STIFFNESS OF REINFORCED CONCRETE STRUCTURES UNDER BENDING WITH TRANSVERSE AND LONGITUDINAL FORCES

2021 ◽  
Vol 98 (6) ◽  
pp. 5-19
Author(s):  
VL.I. KOLCHUNOV ◽  
◽  
O.I. AL-HASHIMI ◽  
M.V. PROTCHENKO ◽  
◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Cross Sections ◽  
Concrete Structures ◽  
Bending Moment ◽  
Reinforced Concrete Structures ◽  
The Matrix ◽  
Local Shear ◽  
The Difference ◽  
Inclined Cracks ◽  
Opening Width

The authors developed a model for single reinforced concrete strips in block wedge and arches between inclined cracks and approximated rectangular cross-sections using small squares in matrix elements. From the analysis of the works of N.I. Karpenko and S.N. Karpenko the "nagel" forces in the longitudinal tensile reinforcement and crack slip , as a function of the opening width and concrete deformations in relation to the cosine of the angle . The experimental " nagel " forces and crack slip dependences for the connection between and in the form of an exponent for the reinforcement deformations and spacing are determined. The forces have been calculated for two to three cross-sections (single composite strips) of reinforced concrete structures. On the bases of accepted hypothesis, a new effect of reinforced concrete and a joint modulus in a strip of composite single local shear zone for the difference of mean relative linear and angular deformations of mutual displacements of concrete (or reinforcement) are developed. The hypothesis allows one to reduce the order of the system of differential equations of Rzhanitsyn and to obtain in each joint the total angular deformations of concrete and the "nagel" effect of reinforcement. The curvature of the composite bars has a relationship from the total bending moment of the bars to the sum of the rigidities. The stiffness physical characteristics of the matrix from the compressed concrete area and the working reinforcement are obtained in a system of equations of equilibrium and deformation, as well as physical equations.

THE INFLUENCE OF BASALT-COMPOSITE PRESTRESSED REINFORCEMENT ON THE OPERATION OF LOW-REINFORCED CONCRETE STRUCTURES WITH INTERBLOCK CONSTRUCTION JOINTS

2020 ◽  
pp. 50-59
Author(s):  
O.D. RUBIN ◽  
◽  
S.E. LISICHKIN ◽  
O.V. ZYUZINA
Keyword(s):  
Reinforced Concrete ◽  
Experimental Studies ◽  
Concrete Structures ◽  
Bending Moment ◽  
Reinforced Concrete Beam ◽  
Hydraulic Structures ◽  
Reinforced Concrete Structures ◽  
Beam Type ◽  
Construction Joints ◽  
Composite Reinforcement

It is proposed to use prestressed basalt composite reinforcement to strengthen reinforced concrete structures of hydraulic structures. In order to substantiate technical reinforcement of reinforced concrete structures of hydraulic structures with prestressed basalt composite inforcement, experimental studies were carried out. For experimental studies, reinforced concrete beam-type structures with vertical interblock construction joints were adopted.The results of experimental studies of reinforced concrete models of beam type with interblock joints reinforced with prestressed basalt composite reinforcement by the method of tension “on concrete”are presented. The models are tested for bending moment and transverse force. A special character of cracking is noted; full restoration of the bearing capacity of reinforced concrete structures, weakened by interblock construction joints, was recorded due to the reinforcement of prestressed basalt composite reinforcement.

The Construction of the Diagrammatic Deformation Model for Calculating the Core Reinforced-Concrete Structures in Finite Increments under Joint Action of Load Increments and Variable by Cross Sections Low and Ultra Low Subzero Temperatures

2021 ◽  
Vol 887 ◽  
pp. 665-671
Author(s):  
N.I. Karpenko ◽  
S.N. Karpenko ◽  
D.Z. Kadiev ◽  
G.A. Moiseenko
Keyword(s):  
Reinforced Concrete ◽  
Cross Sections ◽  
Computer Calculation ◽  
Concrete Structures ◽  
Deformation Model ◽  
Reinforced Concrete Structures ◽  
The Core ◽  
Use Of Time ◽  
Subzero Temperatures ◽  
Iteration Methods

The use of the nonlinear deformation model in computer calculation methods involves the use of time-consuming step-iteration methods for solving systems of resolving equations with problems of convergence. To eliminate these difficulties, the physical relations of the deformation model are established in finite increments. The article considers the construction of such a model in finite increments as applied to the calculation of the core reinforced-concrete structures in the overall case of oblique bending and oblique eccentric compression or tension, taking into account the action by the cross sections of low subzero temperatures.

A solution to the thermal problem of fire resistance of spun reinforced concrete columns

2021 ◽  
Vol 30 (2) ◽  
pp. 49-70
Author(s):  
I. I. Palevoda ◽  
D. S. Nekhan
Keyword(s):  
Reinforced Concrete ◽  
Cross Section ◽  
Cross Sections ◽  
Fire Resistance ◽  
Concrete Structures ◽  
Concrete Columns ◽  
Full Scale ◽  
Reinforced Concrete Structures ◽  
Thermal Problem ◽  
Reinforced Concrete Columns

Introduction. Spun reinforced concrete columns are widely used in the present-day international construction practice. Known formulas, used to calculate temperatures of cross sections of reinforced concrete structures, needed to assess their fire resistance limit, are successfully applied to homogeneous structures that have solid sections. However, they are inapplicable to spun reinforced concrete columns due to their structural features. The purpose of this work is to develop a method for solving a thermal problem of spun reinforced concrete columns and adapt existing calculation formulas.Materials and methods. This work addresses the heating of spun reinforced concrete structures in case of fire. Ansys Workbench was employed to perform the computer simulation needed to study the influence of the characteristics of spun reinforced concrete columns on their heating. Results and discussion. In the course of the theoretical studies, the effect, produced by column cavities, the heterogeneity of spun concrete and thin walls of these structures on the heating of their cross sections was assessed with regard for the results of full-scale fire tests of spun reinforced concrete columns. Correction coefficients were obtained in order to take account of these factors. A regression equation was derived as a result of the simulation performed in the context of a full-scale factorial experiment involving coefficient khol, which takes into account the rising temperature of hollow reinforced concrete structures in comparison with solid ones. Khet heating acceleration coefficient is applicable to spun reinforced concrete structures due to the heterogeneity of concrete in the cross section. This coefficient represents a function of the wall thickness. Coefficient kth, which allows for the heating acceleration in the course of crack opening in thin-walled structures, varies in the range of 1.00…1.40. The concrete cracking temperature is 550 °C.Conclusion. A new method allows to solve the thermal problem of fire resistance of spun reinforced concrete columns. The engineering formula used to calculate the temperature in a cross-section was adapted. The results of computer-aided simulation and calculation of temperature values, performed using the adapted formula, show acceptable convergence with the experimental data.

IMPROVEMENT OF THE METHOD OF CALCULATING THE STRESS-STATE AND STRENGTH OF REINFORCED CONCRETE STRUCTURES OF HYDRAULIC CORNER RETAINING WALLS WITH INTER-BLOCK JOINTS TAKING

2021 ◽  
pp. 62-69
Author(s):  
S. E. LISICHKIN ◽  
◽  
O.D. RUBIN ◽  
F. A. PASHCHENKO ◽  
N. S. KHARKOV
Keyword(s):  
Reinforced Concrete ◽  
Retaining Wall ◽  
Concrete Structures ◽  
Retaining Walls ◽  
Transverse Reinforcement ◽  
Reinforced Concrete Structures ◽  
Wall Structures ◽  
Long Time ◽  
Characteristic Features ◽  
Inclined Cracks

Corner retaining walls are one of the most common structures of waterworks. Most of them were designed and built several decades ago and have been in operation for a long time. In some cases, there is a deviation from the design prerequisites and the strengthening of reinforced concrete structures of retaining walls is required. The main reason for these deviations is incomplete consideration of the characteristic features of retaining wall structures (including horizontal inter-block joints and secondary inclined cracks), as well as the nature of the loads acting on them. As a result, design horizontal transverse reinforcement is practically not installed in retaining walls that is not required by calculation based on traditional calculation methods.Traditional reinforcement schemes for retaining walls do not provide for the presence of horizontal inter-block joints and horizontal transverse reinforcement. As a result of the research carried out,the method for calculating the stress-strain state and strength of reinforced concrete structures of corner retaining walls with inter-block joints has been improved taking into account secondary stresses. Reinforcement schemes for retaining walls have also been improved.

A new method for estimating the scale of fluctuation in reliability assessment of reinforced concrete structures considering spatial variability

2018 ◽  
Vol 21 (13) ◽  
pp. 1951-1962 ◽  
Author(s):  
Yiming Yang ◽  
Jianxin Peng ◽  
Jianren Zhang ◽  
CS Cai
Keyword(s):  
Reinforced Concrete ◽  
Spatial Variability ◽  
Bayesian Information Criterion ◽  
Concrete Structures ◽  
Estimation Method ◽  
Bending Moment ◽  
Information Criterion ◽  
Geometrical Parameters ◽  
Reinforced Concrete Structures ◽  
Scale Of Fluctuation

The scale of fluctuation ( θ) of the material and geometrical parameters is the basis of studying the spatial variability of reinforced concrete structures. In this article, a new estimation method for the scale of fluctuation based on Bayesian information criterion is proposed. And based on the analysis of experimental data recorded on the three 36-year-old beams of the Jianggong Bridge and 246 corroded steel bars, the scale of fluctuation ( θ) of concrete compressive strength ( fc) and steel pitting factor ( R) are estimated. The theoretical bending moment of three test beams are calculated considering the influence of the spatial distributions of fc, R, and other relative variables. The reasonableness and superiority of the Bayesian information criterion model than the auto-correlation function method and the semivariogram function model are verified by comparing the theoretical results with the measured bending moment of the three beams mentioned above.

scholarly journals CALCULATION SCHEME OF REINFORCED CONCRETE STRUCTURES OF CIRCULAR CROSS-SECTION UNDER BENDING WITH TORSION

2021 ◽  
Vol 17 (3) ◽  
pp. 63-82
Author(s):  
Vladimir Kolchunov ◽  
Sergey Bulkin
Keyword(s):  
Reinforced Concrete ◽  
Cross Sections ◽  
Concrete Structures ◽  
Circular Cross Section ◽  
Shear Stresses ◽  
Reinforced Concrete Structures ◽  
Dowel Action ◽  
The Moment ◽  
External Forces ◽  
Spatial Section

The developed design diagram of the ultimate resistance of reinforced concrete structures in bending with torsion of circular cross-sections most fully reflects the features of their actual exploitation. For a spatial crack of a diagonal large ellipse, sections are taken in the form of a swirling propeller with concave and convex spatial parabolas from the first and second blocks between vertical transverse circular sections from the beginning to the end of the crack. For practical calculations in compressed and tensioned concrete, a polyline section of three sections is considered: two longitudinal trapezoids and the third middle section of the radius curve of a small ellipse close to forty-five degrees. When calculating unknown forces, solutions of the equations of equilibrium and deformations of the sections are made up to the end of the crack passing through the moment points for the resultant moments and the projections of internal and external forces. Shear torsional stresses along the linear longitudinal sections of the trapezoid were presented, as well as normal and shear stresses located on the end cross-sections at a distance x from the support. The height of the compressed area of concrete decreases with an increase in bending moments in the spatial section between the first and third cross-sections. It is found in their relationships and connections. The dowel action of reinforcement is determined using a special model of the second level with discrete constants. The static loading scheme was considered from the standpoint of an additional proportional relationship between the torques along the length of the bar in the spatial section and the first and third transverse sections. For a dangerous spatial crack, when projected onto the horizontal axis, the length C was found from a diagonal large ellipse of a round bar.

scholarly journals On direct determination of shear force taken up by concrete in oblique cross-sections of reinforced concrete structures

2021 ◽  
Vol 34 (02) ◽  
pp. 1039-1048
Author(s):  
Aleksei N. Morozov
Keyword(s):  
Reinforced Concrete ◽  
Cross Sections ◽  
Shear Force ◽  
Concrete Structures ◽  
Direct Determination ◽  
Computation Method ◽  
Reinforced Concrete Structures ◽  
Normal Section ◽  
Stress Block

A method has been presented for the direct determination of shear force in oblique cross-sections of reinforced concrete structures using a classic formula Q=bzτ, when the main problems of determining the shear force in oblique cross-sections are related to finding cleaving stresses in concrete and the shape of a stress-block of normal stresses in the design section, with no principles of practical division between the forms of failure in oblique sections due to concrete compression or shear. This work incorporates a criterion for dividing the forms of failure due to concrete compression or shear, based on the assumed shape of a compression stress-block with a segment cut away in a normal section, passing through the top of an inclined crack. The height of the compressed area in this normal section is defined from simultaneous solution of the equations of equilibrium in the moments in normal and oblique sections, from testing the experimental beams made of concrete and gas-concrete. This work deals with seeking the approaches for solving the above-mentioned problems in practice. The data of testing beams from gas-concrete and heavy-weight concrete have been used. Strain gauges were used to measure concrete and reinforcement deformities, computer processed thereafter. The studies have been considered on determination of cleaving stresses in oblique sections, further verified according to this method on certain alternative schemes of their application. A practical method for finding the shear force depending on the value of a shear span has been proposed. The work can encourage active discussion of this computation method.

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