• 제목/요약/키워드: stress - strain relationship

검색결과 607건 처리시간 0.023초

후프띠철근과 보강띠철근으로 횡구속된 정사각단면 콘크리트의 응력-변형률 특성 (Characteristics of the Stress-strain Relationship of Square Sectional Concrete Confined by Hoop Reinforcement with Cross-ties)

  • 정혁창;차수원;김익현
    • 한국지진공학회논문집
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    • 제14권3호
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    • pp.39-48
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    • 2010
  • RC교량의 내진성능은 교각에 충분한 연성도를 제공함으로써 확보할 수 있다. 이러한 연성도는 교각의 소성힌지 영역에 적절한 횡방향철근을 배근함으로써 실현할 수 있다. 횡방향철근에 의한 횡구속력은 유효구속력으로 결정되므로 단면형상과 횡방향철근량이 지배적인 요소가 된다. 동일한 횡방향철근량을 제공하더라도 설치간격, 배치형태, 갈고리 상세 등의 차이에 의해 유효구속력에 차이가 있게 된다. 후프띠철근에 의해 횡구속력을 발휘하는 원형단면과는 달리 사각 또는 중공사각단면에서는 유효구속력을 증가시키기 위해 보강띠철근이 함께 사용된다. 이러한 보강띠철근을 어떻게 고려하느냐에 따라 횡구속된 콘크리트의 응력-변형률 관계는 달라지게 된다. 본 연구에서는 실험을 통해 후프띠철근과 함께 보강띠철근을 갖는 정사각단면 콘크리트의 응력-변형률 관계를 파악하였으며 기존의 평가식과 비교를 통해 역학적 특성을 분석하였다.

반복하중을 받는 실트질 점토에 관한 실험적 연구 -과압밀 점토를 중심으로- (An Experimental Study on Silty Clay Subjected to Repeated Loads)

  • 김팔규;김경진;송전섭
    • 한국지반공학회지:지반
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    • 제5권4호
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    • pp.37-46
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    • 1989
  • 본 논문은 반복하중을 받는 과추밀 실트질 점토의 일반적 특성에 관한 연구로서 재성형 시료를 과압밀 상태로 제작하여 일련의 변형-제어 반복 삼축시험을 수행하였다. 일반적으로 단일하중의 경우에 과압밀점토의 축차응력-축변형률 관계는 그 형태에 있어 정규압밀점토의 결과와 흡사하지만, 반복하중을 받게 쾨면 시료 내의 간극수압 거동은 시료의 압밀리력 과 반복응력의 크기에 따라 변화하게 된다. 그러므로 서로 다른 과압밀비를 가진 시료에 대한 반복 하중시험 결과를 통하여 나타난 일반적 응력-변형 특성에 관하여 상호 비교 분석하고,이들의 종합적인 관계로부터 변형 및 강도 특성을 찾고자 하였다. 또한 시료가 평형상웅로 존재할 수 있는 반복응력의 한계치를 의미하는 직선 혹은 곡선형태의 평형상태선을 결정하고 과압밀비 의 변화에 따른평형상태선의 경향을 관찰하였다.

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성능 중심 설계기준을 위한 콘크리트 압축응력 분포 (Compressive Stress Distribution of Concrete for Performance-Based Design Code)

  • 이재훈;임강섭;황도규
    • 콘크리트학회논문집
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    • 제23권3호
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    • pp.365-376
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    • 2011
  • 현행 콘크리트구조설계기준(2007)은 콘크리트 구조물의 설계에 적용하는 콘크리트의 압축응력 분포로 ACI 318의 등가 직사각형 응력 분포를 규정하고 있다. 단면의 휨강도 해석에는 등가 직사각형 응력 분포가 충분하겠지만, 성능 중심 설계의 한계 상태 검증에는 실제와 가까운 압축응력-변형률 관계가 필요하다. 또 등가 직사각형 응력 분포는 고강도 콘크리트 기둥의 휨강도 해석에 비안전측의 결과를 준다는 것이 알려져 있으므로, 이를 대신하는 새로운 응력 분포 모델이 필요하다. 이 연구에서는 Eurocode와 일본 토목학회의 설계기준에서 채택하고 있는 포물선-직선 형상의 새로운 모델을 제안하였다. 이 응력 분포 모델은 이 연구에서 수행된 압축응력 분포 실험과 타 연구자들의 실험 결과를 분석하여 도출된 것으로서, 보통 강도뿐만 아니라 고강도 콘크리트를 포함한 것이다. 제안 모델의 특성은 미국 ACI 318, 캐나다 CSA, 유럽의 Eurocode, 일본 토목학회 설계기준의 응력 분포 모델과 함께 실험 결과와 비교하여 정리하였다.

급냉응고된 과공정 Al-Si합금의 고온변형특성에 관한 연구 (High Temperature Deformation Behavior of Rapid-Solidification Processed Al-18Si Alloy)

  • 김성일
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 2000년도 춘계학술대회논문집
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    • pp.183-186
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    • 2000
  • The high temperature deformation behavior of spray-formed Al-19wt%Si-1.87wt%Mg-0.085wt.%Fe alloy was studied by torsion testing in the strain rate range of 0.001-1 sec-1 and in the temperature range of 300-500 $^{\circ}C$. The relationship between stress temperature and strain rate is expressed using the Power law. the behavior of dynamic recrystallization is showed in 300-35$0^{\circ}C$, 1-0.1sec-1 and the behavior of dynamic recovery is showed in 450-50$0^{\circ}C$, 0.01-0.001sec-1 The size of Si particles is mall when the temperature is low and the strain rate is high. The strain rate sensitivity(m) and the apparent activation energy(Q) indicate the dependence on strain rate and temperature for flow stress respectively. The hot ductility is high when m is high and Q is low. The maps of strain rate sensitivity and apparent activation energy suggest the optimum processing conditions.

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Al 6061 합금의 고온 소성변형 조건의 예측 (Prediction of High Temperature Plastic Deformation Variables on Al 6061 Alloy)

  • 김성일;정태성;유연철;오수익
    • 소성∙가공
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    • 제8권6호
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    • pp.576-582
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    • 1999
  • The high temperature behavior of Al 6061 alloy was characterized by the hot torsion test in the temperature ranges of 400∼550℃ and the strain rate ranges of 0.05∼5/sec. To decide optimum deformation condition, three types of deformation maps were individually made from the critical strain (εc). deformation resistance(σp) and deformation efficiency (η). The critical strain(εc) for dynamic recrystallization (DRX) which was decided from the inflection point of strain hardening rate(θ) - effective stress (σ) curve was about 0.65 times of peak strain (εp). The relationship among deformation resistance (peak stress, σp), strain rate (ε), and temperature (T) could be expressed by ε=2.9×1013[sinh(0.0256σp]7.3exp (-216,000/RT). The deformation efficiency (η)which was calculated on the basis of the dynamic materials model (DMM) showed high values at the condition of 500∼550℃, 5/sec for 100% strain. The results from three deformation maps were compared with microstructures. The best condition of plastic deformation could be determined as 500℃ and 5/sec.

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파괴인성시험의 유한요소 시뮬레이션 (Finite Element Simulation of Fracture Toughness Test)

  • 주석재;류총호
    • 대한기계학회논문집A
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    • 제37권4호
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    • pp.491-496
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    • 2013
  • 인장시험을 유한요소 시뮬레이션하여 등가응력-등가소성변형률 곡선, 임계 등가응력과 임계 등가소성변형률을 결정하였다. 그리고, 이 곡선을 입력하여 파괴시험을 유한요소 시뮬레이션하여 평면변형률 파괴인성치를 결정하여 보려고 하였다. 균열선단절점에서 등가소성변형률이 임계 등가소성변형률에 도달할 때 균열개구변위를 임계 균열개구변위로 취하여 균열성장조건으로 사용되었다. 임계 등가소성변형률이나 단면감소율과 파괴시험 임계 균열개구변위와 관련성을 찾아보고, 임계 등가응력과 임계 등가소성변형률을 동시에 적용하여 파괴시험 파괴인성치와의 관련성도 찾아보았다.

미세기공 알루미늄 소재의 기계적 성질 (Mechanical Properties of Aluminium Alloy with Cellular Structure.)

  • 윤성원;이승후;강충길
    • 한국정밀공학회:학술대회논문집
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    • 한국정밀공학회 2002년도 춘계학술대회 논문집
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    • pp.695-698
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    • 2002
  • Induction heating process is one of the most efficient heating process in terms of temperature control accuracy and heating time saving. In the past study, fabrication process of cellular 6061 alloys by powder metallurgical route and induction heating process was studied. To supplement the framing conditions that studied in past study, effect of induction heating capacity and holding time at foaming temperature were investigated. Under the achieved framing conditions, teamed 6061 alloys were fabricated for variation of foaming temperature, and porosities(%)-foaming temperature curves were obtained by try-error experimental method. Uniaxial compression tests were performed to investigate the relationship between porosities(%) and stress-strain curves of framed 6061 alloy. Also, energy absorption capacity and efficiency were calculated from stress-strain curves to investigated. Moreover, dependence of plateau stress on strain rate was investigated in case of cellular 6061 alloy with low porosities(%)

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Strength model for square concrete columns confined by external CFRP sheets

  • Benzaid, Riad;Mesbah, Habib Abdelhak
    • Structural Engineering and Mechanics
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    • 제46권1호
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    • pp.111-135
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    • 2013
  • An experimental study has been carried out on square plain concrete (PC) and reinforced concrete (RC) columns strengthened with carbon fiber-reinforced polymer (CFRP) sheets. A total of 78 specimens were loaded to failure in axial compression and investigated in both axial and transverse directions. Slenderness of the columns, number of wrap layers and concrete strength were the test parameters. Compressive stress, axial and hoop strains were recorded to evaluate the stress-strain relationship, ultimate strength and ductility of the specimens. Results clearly demonstrate that composite wrapping can enhance the structural performance of square columns in terms of both maximum strength and ductility. On the basis of the effective lateral confining pressure of composite jacket and the effective FRP strain coefficient, new peak stress equations were proposed to predict the axial strength and corresponding strain of FRP-confined square concrete columns. This model incorporates the effect of the effective circumferential FRP failure strain and the effect of the effective lateral confining pressure. The results show that the predictions of the model agree well with the test data.

Confinement effect on the behavior factor of dual reinforced concrete moment-resisting systems with shear walls

  • Alireza Habibi;Mehdi Izadpanah;Yaser Rahmani
    • Structural Engineering and Mechanics
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    • 제85권6호
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    • pp.781-791
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    • 2023
  • Lateral pressure plays a significant role in the stress-strain relationship of compressed concrete. Concrete's internal cracking resistance, ultimate strain, and axial strength are improved by confinement. This phenomenon influences the nonlinear behavior of reinforced concrete columns. Utilizing behavior factors to predict the nonlinear seismic responses of structures is prevalent in seismic codes, and this factor plays a vital role in the seismic responses of structures. This study aims to evaluate the confining action on the behavior factor of reinforced concrete moment resisting frames (RCMRFs) with shear walls (SWRCMRFs). To this end, a diverse range of mid-rise SW-RCMRFs was initially designed based on the Iranian national building code criteria. Second, the stress-strain curve of each element was modeled twice, both with and without the confinement phenomenon. Each frame was then subjected to pushover analysis. Finally, the analytical behavior factors of these frames were computed and compared to the Iranian seismic code behavior factor. The results demonstrate that confining action increased the behavior factors of SW-RCMRFs by 7-12%.

벌크 비정질 Zr-Ti-Cu-Ni-Be 합금의 고온 압축 변형 특성 (High Temperature Compressive Deformation Behavior of the Bulk Metallic Glass Zr-Ti-Cu-Ni-Be Alloy)

  • 이광석;하태권;안상호;장영원
    • 소성∙가공
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    • 제10권7호
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    • pp.565-572
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    • 2001
  • It is well known that a multicomponent $Zr_{4l.2}Ti_{13.8}Cu_{12.5}Ni_{10}Be_{22.5}$ bulk metallic glass alloy shows good bulk glass forming ability due to its high resistance to crystallization in the undercooled liquid state. DSC and XRD have been performed to confirm the amorphous structure of the master alloy. To investigate the mechanical properties and deformation behavior of the bulk metallic $Zr_{4l.2}Ti_{13.8}Cu_{12.5}Ni_{10}Be_{22.5}$ alloy, a series of compression tests has been carried out at the temperatures ranging from $351^{\circ}C$ to $461^{\circ}C$at the various initial strain rates from $2{\times}10^4s^1$ to $2{\times}10^2s^1$. Three types of nominal stress-strain curves have been identified such as linear stress-strain relationship meaning fracture at maximum stress, plastic deformation including stress overshoot and steady-state flow, plastic deformation without stress overshoot depending on the strain rate and test temperature. Also DSC analysis for the compressed specimens was carried out to investigate the change of structure, thermal stability and crystallization behavior for the various test conditions.

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