scholarly journals Axial Compressive Strength Models of Eccentrically-Loaded Rectangular Reinforced Concrete Columns Confined with FRP

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3498
Author(s):  
Haytham F. Isleem ◽  
Muhammad Abid ◽  
Wesam Salah Alaloul ◽  
Muhammad Kamal Shah ◽  
Shayan Zeb ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Large Scale ◽  
Concrete Strength ◽  
Concrete Columns ◽  
Confined Concrete ◽  
Practice Research ◽  
Small Scale ◽  
Technical Literature ◽  
Rc Columns ◽  
Strength Models

The majority of experimental and analytical studies on fiber-reinforced polymer (FRP) confined concrete has largely concentrated on plain (unreinforced) small-scale concrete columns, on which the efficiency of strengthening is much higher compared with large-scale columns. Although reinforced concrete (RC) columns subjected to combined axial compression and flexural loads (i.e., eccentric compression) are the most common structural elements used in practice, research on eccentrically-loaded FRP-confined rectangular RC columns has been much more limited. More specifically, the limited research has generally been concerned with small-scale RC columns, and hence, the proposed eccentric-loading stress-strain models were mainly based on the existing concentric-loading models of FRP-confined concrete columns of small scale. In the light of such demand to date, this paper is aimed at developing a mathematical model to better predict the strength of FRP-confined rectangular RC columns. The strain distribution of FRP around the circumference of the rectangular sections was investigated to propose equations for the actual rupture strain of FRP wrapped in the horizontal and vertical directions. The model was accomplished using 230 results of 155 tested specimens compiled from 19 studies available in the technical literature. The test database covers an unconfined concrete strength ranging between 9.9 and 73.1 MPa, and section’s dimension ranging from 100–300 mm and 125–435 mm for the short and long sides, respectively. Other test parameters, such as aspect ratio, corner radius, internal hoop steel reinforcement, FRP wrapping layout, and number of FRP wraps were all considered in the model. The performance of the model shows a very good correlation with the test results.

scholarly journals Analytical Review on Eccentric Axial Compression Behavior of Short and Slender Circular RC Columns Strengthened Using CFRP

Polymers ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2763
Author(s):  
Muhammad Abid ◽  
Haytham F. Isleem ◽  
Muhammad Kamal Kamal Shah ◽  
Shayan Zeb
Keyword(s):  
Reinforced Concrete ◽  
Axial Compression ◽  
Slenderness Ratio ◽  
Concrete Columns ◽  
Practice Research ◽  
Small Scale ◽  
Stress Strain ◽  
Eccentric Load ◽  
Rc Columns ◽  
Proposed Model

Although reinforced concrete (RC) columns subjected to combined axial compression and flexural loads (i.e., eccentric load) are the most common structural members used in practice, research on FRP-confined circular RC columns subjected to eccentric axial compression has been very limited. More specifically, the available eccentric-loading models were mainly based on existing concentric stress–strain models of FRP-confined unreinforced concrete columns of small scale. The strength and ductility of FRP-strengthened slender circular RC columns predicted using these models showed significant errors. In light of such demand to date, this paper presents a stress–strain model for FRP-confined circular reinforced concrete (RC) columns under eccentric axial compression. The model is mainly based on observations of tests and results reported in the technical literature, in which 207 results of FRP-confined circular unreinforced and reinforced concrete columns were carefully studied and analyzed. A model for the axial-flexural interaction of FRP-confined concrete is also provided. Based on a full parametric analysis, a simple formula of the slenderness limit for FRP-strengthened RC columns is further provided. The proposed model considers the effects of key parameters such as longitudinal and hoop steel reinforcement, level of FRP hoop confinement, slenderness ratio, presence of longitudinal FRP wraps, and varying eccentricity ratio. The accuracy of the proposed model is finally validated through comparisons made between the predictions and the compiled test results.

scholarly journals Experimental Behavior of Concrete Columns Confined by Transverse Reinforcement with Different Details

2020 ◽  
Vol 14 (1) ◽  
pp. 250-265 ◽  
Author(s):  
Mariateresa Guadagnuolo ◽  
Alfonso Donadio ◽  
Anna Tafuro ◽  
Giuseppe Faella
Keyword(s):  
Reinforced Concrete ◽  
Concrete Strength ◽  
Concrete Columns ◽  
Confined Concrete ◽  
Experimental Program ◽  
Transverse Reinforcement ◽  
Eurocode 8 ◽  
Strength Increase ◽  
Existing Buildings ◽  
Concrete Confinement

Introduction: Most of the existing reinforced concrete buildings often have columns with poor transverse reinforcement details. Models for computing the confined concrete strength were developed using experimental tests performed on specimens with transverse reinforcement typical of seismic design. The paper presents the results of an experimental program performed to investigate the effect of type, amount and pitch of transverse reinforcement on the behavior of confined concrete. Aim: The paper is also aimed at evaluating whether the current code models are suitable for estimating the confined strength of concrete in existing buildings. Methods: A total of 45 reinforced concrete columns with four volume ratios of transverse reinforcement were tested under axial loads. Type and pitch of transverse reinforcement typical of existing r/c buildings not designed according to seismic standards were considered. Therefore, columns reinforced by spiral and hoops with 135° or 90° hooks at the end are investigated for comparing their behavior. The confinement of spirals and hoops to core concrete is discussed as the amount of transverse and longitudinal reinforcement varies. Small increases in strength due to the concrete confinement were measured for hoop pitch of 150 mm (ranging between 2% and 7%), but also for hoops with 90° hook and pitch of 75 mm. Greater increments were obtained by spirals and hoops with 135° hook in the case of 75 mm pitch and when rhomboidal hoops or cross-ties were arranged in addition to the perimeter hoops. A comparison with some similar experimental results is also performed, achieving quite similar results. The mean experimental stress-strain curves are also analyzed. Results: The results show how the increase in concrete strength due to the confinement is more dependent on the transverse reinforcement pitch than the type and detail of transverse reinforcement or even less diameter of longitudinal bars. Finally, the experimental strength of confined concrete is then compared with the values provided by Eurocode 8 and the new Italian Building Code, showing that the higher the volumetric percentage of transverse reinforcement, the greater the overestimation of code models. Conclusion: An overestimation of codes up to 30% is assessed, systematically lower in the case of spirals, and higher in the case of hoops with 90° hooks at the end. The results highlight the need to develop specific equations to determine the strength increase due to the concrete confinement in the case of existing buildings with poor transverse reinforcement.

scholarly journals Performance of piezoceramic sensors

2021 ◽  
Author(s):  
Rummaan Syed Ahmed
Keyword(s):  
Reinforced Concrete ◽  
Crack Width ◽  
Large Scale ◽  
Failure Modes ◽  
Concrete Strength ◽  
Small Scale ◽  
Active Monitoring ◽  
Concrete Members ◽  
Concrete Crack ◽  
Base Width

This study is in continuation of the previous research conducted at Ryerson University to develop a model for active monitoring of reinforced concrete members using piezo-ceramic sensor. In the previous research large concrete beam were investigated. The following study examines the performance of piezo-ceramic sensor to monitor maturity of concrete and to evaluate crack width of large base width concrete plates. Small scale beams and large scale slabs specimens were tested under three and four points bending respectively to evaluate the effectiveness of piezo-sensors at different failure modes. Test results from small scale beams were used to model correlation between concrete crack width/strains and sensor signals. The test result indicated that piezo-sensor can be used for active concrete strength monitoring at later stages. It can also be used as an effective indicator of crack width for reinforced concrete members with small base width.

scholarly journals Evolutionary Modeling to Evaluate the Shear Behavior of Circular Reinforced Concrete Columns

2014 ◽  
Vol 2014 ◽  
pp. 1-14 ◽  
Author(s):  
Alessandra Fiore ◽  
Giuseppe Carlo Marano ◽  
Daniele Laucelli ◽  
Pietro Monaco
Keyword(s):  
Experimental Data ◽  
Shear Strength ◽  
Reinforced Concrete ◽  
Concrete Columns ◽  
Shear Behavior ◽  
Evolutionary Modeling ◽  
Technical Literature ◽  
Strength Models ◽  
Structured Representation ◽  
Conversion Rules

Despite their frequent occurrence in practice, only limited studies on the shear behavior of reinforced concrete (RC) circular members are available in the literature. Such studies are based on poor assumptions about the physical model, often resulting in being too conservative, as well as technical codes that essentially propose empirical conversion rules. On this topic in this paper, an evolutionary approach named EPR is used to create a structured polynomial model for predicting the shear strength of circular sections. The adopted technique is an evolutionary data mining methodology that generates a transparent and structured representation of the behavior of a system directly from experimental data. In this study experimental data of 61 RC circular columns, as reported in the technical literature, are used to develop the EPR models. As final result, physically consistent shear strength models for circular columns are obtained, to be used in different design situations. The proposed formulations are compared with models available from building codes and literature expressions, showing that EPR technique is capable of capturing and predicting the shear behavior of RC circular elements with very high accuracy. A parametric study is also carried out to evaluate the physical consistency of the proposed models.

scholarly journals Performance of piezoceramic sensors

2021 ◽  
Author(s):  
Rummaan Syed Ahmed
Keyword(s):  
Reinforced Concrete ◽  
Crack Width ◽  
Large Scale ◽  
Failure Modes ◽  
Concrete Strength ◽  
Small Scale ◽  
Active Monitoring ◽  
Concrete Members ◽  
Concrete Crack ◽  
Base Width

This study is in continuation of the previous research conducted at Ryerson University to develop a model for active monitoring of reinforced concrete members using piezo-ceramic sensor. In the previous research large concrete beam were investigated. The following study examines the performance of piezo-ceramic sensor to monitor maturity of concrete and to evaluate crack width of large base width concrete plates. Small scale beams and large scale slabs specimens were tested under three and four points bending respectively to evaluate the effectiveness of piezo-sensors at different failure modes. Test results from small scale beams were used to model correlation between concrete crack width/strains and sensor signals. The test result indicated that piezo-sensor can be used for active concrete strength monitoring at later stages. It can also be used as an effective indicator of crack width for reinforced concrete members with small base width.

scholarly journals Strengthening of Low-Strength Concrete Columns with Fibre Reinforced Polymers. Full-Scale Tests

2020 ◽  
Vol 5 (11) ◽  
pp. 91
Author(s):  
Sonia Martínez ◽  
Ana de Diego ◽  
Viviana J. Castro ◽  
Luis Echevarría ◽  
Francisco J. Barroso ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Concrete Columns ◽  
Experimental Program ◽  
Small Scale ◽  
Rc Columns ◽  
Reinforced Polymers ◽  
Strain Capacity ◽  
Strength Concrete ◽  
Low Strength ◽  
Low Strength Concrete

Confinement of columns with externally bonded fibre reinforced polymers (FRP) sheets is an easy and effective way of enhancing the load carrying and strain capacity of reinforced concrete (RC) columns. Many experimental studies have been conducted on cylindrical small-scale un-reinforced concrete specimens externally confined with FRP. It is widely accepted that confinement of square or rectangular columns is less efficient than the confinement of circular columns. The theoretical models for rectangular sections are mostly based on approaches for circular columns modified by a shape factor, but the different models do not give similar results. This paper presents an experimental program on large-scale square and rectangular RC columns externally strengthened with carbon FRP sheets and subjected to axial load. The main variables were the side-aspect ratio of the cross-section, the radius of curvature of the corners and the amount of FRP reinforcement. The results show that the FRP confinement can increase the strength and strain capacity of rectangular concrete columns with low strength concrete. The FRP hoop ultimate strain was much lower than the material ultimate tensile strain obtained from flat coupon tests and the strain efficiency factor achieved in the tests was less than the value usually recommended by design guides.

Seismic assessment of reinforced concrete columns with short lap splices

2021 ◽  
pp. 875529302199483
Author(s):  
Eyitayo A Opabola ◽  
Kenneth J Elwood
Keyword(s):  
Reinforced Concrete ◽  
Failure Mode ◽  
Failure Modes ◽  
Concrete Columns ◽  
Seismic Assessment ◽  
Rc Columns ◽  
Lap Splices ◽  
Displacement Response ◽  
Force Displacement ◽  
Probable Failure

Existing reinforced concrete (RC) columns with short splices in older-type frame structures are prone to either a shear or bond mechanism. Experimental results have shown that the force–displacement response of columns exhibiting these failure modes are different from flexure-critical columns and typically have lower deformation capacity. This article presents a failure mode-based approach for seismic assessment of RC columns with short splices. In this approach, first, the probable failure mode of the component is evaluated. Subsequently, based on the failure mode, the force–displacement response of the component can be predicted. In this article, recommendations are proposed for evaluating the probable failure mode, elastic rotation, drift at lateral failure, and drift at axial failure for columns with short splices experiencing shear, flexure, or bond failures.

SEISMIC PERFORMANCE OF GFRP-RC RECTANGULAR COLUMNS: NUMERICAL STUDY

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Ehab El-Salakawy ◽  
Fangxin Ye ◽  
Yasser Mostafa Selmy
Keyword(s):  
Reinforced Concrete ◽  
Cyclic Loading ◽  
Axial Load ◽  
Numerical Study ◽  
Concrete Strength ◽  
Weight Ratio ◽  
Concrete Columns ◽  
Load Level ◽  
Reinforced Concrete Columns ◽  
Rectangular Columns

Composite materials like glass fiber-reinforced polymer (GFRP) is becoming widely acceptable to be used as a reinforcing material due to its high ultimate tensile strength-to-weight ratio and excellent resistance to corrosion. However, the seismic behavior of GFRP-reinforced concrete columns has not been fully investigated yet. This paper presents the results of a numerical analysis of full-size GFRP-RC rectangular columns under cyclic loading. The simulated column depicts the lower part of a building column between the foundation and the point of contra-flexure at the mid-height of the column. GFRP reinforcement properties and concrete modeling based on fracture energy have been incorporated in the numerical model. Experimental validation has been used to examine the accuracy of the constructed finite element models (FEMs) using a commercially available software. The validated FEM was used to perform a parametric study, considering several concrete strength values and axial load levels, to study its influence on the performance of the GFRP-reinforced concrete columns under cyclic loading. It was concluded that the hysteretic dissipation capacity deteriorates under high axial load level due to severe softening of the concrete. The FE results showed a substantial improvement of the lateral load-carrying capacities by increasing concrete compressive strength.

Strength model of FRP confined concrete columns based on analytical analysis and experimental test

2019 ◽  
Vol 11 (1) ◽  
pp. 82-106 ◽  
Author(s):  
Mahfoud Touhari ◽  
Ratiba Kettab Mitiche
Keyword(s):  
Concrete Strength ◽  
Compressive Force ◽  
Concrete Columns ◽  
Fiber Reinforced Concrete ◽  
Confined Concrete ◽  
Fiber Reinforced ◽  
Reinforced Concrete Column ◽  
Theoretical Assumption ◽  
Hoop Strain ◽  
Content Type

Purpose Covering a fiber-reinforced concrete column (fiber reinforced plastic (FRP)) improves the performance of the column primarily. The purpose of this paper is to investigate the behavior of small FRP concrete columns that are subject to axial pressure loading, in order to study the effect of many parameters on the effectiveness of FRP couplings on circular and square concrete columns. Design/methodology/approach These parameters include the shape of the browser (circular and square), whole core and cavity, square radius of square columns, concrete strength (low strength, normal and high), type of FRP (carbon and glass) and number of FRP (1–3) layers. The effective fibrillation failure strain was investigated and the effect of effective lateral occlusion pressure. Findings The results of the test showed that the FRP-coated columns improved significantly the final conditions of both the circular and square samples compared to the unrestricted columns; however, improvement of square samples was not as prominent as improvement in circular samples. The results indicated that many parameters significantly affected the behavior of FRP-confined columns. A new model for predicting compressive force and the corresponding strain of FRP is presented. A good relationship is obtained between the proposed equations and the current experimental results. Originality/value The average hoop strain in FRP wraps at rupture in FRP-confined concrete specimens can be much lower than that given by tensile coupon tests, meaning the theoretical assumption that the FRP-confined concrete cylinder ruptures when the FRP material tensile strength attained at its maximum is not suitable. Based on this observation, the effective peak strength and corresponding strain formula for FRP concrete confined columns must be based on the effective hoop rupture strain composite materials.

Mechanical Properties of Large Scale Confined Concrete

2011 ◽  
Vol 94-96 ◽  
pp. 1983-1988
Author(s):  
Jia Song ◽  
Zhen Bao Li ◽  
Yong Ping Xie ◽  
Xiu Li Du ◽  
Yue Gao
Keyword(s):  
Mechanical Properties ◽  
Experimental Study ◽  
Axial Compression ◽  
Large Scale ◽  
Plain Concrete ◽  
Concrete Columns ◽  
Confined Concrete ◽  
Transverse Reinforcement ◽  
Test Results ◽  
Reinforcement Configuration

An experimental study was made of the mechanical properties of large scale confined concrete subjected to the axial compression test. Eleven tied concrete columns and six plain concrete prisms were tested. In the test, each specimen had the same transverse reinforcement configuration, and similar volumetric ratio of lateral steel, while different size. The test results in this paper indicate that the size of the specimen has no obvious relationship with the ultimate strength, however, it does affect the post-peak ductility to some extent. As a supplement to the experimental study, a finite element method was adopted to imitate the mechanical behavior of the confined concrete under axial compression. The results of the imitation in this paper indicate the confinement mechanism of large scale specimens.

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