Fiber-reinforced Concrete Columns Research Articles

Enhancing structural behaviour of polypropylene fibre concrete columns longitudinally reinforced with fibreglass bars

Abstract The research aims to study the behaviour of concrete columns reinforced with fibreglass as bars exposed to seawater. Firstly, hardened concrete properties as the compressive strength and the tensile strength were investigated at ages 14, 28, and 56 days. Secondly, the experimental testing also involved casting 18 short concrete columns that have a length of 300 mm with the cross-sectional dimensions of 100 mm × 100 mm. Six samples were plain concrete, six were reinforced with a diameter of 6 mm longitudinal fibreglass bars, and six polypropylene fibre concrete columns were reinforced with a diameter of 6 mm fibreglass bars. The results added useful information using fibreglass bars (anti-corrosion materials) as reinforced longitudinal concrete columns, so the ultimate load of the reinforced concrete column with fibreglass rod exposed to seawater was 174.8 kN that it was higher than that of the plain concrete column at 104.9 kN. Thus, the fibreglass reinforcement technology enhances the capacity of the columns. So, it could be used in non-impacting structural parts. Meanwhile, the ultimate load of the fibre-reinforced concrete column with fibreglass rod exposed to seawater was 201.8 kN. It is 15.4% higher than that of the ultimate axial load of the reinforced concrete column with fibreglass rods only. Also, the results achieved of this research were encouraging, as the maximum failure load for short columns reinforced with fibreglass rods reached approximately 84 to 87% of failure load relative to polypropylene fibre concrete columns containing reinforcing fibreglass bars. As a result, the structural behaviour bars have been enhanced using fibreglass rod and polypropylene fibre.

Residual strength of ultrahigh-performance hybrid fibre-reinforced concrete columns subjected to high temperatures

The main goal of this research is to experimentally investigate the effects of hybrid fibres on the residual strength of ultrahigh-performance fibre-reinforced concrete (UHPFRC) columns subjected to high temperatures. Eight UHPFRC mixtures incorporating various types of fibres, namely, steel fibre (SF), polypropylene fibre (PP), polyvinyl alcohol fibre (PVA) and natural jute fibre (JF), were designed. Sixteen UHPFRC columns (two columns for each mixture) were tested under axial loading. Eight columns were tested at room temperature (unheated), and the other eight were subjected to 500 °C for 30 min. Results indicated that the hybrid fibres were effective in overcoming explosive spalling at high temperatures. The combination of polymer fibres (PP, PVA and JF) in addition to SF effectively improved the residual strength and fire resistance of heated UHPFRC columns. Moreover, the ultimate load capacity of the tested columns was compared with those calculated by the ACI 318–2014 design code and an existing theoretical approach.

Shear Strength Model for Steel Fiber-Reinforced Concrete Columns

Shear Strength Model for Steel Fiber-Reinforced Concrete Columns

Compressive Behavior of Fiber Reinforced Concrete Columns Rehabilitated with CFRP Warps

Compressive Behavior of Fiber Reinforced Concrete Columns Rehabilitated with CFRP Warps

Fire-resistance behavior of concrete columns produced with recycled ceramic and silica aggregates: An experimental and numerical approach

This article aims to fully assess the fire-resistance behavior of fiber-reinforced concrete (FRC) columns made with recycled ceramic aggregates when subjected to severe thermal loading. In addition, the effects of fiber reinforcements and ceramic recycled aggregates (RAs) on the thermal behavior of concrete columns were addressed and compared with that of the conventional silica-made concrete columns. In this regard, twelve small-scale FRC columns containing recycled ceramic and silica aggregates are prepared and placed in a heating chamber for 90 min. Next, the columns were axially loaded until failure, and variations in compressive stress and axial strain of the specimens were measured, aiming to capture the thermal effects on the load-carrying capacity, axial strain, and failure modes of the concrete columns. The specimens were exposed to high temperatures of 20 °C, 600 °C, and 1000 °C according to ISO 834 Fire Standard, and were tested in humid and dry environmental conditions. Moreover, the failure modes of the columns (e.g., concrete spalling, crack pattern, etc.) are presented in terms of macroscopic imaging. In addition, in-depth analyses of the effects of fibers (steel and polypropylene) and moisture content on the thermal behavior of concrete columns is addresses utilizing scanning electronic microscope (SEM) technique. The results indicate that below the temperature of 600 °C, the axial behavior of the FRC columns with silica and ceramic aggregate are similar. However, as the temperature rises, the reduction in axial load-bearing capacity of the columns with silica aggregates is higher than that of the columns with ceramic aggregates. Also, it was observed that the environmental humidity negatively affects the overall fire-resisting behavior of the columns. Furthermore, a numerical procedure is presented in ABAQUS to estimate the behavior of FRC columns subjected to thermal loading and validated using the experimental results.

Experiments and predictive modeling of optimized fiber-reinforced concrete columns having FRP rebars and hoops

This research studies the structural performance of glass fiber-reinforced polymer (glass-FRP) reinforced concrete (RC) columns incorporating glass hybrid fibers (GFC) and steel rebars RC columns having steel hybrid fibers (SFC) using experiments, artificial neural networks (NN), and theoretical modeling. A set of 18 circular concrete columns, each with a diameter of 300 mm and a height of 1200 mm, was constructed and axially loaded to failure. Glass fibers and steel fibers were incorporated to produce hybrid fiber-RC (HFRC). Nine samples were manufactured with glass-FRP reinforcement, while the remaining nine were manufactured with steel reinforcement. According to the findings, the GFC columns had lower axial strengths (ASs) up to 20%, and higher ductility indices up to 26% than the SFC columns. Both GFC and SFC columns showed the same influence of eccentric loading in the form of a decrease in AS. To develop a novel NN model, a database of 275 specimens of glass-FRP-RC columns was gathered from previous studies. To achieve an optimum model, the NN model was calibrated for different numbers of neurons in the hidden layers (HLs). A novel theoretical equation for determining the AS of GFC columns was also suggested. The proposed theoretical and NN models showed average discrepancies of 3.2 and 1.9% from the test results of both GFC and SFC columns.

Experimental Investigation on the Behavior of Hollow-Core Glass Fiber-Reinforced Concrete Columns with GFRP Bars

Experimental Investigation on the Behavior of Hollow-Core Glass Fiber-Reinforced Concrete Columns with GFRP Bars

Cyclic Behavior of High-Strength Fiber-Reinforced Concrete Columns under High Axial Loading Level

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Effect of elevated temperature on strength and ductility of axially loaded hybrid fiber reinforced concrete columns

This paper presents the results of a research program conducted on the structural behavior of fiber-reinforced concrete columns subjected to elevated temperatures (27 °C, 200 °C, 400 °C, and 800 °C). For this purpose, three groups of reinforced concrete columns were fabricated, and a comparative study has been done on the strength properties under axial load without and with (mono and hybrid) fibers of various types (microsteel, Polypropylene, and Sisal fibers) with a constant volume fraction of 1%. The properties evaluated were the load carrying capacity, load–deflection characteristics, and failure pattern of columns, and the results were compared with the control column without fiber. The experimental study reveals that the columns reinforced with mono microsteel fiber performed well in comparison with the columns with fibers in terms of superior load carrying capacity, ultimate deflection,energy absorption capacity, ductility characteristics, and thermal resistance. Whereas the columns with hybrid fibers did not show any signs of spalling and performed functionally better than the columns without fibers. The addition of sisal, microsteel, and polypropylene fibers in hybrid form provides better fire resistance, strength, and spalling resistance compared to cement concrete columns without fiber.

Uniaxial performance of circular hybrid fibre-reinforced lightweight aggregate concrete columns

To investigate the compressive performance of fibre-reinforced concrete columns, 20 circular columns with a consistent size of Φ250 × 750 mm were tested, considering different concrete types, steel spiral spacing, fibre types, and volumetric fibre fractions. Polypropylene fibres prevented the initial cracking and premature spalling of the cover more obviously than carbon fibres. The compressive strength of spirally confined lightweight aggregate concrete (LWAC) was improved to 1.45 times the unconfined strength, and the fibre-reinforced LWAC exhibited a greater enhancement in the compressive strength provided by the confining pressure than the plain LWAC. The incorporation of both single carbon fibres and hybrid carbon–polypropylene fibres enhanced the ductility of LWAC columns, while the polypropylene fibres exhibited an insignificant influence on the compressive properties of LWAC. Identical volumetric fractions of the two fibres contributed more significantly to the ductility of LWAC. Concerning the improved peak strain and residual strength, a confinement model of fibre-reinforced LWAC that accounted for the superposition of individual confinement effects, including lateral reinforcement and fibres, was proposed and compared with the experimental results. The predictions exhibited better agreement with the experimental curves than the existing typical models.

Prediction of residual strength of FRC columns under blast loading using the FEM method and regression approach

This study presents a development of empirical equation which can be used for predicting the residual strength of fiber reinforced concrete (FRC) columns subjected to a TNT explosion. For that purpose, numerical investigations on the structural behavior and damage of FRC column under blast loading were carried out. Finite element (FE) modelling of FRC column and TNT explosive charges were built using a robust program, LS-DYNA. Those FE modellings were then verified using relevant, recent test data. A series of parametric analyses was conducted with such various main parameters as section, scaled distance, scaled section, fiber type, and fiber content to investigate the effect of these parameters on the structural behavior and damage of the column under explosion. Some interesting discussions were then presented to thoroughly understand the role of each parameter on the resistant capacity of the column. To develop the empirical equation for predicting the residual strength of the FRC column, Multivariate Linear Regression (MLR) and Multilayer Perceptron for Regression (MLP-R) were employed to generate the fitting models. While the MLP-R showed a superior capacity for estimating the result, MLR, on the other hand, could easily achieve the regression coefficient with fairly good estimation. As a result, a reliable empirical equation that can be used to predict the residual strength of the FRC column in practical design was proposed as an important outcome of this study.

Seismic response prediction of FRC rectangular columns using intelligent fuzzy-based hybrid metaheuristic techniques.

This research study focused on the dynamic response and mechanical performance of fiber-reinforced concrete columns using hybrid numerical algorithms. Whereas test data has non-linearity, an artificial intelligence (AI) algorithm has been incorporated with different metaheuristic algorithms. About 317 datasets have been applied from the real test results to detect the promising factor of strength subjected to the seismic loads. Adaptive neuro-fuzzy inference system (ANFIS) was carried out as an AI beside the combination of particle swarm optimization (PSO) and genetic algorithm (GA). Extreme Machine Learning (ELM) was also performed in order to approve the obtained results. According to the findings, it is demonstrated that ANFIS–PSO predicts the lateral load with promising evaluation indexes [R2 (test) = 0.86, R2 (train) = 0.90]. Mechanical performance prediction was also carried out in this study, and the results showed that ELM predicts the compressive strength with promising evaluation indexes [R2 (test) = 0.66, R2 (train) = 0.86]. Finally, both ANFIS–GA and ANFIS–PSO techniques illustrated a reliable performance for prediction, which encourage scholars to replace costly and time-consuming experimental tests with predicting utilities.

Influence of synthetic fibers on the seismic behavior of reinforced-concrete circular columns

The addition of discrete fibers to the concrete mixture to enhance its toughness and tensile strength is well acknowledged. Studies have also shown that fiber-reinforced concrete (FRC) can be favorable for its enhanced behavior in compression. This behavior, which is attributed to the confinement action of the fibers, is, in general, superior in terms of strength and ductility, compared to plain concrete. Reversed cyclic loading in flexure under constant axial load of large scale synthetic fiber-reinforced concrete columns is scarce as opposed to steel fiber-reinforced concrete columns. This paper presents an experimental study on the behavior of large-scale synthetic fiber-reinforced concrete columns with hoops transverse steel reinforcement under constant axial load and reversed flexure simulating seismic loading. The results from this study show slightly improved cyclic behavior compared to results obtained on similar columns reinforced with spiral transverse reinforcement. Enhanced behavior of synthetic fiber-reinforced concrete is achieved for practical transverse steel reinforcement spacings (⩾75 mm). In this case, similar ductile behavior of a reinforced-concrete column can be reached with a reduced amount of transverse steel reinforcement and the inclusion of synthetic fibers with an aspect ratio of 50–100 to the concrete mixture. Difficulty in placing synthetic fiber-reinforced concrete in very congested columns precludes its use in columns with hoops or spiral spacing less than 75mm until self leveling concrete with large amount of synthetic fibers is developed.

Eccentric compressive behavior of steel fiber-reinforced RC columns strengthened with CFRP wraps: Experimental investigation and analytical modeling

Today, one of the most commonly used retrofitting techniques for reinforced concrete (RC) columns for enhancing their structural performance is to externally confine these columns with carbon fiber-reinforced polymers (CFRPs). From another aspect, the presence of steel fibers in the concrete mixture enhances the behavior of structural members. In this research, the eccentric compressive behavior of steel fiber-reinforced concrete columns strengthened with CFRP wraps, which has remained mainly under-researched, is explored experimentally and analytically. For that end, eighteen RC columns with plain concrete and fiber-reinforced concrete, confined and unconfined with CFRP sheets, length to width ratios (L/h) of 4.2 and 8.3, and load eccentricity ratios (e/h) of 0.29, 0.46, and 0.63 were manufactured and tested under eccentric compressive loading. The findings indicated that the CFRP sheets improved the loading capacity and ductility of the RC columns, while the presence of steel fibers in the concrete affected the loading capacity of the columns negligibly but made them more ductile. Further, the eccentricity of the applied load mitigated the effect of confinement with CFRP sheets on the reinforced concrete strength. Regarding the significance of the performance of these columns, an analytical model with the purpose of predicting the behavior of fibrous RC concrete columns strengthened with CFRP sheets under an eccentric compressive load was developed. In this model, by considering the simultaneous effects of the confinement with CFRP sheets and transverse reinforcement, the moment–curvature and the load–deflection diagrams were determined using the fiber section analysis method. Assessing the analytical findings against the experimental ones of the present work and those of others indicated that the proposed model is able to properly predict the behavior of fibrous concrete columns confined with transverse reinforcement and CFRP sheets under eccentric compressive loading.

Analysis of Forced Longitudinal Vibrations of Columns Taking into Account Internal Resistance in Resonance Zones

In analytical form, formulas are obtained for the amplitude of forced harmonic longitudinal vibrations of reinforced concrete and fiber-reinforced concrete columns with fixed edges. In order to verify the proposed approach, columns were simulated in the ANSYS program and calculated by the finite element method. Analysis of the calculations shows that a significant raise in the amplitude of the forced vibrations is observed only in the region of the first resonant frequency. It has been established that the value of the maximum amplitude of the vibrations of the fiber reinforced concrete column is 16% less than that for a reinforced concrete column.

Bond Differences at Two Ends of Steel Fiber-Reinforced Concrete Columns

Bond Differences at Two Ends of Steel Fiber-Reinforced Concrete Columns

Strength Characteristics and Corrosion of Glass Fibre Reinforced Concrete Column Exposed in Sea Water Environmental Condition

This paper highlights the investigation on the strength and corrosion study of glass fibre reinforced concrete (GFRP) column in sea water environmental condition. Specimen of size 600 mm length x 150 mm wide x 300 mm deep columns were cast. Totally 8 columns were cast. Out of which, 4 columns were cured using potable water and 4 columns were cured using in artificial sea water. Among 8 reinforced concrete columns, two concrete columns were used, as the reference column containing steel rods both in longitudinal and horizontal ties and were cured both in potable and artificial sea water. For the corrosion study, 2 concrete columns reinforced by GFRP bars in the longitudinal direction and steel rods as horizontal ties and were cured using artificial sea water. Rebound hammer and Ultrasonic Pulse Velocity tests were performed on columns to evaluate the strength characteristics at the end of 7, 14, 28, 56 and 90 days of curing. The results will also be validated using destructive methods. Corrosion study was also performed by single Cu-CuSo4 Half-Cell equipment. Based on the observation, it was found that the compressive strength in artificial sea water curing exhibited better performance than in potable water curing.

A calibration of the material model for FRC

This paper presents a calibration of a constitutive material model, which can be applied to describe the complex static and dynamic behavior of the fiber reinforced concrete (FRC) structures subjected to static and high-rate loading conditions. The well-known K&C material model, which is MAT072r3 as executed in LS-DYNA, is employed for the purposed of this calibration. Various experimental data on tension, compression, and high-rate behaviors of FRC material using axial and tri-axial tests are used to generate the input parameters. Numerical simulation of single specimens on compression and bending subjected to static loading, and of an FRC column under blast loading are implemented to illustrate the performance of the calibrated material model. It is shown that the calibrated material model proposed in this study presents a good agreement compared to the experimental results.

Computational estimation of the earthquake response for fibre reinforced concrete rectangular columns

Due to the impressive flexural performance, enhanced compressive strength and more constrained crack propagation, Fibre-reinforced concrete (FRC) have been widely employed in the construction application. Majority of experimental studies have focused on the seismic behavior of FRC columns. Based on the valid experimental data obtained from the previous studies, the current study has evaluated the seismic response and compressive strength of FRC rectangular columns while following hybrid metaheuristic techniques. Due to the non-linearity of seismic data, Adaptive neuro-fuzzy inference system (ANFIS) has been incorporated with metaheuristic algorithms. 317 different datasets from FRC column tests has been applied as one database in order to determine the most influential factor on the ultimate strengths of FRC rectangular columns subjected to the simulated seismic loading. ANFIS has been used with the incorporation of Particle Swarm Optimization (PSO) and Genetic algorithm (GA). For the analysis of the attained results, Extreme learning machine (ELM) as an authentic prediction method has been concurrently used. The variable selection procedure is to choose the most dominant parameters affecting the ultimate strengths of FRC rectangular columns subjected to simulated seismic loading. Accordingly, the results have shown that ANFIS-PSO has successfully predicted the seismic lateral load with R2 = 0.857 and 0.902 for the test and train phase, respectively, nominated as the lateral load prediction estimator. On the other hand, in case of compressive strength prediction, ELM is to predict the compressive strength with R2 = 0.657 and 0.862 for test and train phase, respectively. The results have shown that the seismic lateral force trend is more predictable than the compressive strength of FRC rectangular columns, in which the best results belong to the lateral force prediction. Compressive strength prediction has illustrated a significant deviation above 40 Mpa which could be related to the considerable non-linearity and possible empirical shortcomings. Finally, employing ANFIS-GA and ANFIS-PSO techniques to evaluate the seismic response of FRC are a promising reliable approach to be replaced for high cost and time-consuming experimental tests.

Fire Resistance Performance of Aramid Fiber-Reinforced Concrete Columns with Embedded Cerak Wool Boards

Fire Resistance Performance of Aramid Fiber-Reinforced Concrete Columns with Embedded Cerak Wool Boards