The residual cross section factor as a key parameter for the static evaluation of corroding reinforced concrete structures

2015 ◽  
Vol 66 (9) ◽  
pp. 829-838 ◽  
Author(s):  
J. Harnisch ◽  
M. Raupach
Keyword(s):  
Reinforced Concrete ◽  
Cross Section ◽  
Concrete Structures ◽  
Reinforced Concrete Structures ◽  
Static Evaluation ◽  
Key Parameter

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.

scholarly journals CRITICAL DEPTH OF NORMAL CRACKS IN REINFORCED CONCRETE BEAMS OF RECTANGULAR CROSS-SECTION

2013 ◽  
Vol 19 (4) ◽  
pp. 583-590 ◽  
Author(s):  
Vidmantas Jokūbaitis ◽  
Linas Juknevičius
Keyword(s):  
Reinforced Concrete ◽  
Stress State ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Analytical Data ◽  
Concrete Structures ◽  
Reinforced Concrete Beams ◽  
Reinforced Concrete Structures ◽  
Concrete Members ◽  
Section Shape

The evaluation of stress state of longitudinal tensile reinforcement is highly important while examining the technical state of under-reinforced concrete structures. The appearance of yield stress in tensile reinforcement could be treated as the start of incipient failure of the flexural structure. The state of tensile reinforcement of flexural reinforced concrete structures could be examined by observing the properties of normal cracks. This paper presents the analysis of the relationship between various parameters of a normal crack during its development. Some elements of fracture mechanics are used for analysis of stress state in flexural reinforced concrete members. The analytical data are compared to the experimental results, and the adjustment functions are proposed for flexural beams of certain cross section shape, dimensions and reinforcing ratio.

RESULTS OF EXPERIMENTAL STUDIES OF REINFORCED CONCRETE STRUCTURES WITH SQUARE CROSS SECTIONS IN TORSION WITH BENDING

2020 ◽  
Vol 91 (5) ◽  
pp. 3-12
Author(s):  
Vl.I. KOLCHUNOV ◽  
◽  
A.I. DEMYANOV ◽  
I.V. PECHENEV ◽  
◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Cross Section ◽  
Cross Sections ◽  
Crack Formation ◽  
Rectangular Cross Section ◽  
Crack Opening ◽  
Experimental Studies ◽  
Concrete Structures ◽  
Strain Gauges ◽  
Reinforced Concrete Structures

The article presents the results of experimental studies of the complex resistance of reinforced concrete structures with a square cross-section, made of B25 heavy-concrete, which includes graphs of deflection and rotation angles, as well as the dependence of concrete deformations obtained from the indications of strain gauges. The main deformations of elongation (and shortening) of concrete were determined using data, obtained from the proposed scheme for installing strain gauges. Rebar for experimental samples was selected in such a way that it achieved yield stress in the stage before destruction. The obtained experimental data is required for evaluation of proposed methods for calculation of structures with a rectangle cross section structures in the considered stress-strain state, for example, to check the values of the general load of crack appearing, its value relative to the distruction load; distance between cracks at different levels of crack formation, width of cracks opening at the level of the main reinforcement axis and at the distance of two diameters from the reinforcement axis, coordinates of spatial cracks formation, schemes of crack formation, crack development and crack opening. It was found, that in the tested structures the width of crack opening at the level of the main reinforcement axis is two to three times less than at a distance of two diameters from the main longitudal (or transverse) reinforcement axis. The parameters and crack patterns established during the experiments allow us to clarify the accepted working hypotheses for constructing a calculation model of the resistance in reinforced concrete structures of rectangular cross-section under torsion with bending.

scholarly journals Main results of experimental studies of reinforced concrete structures of high-strength concrete B100 round and circular cross sections in torsion with bending

2019 ◽  
Vol 15 (1) ◽  
pp. 51-61
Author(s):  
Vladimir I Travush ◽  
Nikolay I Karpenko ◽  
Vladimir I Kolchunov ◽  
Semen S Kaprielov ◽  
Alexey I Dem’yanov ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Cross Section ◽  
High Strength Concrete ◽  
Crack Opening ◽  
Experimental Studies ◽  
Concrete Structures ◽  
Circular Cross Section ◽  
High Strength ◽  
Reinforced Concrete Structures ◽  
Strength Concrete

Aim of the research to verify the proposed calculating apparatus and accumulate new experimental data on the complex resistance of reinforced concrete structures, experimental studies of such structures made of high-strength concrete of circular and circular cross-section were conducted at the testing base of the South-West State University. Method is experimental-theoretical. Results of experimental research the plots of the deflections and rotation angles, the dependency of deformations of concrete according to the testimony of the outlets of electrodesorption with respect to the calculated cross section 1-1. The main deformations of elongation and shortening of concrete were determined; the reinforcement was selected in such a way that in the stage preceding the destruction, it reached fluidity, so the stresses in the reinforcement are known. It is established that for reinforced concrete structures made of high-strength concrete of circular cross-section, as a rule, there is the development of two cracks, i.e. the round shape of the cross-section slightly reduces the concentration due to the structure of high-strength concrete. For the annular section there were several cracks, of which stands out the one on which the destruction occurs. On the steps preceding the destruction, this crack begins to prevail over the rest and has a maximum opening width. On the basis of experimental studies of reinforced concrete structures made of high-strength concrete of square and box sections, reliable data on the complex stress-strain state in the studied areas of resistance, such as: the values of the generalized load of cracking , and destruction ,, its level relative to the limit load; the distance between the cracks at different levels of cracking (up to the moment of destruction, as a rule, two or three levels are formed); crack widths at the level of the axis of the working armature, at a distance of two diameters from the axes of the armature and along the entire crack profile at various stages of loading, from which it follows that the crack opening at the level of the axis of reinforcement in 2-3 times less compared with the crack opening on the removal of 1.5-2 diameters of the working axis (longitudinal and transverse) reinforcement; the coordinates of the spatial formation of cracks; schematic drawings on tablets of education, development and opening of cracks of reinforced concrete constructions in torsion with bending. Thus, the experimental studies and the result provide an opportunity to test the developed computational model and its working hypotheses for assessing the resistance of reinforced concrete structures made of high-strength concrete in torsion with bending.

Design of precast reinforced concrete structures of frame buildings: a new set of rules

2019 ◽  
pp. 4-9 ◽  
Keyword(s):  
Reinforced Concrete ◽  
Concrete Structures ◽  
Reinforced Concrete Structures ◽  
Building Frames ◽  
Fine Grained ◽  
Rigid Frame ◽  
Floor Slabs ◽  
Frame Buildings ◽  
Spatial System ◽  
Precast Elements

Currently, prefabricated reinforced concrete structures are widely used for the construction of buildings of various functional purposes. In this regard, has been developed SP 356.1325800.2017 "Frame Reinforced Concrete Prefabricated Structures of Multi-Storey Buildings. Design Rules", which establishes requirements for the calculation and design of precast reinforced concrete structures of frame buildings of heavy, fine-grained and lightweight structural concrete for buildings with a height of not more than 75 m. The structure of the set of rules consists of eight sections and one annex. The document reviewed covers the design of multi-story framed beam structural systems, the elements of which are connected in a spatial system with rigid (partially compliant) or hinged joints and concreting of the joints between the surfaces of the abutting precast elements. The classification of structural schemes of building frames, which according to the method of accommodation of horizontal loads are divided into bracing, rigid frame bracing and framework, is presented. The list of structural elements, such as foundations, columns, crossbars, ribbed and hollow floor slabs and coatings, stiffness elements and external enclosing structures is given; detailed instructions for their design are provided. The scope of the developed set of rules includes all natural and climatic zones of the Russian Federation, except seismic areas with 7 or more points, as well as permafrost zones.

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.

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