Experimental study on flexural strengthening of reinforced concrete beams with U-shaped steel under secondary load

2021 ◽  
pp. 136943322110369
Author(s):  
Qingli Lin ◽  
Yiyan Lu ◽  
Wenshui Tang ◽  
Dongshan Lei
Keyword(s):  
Reinforced Concrete ◽  
Reference Beam ◽  
Reinforced Concrete Beams ◽  
Bottom Plate ◽  
Strengthening Effect ◽  
Rc Beams ◽  
Flexural Strengthening ◽  
Flexural Performance ◽  
Initial Loading ◽  
Secondary Load

This study proposes a new method to strengthen reinforced concrete (RC) beams with U-shaped steel, which can achieve rapid construction and great improvement in the flexural performance of RC beams. To investigate the influence of secondary load defined as newly applied loads after strengthening on the strengthening effect, a total of nine specimens were tested under four-point bending, including a reference beam, a strengthened beam under initial load, and seven strengthened beams under secondary load. The initial loading degree, the thickness of the bottom plate, and the height of the steel box were the main variables considered in this study. Testing results showed that compared with the reference beam, the flexural performance of strengthened beams was significantly enhanced, indicating the good joint performance of the U-shaped steel and the RC beams. Among the three main variables, the initial loading degree was found to have a minimal effect on the flexural performance while the thickness of the bottom plate and the height of the steel box had considerable influence, with the latter having a more pronounced effect. Testing results also showed that most of the strengthened beams experienced flexural failures, which were reflected by steel web peeling and buckling, and concrete crushing. Moreover, a formula was derived for calculating the flexural capacity of strengthened beams under secondary load. The results from the derived formula were found to be in good agreement with those from experiments.

scholarly journals Experimental assessment of the performance of reinforced concrete beams strengthened with carbon fiber reinforced polymer laminates

2020 ◽  
Vol 39 (1) ◽  
pp. 105-112
Author(s):  
N. Yusuf ◽  
J.M. Kaura ◽  
A. Ocholi ◽  
M. Abbas
Keyword(s):  
Reinforced Concrete ◽  
Failure Modes ◽  
Reinforced Concrete Beams ◽  
Bending Test ◽  
Rc Beams ◽  
Flexural Strengthening ◽  
Cfrp Laminates ◽  
Flexural Performance ◽  
Load Carrying ◽  
Ultimate Load Carrying Capacity

In this study, experimental research is carried out to assess the flexural performance of RC beams strengthened with different amount of CFRP laminates at the tension face. Twelve rectangular RC beams were fabricated and three are un-strengthened and used as reference beams and the remaining nine are strengthened with different amount of CFRP varying from single to triple layers and all are tested to failure under three points bending test. The increase of ultimate strength provided by the bonded CFRP laminates is assessed and failure modes is identified and compared to the un-strengthened RC beams. The results indicated that the flexural capacity of the beams was significantly improved as the amount of the laminates increases that ranged from 20% to 52% increased for single to triple layers laminates. It is concluded that the attachment of CFRP laminates has substantial influence on the performance of CFRP strengthened RC beams. Based on the observed results, recommendations are made that externally application of CFRP laminates can be used for a significant enhancement of the strength deficient RC beams in increasing the ultimate load carrying capacity. Keywords: CPRP laminate, Reinforced concrete, ductility, index, epoxy resin, flexural strengthening

scholarly journals Flexural strengthening of RC beams with NSM CFRP laminates

2020 ◽  
Vol 323 ◽  
pp. 01010
Author(s):  
Damian Szczech ◽  
Łukasz Krawczyk ◽  
Renata Kotynia
Keyword(s):  
Reference Beam ◽  
Concrete Cover ◽  
Reinforced Concrete Beams ◽  
Rc Beams ◽  
Near Surface ◽  
Flexural Strengthening ◽  
Cfrp Laminates ◽  
Carbon Fibre Reinforced Polymer ◽  
Bottom Side ◽  
Cracking Pattern

The paper presents test results of reinforced concrete beams flexurally strengthened with Carbon Fibre Reinforced Polymer (CFRP) laminates using the Near Surface Mounted (NSM) technique. RC beams with a cross section of 200 x 400 mm were tested in four-point bending. Two RC beams were strengthened with one NSM CFRP laminate installed into the concrete cover on the bottom side of the beam. One of the beams was strengthened under the self-weight (B10.1) and the second one under initial preloading equal to 83% of the ultimate load of the reference beam (B10.1o). Failure mechanisms, cracking pattern and flexural behaviour of the beams are described in the paper. All the strengthened beams failed by rupture of the CFRP laminates followed by the internal steel reinforcement yielding. High strengthening efficiency of the NSM strengthening was confirmed by 109% and 130% when compared with the non-strengthened beam, respectively for beams B10.1 and B10.1o.

Study on Flexural Performance of Damage RC Beams Strengthened with near Surface Mounted FRP Strips

2011 ◽  
Vol 94-96 ◽  
pp. 883-886 ◽  
Author(s):  
Chang Zhou Dong ◽  
Jian Zhong Xia
Keyword(s):  
Reinforced Concrete ◽  
Reinforced Concrete Beams ◽  
Rc Beams ◽  
Near Surface ◽  
Flexural Performance ◽  
Damage Degree ◽  
Reinforced Polymer ◽  
Significant Strength ◽  
Near Surface Mounted ◽  
Frp Strips

The contrast tests of 1 reinforced concrete(RC) beams and 4 RC beams strengthened with near-surface mounted carbon fiber reinforced polymer (FRP) strips have been carried out, under conditions of different damage degree of RC beams. It is mainly conducted to investigate the effects of FRP strips reinforcement of flexural strength. The experimental results indicate that significant strength on the ultimate load and rigidity of reinforced concrete beams can be realized by mounting FRP strips to the beams, and propagation of cracks were reduced obviously.

Analysis of Premature Rip-Off Failure Mechanism of Reinforced Concrete Beams Strengthened with FRPs

2006 ◽  
Vol 324-325 ◽  
pp. 1325-1328
Author(s):  
Cheol Woo Park ◽  
Jong Sung Sim ◽  
Sung Jae Park
Keyword(s):  
Reinforced Concrete ◽  
Failure Mechanism ◽  
Failure Load ◽  
Reinforced Concrete Beams ◽  
Shear Stresses ◽  
Strengthening Effect ◽  
Rc Beams ◽  
Premature Failure ◽  
Cfrp Plate ◽  
Proposed Model

Various types and forms of FRP materials have been applied for structural strengthening of reinforced concrete (RC) beams. When CFRP plates are used, however, a premature failure used to occur before strengthening effect appears adequately. This is primarily due to the rip-off of CFRP plate attached on RC beams. Despite of numerous studies on the rip-off failure of externally strengthened RC beams, the failure mechanism is not clearly explained yet. Investigations from the literatures have shown that the rip-off failure is dependant on vertical and shear stresses at the level of main reinforcements in RC beams. This study suggests an analytical model to investigate the ripoff failure load based on the stresses at the level of main reinforcements. The proposed model is relatively simple and produces very comparable results to the test data. Therefore, it is anticipated that the proposed model can be successfully used to provide further information on the rip-off failure mechanisms and its prevention.

scholarly journals Strengthening of Reinforced Concrete Beams with Externally Mounted Sequentially Activated Iron-Based Shape Memory Alloys

Materials ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 345 ◽  
Author(s):  
Emanuel Strieder ◽  
Christoph Aigner ◽  
Gabriele Petautschnig ◽  
Sebastian Horn ◽  
Marco Marcon ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Reference Beam ◽  
Reinforced Concrete Beams ◽  
Rc Beams ◽  
Recovery Stress ◽  
Strengthened Beam ◽  
Iron Based ◽  
Stress States

Iron based shape memory alloys (Fe-SMA) have recently been used as active flexural strengthening material for reinforced concrete (RC) beams. Fe-SMAs are characterized by a shape memory effect (SME) which allows the recovery of previously induced plastic deformations through heating. If these deformations are restrained a recovery stress is generated by the SME. This recovery stress can be used to prestress a SMA applied as a strengthening material. This paper investigates the performance and the load deformation behavior of RC beams strengthened with mechanical end anchored unbonded Fe-SMA strips activated by sequentially infrared heating. The performance of a single loop loaded and a double loop loaded SMA strengthened RC beam are compared to an un-strengthened beam and a reference beam strengthened with commercially available structural steel. In these tests the SMA strengthened beam had the highest cracking load and the highest ultimate load. It is shown that the serviceability behavior of a concrete beam can be improved by a second thermal activation. The sequential heating procedure causes different temperature and stress states during activation along the SMA strip that have not been researched previously. The possible effect of this different temperature and stress states on metal lattice phase transformation is modeled and discussed. Moreover the role of the martensitic transformation during the cooling process on leveling the inhomogeneity of phase state in the overheated section is pointed out.

The Flexural Performance of Pre-Damaged Reinforced Concrete Beam Strengthened with CFRP in Seawater Environment

2012 ◽  
Vol 166-169 ◽  
pp. 1736-1739
Author(s):  
Yu Tian Wang ◽  
Xiu Li Du ◽  
Fu Xiang Jiang ◽  
Wei Zhang
Keyword(s):  
Reinforced Concrete ◽  
Failure Modes ◽  
Concrete Beams ◽  
Reinforced Concrete Beam ◽  
Reinforced Concrete Beams ◽  
Flexural Behavior ◽  
Strengthening Effect ◽  
Flexural Capacity ◽  
Flexural Performance ◽  
Seawater Environment

Experiments on flexural behavior of strengthened pre-damaged reinforced concrete beams with CFRP and those exposed to seawater for different time have been carried out. By comparison, the rule of seawater effecting on failure modes of beams, fissure condition, strain development and flexural capacity, and so on have been studied. The results show that reinforcement treatment on the mechanical damaged reinforced concrete beams with bonding CFRP can effectively improve their flexural capacity and stiffness, and constrain the development of cracks. With the extension of time under seawater environment, although performance of pre-damaged beam strengthened with CFRP is influenced significantly, the strengthening effect is still more reliable.

Flexural Strengthening of RC Beams with Sisal Fiber Composites and Sisal Fiber Rods

2016 ◽  
Vol 860 ◽  
pp. 144-147 ◽  
Author(s):  
Arslan Qayyum Khan ◽  
Qudeer Hussain ◽  
Winyu Rattanapitikon ◽  
Amorn Pimanmas
Keyword(s):  
Reinforced Concrete ◽  
Failure Modes ◽  
Ultimate Load ◽  
Fiber Composites ◽  
Reinforced Concrete Beams ◽  
Sisal Fiber ◽  
Rc Beams ◽  
Flexural Strengthening ◽  
Four Point Bending ◽  
Ultimate Load Carrying Capacity

The present study is conducted to examine the effectiveness of sisal fiber in flexural strengthening of reinforced concrete (RC) beams. In order to obtain this objective, two different strengthening configurations are adopted (use of sisal fiber composites and use of sisal fiber rods). A total of five flexural strengthened reinforced concrete beams are instrumented and tested using a four point bending setup. The results for strength, stiffness and failure modes are discussed for the both strengthening configurations. The results demonstrate that both sisal fiber composites and sisal fiber rods are effective in enhancing ultimate load carrying capacity of RC beams. The beams strengthened with sisal fiber rods showed higher increase in ultimate load as compared with the beams strengthened with sisal fiber composites layers.

Experimental study on the durability of FRP bars reinforced concrete beams in simulated ocean environment

2018 ◽  
Vol 25 (6) ◽  
pp. 1123-1134 ◽  
Author(s):  
Zhiqiang Dong ◽  
Gang Wu ◽  
Jinlong Lian
Keyword(s):  
Reinforced Concrete ◽  
Ultimate Load ◽  
Constant Load ◽  
Reinforced Concrete Beams ◽  
Rc Beams ◽  
Flexural Performance ◽  
Frp Composite ◽  
Steel Bars ◽  
Ocean Environment ◽  
Frp Bars

AbstractIn this paper, the flexural performance of fiber-reinforced polymer (FRP) bars reinforced concrete (RC) beams after conditioning in a simulated seawater wet-dry cycling environment for 6, 9 and 12 months is experimentally investigated. Two types of FRP bars, i.e. basalt FRP (BFRP) bars and steel-FRP composite bars (SFCBs), are adopted. Steel bars are employed for comparison. During the conditioning, a constant load is coupled to the beams. A total of 24 simply supported beams are tested. In addition, microscopic damage to the conditioned BFRP bars is detected by scanning electron microscopy (SEM). The test results indicated that total corrosion was observed at the surface of the bottom longitudinal steel bars after a maximum exposure of 12 months. However, the degradation of the macro-mechanical properties of the steel bars RC beam was not distinct. The ultimate load of the BFRP bars RC beams after 6 months, 9 months and 12 months was reduced by 22%, 33% and 42%, respectively. The yield load and ultimate load of the SFCBs RC beams were reduced by a maximum of 18% and 38%, respectively. The SEM observations revealed that there were distinct damages at the outer layer of the BFRP bars after 12-month conditioning.

scholarly journals Study on the flexural performance of RC beams anchored with CFRP plates under secondary load

2021 ◽  
Vol 233 ◽  
pp. 03024
Author(s):  
Xiangrui Feng ◽  
Xian Cui ◽  
Haikun Luo
Keyword(s):  
Bearing Capacity ◽  
Bending Strength ◽  
Concrete Beams ◽  
Ultimate Bearing Capacity ◽  
Reinforced Concrete Beams ◽  
Rc Beams ◽  
Flexural Performance ◽  
Cfrp Plate ◽  
Secondary Load ◽  
Structural Indicators

In order to explore the influence of length and width of CFRP as well as anchor spacing on the reinforcement effectiveness of CFRP plates on reinforcement concrete beams (RC beams) under secondary load, 7 anchored damaged FRP reinforced concrete beams are used as test beams, 1 unanchored beam is used as a control beam, and structural indicators such as ultimate load and bending strength are analyzed in the result. The conclusion is that composite CFRP plate can effectively prevent the early peeling and failure of carbon plates and improve the ultimate bearing capacity of the beam. When the width of the CFRP plate decreases, the thickness increases and the steel plate anchor spacing increases appropriately, the ultimate bearing capacity and ductility of the beam are significantly improved.

scholarly journals TEXTILE REINFORCED MORTAR BASED FLEXURAL STRENGTHENING OF REINFORCED CONCRETE BEAMS

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Muhammad Imran Rafiq ◽  
Ameer Baiee
Keyword(s):  
Reinforced Concrete ◽  
Basalt Fiber ◽  
High Strength ◽  
Reinforced Concrete Beams ◽  
Experimental Program ◽  
Rc Beams ◽  
Rc Structures ◽  
Flexural Strengthening ◽  
Strengthening Technique ◽  
Textile Reinforced Mortar

Strengthening of reinforced concrete (RC) structures is often necessary due to the change of using or to enhance the strength of deteriorated existing RC structures attributed to aging and environmental effects. Interfacial bond between the existing RC member and the strengthening layer is known to be the main factor for any successful strengthening technique. This study investigates the efficiency of utilizing high strength cementitious connectors in preventing the debonding of textile reinforced mortar (TRM) strengthening layer from substrate concrete of RC beams. An experimental program is developed to investigate the effect of strength of mortars and the distribution of cementitious connectors on the behavior of the strengthened beams. TRM comprising eight and sixteen textile basalt fiber layers were utilized in these experiments. The results demonstrate the effectiveness of cementitious connectors on the failure mode of strengthened beams by means of controlling the debonding of TRM. The increase in cracking and ultimate loads is demonstrated due to the strengthening of RC beams using TRM.

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