Numerical Evaluation of Residual Fire-Resistance of Reinforced Concrete Structures After-Cooling

Purpose The aim of the research was to investigate the effect of concrete strength on the fire resistance of structures. At first, it may seem contradictory that higher concrete strengths can decrease the fire resistance of building structures. However, if the strength of the concrete exceeds a maximum value, the risk of spalling (the detachment of the concrete surface) significantly. Design/methodology/approach Prefabricated structural elements are often produced with higher strength. The higher concrete strengths generally do not cause a reduction in the load bearing capacity, but it can have serious consequences in case of structural fire design. Results of two prefabricated elements, namely, one slab (TT shaped panel) and one single layer wall panel, were examined. Results of the specimen with the originally designed composition and a specimen with modified concrete composition were examined, were polymer fibres were added to prevent spalling. Findings As a result of the experiments, more strict regulations in the standards the author is suggested including more strict regulations in the standards. It has been proved that to ensure the fire safety of the reinforced concrete structures, it is required after polymer fibres even in lower concrete strength class than prescribed by the standard. In addition, during the classification and evaluation of structures, it is advisable to introduce an upper limit of allowed concrete strength for fire safety reasons. Originality/value As a result of the experiments, the author suggests including more strict regulations in the standards. It has been proved that to ensure the fire safety of the reinforced concrete structures, it is necessary to require the addition of polymer fibres even in lower concrete strength class than prescribed by the standard. In addition, during the classification and evaluation of structures, it is advisable to introduce an upper limit of allowed concrete strength for fire safety reasons.

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

ПОЖАРОВЗРЫВОБЕЗОПАСНОСТЬ ◽

10.22227/pvb.2021.30.02.49-70 ◽

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.

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EVALUATION OF FIRE-RESISTANCE OF STRUT REINFORCED CONCRETE STRUCTURES

URBAN CONSTRUCTION AND ARCHITECTURE ◽

10.17673/vestnik.2015.01.13 ◽

2015 ◽

Vol 5 (1) ◽

pp. 82-89 ◽

Cited By ~ 3

Author(s):

Nikolay A. ILYIN ◽

Denis A. PANFILOV ◽

Denis V. LITVINOV ◽

Pavel N. SLAVKIN

Keyword(s):

Reinforced Concrete ◽

Fire Resistance ◽

Fire Hazard ◽

Concrete Structures ◽

Hazard Evaluation ◽

Reinforced Concrete Structures ◽

Engineering Analysis ◽

Temperature Impact ◽

Actual Fire

In SGASU a new engineering solution for buildings fire protection is developped. Its especially efficient for classification of reinforced concrete structures according to their resistance to high-temperature impact in case of fire or technological emergency that gives an opportunity to use a structure with actual fire resistance grading in buildings of different structural fire hazard. Evaluation of actual fi re resistance grading by engineering analysis (as opposed to inplace tests of reinforced concrete structures) makes possible resource and energy saving.

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Increase of Temperature and Fire Resistance for Reinforced-Concrete Structures by Surface Treatment with Protective Coating

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.788.36 ◽

2018 ◽

Vol 788 ◽

pp. 36-44

Author(s):

Liudmyla Demydchuk ◽

Dmytro Sapozhnyk

Keyword(s):

Reinforced Concrete ◽

Fire Resistance ◽

Protective Coating ◽

Concrete Structures ◽

Fire Retardant ◽

Reinforced Concrete Structures ◽

Building Structures ◽

Fire Tests ◽

Normative Documents ◽

Concrete Building

The normative documents of Ukraine (DBN V.1.1.7 ̶ 2016) [1] establish that the limit of fire resistance of reinforced-concrete building structures is determined by the calculation method or by fire tests, and shall be at least 45 minutes. Taking into account the modern construction technologies, namely, the reduction of the section of the main building reinforced-concrete structures, it is expedient to use fire-retardant coatings to provide the necessary fire resistance limit.

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Increase of fire resistance of reinforced concrete structures with polypropylene microfiber

MATEC Web of Conferences ◽

10.1051/matecconf/201824503005 ◽

2018 ◽

Vol 245 ◽

pp. 03005 ◽

Cited By ~ 1

Author(s):

Marina Gravit ◽

Elena Golub

Keyword(s):

Reinforced Concrete ◽

Fire Resistance ◽

Concrete Structures ◽

Point Of View ◽

Reinforced Concrete Structures ◽

Fibrous Materials ◽

Reinforced Concrete Structure ◽

Explosive Spalling ◽

High Rise ◽

Concrete Mix

The increase in the construction of high-rise, technically complex buildings and structures is a prerequisite for the widespread use of structures of heavy concrete. In this work, a special type of destruction of this type of concrete is considered in the fire action explosive spalling. One method of protection is polypropylene microfiber, the objective of which is to increase the fire resistance of concrete and reinforced concrete structures. The fire resistance tests of the reinforced concrete structure with the use of microfiber and without it have been carried out. It is shown that polypropylene microfiber can completely prevent explosive spelling of concrete. In addition, the introduction of additives in the form of fibrous materials into the concrete mix is the most optimal from the point of view of labor intensity and material costs.

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Fire Resistance of Non-Crack Resistant Flexural Reinforced Concrete Elements

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.725-726.15 ◽

2015 ◽

Vol 725-726 ◽

pp. 15-20

Author(s):

Vyacheslav Belov ◽

Valery Morozov

Keyword(s):

Reinforced Concrete ◽

High Temperature ◽

Fire Resistance ◽

Concrete Structures ◽

National Income ◽

Developed Countries ◽

Reinforced Concrete Structures ◽

Reinforced Concrete Structure ◽

Actual Problem ◽

Concrete Elements

In developed countries only loss of property because of fire makes annually up to 2% of their national income [9, 15]. The bearing capacity of reinforced concrete structures at high temperature impact is lost within several dozens of minutes [1, 3, 5, 10, 12, 18, 25]. Disappointing statistics of increase of both the number of fires and the scope of damage due to them aggravates the actual problem of determination of reinforced concrete structures fire-endurance. The main problems and methods of evaluation of reinforced concrete structure fire resistance are stated. Within the framework of block approach to evaluation of strain of flexural reinforced concrete elements with cracks, design model of reinforced concrete thermo-force resistance is made. Extended nomenclature of influences of high temperature at fire on decrease of performance of bearing reinforced concrete structures is considered. Empirical dependencies of strength and strain characteristics of concrete and reinforcement on high temperatures are used. Proposals on specification of evaluation of fire resistance of statically indeterminate reinforced concrete structures are formulated.

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