scholarly journals Torsional Strengthening of Reinforced Concrete Beams with Externally-Bonded Fibre Reinforced Polymer: An Energy Absorption Evaluation

2020 ◽  
Vol 6 ◽  
pp. 69-85
Author(s):  
Mahir M. Hason ◽  
Ammar N. Hanoon ◽  
Ahmed W. Al Zand ◽  
Ali A. Abdulhameed ◽  
Ali O. Al-Sulttani
Keyword(s):  
Compressive Strength ◽  
Reinforced Concrete ◽  
Energy Absorption ◽  
Structural Damage ◽  
Absorption Capacity ◽  
Reinforced Concrete Beams ◽  
Rc Beams ◽  
Concrete Compressive Strength ◽  
Externally Bonded ◽  
The Impact

The impacts of numerous important factors on the Energy Absorption (EA) of torsional Reinforced Concrete (RC) beams strengthened with external FRP is the main purpose and innovation of the current research. A total of 81 datasets were collected from previous studies, focused on the investigation of EA behaviour. The impact of nine different parameters on the Torsional EA of RC-beams was examined and evaluated, namely the concrete compressive strength (f’c), steel yield strength (fy), FRP thickness (tFRP), width-to-depth of the beam section (b/h), horizontal (ρh) and vertical (ρv) steel ratio, angle of twist (θu), ultimate torque (Tu), and FRP ultimate strength (fy-FRP). For the evaluation of the energy absorption capacity at different levels, Response Surface Methodology (RSM) was implemented in this study. Also, to fit the measured results, Quadratic and Line models were created. The results show that the RSM technique is a highly significant tool that can be applied not only to energy absorption-related problems examined in this research, but also to other engineering problems. An agreement is observed between Pareto and standardized charts with the literature showing that the EA capacity of the torsional FRP-RC beams is mostly affected by the concrete compressive strength, followed by the vertical reinforcement ratio. The newly suggested model in this article exhibits a satisfactory correlation co-efficient (R), of about 80%, with an adequate level of accuracy. The obtained results also reveal that the EA acts as a safety index for the FRP-strengthened RC beams exposed to torsional loadings to avoid sudden structural damage. Doi: 10.28991/cej-2020-SP(EMCE)-07 Full Text: PDF

scholarly journals Energy Absorption Evaluation of CFRP-Strengthened Two-Spans Reinforced Concrete Beams under Pure Torsion

2019 ◽  
Vol 5 (9) ◽  
pp. 2007-2018 ◽  
Author(s):  
Ammar N. Hanoon ◽  
Ali A. Abdulhameed ◽  
Haider A. Abdulhameed ◽  
Saad K. Mohaisen
Keyword(s):  
Reinforced Concrete ◽  
Energy Absorption ◽  
Concrete Beams ◽  
Absorption Capacity ◽  
Reinforced Concrete Beams ◽  
Experimental Program ◽  
Rc Beams ◽  
Pure Torsion ◽  
Energy Absorption Capacity ◽  
Strengthened Beam

For more than a decade, externally bonded carbon fiber reinforced polymer (CFRP) composites successfully utilized in retrofitting reinforced concrete structural elements. The function of CFRP reinforcement in increasing the ductility of reinforced concrete (RC) beam is essential in such members. Flexural and shear behaviors, ductility, and confinement were the main studied properties that used the CFRP as a strengthening material. However, limited attention has been paid to investigate the energy absorption of torsion strengthening of concrete members, especially two-span concrete beams. Hence, the target of this work is to investigate the effectiveness of CFRP-strengthening technique with regard to energy absorption of two-span RC beams subjected to pure torsion. The experimental program comprises the investigation of two groups; the first group comprises eight un-strengthened beam specimens, while the second group consists of eight strengthened beam specimens tested under torsional forces. The energy absorption capacity measured from the area under the curve of torque-angle of twist for tested beams. Two parameters were studied, the influence of concrete compressive strength and the angle of a twist. Experimental results indicated that all beams wrapped with CFRP sheet display superior torsional energy absorption capacity compared to the control specimens. The energy absorption may consider as a safety index for the torsional capacity of two-span RC beams under service loadings. Therefore, it is possible to avoid structural as well as material damages by understanding the concept of energy absorption that is one of the important experimental findings presented in this study.

scholarly journals Impact Behavior of Composite Reinforced Concrete Beams with Pultruded I-GFRP Beam

Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 441
Author(s):  
Teghreed H. Ibrahim ◽  
Abbas A. Allawi ◽  
Ayman El-Zohairy
Keyword(s):  
Compressive Strength ◽  
Reinforced Concrete ◽  
Impact Loading ◽  
Static Loading ◽  
Reinforced Concrete Beams ◽  
Impact Behavior ◽  
Drop Height ◽  
Concrete Compressive Strength ◽  
Shear Connectors ◽  
The Impact

The present study experimentally and numerically investigated the impact behavior of composite reinforced concrete (RC) beams with the pultruded I-GFRP and I-steel beams. Eight specimens of two groups were cast in different configurations. The first group consisted of four specimens and was tested under static load to provide reference results for the second group. The four specimens in the second group were tested first under impact loading and then static loading to determine the residual static strengths of the impacted specimens. The test variables considered the type of encased I-section (steel and GFRP), presence of shear connectors, and drop height during impact tests. A mass of 42.5 kg was dropped on the top surface at the mid-span of the tested beams from five different heights: 250, 500, 1000, 1500, and 1900 mm. Moreover, nonlinear Finite Element (FE) models were developed and validated using the experimental data. Static loading was defined as a displacement-controlled loading and the impact loading was modeled as dynamic explicit analysis with different drop velocities. The validated models were used to conduct a parametric study to investigate the effect of the concrete compressive strength on the performance of the composite beams under static and impact loadings. For the composite specimen with steel I-sction, the maximum impact force was 190% greater than the reference specimen NR-I at a drop height of 1900 mm, whereas the maximum impact forces for the specimens composite specimens with GFRP I-sction without and with shear connectors were 19% and 77%, respectively, more significant than the reference beam at the same drop height. The high stiffness for the steel I-beams relative to the GFRP I-beam was the reason for this difference in behavior. The concrete compressive strength was more effective in improving the impact behavior of the composite specimens relative to those without GFRP I-beams.

scholarly journals Numerical Assessment of Reinforced Concrete Beams Strengthened with CFRP Sheets under Impact Loading

2021 ◽  
Vol 15 (58) ◽  
pp. 48-64
Author(s):  
Mohamed Emara ◽  
Nada Elkomy ◽  
Hilal Abdel Kader
Keyword(s):  
Reinforced Concrete ◽  
Impact Velocity ◽  
Impact Loading ◽  
Impact Load ◽  
Reinforced Concrete Beams ◽  
Fiber Reinforced Polymers ◽  
Rc Beams ◽  
Cfrp Sheets ◽  
Externally Bonded ◽  
The Impact

This paper investigates numerically the behavior of Reinforced Concrete (RC) beams, strengthened using Carbon Fiber Reinforced Polymers (CFRP) sheets, subjected to impact loading. Three-dimensional finite element analysis was performed and its results were verified against experimental ones available in the literature showing good agreement. Then, a comprehensive parametric study was performed to investigate the effect of studied parameters on the strengthened RC beams. The main studied parameters were type and size of reinforcing bars, geometric characteristics of externally bonded CFRP sheets (width, length, and thickness), impact velocity, and the position of the impactor with respect to the beam. Results showed that the use of externally bonded CFRP sheets enhanced the beam capacity and failure mode, and reduced the mid-span deflection. Moreover, a reduction in the mid-span deflection was observed due to the use of CFRP bars as internal reinforcement. On the other hand, the deflection was increased due to the increase of the impact velocity, and the change of the impact load position.

Guidelines for flexural design of FRP reinforced concrete beams

2020 ◽  
pp. 002199832097373
Author(s):  
Fares Jnaid
Keyword(s):  
Compressive Strength ◽  
Reinforced Concrete ◽  
Carrying Capacity ◽  
Concrete Beams ◽  
Large Diameter ◽  
Reinforced Concrete Beams ◽  
Load Carrying Capacity ◽  
Concrete Compressive Strength ◽  
Load Carrying ◽  
Multiple Variables

This paper investigates the effects of different parameters on the live load carrying capacity of concrete beams reinforced with FRP bars. The author performed a parametric study utilizing an innovative numerical approach to inspect the effects of multiple variables such as reinforcement ratio, concrete compressive strength, span to depth ratio, FRP type, and bar diameter on load carrying capacity of FRP reinforced concrete beams. This study concluded that unless the span to height ratio is smaller than 8, tension-controlled sections are impractical as they do not meet code requirements for serviceability. In addition, it is recommended to use higher reinforcement ratios when using larger span to depth ratios and/or when using CFRP reinforcing bars. Moreover, larger number of bars with small diameter is more practical than fewer large diameter bars. Furthermore, this research suggests that increasing the concrete compressive strength is associated with a significant increase in the ultimate flexural capacity of FRP reinforced beams.

scholarly journals Mechanical Behavior and Chloride Penetration of Precracked Reinforced Concrete Beams with Externally Bonded CFRP Exposed to Marine Environment

2016 ◽  
Vol 2016 ◽  
pp. 1-8
Author(s):  
Yan Xie ◽  
Kunhua Guan ◽  
Lei Zhan ◽  
Qichen Wang
Keyword(s):  
Reinforced Concrete ◽  
Marine Environment ◽  
Chloride Penetration ◽  
Reinforced Concrete Beams ◽  
Bending Test ◽  
Chloride Diffusion ◽  
Accelerated Ageing ◽  
Rc Beams ◽  
Cfrp Sheets ◽  
Externally Bonded

Cracked reinforced concrete (RC) beams can be repaired effectively by using externally bonded CFRP sheets. However, when the strengthened beams are subjected to marine environment, long-term performance will be affected by the material and the interface deterioration of concrete and CFRP. Therefore, to evaluate the service life of the strengthened beams, this study investigates the behavior of precracked RC beams strengthened with CFRP sheets exposed to marine environment. Accelerated ageing experiments were carried out by exposing specimens to cyclic wetting in sea water and drying in 40°C air for 3 months and 6 months, respectively. After the environment exposure, four-point bending test was conducted and then the diffusion of chlorides in the strengthened beams was analysed. The results show that the bonding behavior of the adhesive was weakened and the ductility of the strengthened beams was slightly reduced due to the marine environment. But there is no obvious strength difference between the strengthened beams suffered from marine environment for 3 months and 6 months. Besides, the precracks in the RC beams accelerated the chloride diffusion, while CFRP bonding reduced the chloride penetration. In addition, NEL method was employed to validate the effect of the cracks on chloride permeability. The results showed that the chloride diffusion coefficients increased with the depth of the cracks.

Test Analysis for RC Beams Strengthened with Externally Bonded Prestressed CFRP Laminates

2008 ◽  
Vol 385-387 ◽  
pp. 41-44 ◽  
Author(s):  
Shi Qi Cui ◽  
Jin Shan Wang ◽  
Zhao Zhen Pei ◽  
Zhi Liu
Keyword(s):  
Reinforced Concrete ◽  
Bearing Capacity ◽  
Concrete Beams ◽  
Reinforced Concrete Beams ◽  
Rc Beams ◽  
Test Results ◽  
Test Analysis ◽  
Cfrp Laminates ◽  
Cfrp Sheet ◽  
Externally Bonded

Reinforced concrete beams strengthened with externally bonded CFRP sheet and prestressed CFRP are analyzed in this paper. Crack developments and displacements with curvatures for different beams are analyzed. Test results show that prestressed CFRP are able to control the development of macro cracks in concrete and prestressed CFRP is an effective method to improve the toughness of concrete, reduce strengthening cost and meanwhile enhance bearing capacity of concrete beams.

scholarly journals Evaluation of Effective Polymer Fiber Length on Energy Absorption Capacity of Reinforced Beams by EBR and NSM Methods

2021 ◽  
Vol 30 (3) ◽  
Author(s):  
Komeyl Karimi-Moridani
Keyword(s):  
Energy Absorption ◽  
Crack Nucleation ◽  
Absorption Capacity ◽  
Rc Beams ◽  
Energy Absorption Capacity ◽  
Near Surface ◽  
Cfrp Sheets ◽  
Reinforced Beams ◽  
Cfrp Sheet ◽  
Externally Bonded

This study presents a comparison of two methods used for retrofitting Reinforced Concrete (RC) beams, namely, the Externally Bonded Reinforcement (EBR) and the Near-Surface Mounting (NSM) methods. A parametric analysis was carried out using variables such as the retrofitted, the retrofitting method (EBR and NSM), and the thickness of the Carbon Fiber-Reinforced Polymer (CFRP) sheets. To achieve this goal, the finite element method and ABAQUS software were employed. An un-retrofitted beam was also simulated as the control specimen for comparison. Beam responses were compared through load–displacement and energy absorption capacity diagrams. Results show that the higher energy absorption capacity in all CFRP-retrofitted RC beams, which was 1.69–5.54 times higher than in un-retrofitted beams. In the case where half of the beam was reinforced using CFRP sheets, the entire beam assembly and the CFRP sheet contributed to load-bearing, thus delaying crack nucleation in the beam and increasing its energy absorption capacity. As a result, the energy absorption capacity of the beam, in this case, was less than that obtained in the previous one where half the span of the beam was retrofitted.

scholarly journals Debonding-Related Strain Limits for Externally Bonded FRP Sheets in Flexurally Strengthened Reinforced Concrete Beams

2013 ◽  
Vol 7 (1) ◽  
pp. 58-67 ◽  
Author(s):  
Guibing Li ◽  
Aihui Zhang ◽  
Yugang Guo
Keyword(s):  
Reinforced Concrete ◽  
Tensile Strain ◽  
Concrete Beams ◽  
Experimental Tests ◽  
Critical Issue ◽  
Reinforced Concrete Beams ◽  
Rc Beams ◽  
Externally Bonded ◽  
Strengthening Technique ◽  
Code Provisions

Debonding problems of externally bonded fiber reinforced polymer (FRP) sheets in flexurally FRP-strengthened reinforced concrete (RC) beams have been a concern and a research challenge since their application of this strengthening technique. Intermediate crack induced debonding is the most common failure mode which is that the debonding initiates at the critical flexural-shear or flexural cracks and propagates towards the direction of moment decrease. To mitigate debonding failure, most Codes and proposed models take the method by limiting the allowable tensile strain in FRP laminates. This paper presents experimental tests of concrete beams flexurally strengthened with externally bonded CFRP sheets to investigate debonding initiation and tensile strain of FRP laminates. The allowable tensile strain of FRP sheets in flexurally FRP-strengthened RC beams proposed by prevalent Code provisions and models was assessed based on the data obtained from experimental programs. It has beenshown that the allowable tensile strains provided by these provisions and models have a great difference with that of experimental results and exhibit a high level of dispersion. Furthermore, the FRP laminates of most tested RC beams were debonded before reaching the proposed allowable tensile strain. The Code provisions and models are inadequate to effectively prevent intermediate crack induced debonding failure in flexurally FRP-strengthened RC members. This is known to be a critical issue in engineering design and application of RC beams flexurally strengthened by FRP sheets.

Influence of Minimum Tension Steel Reinforcement on the Behavior of Singly Reinforced Concrete Beams in Flexure

2020 ◽  
Vol 38 (7A) ◽  
pp. 1034-1046
Author(s):  
Ali ِA. Abdulsada ◽  
Raid I. Khalel ◽  
Kaiss F. Sarsam
Keyword(s):  
Compressive Strength ◽  
Reinforced Concrete ◽  
Concrete Beams ◽  
Rectangular Cross Section ◽  
Steel Reinforcement ◽  
Reinforced Concrete Beams ◽  
Concrete Compressive Strength ◽  
Minimum Reinforcement ◽  
Flexural Reinforcement ◽  
New Formula

The requirements of minimum flexural reinforcement in the last decades have been a reason for controversy. The structural behavior of beams in bending is the best way of investigating and evaluating the minimum reinforcement in flexure. For this purpose, twelve singly reinforced concrete beams with a rectangular cross-section of (125 mm) width by (250 mm) height and (1800 mm) length were cast and tested under two-point loads up to failure. These beams were divided into three groups with different compressive strengths (25, 50, and 80 MPa). Each group consists of four beams with different amounts of tension steel reinforcement approximately equal to (0% Asmin, 50% Asmin, 100% Asmin and 150% Asmin), two bar diameters (Ø6 mm and Ø8 mm) were used as the longitudinal tension reinforcement with different yield and ultimate strengths, the minimum amount of reinforcement required is calculated based on ACI 318M-2014 code. The results show that for the reinforced concrete beams, the flexural reinforcement in NSC beams increases the first cracking load and the increment increased with an increasing amount of reinforcement, while for HSC beams the increasing in first cracking load are very little when the quantity of reinforcement less than the minimum flexural reinforcement and increased with the increasing amount above the minimum flexural reinforcement. The equation of ACI 318M-14 code gives adequate minimum flexural reinforcement for NSC and overestimate value for HSC up to (83 MPa), A new formula is proposed for HSC rectangular beams up to (90 MPa) concrete compressive strength by reducing the equation of ACI 318M-14 code for minimum flexural reinforcement by a factor depending on concrete compressive strength.  

An Effective Framework for Performance Evaluation of Reinforced Concrete Beams Under Impact Loadings

2020 ◽  
Vol 20 (11) ◽  
pp. 2050117
Author(s):  
Wuchao Zhao ◽  
Jihong Ye
Keyword(s):  
Performance Evaluation ◽  
Reinforced Concrete ◽  
Impact Analysis ◽  
Reinforced Concrete Beams ◽  
Effective Model ◽  
Rc Beams ◽  
Probabilistic Framework ◽  
Maximum Displacement ◽  
Damage Degree ◽  
The Impact

Extreme actions, such as impact loads, contain many uncertainties and hence, may not be analyzed by a deterministic approach. In this paper, an effective framework for performance evaluation of reinforced concrete (RC) beams subjected to impact loadings is proposed. For this purpose, a simple yet effective model considering the shear-flexural interaction is developed based on available impact test results. By incorporating the shear effect, both the maximum displacement and impact force are well predicted, by which the proposed model for the impact analysis of RC beams is validated. The joint probability density function (PDF) of two damage indexes, i.e. local drift ratio and overall support rotation, is used to represent the local shear damage degree and the overall flexural damage degree. Taking advantage of the probabilistic framework and the effective model, reliability analysis of the RC beams under different impact scenarios is performed. The damage, described in this study by the joint PDF, is highly affected by the combination of impact mass and velocity. Thus, the mass–velocity ([Formula: see text]–[Formula: see text] diagrams for various performance levels are generated for the damage assessment of the RC beams. Furthermore, the contribution of the local and global responses to the failure probability is quantified using the proposed probabilistic framework.

Sign in / Sign up

Export Citation Format

Share Document