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.

Relation between Breaking Stresses in the Strength Calculations of Reinforced Concrete Elements under the Deformation Mode in the Edition of Russian and Foreign Regulatory Documents

2019 ◽  
Vol 974 ◽  
pp. 653-658
Author(s):  
Valeriy A. Eryshev
Keyword(s):  
Compressive Strength ◽  
Reinforced Concrete ◽  
Deformation Mode ◽  
Concrete Element ◽  
Regulatory Documents ◽  
Functional Relations ◽  
Base Points ◽  
Requirements Documents ◽  
Concrete Elements ◽  
Analytical Expressions

Сorrespondence was established between the compressive strength grades of concrete numerically equal to the guaranteed compressive strength of a standard concrete cube and a standard concrete cylinder. Designated concrete resistances are assigned for the limiting states of the first group with a compressive strength grade of concrete. For the corresponding concrete grades, the reduction to unambiguous strains values at the base diagrams points is justified: at the top and at the end of the falling branch of the curvilinear diagrams. In accordance with the regulatory requirements, restrictions are imposed on the stress levels at the end of the falling diagrams branch at the maximum normalized strains values. Mathematical models establishing a uniform format for calculating single-valued strains values at base points of concrete diagrams have been developed taking into account accepted functional relations and the their assignment rules using the requirements documents tables. It is shown that with equal strains values and stresses at base points, analytical expressions describing diagrams recommended by requirement documents, different in their structure, give their identical outlines, the diagrams branches are the same. Relation between design models in the edition of Russian and foreign regulatory documents is correlated by the comparison of integral diagrams parameters and breaking stresses obtained with the calculation of reinforced concrete element under the deformation mode. As integral parameters of concrete deformation diagrams, it is recommended to use the areas bounded by diagrams branches and diagrams fineness coefficient. The diagram area for given values of the element curvature is equivalent to the magnitude of the breaking stress in the compressed concrete zone in the bent and compressed elements, and the stress diagram in outline corresponds to this diagram.

scholarly journals MODELING OF STRESS-DEFORMED STATE OF BENDED REINFORCED CONCRETE ELEMENTS IN ZONES OF CLEAN AND TRANSVERSE BEND

2021 ◽  
Vol 11 (1) ◽  
pp. 26-33
Author(s):  
Anatoly A. PROKOPOVICH ◽  
Yana A. BUZOVSKAYA
Keyword(s):  
Reinforced Concrete ◽  
Experimental Studies ◽  
Element Model ◽  
Successive Approximations ◽  
Method Of Successive Approximations ◽  
Concrete Element ◽  
Nite Element ◽  
Deformed State ◽  
System Of Cracks ◽  
Concrete Elements

The article deals with the analysis of the stress-strain state (SSS) of a bent reinforced concrete element in zones of pure and transverse bending. It is assumed that a bent element in the process of loading (after the formation of normal and oblique cracks) is divided into blocks, united by uncracked concrete and reinforcement that has adhesion to concrete. SSS was formed using the results of experimental studies of special prototypes in the PC “Lira-SAPR”. A fi nite element model of a prototype has been developed in the form of a reinforced concrete rectangular beam loaded with two identical concentrated forces in the span. By the method of successive approximations, the process of formation and formation of a system of cracks is realized, with which the beam is divided into blocks during loading. The results of calculating the fi nite element model and their comparison with experimental data are presented.

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.

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.

scholarly journals Приближенные граничные условия для задачи нахождения оптических коэффициентов ультратонких металлических пленок в СВЧ и ТГЦ диапазонах

2020 ◽  
Vol 128 (9) ◽  
pp. 1327
Author(s):  
П.С. Глазунов ◽  
В.А. Вдовин ◽  
В.Г. Андреев
Keyword(s):  
Boundary Conditions ◽  
Maximum Error ◽  
Dielectric Substrate ◽  
Thickness Dependence ◽  
Successive Approximations ◽  
Method Of Successive Approximations ◽  
Transmission Coefficients ◽  
Fabry Perot ◽  
Approximate Boundary Conditions ◽  
Analytical Expressions

Approximate boundary conditions for a problem of calculating the optical coefficients of a system composed of inhomogeneous ultrathin metallic film with an arbitrary thickness dependence of conductivity deposited on dielectric substrate are obtained. The derivation of the boundary conditions is based on the Picard method of successive approximations. Analytical expressions for the errors in calculating the optical coefficients with use of the proposed approximate boundary conditions are presented. It is shown that the error increases with the frequency and the film thickness increasing. The maximum error for films of 10 nm-thickness does not exceed 10.7% at 1 THz. As an example, the complex optical coefficients of a system similar to Fabry-Perot etalon and a metal film without a substrate with model thickness dependence of conductivity are calculated. The coincidence between the results of numerical simulation and calculations performed with approximate boundary conditions is shown. The possibility of direct calculating the average conductivity of a film from experimentally measured reflection and transmission coefficients is demonstrated.

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.

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.

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.

Improvement Of Curvilinear Diagrams Of Concrete Deformation

2019 ◽  
pp. 99-104
Keyword(s):  
Reinforced Concrete ◽  
Peak Load ◽  
Experimental Studies ◽  
Concrete Structures ◽  
Deformation Model ◽  
Reinforced Concrete Structures ◽  
Significant Difference ◽  
Deformation Diagrams

Problems when calculating reinforced concrete structures based on the concrete deformation under compression diagram, which is presented both in Russian and foreign regulatory documents on the design of concrete and reinforced concrete structures are considered. The correctness of their compliance for all classes of concrete remains very approximate, especially a significant difference occurs when using Euronorm due to the different shape and sizes of the samples. At present, there are no methodical recommendations for determining the ultimate relative deformations of concrete under axial compression and the construction of curvilinear deformation diagrams, which leads to limited experimental data and, as a result, does not make it possible to enter more detailed ultimate strain values into domestic standards. The results of experimental studies to determine the ultimate relative deformations of concrete under compression for different classes of concrete, which allowed to make analytical dependences for the evaluation of the ultimate relative deformations and description of curvilinear deformation diagrams, are presented. The article discusses various options for using the deformation model to assess the stress-strain state of the structure, it is concluded that it is necessary to use not only the finite values of the ultimate deformations, but also their intermediate values. This requires reliable diagrams "s–e” for all classes of concrete. The difficulties of measuring deformations in concrete subjected to peak load, corresponding to the prismatic strength, as well as main cracks that appeared under conditions of long-term step loading are highlighted. Variants of more accurate measurements are proposed. Development and implementation of the new standard GOST "Concretes. Methods for determination of complete diagrams" on the basis of the developed method for obtaining complete diagrams of concrete deformation under compression for the evaluation of ultimate deformability of concrete under compression are necessary.

Sign in / Sign up

Export Citation Format

Share Document