Enhancing flexural capacity of RC columns through near surface mounted SMA and CFRP bars

This study explores the flexural behavior of reinforced concrete (RC) columns strengthened with near surface mounted (NSM) shape memory alloy (SMA) bars or carbon fiber reinforced polymer (CFRP) bars. Seven RC column specimens were designed and fabricated to study the influence of different variables on the flexural response of the strengthened columns. These parameters include type of NSM reinforcement (SMA bars or CFRP bars), ratio of NSM reinforcement, and effect of CFRP jacketing. The columns were tested under cyclic lateral loading with constant axial force. The flexural behavior of each specimen was examined in terms of peak load, failure load, drift ratios, displacement ductility, stiffness degradation, energy dissipation, and seismic damage index. The experimental results indicate that strengthening of RC columns with NSM SMA or CFRP bars improves the flexural behavior of the columns through increasing the lateral load capacity, reducing the stiffness degradation and increasing the cumulative energy absorption up to failure. Further enhancement in the lateral response of RC columns was obtained by combining NSM bars and CFRP jacketing as the later provides an additional confinement to the critical sections of the test specimens.

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PERFORMANCE ADVANCEMENT OF RC COLUMNS BY APPLYING BASALT FRP COMPOSITES WITH NSM AND CONFINEMENT SYSTEM

Journal of Earthquake and Tsunami ◽

10.1142/s1793431113500073 ◽

2013 ◽

Vol 07 (02) ◽

pp. 1350007 ◽

Cited By ~ 11

Author(s):

LINING DING ◽

GANG WU ◽

SHENYIN YANG ◽

ZHISHEN WU

Keyword(s):

Performance Enhancement ◽

Load Capacity ◽

Basalt Fiber ◽

Chemical Properties ◽

Strength Degradation ◽

Rc Columns ◽

Near Surface ◽

Displacement Ductility ◽

Frp Composites ◽

Yield Displacement

Basalt fiber reinforced polymer (BFRP) composites are regarded as promising structural strengthening material due to their environmental friendly and superior mechanical and chemical properties. In order to enhance the overall seismic performance of RC columns, a strengthening system is developed by applying BFRP composites with both near surface mounted (NSM) and confinement approaches. The variables taken into account consisted of the diameters and anchorage lengths of BFRP bars, as well as the confinement amounts of BFRP sheets. A total of eight column specimens including one control were tested subjected to simultaneous axial compression and cyclic bend. The structural performance such as load capacity, displacement, ductility, stiffness degradation, energy dissipation capacity, curvature and post-yield stiffness were investigated. The test results indicate that the combination of NSM and confinement techniques contributes to the comprehensive performance enhancement of RC columns, which lies in (1) constantly enlarging diameters of BFRP bars increases the yield and peak loads, the ultimate displacement, the initial and post-yield stiffness as well as the ductility, whereas it has no obvious influence on the yield displacement; (2) longer bonding length results in higher seismic performances although it makes no changes to the yield displacement, the post-yield stiffness, and the degradation of strength and stiffness as well; (3) the adoption of BFRP confinement significantly improves the ductility and the strength degradation performance; (4) the largest post-yield stiffness can be achieved by enlarging diameter to 12 mm, whereas the ductility and the strength degradation characteristics deteriorate due to the weakness of interfacial bonding between BFRP bars and concrete.

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

Journal of Engineering and Sustainable Development ◽

10.31272/jeasd.conf.2.4.10 ◽

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.

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

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.163-167.3610 ◽

2010 ◽

Vol 163-167 ◽

pp. 3610-3614 ◽

Cited By ~ 1

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.

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Reseach on Flexural Behavior of Reinforced Concrete Beams Strengthened with Prestressed Near Surface Mounted CFRP Tendons

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.163-167.3537 ◽

2010 ◽

Vol 163-167 ◽

pp. 3537-3544 ◽

Cited By ~ 1

Author(s):

Ya Hong Ding ◽

Yan Jie Ma

Keyword(s):

Reinforced Concrete ◽

Engineering Application ◽

Reinforced Concrete Beams ◽

Flexural Behavior ◽

Rc Beams ◽

Near Surface ◽

Displacement Ductility ◽

Near Surface Mounted ◽

Strengthening Technique ◽

Strengthening Method

The effectiveness of strengthening reinforced concrete (RC) beams with prestressed near- surface mounted (NSM) carbon fiber reinforced polymer (CFRP) rods has been investigated. The RC beams are tested under monotonic loading. The stressing process, failure capacity, flexural capaticy, displacement ductility and deformation are systematically studied. The text results show that the new strengthening technique with prestressed NSM CFRP rods can enhance the first-crack load, steel-yielding load of beams compared to the control beam. It is worth noting that the prestress can limit the crack width all the way up to failure, reduce the midpoint deflection, and improve the service performance of the strengthened beams. The strengthening method offers an alternative way to existing strengthening method. The results provide a reference for engineering application.

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A comparative study of flexural behavior of reinforced masonry walls strengthened with near-surface mounted FRP bars or externally bonded FRP sheets

Insights and Innovations in Structural Engineering, Mechanics and Computation ◽

10.1201/9781315641645-239 ◽

2016 ◽

pp. 1459-1464

Author(s):

Z Aljaberi ◽

J Myers ◽

M ElGawady

Keyword(s):

Comparative Study ◽

Flexural Behavior ◽

Masonry Walls ◽

Near Surface ◽

Reinforced Masonry ◽

Externally Bonded ◽

Near Surface Mounted ◽

Frp Bars

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Flexural behavior of large-size RC beams strengthened with side near surface mounted (SNSM) CFRP strips

Composite Structures ◽

10.1016/j.compstruct.2018.06.031 ◽

2018 ◽

Vol 201 ◽

pp. 178-192 ◽

Cited By ~ 8

Author(s):

Zewen Zhu ◽

Eryu Zhu

Keyword(s):

Flexural Behavior ◽

Rc Beams ◽

Near Surface ◽

Large Size ◽

Near Surface Mounted

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Flexural Behavior of Fire-Damaged Prefabricated RC Hollow Slabs Strengthened with CFRP versus TRM

Materials ◽

10.3390/ma13112556 ◽

2020 ◽

Vol 13 (11) ◽

pp. 2556

Author(s):

Zheng-Ang Sui ◽

Kun Dong ◽

Jitong Jiang ◽

Shutong Yang ◽

Kexu Hu

Keyword(s):

Failure Modes ◽

Early Stage ◽

Load Capacity ◽

Peak Load ◽

Flexural Behavior ◽

Masonry Building ◽

Fire Exposure ◽

Standard Fire ◽

Four Point Bending ◽

Strengthening Technique

In this paper, carbon fiber reinforced polymer (CFRP) and textile reinforced mortar (TRM) strengthening techniques were proposed to retrofit and strengthen fire-damaged prefabricated concrete hollow slabs. A total of six slabs, from an actual multi-story masonry building, were tested to investigate the flexural performance of reinforced concrete (RC) hollow slabs strengthened with TRM and CFRP. The investigated parameters included the strengthening method (CFRP versus TRM), the number of CFRP layers, and with or without fire exposure. One unstrengthened slab and one TRM strengthened slab served as the control specimens without fire exposure. The remaining four slabs were first exposed to ISO-834 standard fire for 1 h, and then three of them were strengthened with CFRP or TRM. Through the four-point bending tests at ambient temperature, the failure modes, load and deformation response were recorded and discussed. Both CFRP and TRM strengthening methods can significantly increase the cracking load and peak load of the fire-damaged hollow slabs, as well as the stiffness in the early stage. The prefabricated hollow slabs strengthened by CFRP have better performance in the ultimate bearing capacity, but the ductility reduced with the increase of CFRP layers. Meanwhile, the TRM strengthening technique is a suitable method for the performance improvement of fire-damaged hollow slabs, in terms of not only the load capacity, especially the cracking load, but also the flexural stiffness and deformation capacity.

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Characterization and Simulation of the Bond Response of NSM FRP Reinforcement in Concrete

Materials ◽

10.3390/ma13071770 ◽

2020 ◽

Vol 13 (7) ◽

pp. 1770 ◽

Cited By ~ 3

Author(s):

Javier Gómez ◽

Lluís Torres ◽

Cristina Barris

Keyword(s):

Load Capacity ◽

Numerical Procedure ◽

Fiber Reinforced Polymer ◽

Near Surface ◽

Bond Slip ◽

Pull Out ◽

Reinforced Polymer ◽

Frp Reinforcement ◽

Near Surface Mounted ◽

Shear Stress And Strain

The near-surface mounted (NSM) technique with fiber reinforced polymer (FRP) reinforcement as strengthening system for concrete structures has been broadly studied during the last years. The efficiency of the NSM FRP-to-concrete joint highly depends on the bond between both materials, which is characterized by a local bond–slip law. This paper studies the effect of the shape of the local bond–slip law and its parameters on the global response of the NSM FRP joint in terms of load capacity, effective bond length, slip, shear stress, and strain distribution along the bonded length, which are essential parameters on the strengthening design. A numerical procedure based on the finite difference method to solve the governing equations of the FRP-to-concrete joint is developed. Pull-out single shear specimens are tested in order to experimentally validate the numerical results. Finally, a parametric study is performed. The effect of the bond–shear strength slip at the bond strength, maximum slip, and friction branch on the parameters previously described is presented and discussed.

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

Advances in Materials Science and Engineering ◽

10.1155/2018/9807140 ◽

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.

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