• 제목/요약/키워드: Strength level

검색결과 3,201건 처리시간 0.027초

압축강도 수준에 따른 HPFRCC의 동적충격 인장강도 평가 (Evaluation of Dynamic Tensile Strength of HPFRCC According to Compressive Strength Level)

  • 박기준;김원우;박정준;문재흠;김성욱
    • 한국구조물진단유지관리공학회 논문집
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    • 제22권3호
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    • pp.31-37
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    • 2018
  • 이 논문은 압축강도 수준(100, 140, 180 MPa급)에 따른 HPFRCC의 동적충격 인장강도를 평가하였다. 먼저 100, 140, 180 MPa급 HPFRCC의 압축응력-변형률 관계를 분석한 결과 압축강도는 각각 112, 150, 202 MPa로 나타났으며, 압축강도가 높아짐에 따라 탄성계수도 증가하는 경향을 나타내었다. 100, 140, 180 MPa급 HPFRCC의 정적 인장강도는 각각 10.7, 11.5, 16.5 MPa로 나타났으며, 압축강도가 높아질수록 인장강도도 증가하는 경향을 나타내었다. 반면 100 및 140 MPa급 HPFRCC에서의 인장강도 및 에너지 흡수능력은 압축강도 수준에 따라 큰 차이를 보이지 않았다. 이는 시험체의 규격 및 강섬유의 배열에 영향을 받은 것으로 판단된다. HPFRCC의 동적충격 인장강도를 평가한 결과, 변형률 속도가 10-1/s에서 150/s로 증가할수록 모든 HPFRCC의 인장강도와 동적증가계수는 증가하는 경향을 보였다. 한편 동일한 범위의 변형률 속도에서 HPFRCC의 압축강도가 낮을수록 인장강도에 대한 DIF가 높게 측정되어 효율적인 측면에서는 100 MPa급 HPFRCC가 가장 우수한 것으로 나타났다. 따라서 높은 수준의 인장성능이 요구되는 경우 높은 압축강도를 가지는 HPFRCC를 사용하는 것이 유리하며, 폭발과 같은 고속변형률 속도에서 보다 효율적인 접근을 위해서는 목표 압축강도에 근접한 HPFRCC를 사용하는 것이 바람직한 것으로 판단된다.

Effect of Joint Reformation on Adhesive Strength of 6061 Aluminum Alloy to Polycarbonate Lap Structures

  • D. W. Seo;Kim, H. J.;J. K. Lim
    • International Journal of Korean Welding Society
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    • 제4권1호
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    • pp.53-60
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    • 2004
  • Adhesive-bonded joints are widely used in the industry. Recently, applications of adhesive bonding joints have been increased extensively in automobile and aircraft industry. The strength of adhesive joints is influenced by the surface roughness, adhesive shape, stress distribution, and etc. However, the magnitude of the influence has not yet been clarified because of the complexity of the phenomena. In this study, as the fundamental research of adhesive bonding joints, the effects of adhesive shape and loading speed on bonding strength properties and durability of aluminum to polycarbonate single-lap joints were studied. To evaluate the effect of adhesive shape, several modified shapes were used, and loading speeds were varied from 0.05 to 5mm/min. As a result, the load distribution showed a brittle fracture tendency. The trigonal edged single lap and bevelled lap joints showed the higher strength than the plain single lap, trigonal single lap, joggle lap and double lap joints in same adhesive area. The fractures of trigonal single lap and trigonal edged single lap joints that had the higher strength level were shown as the mixture type of the cohesive and interfacial-failure, mostly joggle lap joints that had the lower strength level were shown as the adhesive-failure.

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에폭시 접착제 접합구조물의 강도향상을 위한 접착부 형상설계 (Shape Design of Adhesive Joints for Strength Improvement of Epoxy Adhesive Structures)

  • 서도원;김효진;임재규
    • 대한기계학회논문집A
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    • 제28권6호
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    • pp.783-790
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    • 2004
  • Adhesive-bonded joints are widely used in the industry. Recently, applications of adhesive bonding joints have been increased extensively in automobile and aircraft industry. The strength of adhesive joints is influenced by the surface roughness, adhesive shape, stress distribution, and etc. However, the magnitude of the influence has not yet been clarified because of the complexity of the phenomena. In this study, as the fundamental research of adhesive bonding joints, the effects of adhesive shape and loading speed on bonding strength properties and durability of aluminum to polycarbonate single-lap joints were studied. To evaluate the effect of adhesive shape, several modified shapes were used, and loading speeds were varied from 0.05 to 5 mm/min. As a result, the load-displacement distribution was shown a brittle fracture tendency. The trigonal edged single lap and bevelled lap joints showed the higher strength than the plain single lap, trigonal single lap, joggle lap and double lap joints in same adhesive area. The fractures of trigonal single lap and trigonal edged single lap joints that had the higher strength level were shown as the mixture type of the cohesive and interfacial-failure, mostly joggle lap joints that had the lower strength level were shown as the adhesive-failure.

Parametric study on the lateral strength of URM wall, retrofitted using ECC mortar

  • Niasar, Alireza Namayandeh;Alaee, Farshid Jandaghi;Zamani, Sohail Majid
    • Earthquakes and Structures
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    • 제18권4호
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    • pp.451-466
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    • 2020
  • In this paper, the effect of Engineered Cementitious Composites (ECC) on the lateral strength of a bearing unreinforced Masonry (URM) wall, was experimentally and numerically investigated. Two half scale solid walls were constructed and were tested under quasi-static lateral loading. The first specimen was an un-retrofitted masonry wall (reference wall) while the second one was retrofitted by ECC mortar connected to the wall foundation via steel rebar dowels. The effect of pre-compression level, ECC layer thickness and one or double-side retrofitting on the URM wall lateral strength was numerically investigated. The validation of the numerical model was carried out from the experimental results. The results indicated that the application of ECC layer increases the wall lateral strength and the level of increment depends on the above mentioned parameters. Increasing pre-compression levels and the lack of connection between the ECC layer and the wall foundation reduces the influence of the ECC mortar on the wall lateral strength. In addition, the wall failure mode changes from flexure to the toe-crashing behavior. Furthermore, in the case of ECC layer connected to the wall foundation, the ECC layer thickness and double-side retrofitting showed a significant effect on the wall lateral strength. Finally, a simple method for estimating the lateral strength of retrofitted masonry walls is presented. The results of this method is in good agreement with the numerical results.

탄소섬유/에폭시 복합재료의 잔류강도 저하해석에 의한 피로수명 평가 (Evaluation of the Fatigue Life for Carbon/Epoxy Composite Material by the Residual Strength Degradation Analysis)

  • 심봉식;성낙원;옹장우
    • 대한기계학회논문집
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    • 제15권6호
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    • pp.1908-1918
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    • 1991
  • 본 연구에서는 피로 잔류강도저하(fatigue residual strength degradation) 개념을 이용하여 복합재료의 잔류강도와 피로수명을 예측하고 실험을 통하여 비교 평 가하였으며, 설계시 고려되어야 할 인자를 파악하여 파손방지를 위한 유한 수명설계 및 손상허용설계의 기본자료를 집적함으로서 새로운 소재인 탄소섬유 강화 복합재료의 신뢰성 향상을 위한 개발과 고강도 경량화를 위한 이용설계에 활용할 수 있도록 하는 데 그 목적이 있다.

가정노인과 양로원노인의 체력, 자기효능, 일상생활활동능력 및 삶의 질에 관한 연구 (Comparisons of physical Fitness, Self Efficacy, Instrumental Activities of Daily Living, and Quality of Life between Institutionalized and Noninstitutionalized Elderly)

  • 노유자;김춘길
    • 대한간호학회지
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    • 제25권2호
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    • pp.259-278
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    • 1995
  • This study was done to investigate levels of physical fitness, self efficacy(SE), instrumental activities of daily living(IADL), and quality of life (QL), and their relationships among the elderly Data were collected from 47 noninstitutionalized elderly dwell-ing in their own homes and 43 institutionalized elderly living in homes for older people. The ages of the subjects were 65 years and over. The data were col lected from January 20th to February 20th, 1995. Physical fitness was measured with T.K. K dyna mometer, grip dynamometer, stop watch, and Purdue pegboard. Structured questionnaires developed by Kim by Lawton & Brody, and by Ro were adopted to measure SE, IADL, and QL, respectively. The data were analyzed using t-test, ANOVA, and Pearson correlation coefficients. The results were as follows : 1. The noninstitutionalized elderly had higher scores in such measures of physical fitness as body weight, skinfold thickness, flexibility and coordination as compared to the institutionalized elderly. 2. On the following measures of physical fitness, men showed higher levels than women ; in height when standing, height when sitting, body weight, and muscle strength. Women had more trunk flexibility than men. 3. Muscle strength was positively correlated with height when standing, height when sitting, and body weight. The following measures of physical fitness, muscle strength, flexibility and coordi nation, were negatively correlated with "up and go”. 4. The noninstitutionalized elderly had higher scores in SE(t=2.28, p<0.05), IADL(t=2.24, p<0.05), and QL(t=2.41, p<0.05) as compared to the institutionalized elderly. 5. SE was positively correlated with both IADL(r=0.41, p<0.001) and QL(r=0.54, p<0.001), and the latter two variables were a positively correlated (r=0.30, p<0.001). 6. SE was positively correlated with the physical fitness measures of height when standing, body weight, strength of leg muscles, strength of back muscles, grip strength, and level of touching the floor, but negatively correlated with "up and go”. 7. Positive correlations were revealed between IADL and the physical fitness measures of height, strength of leg muscles, level of trunk muscle extension, level of touching the floor, and coordination. The IADL was negatively correlated with “up and go”. 8. QL was positively correlated with body weight (r=0.28, p<0.01) and skinfold thickness (r=0.26, p<0.05). 9. Age was negatively correlated with the physical fitness measures of height when standing, height when sitting, “up and go”, strength of leg muscles, strength of back muscles, grip strength, level of trunk muscle extension, and coordination. 10. Age was also negatively correlated with SE (r=-0.24, p<0.05) and IADL(r=-0.22, p<0.05). The above results suggest that caring elderly in their own homes were more effective and that nursing interventions to enhance physical fitness, SE, IADL, and QL especially for the institutionalized elderly are stressed.

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철도차량 슬라이드식(텔레스코픽) 승강문 스텝의 강도평가 (Strength Evaluation of Telescopic Sliding Doorstep Equipment for Railway Vehicle)

  • 김철수;박민흥
    • 한국철도학회논문집
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    • 제15권4호
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    • pp.352-356
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    • 2012
  • 국내 여객열차 전용 승강장은 높이에 따라 두 가지 종류로서, 일반 간선열차에서 주로 사용하는 저상 승강장과 수도권 전동차에서 주로 사용하는 고상승강장으로 구분된다. 중 고속 열차가 수도권 전철구간과 본 선구간에서 혼용할 경우에 안전운전 및 승객편의를 함께 고려하기 위해서는 저상/고상 승강장에 상관없이 승하차할 수 있는 승강문 스텝장치가 필요하다. 본 연구에서는 전철역사 및 일반 철도역사에서 모두 승하차가 가능한 저상/고상 승강장 겸용 승강문 스텝 개념설계(안)의 구조해석 및 강도시험을 수행하고 이의 안전성을 검토하였다.

탄소/에폭시 복합재판의 압축강도 두께효과에 대한 연구 (Thickness Effect on the Compressive Strength of T800/924C Carbon Fibre-Epoxy Laminates)

  • 공창덕;이정한
    • 한국복합재료학회:학술대회논문집
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    • 한국복합재료학회 2004년도 춘계학술발표대회 논문집
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    • pp.173-177
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    • 2004
  • In this study, the effect of laminate thickness on the compressive behaviour of composite materials was investigated through systematic experimental work using the stacking sequences, [04]ns, [45/0/-45/90]ns and [45n/0n/-45n/90n]s (n = 2 to 8). The stacking sequence effects on failure strength of multidirectional laminates were examined. For this purpose, two different scaling techniques were used; (1) ply-level technique [45n/0n/-45n/90n]s and (2) sub laminate level technique [45/0/-45/90]ns. An apparent thickness effect existed in the lay-up with blocked plies, i.e. unidirectional specimens $([0_4]ns)$ and ply-level scaled multidirectional specimens ([45n/0n/-45n/90n]s). From the investigation of the stacking sequence effect, the strength values obtained from the sub laminate level scaled specimens were slightly higher than those obtained from the ply level scaled specimens. The measured failure strengths were compared with the predicted values

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잔향음의 음압레벨 변화에 따른 연주자의 무대음향 주관평가 (Subjective Evaluation of Stage Acoustics with the Alteration of the Sound Pressure Level of Reverberation)

  • 김영선;정정호;전진용
    • 한국소음진동공학회논문집
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    • 제27권2호
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    • pp.129-138
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    • 2017
  • The subjective experiments on professional musicians using the four channel real-time convolution system were conducted to investigate the effect of reverberant sound pressure level ($L_{rev}$) for stage acoustics. The strength of $L_{rev}$ was changed to 2 dB steps to investigate the optimal strength for ease of performance and the subjective questionnaire survey was conducted to investigate the effect of subjective factor by $L_{rev}$. From the experimental results, a specific strength of $L_{rev}$ is related to ease of music performance. Loudness and directivity are highly correlated.

경량잔골재 치환율에 따른 경량콘크리트의 슬럼프 손실과 압축강도 (Slump Loss and Compressive Strength of Lightweight Concrete according to the Replacement Level of Lightweight Fine Aggregate)

  • 심재일;양근혁;이재삼
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 2010년도 춘계 학술대회 제22권1호
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    • pp.227-228
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    • 2010
  • 경량콘크리트의 유동성과 압축강도에 대한 경량잔골재 치환율의 영향을 평가하기 위해 경량잔골재치환율을 주요변수로 5배합의 경량콘크리트가 배합되었다. 실험결과 경량잔골재의 치환율이 증가할수록 슬럼프 손실 기울기는 증가하였으며, 압축강도 발현율에는 큰 영향이 없었다.

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