• Title/Summary/Keyword: Polymer Concrete

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Data-driven prediction of compressive strength of FRP-confined concrete members: An application of machine learning models

  • Berradia, Mohammed;Azab, Marc;Ahmad, Zeeshan;Accouche, Oussama;Raza, Ali;Alashker, Yasser
    • Structural Engineering and Mechanics
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    • v.83 no.4
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    • pp.515-535
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    • 2022
  • The strength models for fiber-reinforced polymer (FRP)-confined normal strength concrete (NC) cylinders available in the literature have been suggested based on small databases using limited variables of such structural members portraying less accuracy. The artificial neural network (ANN) is an advanced technique for precisely predicting the response of composite structures by considering a large number of parameters. The main objective of the present investigation is to develop an ANN model for the axial strength of FRP-confined NC cylinders using various parameters to give the highest accuracy of the predictions. To secure this aim, a large experimental database of 313 FRP-confined NC cylinders has been constructed from previous research investigations. An evaluation of 33 different empirical strength models has been performed using various statistical parameters (root mean squared error RMSE, mean absolute error MAE, and coefficient of determination R2) over the developed database. Then, a new ANN model using the Group Method of Data Handling (GMDH) has been proposed based on the experimental database that portrayed the highest performance as compared with the previous models with R2=0.92, RMSE=0.27, and MAE=0.33. Therefore, the suggested ANN model can accurately capture the axial strength of FRP-confined NC cylinders that can be used for the further analysis and design of such members in the construction industry.

Numerical and analytical investigation of parameters influencing the behavior of shear beams strengthened by CFRP wrapping

  • Ceyhun Aksoylu;Yasin Onuralp Ozkilic;Sakir Yazman;Mohammed Alsdudi;Lokman Gemi;Musa Hakan Arslan
    • Steel and Composite Structures
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    • v.47 no.2
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    • pp.217-238
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    • 2023
  • In this study, a parametric study was performed considering material properties of concrete, material properties of steel, the number of longitudinal reinforcement (reinforcement ratio), CFRP ply orientations, a number of layers as variables by using ABAQUS. Firstly, the parameters used in the Hashin failure criteria were verified using four coupon tests of CFRP. Secondly, the numerical models of the beams strengthened by CFRP were verified using five experimental data. Finally, eighty numerical models and eighty analytic calculations were developed to investigate the effects of the aforementioned variables. The results revealed that in the case of using fibrous polymer to prevent shear failure, the variables related to reinforced concrete significantly affected the behavior of specimens, whereas the variables related to CFRP composite have a slight effect on the behavior of the specimens. As a result of numerical analysis, while the increase in the longitudinal tensile and compression reinforcement, load bearing capacity increases between 23.6%-70.7% and 5.6%-12.2%, respectively. Increase in compressive strength (29 MPa to 35 MPa) leads to a slight increase in the load-carrying capacity of the specimens between 4.6% and 7.2%. However, the decrease in the compressive strength (29 MPa to 20 MPa) significantly affected (between 6.4% and 8.1% decrease observed) the behavior of the specimens. As the yield strength increases or decreases, the capacity of specimens increase approximately 27.1% or decrease 12.1%. The effects of CFRP ply orientation results have been obtained as a negligible well approximately 3.7% difference. An increasing number of CFRP layers leads to almost no effect (approximately 2.8%) on the behavior of the specimen. Finally, according to the numerical analysis, the ductility values obtained between 4.0 and 6.9 indicate that the beams have sufficient ductility capacity.

Service and Ultimate Load Behavior of Bridge Deck Reinforced with GFRP Rebars (GFRP 보강근으로 보강된 교량 바닥판의 성능과 사용성에 관한 실험연구)

  • Yu, Young Jun;Park, Young Hwan;Park, Ji Sun
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.28 no.5A
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    • pp.719-727
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    • 2008
  • The tensile and bond performance of GFRP rebar are different from those of conventional steel reinforcement. It requires some studies on concrete members reinforced with GFRP reinforcing bars to apply it to concrete structures. GFRP has some advantages such as high specific strength, low weight, non-corrosive nature, and disadvantage of larger deflection due to the lower modulus of elasticity than that of steel. Bridge deck is a preferred structure to apply FRP rebars due to the increase of flexural capacity by arching action. This paper focuses on the behavior of concrete bridge deck reinforced with newly developed GFRP rebars. A total of three real size bridge deck specimens were made and tested. Main variables are the type of reinforcing bar and reinforcement ratio. Static test was performed with the load of DB-24 level until failure. Test results were compared and analyzed with ultimate load, deflection behavior, crack pattern and width.

A Study on Methodology for Improvement of Bond of FRP reinforcement to Concrete (초단유리섬유(milled glass fibers)와 에폭시 혼합물을 이용한 FRP 보강근 표면성형기법 연구)

  • Moon, Do-Young;Sim, Jongsung;Oh, Hongseob
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.26 no.4A
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    • pp.775-785
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    • 2006
  • This study focused on the development of surface deformations of GFRP rebars with a better bond characteristic for reinforcing concrete, and simultaneously, of GFRP rebars with more simple and economic production process. This research paper describes a development and bond performance of GFRP rebar with molded deformations, which is composed of polymer resin and milled glass fiber. To determine proper mix ration of milled fibers, material test of hardened epoxy and pullout tests of GFRP rebar with various mix ratio were conducted. The test results indicate that the new strategy of using a mixture of epoxy resin and milled fiber could be successfully applied to a surface structure of GFRP rebar to enhance bond with concrete. The bearing resistance of the ribs was further enhanced by the milled fibers at mechanical and environmental loading state.

Investigation of Crack Healing and Optimization of Microbe Carrier for Microbial Self-healing of Concrete Crack (미생물 기반 콘크리트 자기치유를 위한 미생물 담체 최적화 및 균열치유성능 분석)

  • Yun Lee
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.28 no.4
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    • pp.62-67
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    • 2024
  • In this paper, we developed and optimized a chitosan-based polymer microbial bead carrier that is cell-friendly, has a high moisture absorption rate, and effectively provides the conditions for microbial biomineral formation as an optimal microbial carrier that protects microorganisms in concrete, and evaluated the self-healing performance of mortar using it. In order to incorporate circular-shaped microbial endospores, a circular-shaped microbial bead carrier was developed by combining chitosan and alginate polymers, and the amount of calcium carbonate produced could be actively controlled by adjusting the composition of the carrier. The amount of biominerals formed and the size of crystals were maximized in the hydrogel bead carrier containing chitosan, and in the case of mortar cracks using this, it was confirmed that self-healing of cracks with a maximum crack width of 0.3mm was achieved within 96 hours after crack generation.

Numerical analysis on dynamic response and damage assessment of FRP bars reinforced-UHPC composite beams under impact loading

  • Tao Liu;Qi M. Zhu;Rong Ge;Lin Chen;Seongwon Hong
    • Computers and Concrete
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    • v.34 no.4
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    • pp.409-425
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    • 2024
  • This paper utilizes LS-DYNA software to numerically investigate impact response and damage evaluation of fiber-reinforced polymer (FRP) bars-reinforced ultra-high-performance concrete (UHPC) composite beams (FRP-UHPC beams). Three-dimensional finite element (FE) models are established and calibrated by using literature-based static and impact tests, demonstrating high accuracy in simulating FRP-UHPC beams under impact loading. Parametric analyses explore the effects of impact mass, impactor height, FRP bar type and diameter, and clear span length on dynamic response and damage modes. Two failure modes emerge: tensile failure with bottom longitudinal reinforcement fracture and compression failure with local concrete compression near the impact region. Impact mass or height variation under the same impact energy significantly affects the first peak impact force, but minimally influences peak midspan displacement with a difference of no more than 5% and damage patterns. Increasing static flexural load-carrying capacity enhances FRP-UHPC beam impact resistance, reducing displacement deformation by up to 30%. Despite similar static load-carrying capacities, different FRP bars result in varied impact resistance. The paper proposes a damage assessment index based on impact energy, static load-carrying capacity, and clear span length, correlating well with beam end rotation. Their linearly-fitting coefficient was 1.285, 1.512, and 1.709 for the cases with CFRP, GFRP, and BFRP bars, respectively. This index establishes a foundation for an impact-resistant design method, including a simplified formula for peak midspan displacement assessment.

Analytical Evaluation of High Velocity Impact Resistance of Two-way RC Slab Reinforced with Steel Fiber and FRP Sheet (강섬유 및 FRP Sheet로 보강한 2방향 RC 슬래브의 고속 충격저항성능에 대한 해석적 평가)

  • Lee, Jin Young;Shin, Hyen Oh;Min, Kyeng Hwan;Yoon, Young Soo
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.17 no.3
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    • pp.1-9
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    • 2013
  • This paper presents high-velocity impact analysis of two-way RC slabs, including steel fibers and strengthening with fiber reinforced polymer (FRP) sheets for evaluating impact resistance. The analysis uses the LS-DYNA program, which is advanced in impact analysis. The present analysis was performed similarly to the high-velocity impact tests conducted by VTT, the technical research center of Finland, to verify the analysis results. High-velocity impact loads were applied to $2100{\times}2100{\times}250$ mm size two-way RC slab specimens, using a non-deformable steel projectile of 47.5kg mass and 134.9m/s velocity. In this research, extra impact analysis of material specimens was carried out to verify the material models used to the analysis. The elastic-plastic hydrodynamic model, concrete damage model and orthotropic elastic model were used to simulate the non-linear softening behavior of steel fiber reinforced concrete (SFRC), and material properties of normal concrete and FRP sheets, respectively. It is concluded that the suggested analysis technique has good reliability, and can be effectively applied in evaluating the effectiveness of reinforcing/retrofitting materials and techniques. Also, the Steel fiber and FRP sheet strengthening systems provided outstanding performance under high-velocity impact loads.

Shear Behavior of Slender HSC Beams Reinforced with Stirrups using Headed Bars, High Strength Steels, and CFRP Bars (헤디드 바, 고장력 철근 및 CFRP 바로 전단보강된 세장 고강도콘크리트 보의 전단 거동 평가)

  • Yang, Jun-Mo;Kwon, Ki-Yeon;Choi, Hong-Shik;Yoon, Young-Soo
    • Journal of the Korea Concrete Institute
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    • v.19 no.6
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    • pp.717-726
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    • 2007
  • If conventional reinforcements are used for high-strength concrete (HSC) structures, a large amount of the reinforcement must be required to compensate for the brittleness of HSC and make the best use of HSC. This raises some structural problems such as steel congestion and an increase in self-weight. Therefore, alternative reinforcing materials and methods for HSC structures are needed. In this study, four full-scale beam specimens constructed with HSC (100 MPa) were tested to investigate the effect of the different shear reinforcements on the shear behavior. These four specimens were reinforced for shear stirrups with normal and high strength steels, headed bars, and carbon fiber-reinforced polymer (CFRP) bars, respectively. In addition, steel fibers were added to the HSC in the two of the specimens to observe their beneficial effects. The use of high strength steels resulted in the improvement of the shear capacity since the shear resistance provided by the shear reinforcements and the bond strength were increased. The specimen reinforced with headed bars also showed a superior performance to the conventional steel reinforced specimen due to the considerably high anchorage strength of headed bar. CFRP bars used in this research, however, seemed to be inadequate for shear reinforcement because of the inferior bond capacity. The presence of the steel fibers in concrete led to remarkable improvement in the ductility of the specimens as well as in the overall cracks control capability.

An Experimental Study on the Flexural Behavior of One-Way Concrete Slabs Using the Restorative Mortar and Crimped Wire Mesh (크림프 철망 및 단면복구 보수 모르타르를 사용한 일방향 슬래브의 휨 거동에 관한 실험적 연구)

  • Lee, Mun-Hwan;Song, Tae-Hyeob
    • Journal of the Korea Concrete Institute
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    • v.19 no.5
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    • pp.569-575
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    • 2007
  • The repair of concrete surfaces does not normally take into account structural tolerance for longer service lift and better capabilities of concrete structures. In particular, the repair of surface spelling completes as mortar is applied, which does not display additional structural performances. The use of crimped wire mesh for better construction and fracture resistance, however, expects to have some reinforcement effects. Particularly, it is also expected that the repair of bottom part in structures built between bridges like irrigation structures results in the increase of flexural resistance. Therefore, this study is intended to perform the repair using crimp wire mesh and examine strength depending on the repair section and depth. For this, a slab with 150 mm in depth, 3,000 mm in length and 600 mm in width and total 8 objects to experiment such as upper part, upper whole, bottom part, bottom whole and crimp wire mesh reinforced are manufactured to perform flexural performance. The results of the analysis show that yield strength and failure load increase as the depth of repair materials in the experiment reinforced with crimp wire mesh get bigger. In the same condition, repair of bottom part is able to increase internal force of bending force. Besides, the results show that partial repair of structures under bending force cannot produce flexural performance. Consequently, the repair method with crimp wire mesh results in the increase of flexural resistance.

Pseudo-Ductile Hybrid FRP Sheet for Strengthening Reinforced Concrete Beams (유사연성 하이브리드 FRP 시트를 이용한 RC 보의 휨 보강)

  • Ha, Sang-Su;Choi, Dong-Uk;Lee, Chin-Yong;Kim, Kil-Hee
    • Journal of the Korea Concrete Institute
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    • v.20 no.2
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    • pp.239-247
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    • 2008
  • Use of both carbon fiber (CF) and glass fiber (GF) at the same time to strengthen existing flexural members was exploited. Using a proper volumetric GF / CF ratio, the CF can rupture first followed by subsequent rupture of GF at higher stress and strain showing a pseudo-ductile behavior. A theoretical study indicated that the ratio is 4.62 : 1 and higher where the pseudoductile effect can be shown. Flexural tests of plain concrete beams strengthened using fibers were first carried out. Hybrid FRP sheet using 8.8 : 1 ratio was then fabricated and the sheet was used to strengthen reinforced concrete beams. The RC beams strengthened using 1-ply and 2-ply hybrid sheets both revealed increased strength over a non-strengthened beam and ductile flexural behavior. A comparable beam strengthened using CF also showed increased strength but with limited ductility.