scholarly journals THE EFFECT OF HIGH TEMPERATURE ON REINFORCED CONCRETE STRUCTURES

2010 ◽  
Vol 2 (1) ◽  
pp. 12-21 ◽  
Author(s):  
Robertas Zavalis ◽  
Arnoldas Šneideris
Keyword(s):  
Reinforced Concrete ◽  
High Temperature ◽  
Cross Sections ◽  
Concrete Strength ◽  
Temperature Fields ◽  
Concrete Element ◽  
Zone Method ◽  
Standard Fire ◽  
Fire Curve ◽  
Zone Dimension

The article represents the behaviour of reinforced concrete and its components (concrete and reinforcement) under high temperature. The comparing analysis of the experimentally and theoretically obtained results has been performed. The carried out experiment has disclosed that the mechanical properties of concrete alters differently in cases of temperature rise and theoretical reference. The most visible difference has been noticed at a temperature of 100 °C (Fig 4, Fig 5). The main fire resistance calculation basics are discussed. The temperature fields of the reinforced concrete element cross-section are calculated according to the standard fire curve using the program COSMOS/M of the finite element method. Concrete thermal properties, thermal conductivity and specific heat capacity dependence on temperature are taken into account in the model (Fig 10, Fig 11). By means of this model, the corresponding algorithm (Table 2) was made and can be used for obtaining temperature distribution for the reinforced concrete element of different cross-sections. According to the received temperature fields and applying the zone method, the influence of differences in theoretical and experimental results on element load bearing capacity is determined. The residual strength of the element considering the theoretical reduction curve of concrete strength is 5% larger than the results obtained in cases of 30 and 60 minutes heating. 90 and 120 minutes heating indicates that element strength is only 2% larger than the results calculated experimentally. The reduced zone dimension determined due to a decrease in the reduction coefficient at a temperature of 100 °C has affected residual element strength.

scholarly journals Strength criterion for a plane stress reinforced concrete element under a special action

Vestnik MGSU ◽  
2020 ◽  
pp. 1513-1522
Author(s):  
Natalia V. Fedorova ◽  
Vu Ngoc Tuyen ◽  
Igor A. Yakovenko
Keyword(s):  
Reinforced Concrete ◽  
Progressive Collapse ◽  
Concrete Strength ◽  
Limit State ◽  
Strength Criterion ◽  
Structural Systems ◽  
Variable Loading ◽  
Concrete Element ◽  
Theory Of Plasticity ◽  
Concrete Elements

Introduction. Problem solving focused on the protection of buildings and structures from progressive collapse and minimization of resources, needed for this purpose, is becoming increasingly important. In many countries, including Russia, this type of protection is incorporated into national regulatory documents, and, therefore, any research, aimed at developing effective ways to protect structural systems from progressive collapse under special actions, is particularly relevant. In this regard, the present article aims to formulate effective strength criteria for such anisotropic materials as reinforced concrete to analyze plane stressed reinforced concrete structures exposed to sudden structural transformations caused by the removal of one of bearing elements. Materials and methods. To solve this problem, a variant of the generalized theory of plasticity of concrete and reinforced concrete, developed by G.A. Geniev, is proposed for application to the case of variable loading of a plane stressed reinforced concrete element. The acceptability of generalization of the strength criterion, pursuant to the theory of plasticity of concrete and reinforced concrete under static loading, and the applicability of this criterion to variable static-dynamic loading of reinforced concrete are used as the main hypothesis. An algorithm of an approximate method is presented as a solution to this problem; it allows to analyze the considered stress-strain state of plane stressed reinforced concrete elements. Results. The numerical analysis of the obtained solution, compared with the results of the experimental studies, was used to evaluate the designed strength criterion for reinforced concrete elements located in the area where the column is connected to the girder of a monolithic reinforced concrete frame in case of a sudden restructuring of a structural system. It is found out that the qualitative nature of the destruction pattern of the area under research, obtained in experiments, corresponds to the destruction pattern, identified by virtue of the analysis performed using the proposed criterion. Conclusions. The variant of the reinforced concrete strength criterion designated for the variable loading of a plane stressed reinforced concrete element and an algorithm for its implementation, based on the theory of plasticity of concrete and reinforced concrete developed by G.A. Geniev, is applicable to the analysis of a special limit state of reinforced concrete elements of structural systems of frames of buildings and structures.

Comparison Study of Structural Stabilities for H-Section Columns Built with Ordinary Grade Strength Structural Steels According to Boundary Conditions and Lengths at High Temperature

2014 ◽  
Vol 937 ◽  
pp. 424-427
Author(s):  
In Kyu Kwon
Keyword(s):  
Boundary Condition ◽  
High Temperature ◽  
Boundary Conditions ◽  
Fire Resistance ◽  
Structural Steels ◽  
Structural Members ◽  
Steel Buildings ◽  
Standard Fire ◽  
Fire Curve ◽  
Resistance Performance

Fire resistance performance of structural members has been evaluated from each singular section and standard fire curve since the beginning of fire tests. However, the need of the exact fire resistance of H-section columns applied in the steel buildings has increased. The main reason for this is there is a difference between the conditions being conducted during the fire test and that from real situation. In this paper, the structural stability of H-section column made of an ordinary strength grade structural steels, SS 400, SM 400, and SM 490 at high temperature were evaluated and compared with boundary conditions and column’s length. This was done in order to suggest a new guideline for the application of fire protective materials in steel column in which the boundary conditions and column lengths are different from that tested with hinge to hinge and 3500 mm. The findings from this study showed hinge to hinge boundary condition was more conservative. And fire resistance performance of longer columns in the case of hinge to fixed and fixed to fixed boundary condition than from 3500 mm and hinge to hinge boundary condition can sustain at high temperature without adding fire protective materials.

Fire Performance of Reinforced Concrete Beams Strengthened with CFRP Sheets Bonded with an Inorganic Adhesive

2011 ◽  
Vol 255-260 ◽  
pp. 574-579 ◽  
Author(s):  
Fu Xiong Wan ◽  
Wen Zhong Zheng
Keyword(s):  
Reinforced Concrete ◽  
Steel Structure ◽  
Reinforced Concrete Beams ◽  
Bottom Surface ◽  
Rc Beams ◽  
Cfrp Sheets ◽  
Standard Fire ◽  
Fire Curve ◽  
Fireproof Coating ◽  
In Fire

Considering softening temperatures of ordinary organic epoxy adhesives are too low, this study develops an inorganic adhesive which strength at 600°C is not lower than that at normal room temperature. Four reinforced concrete (RC) beams strengthened with CFRP sheets bonded with the inorganic adhesive are tested. The fire protection of the CFRP sheets is done using the thick-type fireproofing coatings for tunnel (TFCT) and steel structure (TFCSS) respectively. All specimens are tested in the furnace together. Specimens are exposed to fire for 1.5 hours in according to the ISO834 standard fire curve, and then naturally cooled for 1 hour. CFRP sheets at center point of bottom surface of beams are 300~470°C, and the corresponding displacements at mid-span are 1/1400~1/318 of the actual span. The CFRP sheets keep a good state and are tightly bonded on RC beams by the inorganic adhesive after fire. Temperature and deformation are analyzed by ABAQUS, and the simulation and measured results are in good agreement. The results indicate that, under the protection of fireproof coating, the CFRP sheets work well in cooperation with RC beams and slabs during fire. TFCSS is inferior to TFCT because the former is easier to drop and crack in fire. Analysis method of the finite element supplies a good way to temperature field and deformation calculation of structures in fire.

Methodology for Calculating the Technical State of a Reinforced-Concrete Fragment in a Building Influenced by High Temperature

2020 ◽  
Vol 1006 ◽  
pp. 166-172
Author(s):  
Olha Bashynska ◽  
Yurii Otrosh ◽  
Oleksandr Holodnov ◽  
Andrey Tomashevskyi ◽  
Galyna Venzhego
Keyword(s):  
Reinforced Concrete ◽  
High Temperature ◽  
Technical State ◽  
Temperature Fields ◽  
Fire Extinguishing ◽  
Load Carrying ◽  
Calculation Methodology ◽  
Temperature Exposure ◽  
Temperature Heating

The purpose of research was to develop a methodology for testing the fire-resistant quality of a building fragment influenced by a real fire to substantiate the main calculation methodology provisions and determine the residual load-carrying ability. While testing, it was supposed to determine the technical state of reinforced-concrete structures after high-temperature exposure and further intensive extinguishment. High-temperature heating and further fire extinguishing with water leads to the surface layers’ destruction and weakening of concrete. Impact on the structures of the open air leads to destruction and delamination of weakened concrete with further exposing of reinforcement and its corrosion. The approach, implemented in LIRA-SAPR software package, makes possible to take into account the influence of changes in the temperature regime of operation on the stress-strain state of the structure. After determining the temperature fields, it is necessary to reduce the rigidity characteristics of materials and perform a calculation of strength. When using this approach in order to determine the total deformations of the structure, it is necessary to take into account the creep deformation.

scholarly journals REACTION OF R/C SLABS CROSS-SECTIONS TO FIRE, Calculation of simplified substitute temperature loads induced by an unsteady heat flow

2016 ◽  
Author(s):  
Robert Kowalski ◽  
Marian Abramowicz ◽  
Paweł Chudzik
Keyword(s):  
Reinforced Concrete ◽  
Temperature Distribution ◽  
Heat Flow ◽  
Cross Sections ◽  
Average Temperature ◽  
Standard Fire ◽  
Reinforced Concrete Slabs ◽  
Nonlinear Temperature ◽  
Advanced Analysis ◽  
Temperature Loads

<p>An important issue in advanced analysis of reinforced concrete structures exposed to fire is to determine the response of structural elements (cross-sections) to the effect of high temperature. The unsteady heat flow results in a nonlinear temperature distribution. In practical structural calculations performed by simplified computer programs the average temperature value and the appropriate temperature gradient are used. This paper presents substitute values of these parameters and detailed analysis of nonlinear temperature distribution in 20, 25, 30 cm thick reinforced concrete slabs exposed to one-sided standard fire.</p>

scholarly journals Examining the Distribution of Strength across the Thickness of Reinforced Concrete Elements Subject to Sulphate Corrosion Using the Ultrasonic Method

Materials ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 2519 ◽  
Author(s):  
Bohdan Stawiski ◽  
Tomasz Kania
Keyword(s):  
Compressive Strength ◽  
Reinforced Concrete ◽  
Chemical Reactions ◽  
Cross Sections ◽  
Ultrasonic Method ◽  
Concrete Strength ◽  
Corrosive Environment ◽  
Standard Samples ◽  
Actual Distribution ◽  
Initial Strength

Sulphate corrosion of concrete is a complex chemical and physical process that leads to the destruction of construction elements. Degradation of concrete results from the transportation of sulphate compounds through the pores of exposed elements and their chemical reactions with cementitious material. Sulphate corrosion can develop in all kind of structures exposed to the corrosive environment. The mechanism of the chemical reactions of sulphate ions with concrete compounds is well known and described. Furthermore, the dependence of the compressive strength of standard cubic samples on the duration of their exposure in the sulphate corrosion environment has been described. However, strength tests on standard samples presented in the scientific literature do not provide an answer to the question regarding the measurement methodology and actual distribution of compressive strength in cross-section of reinforced concrete structures exposed to sulphate ions. Since it is difficult to find any description of this type of test in the literature, the authors undertook to conduct them. The ultrasonic method using exponential heads with spot surface of contact with the material was chosen for the measurements of concrete strength in close cross-sections parallel to the corroded surface. The test was performed on samples taken from compartments of a reinforced concrete tank after five years of operation in a corrosive environment. Test measurements showed heterogeneity of strength across the entire thickness of the tested elements. It was determined that the strength of the elements in internal cross-sections of the structure was up to 80% higher than the initial strength. A drop in the mechanical properties of concrete was observed only in the close zone near the exposed surface.

Comparison Study of Fire Resistance According to Differences of Length of H-Section Made of Submarine Structural Steels

2014 ◽  
Vol 909 ◽  
pp. 8-11
Author(s):  
In Kyu Kwon
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Structural Stability ◽  
Fire Resistance ◽  
Structural Steels ◽  
Rapid Decrease ◽  
Comparison Study ◽  
Standard Fire ◽  
Fire Curve ◽  
Standard Fire Curve

Submarine structural steels, such as SM 400, SM 490, and SM 520, have the same structural properties and same grades as general structural steels, but those have better weldability than general structural steels. For that reason, their usage is increasing. However, their fire resistance is not well defined, except for individual fire resistance, such as column and beam. The fire resistance of H-section made of submarine structural steels can be applied with various column lengths. The fire resistance of them is not clear to engineers and residents. To determine the fire resistance, in this paper an analysis was conducted using their mechanical properties at high temperature and related theories with a standard fire curve. As the strength of submarine structural steels is increased, the structural stability showed a rapid decrease while the longer the length of column, the less structural stability of the column represented.

A Study of Fire Resistance According to Boundary Condition of Ordinary Grade Structural Steels

2014 ◽  
Vol 510 ◽  
pp. 97-100
Author(s):  
In Kyu Kwon
Keyword(s):  
Boundary Condition ◽  
High Temperature ◽  
Fire Resistance ◽  
Structural Steels ◽  
Mechanical And Thermal Properties ◽  
Allowable Stress ◽  
Standard Fire ◽  
Fire Engineering ◽  
The Difference ◽  
Fire Curve

Building construction has been developed with an increase of steel application at main members, but the weakness should be resolved with a proper fire resistance. The fire engineering method is regarded as an alternative way to evaluate the fire resistance with mechanical and thermal properties at high temperature. In this paper, the fire resistance of H-section built with ordinary grade structural steels such as SS 400 and SM 490 those are representative structural steels at the construction market were analyzed by the difference of boundary conditions. The study showed that the H-section made of SM 490 represented little difference in reduction ratio of an allowable stress at one hour standard fire curve. And the hinge to hinge boundary condition from both H-sections was the lowest. As the grade of structural steel rises, the difference in an allowable stress at high temperature according to grade of structural steels is inclined to increase.

scholarly journals Simplified calculation of flexural strength deterioration of reinforced concrete T-beams exposed to ISO 834 standard fire

2021 ◽  
Vol 15 (4) ◽  
pp. 123-135
Author(s):  
Nguyen Truong Thang ◽  
Nguyen Hai Viet
Keyword(s):  
Reinforced Concrete ◽  
Flexural Strength ◽  
Cross Sections ◽  
Temperature Dependent ◽  
Strength Deterioration ◽  
Standard Fire ◽  
Parametric Studies ◽  
Simplified Calculation ◽  
T Beam

Reinforced concrete (RC) T-shaped cross-section beam (so-called T-beam) is a common structural member in buildings where beams and slabs are monolithically cast together. In this paper, a simplified calculation method based on Russian design standard SP 468.1325800.2019 is introduced to determine the flexural strength of RC T-beams when exposed to ISO 834 standard fire. The idea of 500oC isotherm method, which is stipulated in both Eurocodes (EC2-1.2) and SP 468, is applied associated with specifications of temperature distribution on T-beams’ cross sections and the temperature-dependent mechanical properties of concrete and reinforcing steel. A case study is conducted to explicitly calculate the flexural strength deterioration (FSD) of T-beams compared to that at ambient temperature. A calculation sheet is established for parametric studies, from which the results show that the FSD factor of RC T-beams is adversely proportional to the dimensions of the beam’s web and flange. However, the effect of these components of T-beams is not significant.

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