scholarly journals CALCULATION MODEL OF A COMPLEX STRESS REINFORCED CONCRETE ELEMENT OF A BOXED SECTION DURING TORSION WITH BENDING

2021 ◽  
pp. 7-26
Author(s):  
N. I. Karpenko ◽  
Vl. I. Kolchunov ◽  
V. I. Travush
Keyword(s):  
Reinforced Concrete ◽  
Residential Building ◽  
High Strength ◽  
Complex Stress ◽  
Calculation Model ◽  
Deformation Model ◽  
Concrete Element ◽  
Scientific Publications ◽  
Curvature And Torsion ◽  
Deformation Models

Statement of the problem. Based on the analysis of domestic and foreign scientific publications and guidelines, it is found that the known deformation models for the calculation of complex tensile reinforced concrete elements during torsional bending are quite conditional. Therefore the article considers the solution of the problem of designing a computational model of a reinforced concrete element during torsion with bending in the post-crack stage, which most fully accounts for the specifics of crack formation, deformation and destruction of such elements. The case is considered for when among all possible external influences the action of torques and bending moments has the greatest influence on the stress-strain. Results. Using the equations of statics and physical ratios of reinforced concrete, the calculated parameters are identified such as stresses in concrete of compressed zone, height of compressed concrete, stresses in clamps, deformations in concrete and reinforcement, curvature and torsion angle of reinforced concrete element. Conclusions. The obtained analytical dependences were tested by means of numerical calculation of the reinforced concrete strapping crossbar of the outer contour of a residential building of box section of high-strength concrete. The suggested deformation model can be employed in the design of a wide class of reinforced concrete structures working on torsional bending.

Calculation Model of a Complex Stress Reinforced Concrete Element of a Boxed Section During Torsion with Bending

2021 ◽  
pp. 9-26
Author(s):  
Н. И. Карпенко ◽  
Вл. И. Колчунов ◽  
В. И. Травуш
Keyword(s):  
Reinforced Concrete ◽  
Residential Building ◽  
High Strength ◽  
Complex Stress ◽  
Calculation Model ◽  
Deformation Model ◽  
Concrete Element ◽  
Scientific Publications ◽  
Curvature And Torsion ◽  
Deformation Models

Постановка задачи. На основе анализа отечественных и зарубежных научных публикаций и нормативных документов установлено, что известные деформационные модели для расчета сложнонапряженных железобетонных элементов при кручении с изгибом носят достаточно условный характер. В связи с этим в статье рассматривается решение задачи создания расчетной модели железобетонного элемента при кручении с изгибом в стадии после образования трещин, наиболее полно учитывающей специфику трещинообразования, деформирования и разрушения таких элементов. Рассмотрен случай, когда из возможных внешних воздействий наибольшее влияние на напряженно-деформированное состояние оказывает действие крутящего и изгибающего моментов. Результаты. На основе уравнений статики и физических соотношений железобетона определены расчетные параметры, такие как напряжения в бетоне сжатой зоны, высота сжатого бетона, напряжения в хомутах, деформации в бетоне и арматуре, кривизна и угол закручивания железобетонного элемента. Выводы. Полученные аналитические зависимости апробированы численным расчетом железобетонного обвязочного ригеля наружного контура жилого здания коробчатого сечения из высокопрочного бетона. Предложенная деформационная модель может быть использована при проектировании широкого класса железобетонных конструкций, работающих на изгиб с кручением. Statement of the problem. Based on the analysis of domestic and foreign scientific publications and guidelines, it is found that the known deformation models for the calculation of complex tensile reinforced concrete elements during torsional bending are quite conditional. Therefore the article considers the solution of the problem of designing a computational model of a reinforced concrete element during torsion with bending in the post-crack stage, which most fully accounts for the specifics of crack formation, deformation and destruction of such elements. The case is considered for when among all possible external influences the action of torques and bending moments has the greatest influence on the stress-strain. Results. Using the equations of statics and physical ratios of reinforced concrete, the calculated parameters are identified such as stresses in concrete of compressed zone, height of compressed concrete, stresses in clamps, deformations in concrete and reinforcement, curvature and torsion angle of reinforced concrete element. Conclusions. The obtained analytical dependences were tested by means of numerical calculation of the reinforced concrete strapping crossbar of the outer contour of a residential building of box section of high-strength concrete. The suggested deformation model can be employed in the design of a wide class of reinforced concrete structures working on torsional bending.

Improving the Methodology for Calculating the Bearing Capacity of Eccentrically Compressed Reinforced Concrete Elements Based on the Use of the Refined Curvilinear Deformation Diagrams of Concrete and Reinforcement

2019 ◽  
Vol 974 ◽  
pp. 570-576
Author(s):  
Alexander I. Nikulin ◽  
Al-Khawaf Ali Fadhil Qasim
Keyword(s):  
Reinforced Concrete ◽  
Bearing Capacity ◽  
Linear Equations ◽  
Resistance Force ◽  
Deformation Model ◽  
Concrete Element ◽  
Element Determination ◽  
Numerical Studies ◽  
Concrete Elements ◽  
Deformation Diagrams

The article proposes a new approach to improving the methodology for calculating the bearing capacity of the eccentrically compressed reinforced concrete elements for cases of their loading with large eccentricities. The basis of this technique is considered as a modified version of the deformation model for the reinforced concrete resistance force. The main feature of this model is the energy approach to transforming the reference diagrams of compression and concrete tension into the diagrams of non-uniform deformation, corresponding to the stress-strain state of the compressed and stretched zones of concrete in the cross section of the eccentrically compressed reinforced concrete structures. This way there is no falling branch in the concrete diagrams obtained by this method. A calculation diagram of the steel reinforcement deformation with a physical yield point was taken as a partial function, consisting of one linear and two non-linear equations. The proposed method also shows the possibility of taking into account the greatest curvature of an eccentrically compressed reinforced concrete element in the plane of its loading. The article presents all the necessary dependencies allowing the theoretical value of the carrying capacity of an eccentrically compressed reinforced concrete element determination. The results of the numerical studies performed using the design software developed by the authors for the personal computer are given.

scholarly journals HISTORY OF THE APPEARANCE OF EULER’S FORMULA. ISSUES OF STABILITY OF COMPRESSED REINFORCED CONCRETE ELEMENTS

2021 ◽  
Vol 11 (1) ◽  
pp. 18-25
Author(s):  
Sergey S. MORDOVSKIY ◽  
Anna A. KISELEVA
Keyword(s):  
Reinforced Concrete ◽  
High Strength Concrete ◽  
High Strength ◽  
Deformation Model ◽  
Reinforced Concrete Structures ◽  
Linear Deformation ◽  
History Of ◽  
Life Path ◽  
Concrete Elements ◽  
Concrete Hardening

The article presents a brief overview of the life path of the Swiss mathematician and mechanic Leonard Euler, considers the history of the emergence of the formula for calculating stability, shows options for taking into account the fl exibility of an element in the calculations of reinforced concrete structures, the disadvantages of the Euler curve and the features of its application in relation to structures made of high-strength concrete and concrete hardening under pressure. An example of the result of using a non-linear deformation model in the calculations of eccentrically compressed reinforced concrete elements with the introduction into the algorithm for calculating a coeffi cient that takes into account the eff ect of buckling (defl ection) of an element on its bearing capacity is given.

scholarly journals INTEGRAL PARAMETERS OF CONCRETE DIAGRAMS FOR CALCULATIONS OF STRENGTH OF REINFORCED CONCRETE ELEMENTS USING THE DEFORMATION MODEL

2020 ◽  
Vol 16 (1) ◽  
pp. 25-37
Author(s):  
Vladimir Eryshev ◽  
Nickolay Karpenko ◽  
Artur Zhemchuyev
Keyword(s):  
Reinforced Concrete ◽  
Successive Approximations ◽  
Method Of Successive Approximations ◽  
Deformation Model ◽  
Concrete Element ◽  
Normative Documents ◽  
Functional Relationships ◽  
Regulatory Documents ◽  
Base Points ◽  
Analytical Expressions

In accordance with the requirements of regulatory documents, restrictions are introduced on stress levels at the end of the falling branch of the diagrams at the maximum normalized strain values. We have developed mathematical models that establish a uniform sequence for calculating the unambiguous values of deformations at the base points of concrete diagrams, taking into account the accepted functional relationships and the rules for their use according to the tables of normative documents. It was shown that for equal values of deformations and stresses at base points, analytical expressions of diagram recommended by regulatory documents, even if it differs in structure, give identical outlines, diagram branches coincide. The correlation between the calculation models by Russian and foreign regulatory documents was established by comparing the values of the integral parameters of the diagrams and the ultimate forces obtained by calculating the reinforced concrete element according to the deformation model. As integral parameters of concrete deformation diagrams, it was recommended to use areas bounded by diagram branches and diagram completeness coefficients. Analytical modeling of integral parameters allowed us to exclude the procedure for numerically summing stresses along elementary strips in a section and solving nonlinear equations by the method of successive approximations when calculating the strength of an element.

Evaluation Of The Effect Of Eccentricity Of Longitudinal Force On The Provision Of Bearing Capacity Of Compressed Concrete Elements

2019 ◽  
pp. 29-34 ◽  
Keyword(s):  
Reinforced Concrete ◽  
Bearing Capacity ◽  
Coefficient Of Variation ◽  
Longitudinal Force ◽  
Deformation Model ◽  
Concrete Element ◽  
Average Value ◽  
Strength And Deformation ◽  
The Given ◽  
Concrete Elements

This work evaluates the influence of the eccentricity of longitudinal force on the provision of the bearing capacity of an eccentrically compressed reinforced concrete element in the normal section at different percentages of longitudinal reinforcement. The nonlinear deformation model was used for probabilistic calculations, which made it possible to take into account the influence of strength and deformation characteristics of concrete on the bearing capacity of the elements of reinforced concrete structures. The dependences of the relative average value of the maximum longitudinal force and the coefficient of variation for the given percent of reinforcement on the eccentricity of the longitudinal force are obtained. The significant influence of the value of the longitudinal force eccentricity on the coefficient of variation of the bearing capacity of the eccentrically compressed concrete element in the normal cross section is shown. It is noted that the revealed dependence of the bearing capacity of eccentrically compressed reinforced concrete elements on the eccentricity of the longitudinal force is not taken into account in the existing methods of calculation.

CRACK RESISTANCE OF PRESTRESSED REINFORCED CONCRETE FRAME STRUCTURE SYSTEMS UNDER SPECIAL IMPACT

2021 ◽  
Vol 95 (3) ◽  
pp. 15-26
Author(s):  
V.I. KOLCHUNOV ◽  
◽  
К.YU. KUZNETSOVA ◽  
S.S. FEDOROV ◽  
◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Crack Resistance ◽  
Concrete Strength ◽  
High Strength ◽  
Fiber Reinforced Concrete ◽  
Reinforced Concrete Beams ◽  
Fiber Reinforced ◽  
Concrete Element ◽  
Concrete Body ◽  
High Strength Fiber

A variant of the crack resistance criterion and the strength criterion of plane-stressed structures made of high-strength fiber-reinforced concrete, fiber-reinforced concrete is proposed. The criteria are based on the theory of plasticity of concrete and reinforced concrete G.A. Genieva. In general, the condition for crack resistance of a plane-stressed fiber-reinforced concrete element is presented in the form of an ellipse with jumps on the coordinate axes of the main reduced stresses. The strength condition of a fiber-reinforced concrete element is described by a complex figure that takes into account cracking in the element under a plane stress state. The characteristic points on the coordinate axes are calculated from the physical and mechanical characteristics of concrete strength, obtained as a result of testing high-strength fiber-reinforced concrete for uniaxial compression and uniaxial tension with “dissolved” fiber in the concrete body and reinforcement reduced to concrete. The results of a comparative analysis of the criteria for crack resistance and strength of high-strength concrete and high-strength fiber-reinforced concrete are given, depending on the percentage of fiber in the concrete body and the type of fiber used. The proposed analytical dependences can be used to analyze the crack resistance and strength of plane-stressed reinforced concrete beams-walls reinforced with fiber, corner zones of shallow shells and other plane-stressed structures made of high-strength fiber-reinforced concrete and fiber-reinforced concrete.

scholarly journals ENHANCEMENT OF THE REINFORCED CONCRETE PLAIN STRUCTURES DESIGN METHODS WITH THE TAKING INTO CONSIDERATION THE TRUE PROPERTIES OF HIGH PERFORMANCE CONCRETES

2018 ◽  
Vol 14 (2) ◽  
pp. 78-89
Author(s):  
Nikolay I. Karpenko ◽  
Sergey N. Karpenko ◽  
Alexey N. Petrov
Keyword(s):  
Reinforced Concrete ◽  
High Performance ◽  
High Strength ◽  
Design Methods ◽  
Design Stage ◽  
Deformation Model ◽  
Deformation Properties ◽  
Strength And Deformation ◽  
Actual Strength ◽  
Nonlinear Deformation Model

The enhancement of the reinforced concrete plain structures design methods on the basis of the deformation theory of the plasticity of reinforced concrete with cracks by N.I. Karpenko is considered. The deformation model of reinforced concrete with cracks taking into account the deformation diagrams of concrete and reinforcement is used for numerical analysis of a deep beam made of high-strength concrete of class B100. The analysis makes it possible to con­clude that taking into account the actual properties of materials significantly improves the accuracy of computer model­ing. The strength of concrete is the decisive factor determining the mechanism of structural failure and the efficiency of using reinforcement. At the design stage, the most reliable and accurate tool for assessing the operational fitness of pla­nar reinforced concrete structures is computer modeling based on a nonlinear deformation model, taking into account the actual strength and deformation properties of concrete and reinforcement

scholarly journals CALCULATION MODEL OF A COMPLEX-STRESSED REINFORCED CONCRETE ELEMENT UNDER TORSION WITH BENDING

2021 ◽  
Vol 17 (1) ◽  
pp. 34-47
Author(s):  
Nikolay Karpenko ◽  
Vladimir Kolchunov ◽  
Vitaly Kolchunov ◽  
Vladimir Travush
Keyword(s):  
Reinforced Concrete ◽  
Cross Sections ◽  
Vertical Section ◽  
Longitudinal Axis ◽  
Calculation Model ◽  
Governing Equations ◽  
Closed Loop System ◽  
Concrete Element ◽  
Tangential Forces ◽  
Spatial Section

The article presents the methodology and principles of creating calculation models for reinforced concrete structures operating in conditions of complex resistance. A block calculation model of reinforced concrete bar structures in torsion with bending is presented. This model consists of a support block formed by a spatial crack and a compressed zone of concrete closed on it and a second block formed by a vertical section running perpendicular to the longitudinal axis of a reinforced concrete element along the edge of the compressed zone closing the spatial spiral. Cases are considered when the torque effec has the greatest influenceon the stress-strain state of structures. In this case, the following forces are taken into account as the calculated forces in the spatial section: normal and tangential forces in the concrete of the compressed zone; components of axial and shear forces in the reinforcement crossed by a spatial crack. A feature of the proposed calculation model is that it considers independently of each other the strength of an element in spatial sections passing along a spatial crack, and the strength of an element between spatial cracks. The spatial section is formed by a crack located on three sides of the element and a compressed zone located on the fourth side and closing the ends of the spiral crack. In this case, the compressed zone, depending on the ratio of the bending and torque moments, can be located along the horizontal and vertical (lateral) edges of the element. The governing equations are written in the form of static equations for the adopted calculation cross-sections and a closed-loop system that unites them, written as a function of many variables with Lagrange multipliers λi. On the basis of the constructed function for all the variables included in it, an additional non-decaying system of equations has been compiled, from which follows a dependence that allows finding the projecton of a dangerous spatial crack.

scholarly journals Strengthening and Repair of a Precast Reinforced Concrete Residential Building

2020 ◽  
Vol 6 (12) ◽  
pp. 2457-2473
Author(s):  
M. Jamal Shannag ◽  
Mahmoud Higazey
Keyword(s):  
Reinforced Concrete ◽  
Residential Building ◽  
Minimum Cost ◽  
High Strength ◽  
Cost Effective ◽  
Steel Beams ◽  
Reinforced Concrete Structure ◽  
Design Error ◽  
Analytical Tools ◽  
Repair Techniques

The deterioration or ageing of the existing infrastructures coupled with increased safety requirements necessitate immediate strengthening. Developing long lasting and cost effective repair techniques and materials continue to capture the attention of concrete professionals worldwide. The main purpose of this investigation was to extend the life span of a multi-storey precast reinforced concrete structure built in Riyadh 40 years ago. The condition assessments relied on analytical tools, visual, field and laboratory experiments for core samples collected from the building. The analytical checks of the building revealed considerable deflections of some slabs because of design error. The field and chemical analysis tests performed, confirmed the occurrence of durability defects as a result of poor workmanship during the construction stage. Several state-of-the-art repair techniques and materials were used for enhancing the service life of the structure at a minimum cost. The Repair strategy implemented included, removal of the deteriorated concrete, pouring a bonding agent on the surface of the damage, followed by injecting high strength cementitious grouts, supporting the deflected slabs using I-section steel beams, using cathodic protection to prevent corrosion, strengthening the columns and beams using carbon fiber reinforced polymer (CFRP) sheets, and steel jackets. Doi: 10.28991/cej-2020-03091630 Full Text: PDF

scholarly journals An experimental study on variability of deformation characteristics of concrete in compression

Vestnik MGSU ◽  
2020 ◽  
pp. 1390-1398
Author(s):  
Mixail G. Plyusnin ◽  
Sergey V. Tsybakin
Keyword(s):  
Experimental Study ◽  
Reinforced Concrete ◽  
Bearing Capacity ◽  
Cross Section ◽  
Strength Analysis ◽  
Deformation Model ◽  
Deformation Characteristics ◽  
Concrete Element ◽  
Linear Deformation ◽  
Concrete Elements

Introduction. An experimental study on variability of deformation characteristics of concrete and an assessment of its influence on the bearing capacity of eccentrically compressed reinforced concrete elements were performed. In pursuance of effective regulatory documents, a non-linear deformation model was applied to perform the strength analysis of standard cross sections of reinforced concrete structures. The application of this method in probabilistic design is also of interest. Analytical functions approximating the true σ–ε diagram, made for concrete, use strength and deformation characteristics of concrete as parameters. However, variability of deformation characteristics of concrete has not been sufficiently studied, although it may have significant influence on results of analyses. Materials and methods. Complete σ–ε diagrams were made for uniaxially compressed concrete to solve this problem. These diagrams were applied to numerically assess the influence of variability of deformation characteristics of concrete on the bearing capacity of an eccentrically compressed reinforced concrete element in terms of its standard cross section. A non-linear deformation model was used to identify the bearing capacity. Results. The experiment has proven substantial variation of diagram shapes within the same strength class. The influence of the εb0 value of ultimate deformations of concrete on the bearing capacity is demonstrated for a standard cross section as a result of the strength analysis of an eccentrically compressed reinforced concrete element. The strength analysis was performed by applying experimental σ–ε diagrams made for uniaxially compressed concrete. Conclusions. The analysis of the findings has shown that the value of ultimate deformations of concrete exposed to uniaxial compression affects the bearing capacity of eccentrically compressed reinforced concrete elements. The degree of influence depends on concrete strength, reinforcement percentage and the eccentricity of a longitudinal force.

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