http://cfrp.blogfa.com/post-67.aspx
Flexural strengthening of reinforced lightweight polystyrene aggregate concrete beams with near-surface mounted GFRP bars

W.C. Tang, R.V. Balendran
, A. Nadeem, H.Y. Leung

Department of Building and Construction, City University of Hong Kong, China

Received 26 November 2004; received in revised form 4 January 2005; accepted 19 May 2005

Abstract

Application of near-surface mounted (NSM) fibre reinforced polymer (FRP) bars is emerging as a promising technology for increasing flexural and shear strength of deficient reinforced concrete (RC) members. In order for this technique to perform effectively, the structural behaviour of RC elements strengthened with NSM FRP bars needs to be fully characterized. This paper focuses on the characterization of flexural behaviour of RC members strengthened with NSM glass-FRP bars. Totally, 10 beams were tested using symmetrical two-point loads test. The parameters examined under the beam tests were type of concretes (lightweight polystyrene aggregate concrete and normal concrete), type of reinforcing bars (GFRP and steel), and type of adhesives.

Flexural performance of the tested beams including modes of failure, moment–deflection response and ultimate moment capacity are presented and discussed in this paper. Results of this investigation showed that beams with NSM GFRP bars showed a reduction in ultimate deflection and an improvement in flexural stiffness and bending capacity, depending on the PA content of the beams. In general, beams strengthened with NSM GFRP bars overall showed a significant increase in ultimate moment ranging from 23% to 53% over the corresponding beams without NSM GFRP bars. The influence of epoxy type was found conspicuously dominated the moment–deflection response up to the peak moment. Besides, the ultimate moment of concrete beams reinforced with GFRP bars could be predicted satisfactorily using the equation provided in ACI 318-95 Building Code.

لینک فایل کامل مقاله

Building and Environment 41 (2006) 1381–1393
http://www.4shared.com/file/51291981/f706a2ab/Flexural_strengthening_of_reinforced_lightweight_polystyrene.html

http://cfrp.blogfa.com/post-68.aspx
On the parameters influencing the performance of reinforced concrete beams strengthened with FRP plates

F. Taheri *, K. Shahin, I. Widiarsa

Department of Civil Engineering, Dalhousie University, 1360 Barrington Street, Halifax, NS, Canada B3J 1Z1

Abstract

This paper presents a summary of our investigations that were aimed to assess the influence of various physical and mechanical parameters on the performance of reinforced concrete (RC) beams strengthened with fiber reinforced plastic (FRP) plates. The work was divided into two phases. The first phase investigated the influence of FRP plate length, fiber orientation, and surface preparation on the performance of FRP-reinforced RC beams. The FRP in this phase of the work was E-glass/epoxy. The second phase of the study was designed to confirm the validity of our hypothesis, which postulated that the delamination of the FRP plate would be a function of the Poisson ratio mismatch between concrete and FRP plate. Results from the second phase also suggested that less expensive glass FRP plates could adequately replace the more expensive carbon FRP plates by offering the beam more ductility, without sacrificing its expected performance. Moreover, results from both phases showed that the lateral stiffness of the FRP plate contributed to the overall flexural stiffness of the strengthened beam.

جهت مطالعه اصل مقاله از لینک زیر استفاده نمایید

Composite Structures 58 (2002) 217–226
http://www.4shared.com/file/51292176/f25cd591/On_the_parameters_influencing_the_performance_of_reinforced.html

http://cfrp.blogfa.com/post-69.aspx
Performance of reinforced concrete beams strengthened by hybrid FRP laminates

Abdelhady Hosny a, Hamdy Shaheen b, Amr Abdelrahman a,*, Tamer Elafandy b

a Structural Engineering Department, Ain Shams University, Cairo, Egypt

b RC Department, Housing and Building Research Center, Giza, Egypt

Abstract

In the last two decades, the use of advanced composite materials such as Fiber Reinforced Polymers (FRP) in strengthening reinforced concrete (RC) structural elements has been increasing. Research and design guidelines concluded that externally bonded FRP could increase the capacity of RC elements efficiently. However, the linear stress–strain characteristics of FRP up to failure and lack of yield plateau have a negative impact on the overall ductility of the strengthened RC elements. Use of hybrid FRP laminates, which consist of a combination of either carbon and glass fibers, or glass and aramid fibers, changes the behaviour of the material to a non-linear behaviour.

This paper aims to study the performance of reinforced concrete beams strengthened by hybrid FRP laminates. This paper presents an experimental program conducted to study the behaviour of RC beams strengthened with hybrid fiber reinforced polymer (HFRP) laminates. The program consists of a total of twelve T-beams with overall dimensions equal to 460 · 300 · 3250 mm. The beams were tested under cyclic loading up to failure to examine its flexural behaviour. Different reinforcement ratios, fiber directions, locations and combinations of carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP) laminates were attached to the beams to determine the best strengthening scheme. Different percentages of steel reinforcement were also used. An analytical model based on the stress–strain characteristics of concrete, steel and FRP was adopted. Recommendations and design guidelines of RC beams strengthened by FRP and HFRP laminates are introduced.

مقاله کامل توسط لینک زیر قابل دسترسی است

Cement & Concrete Composites 28 (2006) 906–913

http://www.4shared.com/file/51292356/c3ee637d/Performance_of_reinforced_concrete_beams_strengthened.html

http://cfrp.blogfa.com/post-70.aspx
Sensitivity analysis of reinforced concrete beams

strengthened with FRP laminates

Carlos A. Coronado a,1, Maria M. Lopez b,*

a Department of Civil and Environmental Engineering, The Pennsylvania State University, 3127 Research Drive CATO Park,

Room 117, State College, PA 16801, USA

b Department of Civil and Environmental Engineering, The Pennsylvania State University, 212 Sackett Building, University Park,

State College, PA 16802-1408, USA

Received 13 July 2004; accepted 19 July 2005

Available online 20 October 2005

Abstract

Numerical procedures are proposed to predict the failure of reinforced concrete (RC) beams strengthened in flexure with fiber-reinforced polymeric (FRP) laminates. The framework of damage mechanics was used during the modeling. Numerical results were validated against experimental data obtained from 19 beams strengthened with different types of FRP. These beams failed by concrete crushing, cover failure and plate debonding. The numerical models were capable of predicting the experimentally observed load–deflection, failure load and failure modes. The sensitivity of the numerical results was studied. In particular, the effect of the concrete constitutive behavior and different modeling considerations was evaluated. It was found that the fracture energy of the concrete–repair interface plays a central part in predicting plate-debonding failures.

Keywords: Composite materials; Fracture energy; Finite element modeling; Damage mechanics; Debonding; Numerical modeling; FRP laminate; Reinforced concrete beam.

جهت مطالعه متن کامل مقاله از لینک زیر استفاده نمایید

Cement & Concrete Composites 28 (2006) 102–114

http://www.4shared.com/file/51292633/e315f29f/Sensitivity_analysis_of_reinforced_concrete_beams.html

http://cfrp.blogfa.com/post-71.aspx

Shear enhancement of reinforced concrete beams strengthened with FRP composite laminates

Ayman S. Mosallam *, Swagata Banerjee

Civil and Environmental Engineering Department, University of California at Irvine, California 92697, United States

Received 1 April 2006; accepted 1 October 2006

Available online 18 January 2007

Abstract

This paper presents the results of an experimental investigation on shear strength enhancement of reinforced concrete beams externally reinforced with fiber-reinforced polymer (FRP) composites. A total of nine full-scale beam specimens of three different classes, as-built (unstrengthened), repaired and retrofitted were tested in the experimental evaluation program. Three composite systems namely carbon/epoxy wet layup, E-glass/epoxy wet layup and carbon/epoxy precured strips were used for retrofit and repair evaluation. Experimental results indicated that the composite systems provided substantial increase in ultimate strength of repaired and strengthened beams as compared to the pre-cracked and as-built beam specimens. A comparative study of the experimental results with published analytical models, including the ACI 440 model, was also conducted in order to evaluate the different analytical models and identify the influencing factors on the shear behavior of FRP strengthened reinforced concrete beams. Comparison indicated that the shear span-to-depth ratio (a/d) is an important factor that actively controls the shear failure mode of beam and consequently influences on the shear strength enhancement. 2007 Elsevier Ltd. All rights reserved.

Keywords: A. Polymer-matrix composites (PMCs); B. Debonding; C. Analytical modelling; D. Mechanical testing; Infrastructure

جهت مطالعه متن کامل مقاله از لینک زیر استفاده نمایید

Composites: Part B 38 (2007) 781–793
http://www.4shared.com/file/51292811/35b3dc3b/Shear_enhancement_of_reinforced_concrete_beams_strengthened.html