Debonding Failures in FRP-Strengthened RC Beams: Failure Modes, Existing Research and Future Challenges

2001 ◽  
Author(s):  
J. G. Teng ◽  
J. F. Chen ◽  
S. T. Smith
Keyword(s):  
Failure Modes ◽  
Rc Beams ◽  
Future Challenges

scholarly journals Torsional Strengthening of Low-Strength RC Beams with Post-Tensioned Metal Straps: An Experimental Investigation

2020 ◽  
Vol 17 (12) ◽  
pp. 1399-1411
Author(s):  
Monthian SETKIT ◽  
Thanongsak IMJAI ◽  
Udomvit CHAISAKULKIET ◽  
Reyes GARCIA ◽  
Komsan DANGYEM ◽  
...  
Keyword(s):  
Failure Modes ◽  
Beam Current ◽  
Experimental Results ◽  
Reinforced Concrete Beams ◽  
Rc Beams ◽  
Control Beam ◽  
Torque Capacity ◽  
Low Strength ◽  
Conservative Values ◽  
Post Tensioned

This article investigates the behaviour of low-strength reinforced concrete beams under pure torsion with and without strengthening. Four beams were cast and tested in torsion: i) a control beam without vertical reinforcement, ii) two beams with internal stirrups designed for shear and torsion demands using different stirrup spacing (50 and 100 mm), and iii) a beam having steel stirrups with a spacing of 100 mm strengthened using high ductile post-tensioned metal straps (PTMS). The main objective of the PTMS strengthening solution was to investigate the enhancement of torsional strength confined along the beam. The failure modes, torsional capacities, rotation, and strengthening performance in torsion are discussed in in this study. The experimental results indicate that the PTMS improved the cracking torque capacity by up to 15 % compared to the control beam. Moreover, the PTMS also increased the ultimate torque by up to 19 % compared to the unstrengthened beam. Current code equations to predict the torsional capacity of RC beams are also compared with the experimental results. It is found that the predictions obtained by current ACI equation gives a good agreement and yield in general conservative values compared to the experimental ones.

Study on the residual performance of RC beams exposed to processed temperatures and fire

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Sachin Vijaya Kumar ◽  
N. Suresh
Keyword(s):  
Failure Modes ◽  
Elevated Temperatures ◽  
Slow Heating ◽  
Maximum Temperature ◽  
Rc Beams ◽  
Heating Rates ◽  
Fast Heating ◽  
Content Type ◽  
Temperature Increment ◽  
Residual Performance

PurposeThe Reinforced Concrete(RC) elements are known to perform well during exposure to elevated temperatures. Hence, RC elements are widely used to resist the extreme heat developing from accidental fires and other industrial processes. In both of the scenarios, the RC element is exposed to elevated temperatures. However, the primary differences between the fire and processed temperatures are the rate of temperature increase, mode of exposure and exposure durations. In order to determine the effect of two heating modalities, RC beams were exposed to processed temperatures with slow heating rates and fire with fast heating rates.Design/methodology/approachIn the present study, RC beam specimens were exposed to 200 °C, to 800 °C temperature at 200 °C intervals for 2 h' duration by adopting two heating modes; Fire and processed temperatures. An electrical furnace with low-temperature increment and a fire furnace with standard time-temperature increment is adapted to expose the RC elements to elevated temperatures.FindingsIt is observed from test results that, the reduction in load-carrying capacity, first crack load, and thermal crack widths of RC beams exposed to 200 °C, and 600 °C temperature at fire is significantly high from the RC beams exposed to the processed temperature having the same maximum temperature. As the exposure temperature increases to 800 °C, the performance of RC beams at all heating modes becomes approximately equal.Originality/valueIn this work, residual performance, and failure modes of RC beams exposed to elevated temperatures were achieved through two different heating modes are presented.

scholarly journals ANALYTICAL AND EXPERIMENTAL STUDY ON REPAIR EFFECTIVENESS OF CFRP SHEETS FOR RC BEAMS

2013 ◽  
Vol 20 (1) ◽  
pp. 21-31 ◽  
Author(s):  
Moatasem M. Fayyadh ◽  
H. Abdul Razak
Keyword(s):  
Experimental Study ◽  
Failure Modes ◽  
Load Capacity ◽  
Fe Model ◽  
Rc Beams ◽  
Shell Elements ◽  
Cfrp Sheets ◽  
Adhesive Interface ◽  
Carbon Fibre Reinforced Polymer ◽  
Fibre Reinforced Polymer

This paper presents the results of both analytical and experimental study on the repair effectiveness of Carbon Fibre Reinforced Polymer (CFRP) sheets for RC beams with different levels of pre-repair damage severity. It highlights the effect of fixing CFRP sheets to damaged beams on the load capacity, mid-span deflection, the steel strain and the CFRP strain and failure modes. The analytical study was based on a Finite Element (FE) model of the beam using brick and embedded bar elements for the concrete and steel reinforcement, respectively. The CFRP sheets and adhesive interface were modelled using shell elements with orthotropic material properties and incorporating the ultimate adhesive strain obtained experimentally to define the limit for debonding. In order to validate the analytical model, the FE results were compared with the results obtained from laboratory tests conducted on a control beam and three other beams subjected to different damage loads prior to repair with CFRP sheets. The results obtained showed good agreement, and this study verified the adopted approach of modelling the adhesive interface between the RC beam and the CFRP sheets using the ultimate adhesive strains obtained experimentally.

Assesment of Main Models for Predicting Debonding Load-Bearing Capacity against Intermediate Crack-Induced Debonding Failure in FRP-Strengthened RC Beams

2011 ◽  
Vol 311-313 ◽  
pp. 1941-1944
Author(s):  
Gui Bing Li ◽  
Yu Gang Guo ◽  
Xiao Yan Sun
Keyword(s):  
Bearing Capacity ◽  
Failure Mode ◽  
Failure Modes ◽  
Rc Beams ◽  
Test Results ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Accuracy Test ◽  
New Models ◽  
Debonding Load

intermediate crack-induced debondingis one of the most dominant failure modes in FRP-strengthened RC beams. Different code models and provisions have been proposed to mitigateintermediate crack-induced debondingfailure.However, these models and provisions can not mitigate this failure mode effectively. Recnetly, new models have been proposed to solve this problem. Out of all the existing models, four typical ones are investigated in the current study. A comprehensivecomparison among these models is carried out in order to evaluate their performance and accuracy. Test results offlexural specimens with intermediate crack-induced debonding failurecollected from the existing literature are used in the current comparison. The effectivenessand accuracy of each model have been evaluated based on these experimental results. It is shown that the current modals are all conservative and inadequite to effectively mitigate intermediate crack-induced debonding in flexurally strengthened members.

Studies on Fire Resistance of FRP Shear Strengthened Reinforced Concrete Beams

2011 ◽  
Vol 94-96 ◽  
pp. 1318-1321
Author(s):  
He Fan ◽  
Ze Fan
Keyword(s):  
Reinforced Concrete ◽  
Fire Resistance ◽  
Failure Modes ◽  
Concrete Beams ◽  
Reinforced Concrete Beams ◽  
Temperature Fields ◽  
Insulation Material ◽  
Rc Beams ◽  
Fire Resistance Rating ◽  
Resistance Rating

Fire-resistance performance experiments with static loading-fire are investigated about two carbon fiber sheet (CFS) shear strengthened reinforced concrete (RC) beams exposed to the ISO834 standard fire. Shear strengthened RC beams are wrapped with fire insulation material- thick painted fire retardant coatings. Relationship between measure points’ temperature and time are achieved. The results suggest that: the ratio of shear-span is the main factor to fire-resistance rating and failure modes of CFS shear strengthened RC beams in fire; shear-failure fire-resistance rating are increased by thickening fire insulation to shear strengthened RC beams. A computer program is developed to calculate the temperature fields of fire insulated concrete beams shear strengthened with CFS coated thick fireproof material. This program is validated comparing with experimental results. Researches can give a supplement to produce overall fire-resistance factors of CFS shear strengthened reinforced concrete beams at high temperatures.

Flexural Fracture and Fatigue Behavior of RC Beams Strengthened with CFRP Laminates under Constant Amplitude Loading

2006 ◽  
Vol 306-308 ◽  
pp. 1343-1348 ◽  
Author(s):  
Guowen Yao ◽  
Pei Yan Huang ◽  
Chen Zhao
Keyword(s):  
Fatigue Damage ◽  
Failure Modes ◽  
Fatigue Behavior ◽  
Bending Stiffness ◽  
Rc Beam ◽  
Rc Beams ◽  
Constant Amplitude ◽  
Damage State ◽  
Engineering Structures ◽  
Damage And Fracture

Externally bonded carbon fiber reinforced polymer (CFRP) materials are well suited to the rehabilitation and reinforcement of civil engineering structures due to their high specific strength, specific stiffness and corrosion resistance. To probe the fatigue behavior of CFRP strengthened concrete structures, three point bending experiments of reinforced concrete (RC) beams strengthened with carbon fibre laminate (CFL) under constant amplitude loading were performed. The histories of midspan flexibility and bending stiffness of strengthened beams were recorded automatically. And the linear curve between fatigue strength and the logarithm of fatigue life was obtained. The failure modes go through concrete cracking, CFL debonding from concrete and steel bars yielding and fracture with increasing cycles of fatigue loading. Bonded CFL increases the ductility of strengthened RC beam and results in dense distribution of cracks compared with normal RC beam, and it’s bending stiffness at damage state as well. The fatigue damage evolvement shows three stages of nucleation, steady expansion and failure. Then the failure mechanism was studied and a cumulative damage model was proposed to describe the fatigue damage and fracture process of CFL strengthened RC beams under constant amplitude loading.

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 Performance of Concrete Beams Reinforced with Various Ratios of Hybrid GFRP/Steel Bars

2020 ◽  
Vol 6 (9) ◽  
pp. 1652-1669
Author(s):  
Phan Duy Nguyen ◽  
Vu Hiep Dang ◽  
Ngoc Anh Vu
Keyword(s):  
Failure Modes ◽  
Concrete Beams ◽  
Peak Load ◽  
Flexural Behavior ◽  
Experimental Program ◽  
Deformation Model ◽  
Rc Beams ◽  
Linear Deformation ◽  
Crack Patterns ◽  
Steel Bars

This paper aims to study the flexural behavior of concrete beams reinforced with hybrid combinations of GFRP/steel bars. To this purpose an experimental program was carried out on four concrete beams reinforced with Glass Fiber Reinforced Polymer (GFRP) and twelve hybrid GFRP/steel Reinforced Concrete (RC) beams. Flexural behavior of the tested beams such as stages of response, failure modes, crack patterns, stiffness, toughness and ductility were analyzed. The experimental results showed that depending on GFRP/steel reinforcement configurations, the behavior of hybrid GFRP/steel RC beams undergoes three or four stages, namely: pre-cracking stage; after concrete cracking and before steel yielding; post-yield stage of the steel bar until peak load and failure stage. Totally six failure modes of hybrid RC beams are reported depending on reinforcement rations and configuration. The effect of reinforcement configuration and ratio of GFRP to steel (ρg) on the crack patterns, stiffness, ductility and toughness of hybrid RC beams are significant. Based on the non-linear deformation model, an analytical model has been developed and validated to determine the steel yielding moment and ultimate moment of hybrid GFRP/steel RC beams. It could be seen that the experimental values were in good agreement with the predicted values.

scholarly journals Flexural Strength Design of Hybrid FRP-Steel Reinforced Concrete Beams

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6400
Author(s):  
Binbin Zhou ◽  
Ruo-Yang Wu ◽  
Yangqing Liu ◽  
Xiaohui Zhang ◽  
Shiping Yin
Keyword(s):  
Reinforced Concrete ◽  
Flexural Strength ◽  
Failure Modes ◽  
Reinforcement Ratio ◽  
Reinforced Concrete Beams ◽  
Rc Beams ◽  
Strength Reduction Factor ◽  
Steel Reinforced Concrete ◽  
Strength Design ◽  
Reinforced Beams

Through proper arranging of a hybrid combination of longitudinal fiber reinforced polymer (FRP) bars and steel bars in the tensile region of the beam, the advantages of both FRP and steel materials can be sufficiently exploited to enhance the flexural capacity and ductility of a concrete beam. In this paper, a methodology for the flexural strength design of hybrid FRP-steel reinforced concrete (RC) beams is proposed. Firstly, based on the mechanical features of reinforcement and concrete and according to the latest codified provisions of longitudinal reinforcement conditions to ensure ductility level, the design-oriented allowable ranges of reinforcement ratio corresponding to three common flexural failure modes are specified. Subsequently, the calculation approach of nominal flexural strength of hybrid FRP-steel RC beams is established following the fundamental principles of equilibrium and compatibility. In addition to the common moderately-reinforced beams, the proposed general calculation approach is also applicable to lightly-reinforced beams and heavily-reinforced beams, which are widely used but rarely studied. Furthermore, the calculation process is properly simplified and the calculation accuracy is validated by the experimental results of hybrid FRP-steel RC beams in the literature. Finally, with the ductility analysis, a novel strength reduction factor represented by net tensile steel strain and reinforcement ratio is proposed for hybrid FRP-steel RC beams.

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