scholarly journals Model of normal cracks level formation and opening in stretched reinforced concrete elements

2021 ◽  
pp. 28-36
Author(s):  
Olena Vasylivna Romashko-Maistruk ◽  
Vasyl Mykolayovych Romashko
Keyword(s):  
Reinforced Concrete ◽  
Crack Formation ◽  
Crack Opening ◽  
Nonlinear Function ◽  
Load Level ◽  
Direct Integration ◽  
Test Results ◽  
Advantages And Disadvantages ◽  
Concrete Elements ◽  
Opening Width

The article highlights the most important studies results of the mechanism of normalcracks formation and opening in stretched reinforced concrete elements during their deformation. Acritical analysis of the existing methods and ways for calculating normal cracks level formation andopening, in which the reinforcement to concrete adhesion is taken into account directly or indirectly,is carried out. The main advantages and disadvantages of each of these methods are indicated. It hasbeen experimentally confirmed that the crack formation process is generally leveled. The mainfeatures and patterns of cracking in stretched reinforced concrete elements and structures arerevealed. The main characteristics of the prototypes are given, according to the test results of whichit was established that in practical calculations of the reinforced concrete elements crack resistance,it is usually possible to restrict oneself to two levels of normal cracking. For the indicated crackinglevels, the corresponding load level, step and crack opening width are established. The expediencyof using in practical calculations the nonlinear function of the reinforcement with concrete averageadhesion stresses is also substantiated. Based on the studies results carried out, the existing methodsfor calculating the normal cracks formation and opening in reinforced concrete elements andstructures were evaluated from the standpoint of local disadvantage of the reinforcement to concreteadhesion.General and simplified methods for calculating normal cracks level formation and opening inreinforced concrete elements have been developed. In them, the direct integration of the expressionfor the concrete and reinforcement mutual displacements is proposed to be replaced not by thenumerical integration of the indicated expression, but by the successive accumulation of the indicateddisplacements. Corresponding statistical comparisons of the calculations results by these methodswith experimental data are carried out. The effectiveness of the developed methods for calculatingnormal cracks level formation and opening by comparing them with existing methods is estimated.

scholarly journals Calculation of the crack resistance of reinforced concrete elements with allowance for the levels of normal crack formation

2018 ◽  
Vol 230 ◽  
pp. 02028 ◽  
Author(s):  
Vasyl Romashko ◽  
Olena Romashko
Keyword(s):  
Reinforced Concrete ◽  
Crack Resistance ◽  
Calculation Method ◽  
Solid Mechanics ◽  
Crack Formation ◽  
Crack Opening ◽  
Nonlinear Function ◽  
Experimental Investigations ◽  
Concrete Element ◽  
Concrete Elements

The separate experimental investigations results and the major drawbacks of existing methods of calculating the reinforced concrete elements crack resistance are considered in detail, taking into account the process of multilevel formation and crack opening. Based on the basic provisions of the deformation and strength model of concrete and reinforced concrete resistance, an engineering method for calculating the formation and disclosure of normal cracks in the reinforced concrete elements and structures at the operational stages of their deformation is proposed. It is implemented on the system of generally accepted static, geometric and physical relations of a deformed solid mechanics. The simplicity of the proposed calculation method is due to the use of the nonlinear function of the average stresses of the reinforcement bond with concrete on the sections of the reinforced concrete element between adjacent cracks. The main advantages of the developed calculation method in comparison with others are outlined.

scholarly journals Normal Sections Calculation of Bending Reinforced Concrete and Fiber Concrete Elements

2018 ◽  
Vol 7 (3.2) ◽  
pp. 176
Author(s):  
Dmytro Kochkarev ◽  
Tatyana Galinska ◽  
Oleksandr Tkachuk
Keyword(s):  
Reinforced Concrete ◽  
Rectangular Cross Section ◽  
Nonlinear Function ◽  
Fiber Reinforced Concrete ◽  
Deformation Model ◽  
Fiber Reinforced ◽  
Deformation Diagram ◽  
First Case ◽  
Fiber Concrete ◽  
Concrete Elements

The basic principles of the normal sections calculation of reinforced concrete and fiber reinforced concrete bending elements are considered. In the article the power and deformation methods of calculation of reinforced concrete and fiber concrete elements of rectangular cross-section are presented. The deformation model of the calculation of reinforced concrete and fiber concrete elements is presented in the framework of the method of calculation resistance of the section. This method makes possible from the common methodological positions to perform calculations of reinforced concrete and fiber concrete elements. Namely, to select reinforcement and to determine the carring capacity. The proposed deformation model for calculating fiber concrete elements is based on generally accepted preconditions. A hypothesis of plane cross sections is accepted as fair. The deformation diagram of compressed concrete is described by a nonlinear function with established parametric points. Distribution of stresses in stretched concrete is taken rectangular with corresponding coefficients which are taken depending on the type of deformation diagram. Determination of the carring capacity of fiber concrete elements occurs under extreme deformation criteria. Two cases of destruction of the investigated elements are considered. The first case is the destruction due to the achievement of limiting deformations in the concrete of the compressed zone with the simultaneous achievement of the fluidity limit in the working reinforcement. The second case is the destruction due to the achievement of limiting deformations in the concrete of the compressed zone without reaching the fluidity limit in the working reinforcement. Both cases of calculation are reduced to one functional dependence. This avoids the delimitation of different calculation cases. The main no dimensional modifier is the mechanical coefficient of reinforcement. According to the developed method, examples of calculations of reinforced concrete, fiber reinforced concrete elements and fiber concrete elements with longitudinal reinforcement are executed. The possibility of a spread variant design of reinforced concrete and fiber concrete elements is shown. 

scholarly journals ANALYSIS OF STRENGTHENING OF COMPRESSED REINFORCED CONCRETE STRUCTURES USING REINFORCED CONCRETE JACKETS / GNIUŽDOMŲJŲ GELŽBETONINIŲ KONSTRUKCIJŲ STIPRINIMO GELŽBETONINIAIS APVALKALAIS ANALIZĖ

2011 ◽  
Vol 3 (2) ◽  
pp. 76-84
Author(s):  
Saulius Pilkavičius
Keyword(s):  
Reinforced Concrete ◽  
Carrying Capacity ◽  
Theoretical Calculations ◽  
Experimental Studies ◽  
Calculation Methods ◽  
Advantages And Disadvantages ◽  
Calculation Algorithms ◽  
Capacity Calculation ◽  
Basic Equations ◽  
Concrete Elements

This article investigates two chosen calculation methods of compressed reinforced concrete elements strengthened using reinforced concrete jackets. Shortly describe carrying capacity calculation algorithms of these calculation methods. Present elements basic equations and dependences of carrying capacity. For calculation methods of carrying capacity comparison and adjustment executed carrying capacity experimental studies of compressed fiber reinforcement concrete elements strengthened using reinforcement concrete jackets. Were compared theoretical calculations of carrying capacity results with experimental carrying capacity results. Shortly describe advantages and disadvantages of analyzed calculation methods and experimental research. By the comparison of calculation methods conclusions and experimental studies conclusions, produces improved calculation method of carrying capacity.

scholarly journals THE INFLUENCE OF SHEAR SPAN RATIO ON LOAD CAPACITY OF FIBRE REINFORCED CONCRETE ELEMENTS WITH VARIOUS STEEL FIBRE VOLUMES

2007 ◽  
Vol 13 (3) ◽  
pp. 209-215 ◽  
Author(s):  
Remigijus Šalna ◽  
Gediminas Marčiukaitis
Keyword(s):  
Experimental Data ◽  
Reinforced Concrete ◽  
Steel Fibre ◽  
Load Capacity ◽  
Fibre Volume ◽  
Fibre Reinforced Concrete ◽  
Test Results ◽  
Shear Span ◽  
Concrete Elements ◽  
Empirical Approaches

This paper analyses the influence of steel fibre volume and shear span ratio on the strength of fibre reinforced concrete elements in various states of stress. 36 beams with three different shear spans (a/h = 1, 1,5, and 2 %) and three different fibre volumes (1, 1,5, and 2 %) were tested to examine how these factors influence the behaviour of such elements. Test results suggest that steel fibre volume and shear span can increase load capacity, plasticity and cracking. Experimental research showed that steel fibre volume has different influence at different shear span ratios. Regression analysis of experimental data was carried out and empirical approach showing different effect of these factors was proposed. Furthermore, test results were compared with different theoretical and empirical approaches of other authors.

scholarly journals THE STUDY OF LEVEL FORMATION AND DISCLOSURE OF NORMAL CRACKS IN REINFORCED CONCRETE ELEMENTS

2020 ◽  
Vol 4 (157) ◽  
pp. 18-24
Author(s):  
O. Romashko-Maistruk
Keyword(s):  
Reinforced Concrete ◽  
Concrete Beams ◽  
Experimental Studies ◽  
Nonlinear Function ◽  
Reinforced Concrete Beams ◽  
The Real ◽  
European Standards ◽  
And Storage ◽  
Concrete Elements ◽  
Formation Step

This article is devoted to the study of the main patterns of normal cracks multilevel formation in reinforced concrete elements and structures. A critical analysis of the latest publications related to the theme of these studies is carried out. The classification is carried out and the main shortcomings of the known works on the four identified areas of research are identified. The most important elements of the method of reinforced concrete beams experimental research are developed and briefly described. The main characteristics of the prototypes, the conditions for their manufacture and storage are given. The most important results of testing reinforced concrete beams, concerning the main parameters and characteristics of level formation and crack disclosure are highlighted. It was confirmed that the process of normal cracks formation is indeed multilevel and is accompanied by a gradual disruption of the bond between reinforcement and concrete. According to the results of experimental studies, it has been established that in the real design of bending reinforced concrete elements, when calculating their crack resistance, it is possible to restrict oneself to only 2 levels of normal cracking. The calculation of the step and normal cracks opening width in beams research was carried out according to the real multilevel and traditional "one-level" schemes of their formation. These calculations were carried out according to the author's general and simplified methods, according to a method that uses a linear function of the average adhesion stresses of reinforcement with concrete, according to the methods of current domestic and European standards and building rules. Their statistical comparison with the experimental studies results confirmed the effectiveness of those calculation methods in which the crack formation step is directly related to the basic laws and parameters of reinforcement to concrete adhesion. The results of this comparison showed that the author's general method, based on the use of a nonlinear function of the reinforcement with concrete average adhesion stresses, turned out to be the most accurate. Keywords: reinforced concrete, elements, adhesion, reinforcement, cracks, levels of formation, step, width.

scholarly journals Nonlinear calculation of reinforced concrete structures to the impact of the air shock wave

Vestnik MGSU ◽  
2019 ◽  
pp. 33-45 ◽  
Author(s):  
Anton Y. Savenkov ◽  
Oleg V. Mkrtychev
Keyword(s):  
Numerical Simulation ◽  
Shock Wave ◽  
Reinforced Concrete ◽  
Nonlinear Dynamic ◽  
Software Package ◽  
Crack Opening ◽  
Concrete Structures ◽  
Reinforced Concrete Structures ◽  
Advantages And Disadvantages ◽  
The Impact

Introduction. Researched methods of accounting for the nonlinear operation of reinforced concrete structures on the example of an industrial structure, when exposed to an air shock wave using modern software systems based on the finite element method. The calculation of reinforced concrete construction to the impact of an air shock wave, if no increased requirements for tightness are presented to it, in accordance with current regulatory documents, must be carried out taking into account the elastic-plastic work, crack opening in the stretched zone of concrete and plastic deformations of reinforcement are allowed. Reviewed by new coupling approach to determining the dynamic loads of a shock wave, implemented in the LS-DYNA software package, which allows to take into account the effects of a long-range explosion and wave-wrapping around a structure. Materials and methods. The study of the stress-strain state of the structures was carried out using numerical simulation. For the nonlinear equivalent-static method, a step-by-step calculation algorithm is used, with gradual accumulation and distribution of stresses, implemented in the LIRA-SAPR software package. For the nonlinear dynamic method, the Lagrangian-Eulerian formulation is used using the methods of gas dynamics in the LS-DYNA software package. Results. As a result of numerical simulation, the following was done analysis of existing methods of nonlinear calculations; analysis of the existing loads during the flow of shock waves around the structure; analysis of the forces and movements in the bearing elements, as well as pictures of the destruction of concrete and reinforcement. Conclusions. According to the results of the comparison of the two approaches, conclusions are drawn about the advantages and disadvantages of the methods. Advantages of nonlinear dynamic calculation methods are noted compared to the equivalent-static ones. Use of the combined approach to the description of the shock wave front gives a reduction in time and allows us to describe the interaction of the wave with the structure with sufficient accuracy. The findings indicate the relevance of the study and provide an opportunity to move to more reasonable computational models.

Probable Calculation of Reinforced Concrete Elements by Deformation

2019 ◽  
Vol 974 ◽  
pp. 614-619
Author(s):  
Valeria A. Pshenichkina ◽  
Fedor F. Leychu ◽  
Kseniya N. Sukhina ◽  
Vyacheslav V. Drozdov
Keyword(s):  
Reinforced Concrete ◽  
Building Material ◽  
Crack Opening ◽  
Concrete Structures ◽  
Reinforced Concrete Structures ◽  
Uniform Deformation ◽  
Operation Stage ◽  
High Degree ◽  
Concrete Elements ◽  
Degree Of Heterogeneity

The article discusses the methodology for the reinforced concrete structures’ probabilistic deformation calculation. The uniform deformation criteria for assessing the reliability of reinforced concrete structures in the operation stage for strength, stiffness and crack opening are proposed. Taking into consideration the relatively high degree of heterogeneity of reinforced concrete as a building material, each criterion is determined with a predetermined provision.

An Innovative Method of Voided Reinforced Concrete One-Way Slabs Using Bundled Waste PET Bottled Tubes

2020 ◽  
Vol 1007 ◽  
pp. 76-84
Author(s):  
Majid S. Mohammed ◽  
Mohammed L. Ahmed ◽  
Ziadoon M. Ali ◽  
Akram S. Mahmoud
Keyword(s):  
Reinforced Concrete ◽  
Polyethylene Terephthalate ◽  
Concrete Structure ◽  
Load Level ◽  
Pet Bottles ◽  
Innovative Method ◽  
New Thinking ◽  
Load Displacement ◽  
Concrete Elements

Sustainability in concrete structure has been developed rapidly for ensuring the requested for a new thinking about construction by concrete elements. This paper deals with using buddle using polyethylene terephthalate PET bottles and steel meshes for fabricating and modeling one way RC voided slab. That is very useful to reduce the weight of slab, also reduced the wastes in same time. For both the voided and solid ones, the load-displacement curves were almost identical from beginning until the load reaches ultimate stages, where the increasing in depth of voided slab showed higher strengths and lower displacement at same load level.

scholarly journals EXPERIMENTAL STUDIES OF DEFORMABILITY AND FRACTURE RESISTANCE OF AIRFIELD SLABS ON MODELS

2021 ◽  
Vol 3 (2) ◽  
pp. 64-74
Author(s):  
I. Korneieva ◽  
◽  
D. Kirichenko ◽  
O. Shyliaiev ◽  
◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Steel Fiber ◽  
Concrete Slab ◽  
Crack Opening ◽  
Experimental Studies ◽  
Measuring Instruments ◽  
Reinforced Concrete Slab ◽  
Fiber Concrete ◽  
Steel Fiber Concrete ◽  
Opening Width

The results of experimental studies of deformability and crack resistance of models of aerodrome slabs made of reinforced concrete and steel-fiber concrete, made on the basis of serial slab PAG-18 taking into account the scale factor, are presented. Two series of slabs were tested - two models of reinforced concrete and two models with one-percent dispersed reinforcement. The load was applied in steps, the instrument readings were recorded twice at each step and the crack opening width was measured starting from the moment of the first crack formation. Dial gauges, deflectometer and microscope MPB-3 were used as measuring instruments. In accordance with the normative documents acting in Ukraine, one of two possible loading schemes was considered - with the loading by the concentrated force applied in the span part of a plate which had a hinged support along its short sides. Plate models were tested on a specially made stand. Each load step ended with a five-minute dwell time, at the beginning and the end of which readings were taken on the measuring instruments. The deformations at the same levels were measured with dial gauges. The process of crack formation was observed with a Brinell tube in the places of the greatest crack opening. Breaking load for fiber concrete slab was 1.52 times higher than for reinforced concrete slab, and the moment of cracking initiation was 1.22 times higher. The process of cracking in the fiber concrete slab begins at higher loads than in the reinforced concrete slab. The initial crack opening width of the slabs is almost the same, and the final crack opening width of all the cracks in the fiber concrete slab is significantly lower than in the reinforced concrete slab. The deformations in steel-fiber concrete slabs when the load is applied in the span, both for compressed and stretched fibers, are higher than in reinforced concrete slabs. The experimental studies indicate that dispersed reinforcement of airfield slabs with steel fiber leads to their higher crack resistance.

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