress-strain state - the neutral axis is tilted relative to the action of the force plane, the ultimate deformations of concrete increase, and the transverse reinforcement decreases. A decrease in the cut-off span from 3d to 1d leads to a significant increase in the bearing capacity, a decrease in the ultimate deformations of the concrete and transverse reinforcement. It is analyzed that among the studied factors, the shear span has the greatest influence, the depth of damage is less, and the angle of damage inclination influences the least.. An improved method for determining the residual bearing capacity of inclined sections of damaged rectangular beams is proposed, the maximum difference with experimental data was 28,13, the coefficient of variation was 10,3.

scholarly journals EXPERIMENTAL STUDIES OF REINFORCED CONCRETE BEAMS STRENGTHENED WITH STEEL FIBER JACKET

2020 ◽  
pp. 34-45
Author(s):  
O. Radaikin ◽  
L. Sharafutdinov
Keyword(s):  
Reinforced Concrete ◽  
Steel Fiber ◽  
Concrete Beams ◽  
Experimental Studies ◽  
Breaking Load ◽  
Fiber Reinforced Concrete ◽  
Reinforced Concrete Beams ◽  
Steel Fiber Reinforced Concrete ◽  
Joint Work ◽  
Loaded Crack

The purpose of the study is to experimentally study the joint work of steel fiber reinforced concrete (SFB) reinforcement jacket and reinforced concrete beams at all stages of loading to further develop a methodology for calculating this method of reinforcing bending elements. The main results of the study consist in assessing the strength, stiffness, fracture toughness, as well as the nature of fracture with a picture of the development of cracks for the examined 4 samples (two with a jacket of reinforcement, two - control - without reinforcement). It has been established that the use of SFB jacket with a thickness of 45 mm and with a fiber content percentage of 2,5% (at a flow rate of 196 kg/m3) increases the breaking load by 20 %, stiffness from 3,4 to 11 times as it is loaded, crack resistance 2,4-2,8 times. The results are compared with computer modeling in ANSYS PC: the discrepancy in the load of crack formation, fracture and deflection values for full-scale samples and a computer model are within 6,3 %, which indicates the reliability of the numerical results and the possibility of using the proposed computer models in further studies on topic of the article.

scholarly journals Stress-strain state of damaged reinforced concrete bended elements at operational load level

2021 ◽  
Vol 27 (4) ◽  
pp. 242-247
Author(s):  
Nadiia Kopiika ◽  
Pavlo Vegera ◽  
Rostyslav Vashkevych ◽  
Zinoviy Blikharskyy
Keyword(s):  
Reinforced Concrete ◽  
Strain State ◽  
Concrete Beams ◽  
Experimental Studies ◽  
Load Level ◽  
Reinforced Concrete Beams ◽  
Safe Operation ◽  
Operational Load ◽  
Initial Load ◽  
Type Of Failure

Abstract Each structure is exposed to different influences during operation. As a result, there are various defects and damages of these elements that affect their safe operation. The article presents the results of experimental studies of reinforced concrete beams with damages to stretched reinforcement made with and without initial load application. As the damages were accepted one or five Ø5.6 mm holes. In one case, the damage was made until the beam destruction (up to the 8.4 mm opening) Control samples of both series were destroyed due to crushing of the compressed zone of concrete. Samples that were damaged without initial loading collapsed due to rupture of the stretched reinforcement. The same type of failure was identified for damages at the operational load level.

scholarly journals Initial crack effect on the strength of oblique cross sections of reinforced concrete beams strengthened with carbon fiber

2019 ◽  
Vol 110 ◽  
pp. 01053
Author(s):  
Alexandr Shilov ◽  
Petr Polskoy ◽  
Dmitriy Mailyan ◽  
Petr Shilov
Keyword(s):  
Reinforced Concrete ◽  
Carbon Fiber ◽  
Cross Sections ◽  
Structural Damage ◽  
Concrete Beams ◽  
Experimental Studies ◽  
Reinforced Concrete Beams ◽  
Shear Span ◽  
The Impact ◽  
Initial Cracks

In the theory of reinforced concrete, the issue on strength of the oblique beam sections is more complicated than that on the standard sections, since it depends on many factors. The change of at least one of them leads to a significant change in the carrying capacity and in the structural damage pattern. This is due to the fact that at the operating level of the load, all conventional reinforced concrete structures work with cracks, which must be considered in the calculation. However, in the existing regulatory documents and public sources, this issue is not specified. This paper considers the effect of initial cracks on the strength of oblique cross sections of the reinforced concrete beams strengthened with carbon fiber. The experimental studies results obtained through the transverse force testing of forty-two prototypes made of heavy concrete of B30 design grade are presented. The test samples had initial oblique cracks of 0.6-0.9 mm width and were reinforced with three composite U stirrups from the fabric based on unidirectional carbon fibers in the shear span. Initial cracks in the beams were formed at three values of the shear span – 1.5h0, 2h0 and 2.5h0. The test data show the impact of initial cracks on the efficiency of composite reinforcement of oblique cross sections of the prototypes at various values of shear spans.

scholarly journals Pilot Studies of Concrete Beams Deformability Reinforced with Composite Reinforcement

2020 ◽  
Vol 24 (1) ◽  
pp. 103-114
Author(s):  
O. A. Vetrova
Keyword(s):  
Experimental Data ◽  
Concrete Beams ◽  
Experimental Studies ◽  
Steel Reinforcement ◽  
Reinforced Concrete Beams ◽  
Pilot Studies ◽  
Loading Level ◽  
Design Load ◽  
Composite Reinforcement

Purpose of research. Analysis is done on the basis of experimental data of loading level impact on deformability of beams with steel and composite fiberglass reinforcement at prolonged loads.Methods. Experimental studies of concrete bending elements of two series were carried out: the first is reinforced with composite fiberglass reinforcement of ASK class, the second is reinforced with steel reinforcement of А400 class. Studies of experimental samples were carried out under long-term loads. The structures were under different loads during the experiment: at design load, at 1.2 level from design load and at 1.5 from the design load. Concrete deformations and deflections of experimental beams of two series were fixed.Results. Dependence on time of concrete deformations of experimental samples of two series at different loading levels, dependence of deflection growth on load application level, influence dependence of loading level of elements on speed and intensity of creep deformation growth of beams with fiberglass and steel reinforcement are stated on the basis of experimental data. In particular, the bends of all samples with fiberglass reinforcement exceeded the maximum permissible value, while the maximum deflection of reinforced concrete beams in the middle of the section did not exceed maximum permissible value.Conclusion. On the basis of the obtained data, conclusions are drawn on the nature and magnitude of long-term deformations of beams with fiberglass and steel reinforcement at different levels of long-term loads. This conclusion is significant in practical sense when using concrete structures with composite reinforcement taking into account a small number of research data.

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