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 Compression Work of Steel Reinforced Concrete Columns

2018 ◽  
Vol 7 (3.2) ◽  
pp. 229
Author(s):  
O I. Lapenko ◽  
O V. Shevchenko ◽  
N Masud
Keyword(s):  
Reinforced Concrete ◽  
Cross Section ◽  
Cross Sections ◽  
Local Stability ◽  
Steel Sheet ◽  
Concrete Columns ◽  
Reinforced Concrete Columns ◽  
Steel Reinforced Concrete ◽  
Steel Sheets ◽  
Total Stability

The article deals with the calculation of steel reinforced concrete columns compression and verification of local stability in fixed formwork. It is concluded that it is expedient to calculate the total stability for the resulted sections, and when checking local stability – to follow the instructions Eurocode 4. When checking the local stability of steel sheets, working as part of reinforced concrete structures, the Eurocode 4 guidelines should be followed, while taking into account the following requirements: leave out of account on the local stability of the concrete cross-section (the steel profile is completely surrounded by concrete); concrete cross-section (steel profile is completely concrete, partially concrete cross-section), the steel profile is only partially covered with concrete, as well as for other cross-sections of reinforced concrete columns provided by Eurocode 4 with the corresponding ratio d/ t. The calculation method for the given sections in the calculation of the overall stability of compressed steel reinforced concrete elements is the simple stand one that gives satisfactory results. Calculations show that the loss of local stability of a steel sheet that works concurrently with reinforced concrete occurs at stresses greater than the force of flow in a steel sheet.  

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 Compressive Performance of Corroded Reinforced Concrete Columns

2020 ◽  
Vol 38 (11A) ◽  
pp. 1618-1628
Author(s):  
Mushtaq S. Radhi ◽  
Maan Hassan ◽  
Iqbal Gorgis
Keyword(s):  
Reinforced Concrete ◽  
Mechanical Performance ◽  
Load Capacity ◽  
Concrete Structures ◽  
Corrosion Damage ◽  
Concrete Columns ◽  
Small Scale ◽  
Uniaxial Compression Test ◽  
Reinforced Concrete Structures ◽  
Reinforced Concrete Columns

Corrosion of reinforcement has been identified as the deterioration mechanism of reinforced concrete structures, which seriously affects the safety and integrity of structures. The corrosion of the embedded reinforcing steel in concrete is a major problem facing civil engineers today, which initiates 80% of the reinforced concrete structures deterioration. This paper reveals the outcomes of an experimental investigation on the mechanical performance (residual strength) of circular steel reinforced columns which have been damaged by corrosion of the steel rebar. Small scale circular reinforced concrete columns with a diameter of 100 mm and 300 mm in height were adopted.  Different rates of steel reinforcement mass loss (corrosion damage) ranged between 10%, 20% to 30 % were created in the columns by using a galvanostatic accelerated corrosion method combined with wetting-drying cycles. The uniaxial compression test was implemented for damaged columns up to failure. Based on the experimental outcomes, it was revealed that the corrosion damage had substantially reduced the performance of columns. The decrement of the load capacity of corroded columns ranged between 19% to 40% and for corrosion, level ranged from 10% to 30%, respectively. The decrement of the final deformation of corroded columns ranged between 15% to 30% and for corrosion, level ranged from 10% to 30%, respectively. Likewise, the failure mode and relationship between the stress and strain for corroded columns had been adversely affected by corrosion.

SETTING A DIAGRAM APPROACH TO CALCULATING VIBRATED, CENTRIFUGED AND VIBROCENTRIFUGED REINFORCED CONCRETE COLUMNS WITH A VARIATROPIC STRUCTURE

2020 ◽  
pp. 22-34
Author(s):  
Л. Р. Маилян ◽  
С. А. Стельмах ◽  
Е. М. Щербань ◽  
М. П. Нажуев
Keyword(s):  
Experimental Data ◽  
Reinforced Concrete ◽  
Bearing Capacity ◽  
Cross Section ◽  
Concrete Columns ◽  
Reinforced Concrete Columns ◽  
The Cross ◽  
Concrete Elements ◽  
Diagram Approach

Состояние проблемы. Железобетонные элементы изготавливаются, как правило, по трем основным технологиям - вибрированием, центрифугированием и виброцентрифугированием. Однако все основные расчетные зависимости для определения их несущей способности выведены, исходя из основного постулата - постоянства и равенства характеристик бетона по сечению, что реализуется лишь в вибрированных колоннах. Результаты. В рамках диаграммного подхода предложены итерационный, приближенный и упрощенный способы расчета несущей способности железобетонных вибрированных, центрифугированных и виброцентрифугированных колонн. Выводы. Расчет по диаграммному подходу показал существенно более подходящую сходимость с опытными данными, чем расчет по методике норм, а также дал лучшие результаты при использовании дифференциальных характеристик бетона, чем при использовании интегральных и, тем более, нормативных характеристик бетона. Statement of the problem. Reinforced concrete elements are typically manufactured according to three basic technologies - vibration, centrifugation and vibrocentrifugation. However, all the basic calculated dependencies for determining their bearing capacity were derived using the main postulate, i.e., the constancy and equality of the characteristics of concrete over the cross section, which is implemented only in vibrated columns. Results. Within the framework of the diagrammatic approach, iterative, approximate and simplified methods of calculating the bearing capacity of reinforced concrete vibrated, centrifuged and vibrocentrifuged columns are proposed. Conclusions. The calculation according to the diagrammatic approach showed a significantly better convergence with the experimental data than that using the method of norms, and also performs better when using differential characteristics of concrete than when employing integral and particularly standard characteristics of concrete.

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