• Title/Summary/Keyword: Flexural Beam

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Flexural Performance of RC Beams Strengthened with NSM-GFRP Exposed to High Temperature (GFRP 표면매립공법으로 보강된 RC보의 고온노출 후 휨 성능)

  • Kim, Hee-Seung;Lee, Hye-Hak;Choi, Kyoung-Kyu
    • Journal of the Architectural Institute of Korea Structure & Construction
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    • v.34 no.4
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    • pp.35-42
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    • 2018
  • This study evaluated the fire resisting capacity and post-fire serviceability of the concrete beams retrofitted by near surface mounted method(NSM) using GFRP plates. Main parameters in the test are grout materials and fire exposure. For the test, two types of grout materials between concrete substrate and GFRP plate were used; flame resisting epoxy and filling mortar. Four RC beam specimens were made and two of them were exposed to fire according to real scale fire curve proposed KS F 2257. After the fire exposure test, flexural test were performed to investigate the flexural performance of concrete beams including strength and deformation. From the test results, it was found that the beam retrofitted by NSM-GFRP presented higher flexural strength than that of the beam without retrofit, which indicates NSM-GFRP retrofit technologies is effective to maintain flexural strength even after fire exposure. In addition, the specimens grouted by epoxy showed good performance in strength but bad performance in ductility.

An Cracking and Ultimate Behavior of Post-tensioned Prestressed High Strength Concrete Beams (포스트텐셔닝 공법의 프리트스레스트 고강도 빔부재의 균열 및 극한 거동)

  • Lee, Seong-Cheol;Choi, Young-Cheol;Oh, Byung-Hwan
    • Proceedings of the Korea Concrete Institute Conference
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    • 2005.11a
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    • pp.323-326
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    • 2005
  • Although many structures. with high strength concrete have been recently constructed, the flexural behavior of reinforced and prestressed concrete beams with high strength concrete is not exactly defined. This paper presents an experimental study on the flexural strength of the high strength concrete beams. Five large scale beams simply supported were tested and measured. Each beam was loaded by two symmetrical concentrated loads applied at 1.25m from the center of span. The concrete strength, the prestressed force and longitudinal tensile reinforcement ratio vary from beam to beam. From the experimental tests, the flexural strength from tests is larger than the nominal flexural strength of codes. Moreover, the initial crack-load is affected by the prestressed force and the crack width and spacing are controlled by the longitudinal tensile reinforcement ratio.

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Development of an analytical method for optimum design of reinforced concrete beams considering both flexural and shear effects

  • Zivari, Ahmad;Habibi, Alireza;Khaledy, Nima
    • Computers and Concrete
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    • v.24 no.2
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    • pp.117-123
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    • 2019
  • Optimization is an important subject which is widely used in engineering problems. In this paper, an analytical method is developed for optimum design of reinforced concrete beams considering both flexural and shear effects. A closed-form formulation is derived for optimal height and rebar of beams. The total material cost of steel and concrete is considered as the objective function which is minimized during the optimization process. The ultimate flexural and shear capacities of the beam are considered as the main constraints. The ultimate limit state is considered for deriving the relations for flexural capacity of the beam. The design requirements are considered according to the item 9 of the Iranian National Building. Analytical formulas and some curves are proposed to be used for optimum design of RC beams. The proposed method can be used to perform the optimization of RC beams without the need of any prior knowledge in optimization. Also, the results of the studied numerical example show that the proposed method results in a better design comparing with the other methods.

Flexural strength of concrete-galvalume composite beam under elevated temperatures

  • Maryoto, Agus;Lie, Han Ay;Jonkers, Hendrik Marius
    • Computers and Concrete
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    • v.27 no.1
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    • pp.13-20
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    • 2021
  • In this paper, the elevated temperature on a concrete-galvalume composite beam's flexural strength based on the numerical and experimental methods is investigated. The strategy is to perform modeling and simulation of the flexural test based on finite element method (FEM) at room temperature and validate its results to experimental data at the same temperature. When the numerical model was proven valid, the model was utilized to simulate the effect of elevated temperatures on the composite element. The study concludes that the flexural strength of the beam decreases at higher temperature. Additionally, it was shown that cracking moments is susceptible to temperature fluctuation and the failure modes are sensitive concerning the elevated temperature.

Strengthening of steel-concrete composite beams with composite slab

  • Subhani, Mahbube;Kabir, Muhammad Ikramul;Al-Amer, Riyadh
    • Steel and Composite Structures
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    • v.34 no.1
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    • pp.91-105
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    • 2020
  • Steel-concrete composite beam with profiled steel sheet has gained its popularity in the last two decades. Due to the ageing of these structures, retrofitting in terms of flexural strength is necessary to ensure that the aged structures can carry the increased traffic load throughout their design life. The steel ribs, which presented in the profiled steel deck, limit the use of shear connectors. This leads to a poor degree of composite action between the concrete slab and steel beam compared to the solid slab situation. As a result, the shear connectors that connects the slab and beam will be subjected to higher shear stress which may also require strengthening to increase the load carrying capacity of an existing composite structure. While most of the available studies focus on the strengthening of longitudinal shear and flexural strength separately, the present work investigates the effect of both flexural and longitudinal shear strengthening of steel-concrete composite beam with composite slab in terms of failure modes, ultimate load carrying capacity, ductility, end-slip, strain profile and interface differential strain. The flexural strengthening was conducted using carbon fibre reinforced polymer (CFRP) or steel plate on the soffit of the steel I-beam, while longitudinal shear capacity was enhanced using post-installed high strength bolts. Moreover, a combination of both the longitudinal shear and flexural strengthening techniques was also implemented (hybrid strengthening). It is concluded that hybrid strengthening improved the ultimate load carrying capacity and reduce slip and interface differential strain that lead to improved composite action. However, hybrid strengthening resulted in brittle failure mode that decreased ductility of the beam.

Theoretical Assessment of Flexural Strength of Unbonded FRP Prestressed Concrete Beams (비부착 FRP 프리스트레스트 콘크리트보의 휨내력 이론 산정)

  • Heo, Seo-Young;Lee, Cha-Don;Jeong, Sang-Mo
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.04a
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    • pp.1045-1048
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    • 2008
  • Fiber reinforced polymer (FRP) usually exhibits inherent brittleness under tensile stress. Application of FRP tendons to concrete beam leads to undesirable flexural behavior due to limited ductility compared to prestressed concrete beam with steel tendons. It has been experimentally observed that partial improvement of flexural behavior can be achieved by releasing FRP tendons' strain by unbonding FRP tendons. In order to estimate and apply the degree of improvement to the design, reasonable yet practical model predicting flexural strength as well as overall flexural behavior of unbonded FRP prestressed concrete beam is needed. In this study, an elaborated model in describing curvature distributions and flexural strength at ultimate stage of unbonded FRP tendons is described. There have been close agreements on the flexural strength of the FRP prestressed concrete beam between the predictions by nonlinear computer program and by the model.

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The Study on Flexural Behavior of Reinforced Concrete Beams Strengthened with the Carbon Fiber Rod (탄소섬유 Rod로 성능향상된 R/C보의 휨 거동 연구)

  • 심종성;문도영;김영호;김동희
    • Proceedings of the Korea Concrete Institute Conference
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    • 2002.10a
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    • pp.611-616
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    • 2002
  • The concrete beam is quickly required to be replaced or strengthened due to decreasing load carrying capacity. Flexural tests on 3.1m long reinforced concrete beams with carbon-fiber rod are reported. The selected experimental variable is the method of the anchoring beam. The effects of this variable in overall behavior are discussed. This paper considered relation of load-displacement and load-strain. The maximum load was increased to the static behavior of the R/C beam strengthened with CFR rod. The results indicated generally that the flexural strength of strengthening beam was increased. It was required a proper anchorage system and can be led the ductility of beams of a carbon-fiber rod.

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Control of Object Transport Direction Using Vibration of Flexural Beam in Ultrasonic Transport System (초음파 이송장치에서 탄성 빔의 진동을 이용한 물체 이송방향 제어)

  • Jeong, Sang-Hwa;Park, Jin-Wan
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2007.11a
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    • pp.1241-1246
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    • 2007
  • In recent years, the semiconductor industry and the optical industry are developed rapidly. The recent demands have expanded for optical components such as the optical lens, the optical semiconductor and the measuring instrument. Object transport systems are driven typically by the magnetic field and the conveyer belt. Recent industry requires more faster and efficient transport system. However, conventional transport systems are not adequate for transportation of optical elements and semiconductors. The conveyor belts can damage precision optical elements by the contact force and magnetic systems can destroy the inner structure of semiconductor by the magnetic field. In this paper, the levitation transport system using ultrasonic wave is developed for transporting precision elements without damages. The steady state flexural vibration of the beam is expressed using Euler-Bernoulli beam theory. The transport direction of an object is examined according to phase difference and frequency. The theoretical results are verified by experiments.

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An Experimental Study on Damage Assessment of Reinforced Concrete Beams (철근 콘크리트 보의 손상평가에 대한 실험적 연구)

  • Roh Won Kyoun;Shim Chang Su;Hong Chang Kuk;Kim Ki Bong
    • Proceedings of the Korea Concrete Institute Conference
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    • 2004.05a
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    • pp.60-63
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    • 2004
  • The paper deals with the damage assessment of the concrete beam using static displacements and the flexural stiffness reduction of the beam was evaluated. Simply supported concrete beams were loaded at the mid-span, and the applied load level ranged $20\%,\;40\%,\;80\%$ of the flexural strength of the beam. When the displacements from the tests were increased more than $10\%$ of the initial values, flexural cracks occured. Judging from the observed cracks, damaged area of the beams were assumed and the stiffness reduction using the smeared-cracking concept was estimated to minimize the error between the test results and analytical results. Four stages of the behavior of a RC beam, which are uncracked, initial cracking, stabilized cracking and post-yielding, can be considered to assess the damage of RC beams. Main parameters for the assessment were cracking area and the stiffness reduction ratio. In each stage, damaged elements and their stiffness reduction were estimated to minimized the error.

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