• Title/Summary/Keyword: Crack moment

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An Experimental Verification of the Moment Redistribution in Continuous Reinforced Concrete Members Depending on Bond Condition of Reinforcement (철근의 부착상태에 따른 철근콘크리트 연속보에서의 모멘트재분배에 대한 실험적 검증)

  • Yoon, Hyeong-Jae;Lee, Seung-Bae;Kim, Sang-Sik;Kim, Kang-Su;Jang, Su-Yuon
    • Journal of the Korea Concrete Institute
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    • v.20 no.1
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    • pp.23-33
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    • 2008
  • The moment redistribution in continuous reinforced concrete beams is very feasible phenomenon, by which the efficiency and the economy in designing reinforced concrete members can be enhanced. However, to understand the structural behavior by moment redistribution phenomenon, it is desirable to verify its mechanism experimentally considering tension stiffening effect, the relationship of moment redistribution and beam deflection, crack pattern, and effective stiffness. Six reinforced concrete continuous beam specimens were fabricated, and each specimen had a dimension of 250 mm $\times$ 350 mm and 7,000 mm long. The location of de-bonding was taken as the primary test parameter to investigate tension stiffening effect. The moment redistribution ratio of the specimens was different depending on the position of de-bonding, and in particular no moment redistribution was observed when de-bonding exist at both ends, the maximum negative moment region and the maximum positive moment region.

Crack Control of the Precast Decks in Negative Moment Region using External Tendon (외부강선을 이용한 부모멘트부 바닥판의 균열제어)

  • 김영신;정철헌;홍민기;박세진;김철영;이병주
    • Proceedings of the Korea Concrete Institute Conference
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    • 2002.05a
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    • pp.291-296
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    • 2002
  • In order to apply precast decks to the continuous composite bridges, several experiments and analytical studies were performed. For the continuous composite bridges, special attention should be paid to the transverse joints in negative moment region. Judging from the results, combination of longitudinal internal prestressing tendon and the external tendon can be effectively used for the prevention of cracking in the negative moment region of precast decks.

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An Experimental Study on the Evaluaiton of Elastic-Plastic Fracture Toughness under Mixed Mode I-II-III Loading Using the Optical PSD (PSD를 이용한 혼합모드 하중하에서 탄소성 파괴인성평가에 관한 실험적인 연구)

  • Kim, Hei-Song;Lee, Choon-Jae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.20 no.4
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    • pp.1263-1274
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    • 1996
  • In this paper, as elastic-plastic fracture toughness test under mixed mode loading was proposed using a single edge-cracked specimen subjected to bending moment(M), shearing force(F), and twisting moment(T). The J-integral of a crack in the specimen is expressed in the form J=$J_I$+ $J_II$$J_III$, where $J_I$, $J_II$ and $J_III$ are the components of mode I, mode II and mode III deformation, respectively. $J_I$, $J_II$ and $J_III$ can be estimated from M-$\theta$ ($\theta$;crack opening angle), F-U(U; crack shear displacement) and T-$\alpha$ ($\alpha$;crack twisting angle). In order to obtain the the M<-TEX>$\theta$, F-U and T-$\alpha$ diagram inreal time, a new deformaiton gage for mixed mode loading was proposed using the optical position sensing device(PSD). The elastic-plastic fracture toughness test was carried out with an aluminum alloy. The loading apparatus was designed and manufactured for this experiment. For the loading condition of the crack initatio in the mixed mode, the MMT -3(mode I+ mode II+ mode III) has the lowest values out of the all specimens. This implies that MMT-3 is possible of the crackinitation at lower load, if the specimen acts on together with the torque under the same loading condition. An elastic-plastic fracture toughness test using the PSD brings a successful experimentation in measuring the crack deformation(mode I+ mode II+ mode III).

Disaster Assessment for the Civil Infrastructure through a Technique of Crack Propagation (변상진전기법을 이용한 토목구조물 피해평가)

  • Park, Si-Hyun
    • Proceedings of the Korean Geotechical Society Conference
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    • 2010.03a
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    • pp.907-910
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    • 2010
  • This study has developed a numerical analysis technique newly which can evaluate the damage propagation characteristics of civil infrastructures. To do this, numerical techniques are incorporated for the concrete members up to the compressive damage due to the bending compressive forces after the tensile crack based on the deformation mechanism. Especially, for the compressive damage stage after the tensile crack, the crack propagation process will be analyzed numerically using the concept of an equivalent plastic hinged length. Using this concept, we investigate the reasonability of the developed module by comparing commercial program for the tunnel structure. It can be established from this study that section forces, such as axial forces and the moment cracks takes place, can be related to the width of the crack making it possible to analyze the crack extension.

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In Situ Observation of Slow Crack Growth in a Whisker-Reinforced Alumina Matrix Composite (SiC 휘스커 보강 알루미나 복합재료에서 Slow Crack Growth 현상의 직접관찰 연구)

  • 손기선;김우상;이성학
    • Journal of the Korean Ceramic Society
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    • v.33 no.2
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    • pp.203-213
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    • 1996
  • In this study the subcritical crack growth behavior in an Al2O3-SiCw composite has been investigated using in situ fracture technique of applied moment double cantilever beam (AMDCB) specimens indside an SEM. This technique allows the detailed observation of whisker and grain bridging in the crack wake region. The experimental results indicated that the KI-a curve was deviated from the conventional powder law form and that the existed a region where the rate of microcrack growth was decreased with increasing the externally applied stress intensity factor. This behavior could be explained by arising crack growth resistance i.e. R-curve behavior which was associated with crack shielding due to whisker and grain bridging. The R-curve was also analyzed from the KI-a curve data in order to quantify the bridging effect in the Al2O3-SiCw composite.

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Theoretical and experimental serviceability performance of SCCs connections

  • Maghsoudi, Ali Akbar
    • Structural Engineering and Mechanics
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    • v.39 no.2
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    • pp.241-266
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    • 2011
  • The Self Compacting Concrete, SCC is the new generation type of concrete which is not needed to be compacted by vibrator and it will be compacted by its own weight. Since SCC is a new innovation and also the high strength self compacting concrete, HSSCC behavior is like a brittle material, therefore, understanding the strength effect on the serviceability performance of reinforced self compacting concretes is critical. For this aim, first the normal and high strength self compacting concrete, NSSCC and HSSCC was designed. Then, the serviceability performance of reinforced connections consisting of NSSCC and HSSCC were investigated. Twelve reinforced concrete connections (L = 3 m, b = 0.15 m, h = 0.3 m) were simulated, by this concretes, the maximum and minimum reinforcement ratios ${\rho}$ and ${\rho}^{\prime}$ (percentage of tensile and compressive steel reinforcement) are in accordance with the provision of the ACI-05 for conventional RC structures. This study was limited to the case of bending without axial load, utilizing simple connections loaded at mid span through a stub (b = 0.15 m, h = 0.3 m, L = 0.3 m) to simulate a beam-column connection. During the test, concrete and steel strains, deflections and crack widths were measured at different locations along each member. Based on the experimental readings and observations, the cracked moment of inertia ($I_{cr}$) of members was determined and the results were compared with some selective theoretical methods. Also, the flexural crack widths of the members were measured and the applicability for conventional vibrated concrete, as for ACI, BS and CSA code, was verified for SCCs members tested. A comparison between two Codes (ACI and CSA) for the theoretical values cracking moment is indicate that, irrespective of the concrete strength, for the specimens reported, the prediction values of two codes are almost equale. The experimental cracked moment of inertia $(I_{cr})_{\exp}$ is lower than its theoretical $(I_{cr})_{th}$ values, and therefore theoretically it is overestimated. Also, a general conclusion is that, by increasing the percentage of ${\rho}$, the value of $I_{cr}$ is increased.

Moment-Curvature Analysis of Steel Fiber-Reinforced Ultra High Performance Concrete Beams with Tension Softening Behavior (인장연화거동을 고려한 강섬유 보강 초고성능 콘크리트 보의 모멘트-곡률 해석)

  • Yang, In-Hwan;Joh, Chang-Bin;Kim, Byung-Suk
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.24 no.3
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    • pp.237-248
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    • 2011
  • Tensile softening characteristics play an important role in the structural behavior of steel fiber-reinforced ultra high performance concrete. Tension softening modeling and numerical analysis method are necessary for the prediction of structural performance of steel fiber-reinforced concrete. The numerical method to predict the flexural behavior is proposed in this study. Tension softening modeling is carried out by using crack equation based on fictitious crack and inverse analysis in which load-crack opening displacement relationship is considered. Thereafter material modeling is performed considering tension softening. The comparison of moment-curvature curves of the numerical analysis results with the test results indicates a reasonable agreement. Therefore, the present numerical results prove that good prediction of flexural behavior of steel fiber-reinforced ultra high performance concrete beams can be achieved by employing the proposed method.

Study on Method of Crack Detection of L-beams with Coupled Vibration (연성진동하는 L형 단면 보의 크랙 검출 방법에 대한 연구)

  • Son, In-Soo;Cho, Jeong-Rae;Ahn, Sung-Jin
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.9 no.6
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    • pp.78-86
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    • 2010
  • This paper aims to investigate the natural frequency of a cracked cantilever L-beams with a coupled bending and torsional vibrations. In addition, a theoretical method for detection of the crack position and size in a cantilever L-beams is presented based on natural frequencies. Based on the Euler-Bernoulli beam theory, the equation of motion is derived by using extended Hamilton's Principle. The dynamic transfer matrix method is used for calculation of a exact natural frequencies of L-beams. In order to detect the crack of L-beams, the effect of spring coefficients for bending moment and torsional force is included. In this study, the differences between the actual data and predicted positions and sizes of crack are less than 0.5% and 6.7% respectively.

A Simple Finite Element Modeling Method for Leak-Before-Break Crack Analysis of Pipe with Overlay Dissimilar Metal Weldments (이종금속 오버레이 용접 배관의 파단전누설균열 해석을 위한 단순 유한요소 모델링 방법)

  • Kim, Maan Won;Park, Young Sup
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.9 no.1
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    • pp.70-76
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    • 2013
  • Several finite element models for the leak-before-break (LBB) assessment of overlay dissimilar metal weldment were constructed and analyzed to develop a simple finite element modeling method. The J-integral, crack opening displacement (COD) and J-integral distribution along the crack front in thickness direction due to the applied moment were obtained from the analysis results of the constructed finite element models, and studied compared to the previous literatures. It is concluded that the modeling with base material only is simple and produces a slightly conservative results compared to the complex modeling composed with weld metal and base metal in the calculation of J-integrals and COD values which are used for the calculation of fracture toughness and postulated leakage crack length respectively.

The Analysis of Fatigue Behavior Using the Delamination Growth Rate(dAD/da) and Fiber Bridging Effect Factor(FBE) in Al/GERP Laminates (층간분리성장률(dAD/da)과 섬유가교효과인자(FBE)를 이용한 Al/GFRP 적층재의 피로거동 해석)

  • Song, Sam-Hong;Kim, Cheol-Woong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.2
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    • pp.317-326
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    • 2003
  • The influence of cyclic bending moment on the delamination and the fatigue crack propagation behavior in Al/GFRP laminate such as the wing section was investigated. The main objective of this study was to evaluate the relationship between crack profile and delamination behavior. And a propose parameter on the delamination growth rate(d $A_{D}$/da) of Al/GFRP laminates with a saw-cut using relationship between delamination area( $A_{D}$) and cycles(N), crack length(a), stress intensity factor range($\Delta$K). Also, the fiber bridging effect factor( $F_{BE}$ ) was propose that the fiber bridging modification factor($\beta$$_{fb}$ ) to evaluate using the delamination growth rate(d $A_{D}$/da). The shape and size of the delamination zone formed along the fatigue crack between aluminum alloy sheet. Class fiber-adhesive layer were measured by an ultrasonic C-scan image. The shape of delamination zone turns out to be semi-elliptic with the contour decreased non-linearly toward the crack tip. It represents that relationship between crack length and delamination growth rate(d $A_{D}$/da) were interdependent by reciprocal action, therefore it's applicable present a model for the delamination growth rate(dA/sib D//da) in Al/GFRP laminates.minates.s.