• 제목/요약/키워드: nominal strength

검색결과 285건 처리시간 0.029초

AE에 의한 SK-5강의 파괴기구 구명 (On Fracture Mechanism of SK-5 Steel by AE Method)

  • 김상철;이억섭;함경춘;오범석
    • 한국정밀공학회지
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    • 제7권4호
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    • pp.130-139
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    • 1990
  • It is well known that mechanisms of fracture and crack growth depend upon material characteristics such as fracture toughness, environmental condition, crack geometry and mechanical properties. It seems to be very important to investighate the effects of the above factors on the behavior of structural components which contain flaws for the detailed evaluation of their integrity. In this experimental research, fracture behaviors of SK-5 high carbon steel was investigated by using Acoustic Emission(AE) technique. Fracturing processes of materials were estimated through both the tension test with nominal specimens and the fracture test with compact tension specimens. The critical applied load which corresponds to the crack initiation and propagation is very improtant for the determination of yield strength of fracture toughness. The critical applied load($P_Q$) was determined through AE method and the source of AE signal was estimated by fractography analysis. The experimental results may contribute to the safety analyses and strength evaluation of structures.

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Hot-spot 응력을 이용한 십자형 필렛 용접재의 피로강도 평가 (Fatigue Strength Assessment of the Cruciform Fillet Welded Joint Using Hot-spot Stress Approach)

  • 석창성;김대진;구재민;서정원;구병춘
    • 대한기계학회논문집A
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    • 제29권11호
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    • pp.1488-1493
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    • 2005
  • In this study, fatigue tests to obtain S-N curves and FE analyses to obtain structural stress concentration factors were conducted for the two types of cruciform fillet welded joints, that is, load-carrying and non load-carrying types. Then we changed the obtained S-N curve of load carrying joint to that based on hot spot stress. As a result, the S-N curve of load carrying joint based on hot-spot stress was almost exactly coincided with that of non load-carrying joint based on nominal stress. So we have conducted that the fatigue strength of a welded joint with different geometry from the non stress distribution along the expected crack path.

응력집중을 고려한 십자형 필렛 용접재의 피로강도 평가 (Fatigue Strength Assessment of the Cruciform Fillet Welded Joint Considering Stress Concentration at Weld Toe)

  • 김대진;석창성;구재민;박재실;서정원;구병춘
    • 한국철도학회:학술대회논문집
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    • 한국철도학회 2004년도 추계학술대회 논문집
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    • pp.222-227
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    • 2004
  • Under cyclic loading, the fatigue failures of welded joints occur at weld toes which induce stress concentration by weld shape. So we need to obtain the peak stress and the S-N curve to assess the fatigue strength of welded joints. However the measurement of peak stress is of high uncertainty and low reproducibility, so we use nominal stress instead in fatigue tests of welded joints. In this study, fatigue tests to obtain S-N curves and FE analyses to obtain stress concentration factors were conducted for the two types of cruciform fillet welded joints, that is, load-carrying and non load-carrying types. Then we changed the obtained S-N curves to that based on peak stress using the hot-spot stress concept. From the analyses of the S-N curves obtained, we have concluded that there is a need to develop a new method to evaluate the fatigue life.

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춤이 깊은 고강도 철근콘크리트 보의 수평전단철근 효과에 관한 연구 (The Effects on Horizontal Web Reinforcements for Reinforced High Strength Concrete Deep Beams)

  • 신성우;성열영;안종문;이광수;박무용;김형준
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 1996년도 가을 학술발표회 논문집
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    • pp.337-344
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    • 1996
  • Reinforced concrete deep beams with conpressive strengths in the range of 500kg/$\textrm{cm}^3$~750kg/$\textrm{cm}^3$ were tested under two-point loding. All the beams were singly reinforced with main steel percent $\rho$=1.29% and with nominal percentage of vertical shear reinflrcements $\rho_v$=0.26%. According to shear-span to depth ratio a/d. The beams were tested for four horizontal shear reinforcement ratio $\rho_h$, ranging from$\rho_h$=0.0 to $\rho_h$=0.53. The results indicate that the horizontal shear reinforcements of beams have an effect on failure load and on ductile behavior of deep beams. The test results are compared with predictions based on the current ACI Building Code. The computated reports in the paper will have designers assured for design of high strength concrete deep beam. Though ACI Code is relatively conservative and tend to non-economical, ACI Code has the merit that is easy to use.

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Seismic performance of high strength steel frames with variable eccentric braces based on PBSD method

  • Li, Shen;Wang, Ze-yu;Guo, Hong-chao;Li, Xiao-lei
    • Earthquakes and Structures
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    • 제18권5호
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    • pp.527-542
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    • 2020
  • In traditional eccentrically braced steel frames, damages and plastic deformations are limited to the links and the main structure members are required tremendous sizes to ensure elasticity with no damage based on the force-based seismic design method, this limits the practical application of the structure. The high strength steel frames with eccentric braces refer to Q345 (the nominal yield strength is 345 MPa) steel used for links, and Q460 steel utilized for columns and beams in the eccentrically brace steel frames, the application of high strength steels not only brings out better economy and higher strength, but also wider application prospects in seismic fortification zone. Here, the structures with four type eccentric braces are chosen, including K-type, Y-type, D-type and V-type. These four types EBFs have various performances, such as stiffness, bearing capacity, ductility and failure mode. To evaluate the seismic behavior of the high strength steel frames with variable eccentric braces within the similar performance objectives, four types EBFs with 4-storey, 8-storey, 12-storey and 16-storey were designed by performance-based seismic design method. The nonlinear static behavior by pushover analysis and dynamic performance by time history analysis in the SAP2000 software was applied. A total of 11 ground motion records are adopted in the time history analysis. Ground motions representing three seismic hazards: first, elastic behavior in low earthquake hazard level for immediate occupancy, second, inelastic behavior of links in moderate earthquake hazard level for rapid repair, and third, inelastic behavior of the whole structure in very high earthquake hazard level for collapse prevention. The analyses results indicated that all structures have similar failure mode and seismic performance.

비내진 설계된 RC 골조에 대한 전단강도 감소 효과를 고려한 수치해석의 비교 (Comparisons of Numerical Analyses considering the Effects of Shear Strength Degradation For Nonseismic Designed RC Frame)

  • 이영욱
    • 한국지진공학회논문집
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    • 제10권1호
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    • pp.1-8
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    • 2006
  • 비내진 설계된 철근콘크리트 골조는 내진상세의 미확보로 인하여 전단파괴의 가능성이 있다. 이러한 전단파괴를 해석 모델링에 반영하기 위하여 Moehle과 ATC 40을 포함한 4개의 전단강도감소 모델을 선택하고 비교하였으며, 각 모델을 예제 건물에 적용하여 Push-over해석을 수행하였다. 해석용 예제 모델은 3층 규모로 하였으며 국내 콘크리트 설계기준에 따라 설계하였다. 전단강도 감소모델 비교 결과, Moehle의 모델은 NZSEE의 모델보다 전단내력을 작게 평가하고 ATC 40 모델에 비하여 휨 연성도에 따른 내력의 변동이 작으며, 대부분의 경우에 고찰된 모델들의 전단내력은 ACI 318의 공칭 전단강도보다 크게 나타남을 알 수 있었다. 예제 모델의 수치해석 비교 결과, 전단강도 감소모델에 따라 건물의 수평 저항 능력에 큰 차이가 나타나며, 전단스프링에 전단강도 감소를 고려한 모델에 비하여 ATC 40의 횡 소성 변형을 제한하는 모델을 사용하면 횡저항 능력을 과소평가하게 됨을 알 수 있었다.

H형강 매입형 합성기둥의 부착강도 및 전단연결재의 전단거동 (Bond Strength between Concrete and Steel and Shear Behavior of Shear Connectors of H-shaped Steel Encased Composite Columns)

  • 왕녕;이혜림;이명재
    • 한국강구조학회 논문집
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    • 제29권5호
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    • pp.377-387
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    • 2017
  • 이 연구에서는 강판 매입형 합성기둥의 Push-out Test를 통해 강재와 콘크리트의 부착면적에 따른 영향을 알아보았다. 이로써 부착면적이 넓을수록 부착응력은 작아진다는 경향이 조사되었다. 또한 소규모 매입형 합성기둥의 경우에는 설계기준에서 제시하는 공칭부착 응력값이 과소하게 적용되는 것을 확인하였다. 다음으로 H형강 매입형 합성기둥의 Push-out Test를 통해 전단연결재의 수와 간격에 따른 영향을 알아보았다. 이로써 전단연결재의 전단거동을 파악할 수 있었다.

Axial behavior of RC columns strengthened with SCC filled square steel tubes

  • Lu, Yi-Yan;Liang, Hong-Jun;Li, Shan;Li, Na
    • Steel and Composite Structures
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    • 제18권3호
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    • pp.623-639
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    • 2015
  • Self-compacting Concrete (SCC) Filled Square steel Tubes (SCFST) was used to strengthen square RC columns. To establish the efficiency of this strengthening method, 17 columns were tested under axial compression loading including 3 RC columns without any strengthening (WRC), 1 RC column strengthened with concrete jacket (CRC), 13 RC columns strengthened with self-compacting concrete filled square steel tubes (SRC). The experimental results showed that the use of SCFST is interesting since the ductility and the bearing capacity of the RC columns are greatly improved. The improvement ratio is significantly affected by the nominal wall thickness of steel tubes (t), the strength grade of strengthening concrete (C), and the length-to-width ratio (L / B) of the specimens. In order to quantitatively analyze the effect of these test parameters on axial loading behavior of the SRC columns, three performance indices, enhancement ratio (ER), ductility index (DI), and confinement ratio (CR), were used. The strength of the SRC columns obtained from the experiments was then employed to verify the proposed mode referring to the relevant codes. It was found that codes DBJ13-51 could relatively predict the strength of the SRC columns accurately, and codes AIJ and BS5400 were relatively conservative.

Shear performance of an innovative UHPFRC deck of composite bridge with coarse aggregate

  • Qi, Jianan;Wanga, Jingquan;Feng, Yu
    • Advances in concrete construction
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    • 제7권4호
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    • pp.219-229
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    • 2019
  • This paper presents an experimental study on the structural performance of an innovative ultra-high performance fiber reinforced concrete (UHPFRC) deck with coarse aggregate of composite bridge under shear force. Test parameters included curing method and shear span-to-height ratio. Test results indicated that more short fine cracks developed beside the existing cracks due to the randomly dispersed fibers, resulting in re-distributing and homogenizing of the concrete stress beside cracks and allowing for the occurrence of more cracks with small spacing compared to normal strength concrete beams. Curing methods, incorporating steam curing and natural curing, did not have obvious effect on the nominal bending cracking strength and the ultimate strength of the test specimens. Shear reinforcement need not be provided for UHPFRC decks with a fiber volume fraction of 2%. UHPFRC decks showed superior load resistance ability after the appearance of cracks and excellent post-cracking deformability. Lastly, the current shear provisions were evaluated by the test results.

새로운 형태의 선설치 인서트 앵커에 대한 단조 인장 및 전단강도 평가 (Tensile and Shear Strengths of New Type of Cast-in-Place Concrete Insert Anchors Under Monotonic Loading)

  • 전주성;김지훈;오창수;이창환
    • 한국공간구조학회논문집
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    • 제21권2호
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    • pp.49-56
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    • 2021
  • The damage to non-structural elements in buildings has been increasing due to earthquakes. In Korea, post-installed anchors produced overseas have been mainly used for seismic anchorage of non-structural components to structures. Recently, a new cast-in-place concrete insert anchor installed in concrete without drilling has been developed in Korea. In this paper, an experimental study was conducted to evaluate the tensile and shear strengths of the newly developed anchor under monotonic load. The failure modes of the tension specimens were divided into concrete breakout failure and steel failure, and all shear specimens showed steel failure. In both tension and shear, the maximum loads of specimens were greater than the nominal strengths predicted by the concrete design code (KDS 14 20 54). As a result, it is expected that the current code can also be used to calculate the strength of the developed cast-in anchor.