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The paper investigates the axial capacity of reinforced columns exposed to fire. The simplified method namely 500 °C isotherm method explained in Eurocode 2 is used to assess the capacity of the column. Finite element software ANSYS is used to perform the thermal analysis. A set of numerical studies were carried out to quantify the effect of variou...
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... can be attributed to the decrease in strength of reinforcement irre- spective of grade of steel. The thermal fire rating is indepen- dent of grade of steel and is constant for all grades which are shown in Table 5. But the fire rating based on strength cri- teria decreases slightly with increase in grade of steel. ...
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... En (Alos et al., 2017;Balaji et al., 2016;Buttignol, 2022;Song et al., 2019) se muestran diferentes investigaciones realizadas en columnas de concreto reforzado en las cuales las propiedades térmicas, tanto del acero como del concreto son modeladas en base a la temperatura, permitiendo ver como varía el comportamiento en función de estas cargas térmicas. Los escenarios de incendio abarcan modelos simples y complejos mostrando las diferencias entre cada opción de modelado. ...
La versatilidad y la alta capacidad de carga del concreto reforzado son las principales razones de su masivo empleo en diversas infraestructuras como edificios, puentes, entre otras. Fuera de las cargas normales de operación estas estructuras, pueden ser sometidas a cargas accidentales como las generadas por incendios localizados. La normativa actual ofrece algunas opciones de análisis de esta clase de fenómenos. Los modelos basados en la Fluidodinámica Computacional (FDC) son los más adecuados; sin embargo, dada su complejidad su uso es poco extendido, optándose por metodologías simplificadas. Este trabajo muestra una metodología que acopla modelos en FDC para la simulación del incendio y térmicos en el Elementos Finitos (EF), para la obtención del campo de temperaturas de una viga de concreto reforzado sometida a un escenario de incendio localizado. El análisis se realizó con un modelo unidireccional secuencialmente acoplado en el cual, después de extraer los coeficientes de transferencia de calor y las temperaturas de la superficie adiabática del modelo en FDC, se incluyen estos valores (previa manipulación mediante un programa en FORTRAN) en el modelo de EF, para obtener los campos de temperaturas.Con los resultados obtenidos se concluye como el empleo de esta metodología, permite estimar adecuadamente las temperaturas en la viga para el caso considerado, siendo posible utilizarlos en un posterior análisis termo-mecánico.
... Balaji et. al. [1] investigated the axial capacity of reinforced columns of different sections exposed to fire. Finite element software ANSYS was used to perform the thermal analysis. ...
Fire resistance analysis is a complex procedure. In this pursuit, engineers design experiments. However, fire tests are expensive and complex and require specialized equipment that is not accessible to many engineers. This further constrains the ability to test and advance fire research. In order to overcome the above challenges, this paper adopts novel machine learning to generate synthetic fire test data via Generative Adversarial Networks (GANs) from real fire tests to expand our knowledge database. Thus, with the addition of new tests, engineers will have access to a much larger pool of data that can help us to better analyze and design structures for fire. In addition, the availability of more data allows us to seriously integrate machine learning into the fire domain. Thus, this paper presents a new approach to expanding fire test data and applying regression and classification machine learning to predict the fire response of reinforced concrete columns. GANs provide an efficient way to generate synthetic data from real fire tests. Moreover, new data additions contribute to improving predictions of classification-based machine learning in comparison with regression-based machine learning. KeywordsClassificationColumnsConcreteFireGANsRegressionSynthetic Data
... Rodrigues et al. (2014) and Liu et al. (2019) carried out the experimental and numerical study on load-bearing capacity RC column narrowed through steel pipes with the occurrence of fire as shown in Fig. 3. Jacintho et al. (2012) have done the computational and experimental study on composite steel and concrete column with and without axial load subjected to high temperature. Faria and Teixeira (2013) have performed the analysis on RC column with IS0 834 fire curve is considered and Balaji et al. (2018) have analysed the RC short column with fire exposure in different faces of column. Fernandes et al. (2018) studied the thermal evaluation on the full-scale column under high temperature with the help of X-ray diffraction and scanning electron microscopy. ...
Many studies have been carried out for understanding the mechanism of failure of RC structural systems under varying temperature circumstances. Similarly, several methods have been developed for improving the fire resistance of concrete buildings, with respect to material selection and detailing aspects. However, only some of the researchers have concentrated on composite behavior of interaction between the structural elements and functional elements, like interaction between masonry infill walls and RC frame elements in the emergence of fire. Several numerical models have been developed for analysis of infilled frames. For simulating the action of fire on full-scale reinforced concrete buildings, three factors, namely, presence of loading, place of fire, its intensity, and duration, must be considered since the material behavior depends on the stress level, intensity and duration of fire and the sensitiveness of structural element to the location and application of fire. To consider the combined effect of load and high temperature, finite element analysis is used. For simulating the intensity and time factor for temperature rise, transient state studies must be done.
... Allam reported that the moment capacity of one-way reinforced concrete slab in fire is provided by reinforcement and concrete [19]. Balaji mentioned that the axial capacity of reinforced concrete columns at high temperature is provided by reinforcement and concrete [22]. At high temperature, the performance of concrete will deteriorate in varying degrees. ...
At present, the research on the high temperature degradation of concrete usually focuses on only the degradation of concrete itself without considering the effect of the plastering layer. It is necessary to take into account the influence of the plastering layer on the high temperature degradation of concrete. With an increase in the water/cement ratio, the explosion of concrete disappeared. Although increasing the water/cement ratio can alleviate the cracking of concrete due to lower pressure, it leads to a decrease in the mechanical properties of concrete after heating. It is proved that besides the water/cement ratio, the apparent phenomena and mechanical properties of concrete at high temperature can be affected by the plastering layer. The plastering layer can relieve the high temperature cracking of concrete, and even inhibit the high temperature explosion of concrete with 0.30 water/cement ratio. By means of an XRD test, scanning electron microscope test and thermogravimetric analysis, it is found that the plastering layer can promote the rehydration of unhydrated cement particles of 0.30 water/cement ratio concrete at high temperature and then promote the mechanical properties of concrete at 400 °C. However, the plastering layer accelerated the thermal decomposition of C-S-H gel of concrete with a water/cement ratio of 0.40 at high temperature, and finally accelerate the decline of mechanical property of concrete. To conclude, the low water/cement ratio and plastering layer can delay the deterioration of concrete at high temperature.
... Muhamed Luquman et al. [17] have analyzed the behaviour of reinforced concrete short column to fire exposure. The axial capacity of the reinforced concrete column at fire exposure was investigated by the simplified method, namely a 500 °C isotherm method made clear in eurocode2. ...
Fire accidents are significant disasters that create massive damage to buildings and other concrete structures. Generally, concrete offers good resistance against fire due to its non-flammable, low thermal conductivity and acts as a protective cover to the steel reinforcement up to certain conditions. However, high temperatures significantly affect the performance of concrete structures. For this reason, in the present study, all the structural elements (beam, column and slab) are subjected to a temperature of 593 ºC for 2 h (condition given in ANSYS software). Moreover, fire effect on the beam, columns with different cover sizes, and slabs with various thicknesses at elevated temperatures have been studied through 3D nonlinear transient thermomechanical finite element analysis. The change in cover and thickness of structural elements has a significant influence on thermal stress. Moreover, increasing every 5 mm cover in beams enriches 0.7% thermal stress resistivity and a raise of 3.5% thermal stress resistivity was noticed with the addition of every 10 mm cover size in columns. Similarly, 11.2% of thermal stress resistivity rise was observed at every 25 mm addition of slab thickness.
... If the fire exposed structure does not collapse, determining the structural damage level and the decision on continuing the use of the structure become crucial [1]. A considerable amount of studies has used numerical methods to evaluate fire damaged structures from different points of view [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. ...
Damages to structures may occur due to construction defects during various stages such as design, construction, and operation phases, or due to natural disasters during their lifetime. The Operational Modal Analysis (OMA) method enables engineers to experimentally determine the changes in dynamic characteristics of the structures that resulted from these undesirable incidents. This method can also help to estimate the structural damages and determine the usage situations depending on stiffness changes. Fire is one of the most important effects that can cause changes in dynamic behavior of structures. Considering the damages caused by fire disasters in recent years, there is a crucial need to address the effects of high temperature on the relevant field of study. This study experimentally examined the effects of elevated temperature on changes in dynamic characteristics of reinforced concrete (RC) and steel structural members. In this regard, a total of 14 (10 columns and 4 frames) laboratory models are built. These models have been constructed with various cross-sectional dimensions considering furnace dimensions. The models have undergone high temperature tests based on ISO 834 standard fire curve. Ambient vibration measurements are conducted to identify and compare the experimental dynamic characteristics both before and after fire exposure. The results show that the damages caused by high temperature significantly affect the dynamic characteristics. Damping ratios generally show a tendency to increase and some minor alterations have been observed in the mode shapes. After the fire the natural frequencies of the models have decreased. It is also observed that increases in the cross-sectional area of RC elements are an effective parameter on these decreases. The use of steel bars affects the dynamic characteristics and temperature distribution within their sections. Besides, different types of steel profiles have an effect on deformations caused by high temperatures.
... The vast majority of the recent numerical efforts use commercial software (Jiang et al. 2017, Nguyen et al. 2018, specific in house developed codes (Wu et al. 2018) or open sources packages (Jiang et al. 2014) with sometimes a limited set of constitutive models by default. The numerical approaches can be classified into two main types, namely: the detailed models (full 3D meshing using solid FE) (Ba et al. 2016, Balaji et al. 2016, Gao et al. 2013, Raouffard & Nishiyama 2018, Sanad et al. 2000 and reduced approaches using fiber/layer cross section discretization in 2D/3D (Cai et al. 2003, Franssen 2005, Kodur & Dwaikat 2008. ...
... average axial strain ε and curvature χ) derived from the nodal displacements. The total axial strain at each layer in a cross section (i.e. at an integration point) ε i x,tot is computed from the generalized strains and is supposed to be the same for both concrete and steel materials, based on a perfect bonding assumption between the steel reinforcements and concrete, as in (Balaji et al. 2016, Bamonte & Lo Monte 2015, Kodur & Dwaikat 2008, Prakash & Srivastava 2018b. Stresses in concrete and steel are computed separately from the layer strain using 1D constitutive laws that can be easily fitted to experimental data from the literature. ...
Fire is a critical risk in reinforced concrete (RC) structures and appropriate structural resistance against it has to be ensured. In this contribution, an approach using corotational layered beam finite elements is employed in which the cross-section temperature is derived from a low-cost closed form model, as opposed to the more commonly used fully computational thermal analysis. The effect of geometrical and material nonlinearities (constitutive behavior fitted to experimental data for concrete and steel), material degradation as a function of temperature rise, and the contributions of thermal, transient, and creep strains are incorporated in the structural analysis. The computational results are favorably compared to experimental data from the literature for an RC beam and for a larger RC frame. Taking benefit of the layered beam formulation offering local insight into the cross-sectional and material behavior, the relationship between the structural degradation and data extracted from the cross-sectional behavior is successfully established. Noteworthy originalities of the contribution are the use of ultimate strain and its evolution as a function of temperature for both materials and the explanation of the observed structural response in fire conditions from cross-sectional data.
... It has been reported that columns with smaller bar diameter and of high grade performed well under gradual cooling. The load-carrying capacity for fire loaded (EN 2 500 °C regime) square reinforced columns were investigated experimentally [10]. Similar columns have been numerically analyzed using ANSYS software, and an interaction curve has been proposed for the design fire rating. ...
The study investigated the strengthening effect of glass fiber and polypropylene fiber-based engineered cementitious composites (GFPPECC) on fire-damaged reinforced concrete short exterior columns. Both moderate (500 °C) and high (900 °C) intensities of fire load corresponding to the ISO834 fire curve were adopted. A total of 15 columns (150 mm × 150 mm × 1000 mm) were cast. The columns were grouped as control column (CC), unstrengthened column-(C2, C3), and strengthened column-(C1, C4) with three columns in each group. The columns in group CC were subjected to axial compression up to failure and kept as the standard reference. The columns in the group (C2, C4) and (C1, C3) were fired up to 900 °C and 500 °C, respectively. Compressive loading on C2 and C3 was applied without any strengthening technique. C1 and C4 were repaired and strengthened using GFPPECC. A similar group of columns, namely unstrengthened-(A-C2, A-C3) and strengthened-(A-C1, A-C4) columns, were analyzed numerically using ANSYS. The parametric analysis was carried out from experimental and numerical results. Variations between experimental and numerical results were negligible. The strengthening has restored to about 68% of the stiffness of columns damaged due to moderate fire intensity. The energy absorption, ductility, and modulus of elasticity were also good, with only about less than 10% reduction compared to the control column. The performance of columns shows that the GFPPECC composite was utilized effectively without any debonding. Whereas for high fire intensity, the GFPPECC composite was not fully used, and premature failure has occurred due to the softening of concrete at high temperatures.
... According to the National Building Code of Canada (NBCC) (2015), fire-resistance rating is the duration of time during which the material can adequately withstand the passage of flame and transmission of heat under standard fire exposure. Some of the factors that affect the fire resistance of a reinforced concrete element include concrete cover thickness, moisture content, configuration of confining reinforcement, duration and type of fire, load intensity and grade of concrete (Kodur et al., 2017;Balaji et al., 2016). Building fires are different and their development, spread and severity are usually unpredictable. ...
Purpose: At elevated temperatures, concrete undergoes changes in its mechanical and thermal properties, which mainly cause degradation of strength and eventually may lead to the failure of the structure. Retrofitting is a desirable option to rehabilitate fire damaged concrete structures. However, to ensure safe reuse of fire-exposed buildings and to adopt proper retrofitting methods, it is essential to evaluate the residual load-bearing capacity of such fire-damaged reinforced concrete structures. The focus of the experimental study presented in this paper aims to investigate the fire performance of concrete columns exposed to a standard fire, and then evaluate its residual compressive strengths after fire exposure of different durations.
Design/methodology/approach: To effectively study the fire performance of such columns, eight identical 200 × 200 × 1,500-mm high reinforced concrete columns test specimens were subjected to two different fire exposure (1- and 2-h) while being loaded with two different load ratios (20% and 40% of the column ultimate design axial compressive load). In a subsequent stage and after complete cooling down, residual compressive strength capacity tests were performed on each fire exposed column.
Findings: Experimental results revealed that the columns never regain its original capacity after being subjected to a standard fire and that the residual compressive strength capacity dropped to almost 50% and 30% of its ambient temperature capacity for the columns exposed to 1- and 2-h fire durations, respectively. It was also noticed that, for the tested columns, the applied load ratio has much less effect on the column’s residual compressive strength compared to that of the fire duration.
Originality/value: According to the unique outcomes of this experimental study and, as the fire-damaged concrete columns possessed considerable residual compressive strength, in particular those exposed to shorter fire duration, it is anticipated that with proper retrofitting techniques such as fiber-reinforced polymers (FRP) wrapping, the fire-damaged columns can be rehabilitated to regain at least portion of its lost load-bearing capacities. Accordingly, the residual compressive resistance data obtained from this study can be effectively used but not directly to adopt optimal retrofitting strategies for such fire-damaged concrete columns, as well as to be used in validating numerical models that can be usefully used to account for the thermally-induced degradation of the mechanical properties of concrete material and ultimately predict the residual compressive strengths and deformations of concrete columns subjected to different load intensity ratios for various fire durations.
... Fire safety of a structure mostly depends on the stability of component of concrete at elevated temperature (Balaji et al., 2016;Murtiadi, 2013). Previously, extensive studies have been achieved on the application of recycled waste as a supplementary cementitious material in concrete for sustainable development (Choe et al., 2015;Kahanji et al., 2018;Khaliq and Taimur, 2018;Xiong and Liew, 2016). ...
The traditional concrete is one of the most energy-intensive construction materials responsible for about 10% of global anthropogenic carbon dioxide emissions. Efforts are being made to develop an alternative binder for concrete. The geopolymer concrete (GPC) has emerged as a promising novel construction material for the production of cement and provides a clean technology option for sustainable development. This paper undertakes a review of the performance behaviour of reinforced geopolymer concrete structural elements and summarizes the findings on the mechanical performance of reinforced GPC elements, e.g., columns, beams, and walls. In this review study, the mechanical properties of GPC structural elements have been investigated and compared with that of OPC concrete. The failure mode of GPC structural element has also been reported, and it was almost in the same manner of OPC concrete failure. The potential of GPC with regards to the chemical resistance and heat resistance could be significantly employed in the various industrial constructions such as marine constructions, pavements,and sewage pipes, etc. Moreover, it was observed that GPC could be safely used in structural elements owing to its excellent mechanical properties using provisions of design codes. More experimental studies are required to give a better understanding of the mechanical properties of GPC for its mass utilization in diversified application areas and spread the clean technology option in the construction industry.
