Implication of Unbondedness in Reinforced Concrete Beams

2012 ◽  
Vol 587 ◽  
pp. 36-41 ◽  
Author(s):  
S.F.A. Rafeeqi ◽  
S.U. Khan ◽  
N.S. Zafar ◽  
T. Ayub
Keyword(s):  
Shear Strength ◽  
Reinforced Concrete ◽  
Failure Mode ◽  
Shear Failure ◽  
Concrete Beams ◽  
Experimental Results ◽  
Reinforced Concrete Beams ◽  
Rc Beams ◽  
Flexural Capacity ◽  
Flexural Reinforcement

In this paper, behaviour of nine (09) RC beams (including two control beams) after unbonding and exposing flexural reinforcement has been studied which were intentionally designed and detailed to observe flexural and shear failure. Beams have been divided into three groups based on failure mode and unbounded and exposed reinforcement. Beams have been tested under two-point loading up to failure. Experimental results are compared in terms of beam behaviour with respect to flexural capacity and failure mode which revealed that the exposed reinforcement does not altered flexural capacity significantly and unbondedness positively influences shear strength; however, serviceability performance of beams with unbonded and exposed reinforcement is less.

scholarly journals DIAGONAL TENSION FAILURE OF RC BEAMS WITHOUT STIRRUPS / SKERSINE ARMATŪRA NEARMUOTŲ GELŽBETONINIŲ SIJŲ TEMPIAMASIS SUIRIMAS ĮSTRIŽAJAME PJŪVYJE

2012 ◽  
Vol 18 (2) ◽  
pp. 217-226 ◽  
Author(s):  
Guray Arslan
Keyword(s):  
Reinforced Concrete ◽  
Shear Failure ◽  
Concrete Beams ◽  
High Strength ◽  
Theory Of Elasticity ◽  
Experimental Results ◽  
Reinforced Concrete Beams ◽  
Rc Beams ◽  
Codes Of Practice ◽  
Slender Beams

The shear failure of reinforced concrete beams is one of the fundamental problems in civil engineering; however, the diagonal tension strength of reinforced concrete (RC) beams without stirrups is still in question. This paper focuses on the prediction of diagonal cracking strength of RC slender beams without stirrups. In slender beams, flexural cracks develop in the tension zone prior to a diagonal cracking. Using the basic principles of mechanics, but cracking included, and theory of elasticity, a diagonal cracking strength equation is proposed for both normal and high strength concrete beams. The proposed equation, the requirements of six codes of practice and seven equations proposed by different researchers are compared to the experimental results of 282 beams available in the literature. It is found that the predictions from the proposed equation are in good agreement with the experimental results. Santrauka Gelžbetoninių sijų suirimas įstrižajame pjūvyje – viena pagrindinių problemų statybos inžinerijoje. Tačiau skersine armatūra nearmuotų gelžbetoninių sijų įstrižasis tempiamasis stipris nėra visiškai ištirtas. Šiame straipsnyje nagrinėjamas siaurų, be skersinės armatūros gelžbetoninių sijų įstrižojo pjūvio pleišėjimas. Siaurose sijose plyšiai tempiamojoje zonoje atsiranda anksčiau negu įstrižajame pjūvyje. Taikant klasikinius mechanikos principus ir tamprumo teoriją, pasiūlyta normalaus stiprio arba stipriojo betono sijų istrižojo pjūvio atsparumo pleišėjimui apskaičiavimo lygtis. Siūloma lygtis, pagrįsta šešių projektavimo normų reikalavimais ir septyniomis kitų autorių lygtimis bei palyginta su literatūroje pateiktais 282 sijų eksperimentinių tyrimų rezultatais. Nustatyta, kad pagal siūlomą lygtį atlikti skaičiavimai gerai sutampa su eksperimentiniais rezultatais.

Investigation on Intermediate Crack Induced Debonding Failure of FRP Laminates in Flexurally FRP-Strengthened RC Beams

2011 ◽  
Vol 243-249 ◽  
pp. 641-644
Author(s):  
Gui Bing Li ◽  
Yu Gang Guo ◽  
Xiao Yan Sun
Keyword(s):  
Reinforced Concrete ◽  
Failure Mode ◽  
Concrete Beams ◽  
Interfacial Shear Stress ◽  
Reinforced Concrete Beams ◽  
Tension Stress ◽  
Rc Beams ◽  
Fundamental Reason ◽  
Three Stages ◽  
Opening Up

Debonding failure is commonly observed in FRP-strengthened RC beams. It can be classified into two types: plate end debonding and intermediate crack induced debonding. Intermediate crack induced debonding is the main failure mode in FRP-strengthened RC beams.There is no specialized experiment study on this failure mode. To investigate intermediate crack induced debonding failure of FRP-strengthened reinforced concrete beams, 9 CFRP-strengthened reinforced concrete beams were tested. Based on the investigation of the strain in the FRP laminates, the width of the main crack and tributary crack, as well as the phenomena of the test beams, the whole debonding process can be separated into three stages: initial debonding stage, stable debonding stage, and the final debonding failure. The fundamental reason of intermediate crack indued debonding are the opening-up of intermediate crack and the flexural deformation induced high interfacial shear stress and peeling stress. When the principal tension stress acting on the concrete substrate exceeded the tension stress of concrete, the CFRP laminate would debond from the concrete substrate.

scholarly journals Effect of Cyclic Loadings on the Shear Strength and Reinforcement Slip of RC Beams

2017 ◽  
Vol 3 (2) ◽  
pp. 111-123 ◽  
Author(s):  
Mohammed A Sakr
Keyword(s):  
Finite Element ◽  
Shear Strength ◽  
Reinforced Concrete ◽  
Finite Element Model ◽  
Failure Mode ◽  
Failure Modes ◽  
Concrete Beams ◽  
Kinematic Hardening ◽  
Element Model ◽  
Reinforced Concrete Beams

Numerous studies of the response of reinforced concrete members under cyclic loadings, many of which have been summarized and have indicated that, in general, the flexural strength of under-reinforced beams remains unimpaired under cyclic loadings consisting of a reasonable number of cycles. However, there is a body of evidence indicating that their shear strength may suffer under such loadings. The first objective of the current study is to construct an accurate 2D shell finite element model of reinforced concrete beams under cyclic loadings. The second objective is carrying out a parametric study on reinforced concrete beams, using the suggested 2D shell model.  The objective of this study was to observe the effect of the stirrup spacing, steel-to-concrete bond properties on the performance of reinforced concrete beams under cyclic loadings. For this purpose, an efficient and accurate finite element model was established taking into account the compression and tensile softening introducing damage in the concrete material, the Baushinger effect using nonlinear isotropic/kinematic hardening in the steel and an adequate bond-slip law for the concrete–steel interface. The simulated results of numerical models were verified by experimental results available in literature in order to validate the proposed model, including hysteretic curves, failure modes, crack pattern and debonding failure mode. The model provided a strong tool for investigating the performances of reinforced concrete beam. The results showed that: Cyclic loadings may change the failure mode of the beam to bond failure even though it has sufficient bond length to resist static loadings. So that under cyclic loadings additional anchorage length must be taken, cyclic loadings also influence the ductility and peak load for beams fail in shear. All these topics are of the utmost importance to RC behaviour to be considered by construction codes.

scholarly journals Efficiency of Hybrid Algorithms for Estimating the Shear Strength of Deep Reinforced Concrete Beams

2022 ◽  
Author(s):  
Mohammad Sadegh Barkhordari ◽  
De-Cheng Feng ◽  
Mohsen Tehranizadeh
Keyword(s):  
Shear Strength ◽  
Reinforced Concrete ◽  
Concrete Beams ◽  
Search Algorithm ◽  
Experimental Tests ◽  
Reinforced Concrete Beams ◽  
Rc Beams ◽  
High Rise ◽  
Beam Depth ◽  
Artificial Neural Network Ann

Earthquakes occurred in recent years have highlighted the need to examine the strength of reinforced concrete (RC) members. RC beams are one of the elements of reinforced concrete structures. Due to the dramatic increase in the population and the number of medium/high-rise buildings, in recent years, the beams of buildings have been mainly designed and executed in the type of deep beams. In this study, the artificial neural network (ANN) with optimization algorithms, including particle swarm optimization (PSO), Archimedes optimization algorithm (AOA), and sparrow search algorithm (SSA), are used to determine the shear strength of reinforced concrete deep (RCD) beams. 271 samples from experimental tests are employed to develop algorithms. The results of this study, design codes equations, and previous research are compared. Comparison between the results shows that the PSO-ANN algorithm is more accurate than previous methods. Finally, SHApley Additive exPlanations (SHAP) method is utilized to explain the predictions. SHAP reveals that the beam span and the ratio of the beam span to beam depth have the highest impact in predicting shear strength.

An Experimental Study on Flexural Behavior of Reinforced Concrete Beams Strengthened with High-Performance Ferrocement

2010 ◽  
Vol 163-167 ◽  
pp. 3772-3776 ◽  
Author(s):  
Hua Ping Liao ◽  
Shi Sheng Fang
Keyword(s):  
Reinforced Concrete ◽  
Comparative Analysis ◽  
High Performance ◽  
Concrete Beams ◽  
Reinforced Concrete Beams ◽  
Flexural Behavior ◽  
Rc Beams ◽  
Test Results ◽  
Flexural Capacity ◽  
Engineering Designs

Three reinforced concrete (RC) beams strengthened by high-performance ferrocement and two control specimens without strengthened are investigated when RC beams have low compressive strength. Flexural behaviors of strengthened RC beams with high-performance ferrocement are evaluated based on comparative analysis with RC beams. The strengthening results of steel meshes with U-shape (i.e. ferrocements are put onto the tension face and two profile faces) are analyzed. The flexural capacity, deflection and crack width of RC flexural beams are measured, and then comparative analysis is carried out for deformation performance and law of crack development. The test results show that ferrocement contributes greatly to increase the flexural capacity and raise crack-resisting capacity. The experimental results can provide a theoretical reference for actual engineering designs.

Strengthening and Characterization of Existing Reinforced Concrete Beams for Flexure by Effective Utilization of External Steel Elements

2020 ◽  
pp. 136943322095061
Author(s):  
Akhtar Gul ◽  
Bashir Alam ◽  
Wisal Ahmed ◽  
Nauman Wahab ◽  
Khan Shahzada ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Shear Failure ◽  
Concrete Beams ◽  
Concrete Cover ◽  
Reinforced Concrete Beams ◽  
Flexural Capacity ◽  
Steel Bars ◽  
External Strengthening ◽  
Steel Angles ◽  
Control Samples

Strengthening of structural members is a common practice around the world that may arise due to deterioration of concrete with age or upgradation of design code. This paper aims to elucidate a technique used for strengthening of the reinforced concrete beam for flexural capacity by using externally welded steel angles and steel bars. For this motive, three beams were strengthened with external steel angles and three with external steel bars. The external strengthening steel elements were attached at the bottom of the beam with shear reinforcement. Control samples without external steel angles and steel bars for comparison purposes were also prepared. All reinforced concrete beams were first constructed using a concrete ratio of 1:2:4, and then external steel elements were added to existing flexural reinforcement by using a fillet weld with tee joints having thickness and length of 5/16" (7.9 mm) and 6" (152.4 mm), respectively. Fourth point loading criteria were used to investigate the flexural capacity of beams in positive bending. All beams were designed strong enough in shear, to resist the ultimate loads without shear failure. Test results indicated that beams strengthened with this technique have an average increase of 238% with steel angles and 106% with steel bars, in load-carrying capacity than control samples. Strengthened beams showed a uniform crack pattern. Moreover, the concrete cover made a good bond with existing concrete and was strong enough to withstand ultimate loads. Conclusively, the steel angles and steel bars can be used as an external strengthening material, to enhance the flexural capacity of reinforced concrete beams.

Experimental Study on Residual Flexural Behavior of Reinforced Concrete Beams after Exposure to Fire

2012 ◽  
Vol 457-458 ◽  
pp. 183-187 ◽  
Author(s):  
Yu Ye Xu ◽  
Bo Wu ◽  
Ming Jiang ◽  
Xin Huang
Keyword(s):  
Reinforced Concrete ◽  
Experimental Studies ◽  
Experimental Results ◽  
Reinforced Concrete Beams ◽  
Flexural Behavior ◽  
Building Structures ◽  
Rc Beams ◽  
Flexural Capacity ◽  
Shaped Beam ◽  
Rectangular Beam

Reinforced Concrete (RC) beams in the building structures are usually assumed as a ‘T’-shaped beam when the effects of adjacent slab flange are considered. However, experimental studies on residual flexural behavior of ‘T’-shaped RC beams are rarely reported. The residual flexural behavior of two RC rectangular beams and one RC ‘T’-shaped beam after exposure to ISO834 standard fire were experimentally investigated in the paper. The detailed experimental results, including the measured temperatures, flexural capacity, load-deflection curves and concrete strain are presented. The effects of flange on temperature distribution and residual flexural behavior of RC beams were analyzed. The experimental results show that: (a) the assumption of plane section is applicable for RC ‘T’-shaped beam. (b) The flexural capacity of RC rectangular beam was decreased 18.5% after exposure to fire for 2 hours, but the ultimate mid-span deflection was increased 55.1%. (c) The residual flexural capacity and the ultimate mid-span deflection of RC rectangular beam after fire was respectively increased 8.4% and 9.9% due to the effect of flange.

scholarly journals Prediction of Deflection of Reinforced Concrete Beams Considering Shear Effect

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6684
Author(s):  
Sang-Woo Kim ◽  
Kil-Hee Kim
Keyword(s):  
Reinforced Concrete ◽  
Concrete Beams ◽  
Virtual Work ◽  
Experimental Results ◽  
Reinforced Concrete Beams ◽  
Elastic Theory ◽  
Shear Effect ◽  
Rc Beams ◽  
Shear Cracks ◽  
Work Method

This paper proposes a method to evaluate the effect of shear on the deflection of reinforced concrete (RC) beams. The deflection of RC beams due to the effects of flexural and shear cracks shows different results from those obtained from the elastic theory. The effect of shear on deflection was compared and analyzed in this study, on the basis of experimental results and elastic theory using the virtual work method. The shear effect on the deflection of RC beams by elastic theory was extremely small. However, experimental results showed a difference of over 40% from the results predicted by elasticity theory. In this study, a new method was developed to reasonably predict the deflection of flexure-critical RC beams using the deflection incremental coefficient due to shear. The proposed method was compared with the existing experimental results obtained from the literature for verification. As a result of the comparison, the deflection obtained using ACI 318-19 underestimated the actual deflection by approximately 33%, whereas the deflection obtained by the proposed method predicted the experimental results relatively accurately.

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