scholarly journals Flexural Behavior of Concrete Beam Strengthened by Near-Surface Mounted CFRP Reinforcement Using Equivalent Section Model

2017 ◽  
Vol 2017 ◽  
pp. 1-16 ◽  
Author(s):  
Woo-tai Jung ◽  
Jong-sup Park ◽  
Jae-yoon Kang ◽  
Moon-seoung Keum
Keyword(s):  
Cross Sections ◽  
Failure Criteria ◽  
Flexural Behavior ◽  
Failure Behavior ◽  
Failure Model ◽  
Bond Failure ◽  
Near Surface ◽  
Near Surface Mounted ◽  
Section Model ◽  
Sectional Shape

FRP (fiber reinforced polymer) has found wide applications as an alternative to steel rebar not only for the repair and strengthening of existing structures but also for the erection of new structures. Near-surface mounted (NSM) strengthening was introduced as an alternative of externally bonded reinforcement (EBR) but this method also experiences early bond failure, which stresses the importance of predicting accurately the bond failure behavior in order to evaluate precisely the performance of NSM reinforcement. This study proposes the equivalent section model assuming monolithic behavior of the filler and CFRP reinforcement. This equivalent section model enables establishing a bond failure model applicable independently of the sectional shape of the CFRP reinforcement. This so-derived bond failure model is then validated experimentally by means of beams flexure-strengthened by NSM CFRP reinforcements with various cross-sections. Finally, analytical analysis applying the bond failure model considering the equivalent section and defined failure criteria is performed. The results show the accuracy of the prediction of the failure mode as well as the accurate prediction of the experimental results regardless of the sectional shape of the CFRP reinforcement.

Numerical simulation of the debonding process in pull-out tests of near-surface mounted FRP rod in concrete

2019 ◽  
Vol 37 (3) ◽  
pp. 1109-1130
Author(s):  
Tie-Lin Chen ◽  
Wenbin Tao ◽  
Wenjun Zhu ◽  
Mozhen Zhou
Keyword(s):  
Three Dimensional ◽  
Crack Model ◽  
Bond Failure ◽  
Near Surface ◽  
Content Type ◽  
Rc Structures ◽  
Pull Out ◽  
Smeared Crack ◽  
Near Surface Mounted ◽  
Debonding Process

Purpose Near-surface mounted (NSM) fiber-reinforced polymer (FRP) rod is extensively applied in reinforced concrete (RC) structures. The mechanical performances of NSM FRP-strengthened RC structures depend on the bond behavior between NSM reinforcement and concrete. This behavior is typically studied by performing pull-out tests; however, the failure behavior, which is crucial to the local debonding process, is not yet sufficiently understood. Design/methodology/approach In this study, a three-dimensional meso-scale finite element method considering the cohesion and adhesion failures is presented to model the debonding failure process in pull-out tests of NSM FRP rod in concrete. The smeared crack model is used to capture the cohesion failures in the adhesive or concrete. The interfacial constitutive model is applied to simulate the adhesion failures on the FRP-adhesive and concrete-adhesive contact interfaces. Findings The present method is first validated by two simple examples and then applied to a practical NSM FRP system. This work studied in detail the debonding process, the bond failure types, the location of peak bond stress, the transmitting deformation in adhesive and the morphology of contact zone. The developed method provides a practical and convenient tool applicable for further investigations on the debonding mechanism for the NSM FRP rod in concrete. Originality/value A three-dimensional meso-scale finite element method considering the cohesion and adhesion failures is presented to model the debonding failure in NSM FRP-strengthened RC structures. The smeared crack model and the interfacial constitutive model are introduced to develop a convenient approach to analyze the failures in adhesive, concrete and related interfaces. The developed numerical method is applicable for studying the debonding process, the bond failure types, the location of peak bond stress, the transmitting deformation in adhesive and the morphology of contact zone in detail.

scholarly journals Experimental Investigation on Flexural Behavior of Granite Stone Slabs with Near Surface Mounted CFRP Bars and Screw-Thread Steels

2018 ◽  
Vol 2018 ◽  
pp. 1-30
Author(s):  
Xiaopeng Gao ◽  
Zhongfan Chen ◽  
Xiaomeng Ding ◽  
Erxiang Dong
Keyword(s):  
Failure Load ◽  
Ductile Failure ◽  
Flexural Behavior ◽  
Screw Thread ◽  
Test Results ◽  
Cracking Behavior ◽  
Near Surface ◽  
Four Point Bending ◽  
Calculation Results ◽  
Near Surface Mounted

An experimental study that investigates the behavior of stone slabs strengthened in fixure with near surface mounted (NSM) technique using screw-thread steels and carbon fiber-reinforced polymer (CFRP) bars is presented. A total of ten full-scale stone slabs were tested under a four-point bending loading to investigate the effect of groove dimension, reinforcement ratios, and reinforcement materials on the flexural performance of stone slabs. The test results included failure characteristics, yield and ultimate capacities, deflection of midspan, and cracking behavior of stone slabs. The test results indicate that with the increase of groove height and groove width, cracking load and middeflection decrease by 6.4%–14.18%; however, failure load and middeflection increase by 4.7%–41.2%. Cracking load, failure load, and failure displacement of stone slabs adopting NSM screw-thread steels increased by 10.9%, 167%, and 617%, respectively, under the maximum reinforcement ratios of 0.629% over the control slab without NSM bars. Meanwhile, with the increase of reinforcement ratios, the failure mode transforms from brittle failure to ductile failure. The calculation results of strength are in agreement with the experimental results. Finally, it can be concluded that NSM CFRP bars are more effective than NSM screw-thread steels to improve flexural capacity with the same reinforcement ratios.

Experimental Study on Flexural Behavior of Damaged Concrete Beams Strengthened with NSM-CFRP Strips

2012 ◽  
Vol 256-259 ◽  
pp. 1012-1016
Author(s):  
Gu Sheng Tong ◽  
Yong Xiang Wang ◽  
Qiu Lan Wu ◽  
Yong Sheng Liu
Keyword(s):  
Failure Modes ◽  
Fiber Reinforced Polymer ◽  
Flexural Behavior ◽  
Rc Beams ◽  
Near Surface ◽  
Damage Level ◽  
Reinforced Polymer ◽  
Near Surface Mounted ◽  
Strengthen Effect ◽  
Capacity Loading

In order to investigate the strengthen effect of different embedment lengths of the NSM strip on different damage levels. A series of tests were conducted on damaged reinforced concrete (RC) beams in flexure strengthened with near surface mounted (NSM) carbon- fiber-reinforced polymer (CFRP) strips, and initial cracking load, ultimate capacity, loading-deflection curves, and failure modes are examined and analyzed in the paper. The results showed that not only the initial cracking loads and ultimate capacities of the beams are significantly increased，but also the flexural stiffness of the beams in the yield and ultimate behavior stages are improved by using NSM-CFRP strips. The strengthen effect on lower damage level RC beams has no obvious difference with that on non-damaged RC beams. Anchoring of the strip end can increase the ultimate load capacities and decrease the ductility of RC beams. Debonding was found to be the primary failure mode in all cases.

scholarly journals EFFICIENCY OF FLEXURAL STRENGTHENING OF REINFORCED CONCRETE BEAMS BY NEAR SURFACE MOUNTED CARBON FIBER REINFORCEMENT POLYMER RODS AND EXTERNALLY BONDED SHEETS

2021 ◽  
Vol 25 (Special) ◽  
pp. 4-100-4-114
Author(s):  
Wissam S. Abdullah ◽  
◽  
Hassan F. Hassan ◽  
Keyword(s):  
Load Capacity ◽  
Reference Beam ◽  
Reinforced Concrete Beams ◽  
Flexural Behavior ◽  
Ultimate Load Capacity ◽  
Near Surface ◽  
Flexural Strengthening ◽  
Cfrp Sheet ◽  
Externally Bonded ◽  
Near Surface Mounted

This study investigated the flexural behavior of reinforcement concrete beam strengthened with different techniques. The purpose of this research to study the various techniques of strengthening and knowing the effect of each technique on the beam behavior .Ten simply supported beams tested in this study. The total length of the beams and clear span were 1800mm and 1650mm, respectively. The cross section was (180×250) mm. Tested beams were divided into two categories’ the first category consist of one beams and considered as reference, while the second category consist of nine beams divided into Two groups according to the Strengthening techniques such as near surface mounted (NSM) and external bonded reinforcement (EBR).The experimental results showed improvement in ultimate load capacity for strengthened beams ranging from (6 to 89%) for NSM and (31 to 96%) for EBR and reduction in deflection for strengthened beams ranging from (6 to 43%) as compared with reference beam. When the number and length of CFRP bars are increased, the number of cracks increase while the width of the cracks and the spacing decrease, and the same observation is made when the width of the CFRP sheet is increased. The experimental load capacities of strengthened beams were compared with the design provisions given by ACI440.2R-17 guideline for NSM and EBR technique and EC2 guideline for EBR technique, the average ratio (1.2 and 0.97) respectively ,which showed that reasonable and a good agreement for all strengthened beams.

Flexural Behavior of RC Beams Strengthened with Near Surface Mounted Prestressed FRP

2007 ◽  
Author(s):  
Sung-Nam Hong ◽  
Jae-Hyun Park ◽  
Jong-Sup Park ◽  
Jun-Myung Park ◽  
Dong-Suk Yang ◽  
...  
Keyword(s):  
Flexural Behavior ◽  
Rc Beams ◽  
Near Surface ◽  
Near Surface Mounted

Flexural Behavior and Ductility of Concrete Beams Strengthened with Near-Surface Mounted GFRP Bars

2010 ◽  
Vol 163-167 ◽  
pp. 3610-3614 ◽  
Author(s):  
Hai Xia Zhang ◽  
Ling Wang ◽  
Guo Rui Liu
Keyword(s):  
Cross Section ◽  
Ultimate Load ◽  
Rectangular Cross Section ◽  
Reinforced Concrete Beam ◽  
Flexural Behavior ◽  
Near Surface ◽  
Displacement Ductility ◽  
Gfrp Bars ◽  
Near Surface Mounted ◽  
Strengthened Beam

The objective of this study is to investigate the flexural behaviors and ductility of reinforced concrete beam with near-surface mounted (NSM) GFRP bars. A total of 5, simply supported rectangular cross-section beams strengthened with NSM GFRP bars and two control beams are tested in this paper. The mode of failure, load-deflection relationship, strain distributions along the height of the beam on mid-span cross-section, and ductility of the beams are analyzed. The studies indicate that the yield and ultimate load have a significant increase compared with the control specimen. Especially, the ultimate load has a more measurable improvement than the yield load. The strain distribution along the height of specimen shows a clear nonlinear characteristic as a result of the crack propagating and steel yield. Also, the studies show that GFRP bars has played an important role in the flexural capacity of the strengthened beam during the stage from the yield to the failure of the beam. Besides, the strengthened beam is considered to be ductile using the displacement ductility index.

scholarly journals A Parametric Study on the Flexural Strengthening of Reinforced Concrete Beams with Near Surface Mounted FRP Bars

2018 ◽  
Vol 4 (8) ◽  
pp. 1917
Author(s):  
Minu Panahi ◽  
Mohsen Izadinia
Keyword(s):  
Reinforced Concrete ◽  
Concrete Beams ◽  
Weight Ratio ◽  
Bending Moment ◽  
Reinforced Concrete Beams ◽  
Flexural Behavior ◽  
Experimental Investigations ◽  
Near Surface ◽  
Finite Element Software ◽  
Near Surface Mounted

FRP rods as lightweight materials with extraordinary properties of high strength to weight ratio, corrosion resistance, potentially high overall durability, tailor ability and high specific attributes are one of the most favorable materials to strengthen existing reinforced structures. The present study aimed to identify the behavior of reinforced concrete flexural beams strengthened with fiber reinforced polymer (FRP) rods through near surface mounted method (NSM). The results of the current study were based on nonlinear finite element software ABAQUS which can accurately simulate the experimental investigations on flexural behavior of reinforced concrete beams strengthened with NSM FRP rods. Validation of the proposed model was confirmed first by making a comparison with the experimental study presented in the literature. A parametric analysis was conducted on validated specimens to investigate the effect of FRP rod diameters, rod arrangements, FRP materials, as well as rods groove intervals on flexural behavior of strengthened reinforced beams. The numerical results of mid-span bending moment deflection, ultimate bending moment, failure deflection and ductility index were reported. For the sake of simplicity to be used by engineers, the results of the current study were drawn in the form of design charts and tables.

Experimental Study on Flexural Bearing Capacity of Concrete Beams Strengthened with NSM CFRP-PCPs Composite Bars

2014 ◽  
Vol 584-586 ◽  
pp. 908-911
Author(s):  
Li Hong Cheng ◽  
Jiong Feng Liang ◽  
Ming Hua Hu
Keyword(s):  
Experimental Study ◽  
Reinforced Concrete ◽  
Concrete Beams ◽  
Flexural Behavior ◽  
Concrete Member ◽  
Near Surface ◽  
Reinforced Concrete Member ◽  
Bonding Area ◽  
Flexural Bearing Capacity ◽  
Near Surface Mounted

The flexural behavior of concrete beams strengthened with near surface mounted (NSM) CFRP-PCPs composite rebars was studied. Experimental results showed that embedded CFRP-PCPs reinforcement method can effectively improve strength, stiffness and cracks of the reinforced concrete member, and PCPs increased with concrete bonding area, thus avoiding the strip damage of the traditional embedded reinforcement.

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