• Title, Summary, Keyword: failure mechanism

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Experimental research on the failure mechanism of foam concrete with C-Channel embedment

  • Liu, Dianzhong;Wang, Fayu;Fu, Feng;Wang, He
    • Computers and Concrete
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    • v.20 no.3
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    • pp.263-273
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    • 2017
  • An experimental investigation is carried out on the failure mechanism of foam concrete with cold formed steel double C-Channels embedment. The foam concrete is made of cement and fly ash with a compressive strength between 9 and 24 MPa with different densities. Forty-eight tests have been carried out in four groups of specimens with various embedment depths of the steel in the concrete. Four modes of failure are observed, which include the independent failure of the C-Channels with and without a concrete block inside the channel as well as the combined failure of the two channels, and the failure of the extrusion block. A theoretical model has been developed to understand the failure process. The peak compressive force applied onto the C-Channels that causes failure is calculated. It is concluded that the failure involves independent slippage between two C-Channels, and the steel and the foam concrete blocks inside the C-Channels. A method to calculate the peak force is also developed based on the test results. The calculations also show that the shear strength of the foam concrete is about 8% of the compressive strength with ${\alpha}$ coefficient of 0.4 between the steel and concrete.

Flexural and Shear Strength of RC Deep Beams related to Anchorage Failure (정착파괴가 관련된 깊은 보의 휨-전단 강도에 관한 연구)

  • 김대진;홍성걸
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.609-612
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    • 1999
  • This study presents the plastic analysis for the flexural and shear strength of RC beams related to anchorage failure. Five failure mechanisms based on the upper bound solution were constructed and the ultimate strength equations were formulated from them. The parametric study herein was carried out to observe the variation of the controlling failure mechanism depending on the parameters in the ultimate strength equations. The results of the parametric study show that controlling failure mechanism and ultimate strength are determined through the interaction of each parameter. This indicated that respective structural configuratins must be treated in a unified manner. Additionally this study proposes the scope of the parameter to induce the flexural of RC deep beams.

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An Experimental Study on the Hysteretic Capacity Evaluation of the Shear-Strengthened RC Column with Carbon Fiber Sheet (탄소섬유쉬트로 전단보강한 RC 기둥의 이력성능평가에 관한 실험적 연구)

  • 이현호;구은숙
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.750-755
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    • 1999
  • When the RC frame structures subjected to the seismic load, brittle shear failure of vertical members induces brittle collapse of whole structures. Failure mechanism like this is not desirable. So shear strengthening method to avoid this failure mechanism is needed. Recently, strengthening method using continuous fiber sheet is studied and used widely which have high elastic and high strength characteristics. In this study, RC columns which is strengthened by carbon fiber sheet in the form of tape or whole sheet were tested under the cyclic load. The parameter of this test is the amount of strengthening. As the amount of strengthening increase, strength, ductility and energy capacity increase. The failure mode of test results are shear and bond-split failure.

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Overview of Failure Mechanisms on Lens for Optical Engine (광학엔진 렌즈의 고장 메커니즘에 대한 고찰)

  • Cha Jong-Bum;Kim Gwang-Sub
    • Journal of Applied Reliability
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    • v.6 no.2
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    • pp.173-186
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    • 2006
  • This paper presents a study on the failure mechanism for optical engine of Projection TV. The lenses of which optical engine composes are failed by various environmental conditions, that is, thermal effect, moisture effect, mechanical shock or chemical effect. By surveying on actual TV working condition, the major factor of failure was turned out the thermal effect. Because the actual surface temperature of optical engine rose at max. $51^{\circ}C$ during it worked, the relative humidity around optical engine was kept at less than 20% that is difficult to do chemical reaction with humidity. Therefore we can make a conclusion that the major failure of optical engine resulted from thermal effect.

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Study on mechanism of macro failure and micro fracture of local nearly horizontal stratum in super-large section and deep buried tunnel

  • Li, Shu-cai;Wang, Jian-hua;Chen, Wei-zhong;Li, Li-ping;Zhang, Qian-qing;He, Peng
    • Geomechanics and Engineering
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    • v.11 no.2
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    • pp.253-267
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    • 2016
  • The stability of surrounding rock will be poor when the tunnel is excavated through nearly horizontal stratum. In this paper, the instability mechanism of local nearly horizontal stratum in super-large section and deep buried tunnel is revealed by the analysis of the macro failure and micro fracture. A structural model is proposed to explain the mechanics of surrounding rock collapse under the action of stress redistribution and shed light on the macroscopic analytical approach of the stability of surrounding rock. Then, some highly effective formulas applied in the tunnel engineering are developed according to the theory of mixed-mode micro fracture. And well-documented field case is made to demonstrate the effectiveness and accuracy of the proposed analytical methods of mixed-mode fracture. Meanwhile, in order to make the more accurate judgment about yield failure of rock mass, a series of comprehensive failure criteria are formed. In addition, the relationship between the nonlinear failure criterion and $K_I$ and $K_{II}$ of micro fracture is established to make the surrounding rock failure criterion more comprehensive and accurate. Further, the influence of the parameters related to the tension-shear mixed-mode fracture and compression-shear mixed-mode fracture on the propagation of rock crack is analyzed. Results show that ${\sigma}_3$ changes linearly with the change of ${\sigma}_1$. And the change rate is related to ${\beta}$, angle between the cracks and ${\sigma}_1$. The proposed simple analytical approach is economical and efficient, and suitable for the analysis of local nearly horizontal stratum in super-large section and deep buried tunnel.

Numerical analysis of Bearing Capacity and Progressive Failure of Footings (기초지반의 지지력 및 진행성 파괴에 대한 수치해석)

  • 김영민
    • Geotechnical Engineering
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    • v.13 no.6
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    • pp.139-146
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    • 1997
  • The failure of footing generally involves the concentration of deformation into one or more narrow bands. With the displacement of the footing, the failure plane will subsequently form The purpose of this paper is to assess the capabilities of numerical techniques to predict bearing capacity and progressive failure of footings. By using the method of large deformation theory and strain softening we have investigated the progressive failure of strip footing on undrained clay. This paper describes the procedure to predict the entire loadfisplacement curve and the failure mechanism of strip footing. The presented results show that it is Possible to analyze the Post Peak behavior of strip footing numerically and to give a progressive failure mechanism clearly.

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An Analysis on the Failure Mechanism of Slope behind a Plant Complex of Gimhae due to Typhoon Rusa (태풍 루사에 의한 김해 OO단지 사면붕괴 발생원인 분석)

  • Kang, In-Kyu;Ryu, Jeong-Soo;Kim, Hong-Taek;Baek, Seung-Cheol
    • 한국방재학회:학술대회논문집
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    • pp.263-266
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    • 2007
  • In this paper, analysis results on the failure of slope behind a Plant Complex of Gimhae due to typhoon Rusa in 2002 are introduced. The left side of the slope was reinforced by soil nails and the right side of the slope was going to construct slope reinforcement works. In the slope failure, the damage area is about $34,000m^2$, the lower width of slope failure is about 230m, the upper width of slope failure is about 50m, and the height of slope failure is about 120m. The elevation of a bedrock in the right side of the slope was lower than the left side of the slope. Due to the depth of weathered soils and weathered rocks in right side of the slope was thick, it will be expected that the effects of pore-water pressure during the rainfalls are large. For the analysis of the failure mechanism, 3-dimensional numerical analysis was carried out by FLAC-3D.

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Characterization of the brittleness of hard rock at different temperatures using uniaxial compression tests

  • Chen, Guoqing;Li, Tianbin;Wang, Wei;Guo, Fan;Yin, Hongyu
    • Geomechanics and Engineering
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    • v.13 no.1
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    • pp.63-77
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    • 2017
  • The failure mechanism of a deep hard rock tunnel under high geostress and high geothermalactivity is extremely complex. Uniaxial compression tests of granite at different temperatures were conducted. The complete stress-strain curves, mechanical parameters and macroscopic failure types of the rock were analyzed in detail. The brittleness index, which represents the possibility of a severe brittleness hazard, is proposed in this paperby comparing the peak stress and the expansion stress. The results show that the temperature range from 20 to $60^{\circ}C$ is able to aggravate the brittle failure of hard rock based on the brittleness index. The closure of internal micro cracks by thermal stress can improve the strength of hard rock and the storage capacity of elastic strain energy. The failure mode ofthe samples changes from shear failure to tensile failure as the temperature increases. In conclusion, the brittle failure mechanism of hard rock under the action of thermal coupling is revealed, and the analysis result offers significant guidance for deep buried tunnels at high temperatures and under high geostress.

A Study on the Failure Behavior of Carbon Fiber Sheet Reinforced Mortar Using Acoustic Emission Technique (AE를 이용한 탄소섬유시트 강화 모르타르의 파괴거동에 관한 연구)

  • 이진경;이준현;장일영
    • Journal of the Korea Concrete Institute
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    • v.12 no.3
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    • pp.67-75
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    • 2000
  • It was well recognized that the damages associated mainly with the aging of civil infrastructures were one of very serious problems for assurance of safety and reliability. Recently carbon fiber sheet(CFS) has been widely used for reinforcement and rehabilitation of damaged concrete beam. However, the fundamental mechanism of load transfer and its load-resistant for carbon fiber sheet reinforced concrete are not fully understood. In this study, three point bending test has been carried out to understand the damage progress and the micro-failure mechanism of CFS reinforced mortars. For this purpose, four different types of specimens are used, that is, mortar, steel bar reinforced mortar, CFS reinforced mortar, and steel bar and CFS reinforced morter. Acoustic Emission(AE) technique was used to evaluate the characteristics of damage progress and the failure mechanism of specimens. in addition, two-dimensional AE source location was also performed to monitor crack initiation and propagation processes for these specimens.

Axial crush and energy absorption characteristics of Aluminum/GERP hybrid square tube (알루미늄/GFRP 혼성 사각튜브의 정적 압축 붕괴 및 에너지 흡수 특성)

  • 김구현;이정주
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.168-171
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    • 1999
  • For the axial crushing tests of various shape of tubes, it was reported that composite tubes need trigger mechanism to avoid brittle failure. In this study, static axial crush tests were performed with the new aluminum/GFRP hybrid tubes. Glass/Epoxy prepregs were wrapped around aluminum tube and co-cured. The failure of hybrid tube was stable and progressive without trigger mechanism, and specific energy absorption was increased to maximum 34% in comparison with aluminum tube. Effective energy absorption is possible for inner aluminum tube because wrapped composite tube constrain the deflection of aluminum tube and reduce the folding length. The failure of hybrid composite tube was stable without trigger mechanism because inner aluminum tube could play the role of crack initiator and controller. Aluminum/Glass-Epoxy hybrid tube is suitable for the vehicle front structure due to effective energy absorption capability, easy production, and simple application for RTM process.

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