• 제목/요약/키워드: static and fatigue load tests

검색결과 87건 처리시간 0.018초

Experimental study of buckling-restrained brace with longitudinally profiled steel core

  • Lu, Junkai;Ding, Yong;Wu, Bin;Li, Yingying;Zhang, Jiaxin
    • Structural Engineering and Mechanics
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    • 제81권6호
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    • pp.715-728
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    • 2022
  • A new type of buckling-restrained braces (BRBs) with a longitudinally profiled steel plate working as the core (LPBRB) is proposed and experimentally investigated. Different from conventional BRBs with a constant thickness core, both stiffness and strength of the longitudinally profiled steel core along its longitudinal direction can change through itself variable thickness, thus the construction of LPBRB saves material and reduces the processing cost. Four full-scale component tests were conducted under quasi-static cyclic loading to evaluate the seismic performance of LPBRB. Three stiffening methods were used to improve the fatigue performance of LPBRBs, which were bolt-assembled T-shaped stiffening ribs, partly-welded stiffening ribs and stiffening segment without rib. The experimental results showed LPBRB specimens displayed stable hysteretic behavior and satisfactory seismic property. There was no instability or rupture until the axial ductility ratio achieved 11.0. Failure modes included the out-of-plane buckling of the stiffening part outside the restraining member and core plate fatigue fracture around the longitudinally profiled segment. The effect of the stiffening methods on the fatigue performance is discussed. The critical buckling load of longitudinally profiled segment is derived using Euler theory. The local bulging behavior of the outer steel tube is analyzed with an equivalent beam model. The design recommendations for LPBRB are presented finally.

박막시험편용 고온 크리프 시험기의 설계 및 제작 (Design and Construction of a High Temperature Creep Tester for Thin Film Specimens)

  • 고경득;이상신;강기주
    • 대한기계학회논문집A
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    • 제31권2호
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    • pp.253-259
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    • 2007
  • A new material tester has been developed to measure mechanical properties of thin film specimens at high temperature. It is useful for observing oxide film growth or local deformation on the surface, and for measuring creep strength. Main characteristics of the tester is as follows; First, high temperature is achieved by Joule heating generated by electricity passing through the specimen, which does not need to enclose the specimen by a furnace or a heating chamber. The exposed specimen enables one to observe the surface during the test. Because the overall size of the test rig is compact, the whole test rig can be placed in a chamber for environmental controlled tests. The loading device is from a level scales. Not only static load with fixed counter weight, but also variable load by moving counter weight controlled remotely can be applied for an ordinary creep test and creep-fatigue test, respectively. The detail of the construction, operation principle, and the specification are described. And also, an example of test result obtained using the creep tester is presented.

태백선을 주행하는 화차 엔드빔의 진동특성에 관한 연구 (Vibrational Characteristics of an End Beam of a Freight Cal- on the Taebaek Line)

  • 문경호;홍재성;이동형;서정원;함영삼
    • 한국소음진동공학회논문집
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    • 제14권10호
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    • pp.962-967
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    • 2004
  • A bogie is the device that connects a car body and wheel sets of a rail vehicle. It is the critical component that determine:; the running safety, The bogie consists of a frame, suspensions, brakes and wheel sets. Various analyses including a numerical simulation using a finite element method, a static load test, a fatigue test, ai)d r running test should be carried out to design the bogie. However cracks have been found at some end beams of the bogies mounted on the freight cars running with the high speed. The cracks of the end beam results in deterioration of the brake performance an the running safety, A new design has been suggested to solve this problem by ROTEM company and it's performance has been tested in this paper. Numerical simulations and dynamic tests are carried out to figure out the causes of cracks in the conventional bogie, and the vibrational characteristics of the improved bogie are compared with those of the conventional one.

기계적 합성이 적용된 FRP-콘크리트 합성 바닥판의 거동 분석 (Behavior of FRP-Concrete Composite Decks with the Mechanical Connection)

  • 김성태;박성용;조정래;김병석;조근희
    • 콘크리트학회논문집
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    • 제22권5호
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    • pp.609-616
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    • 2010
  • FRP-콘크리트 합성 바닥판은 압축에 강한 콘크리트를 상부에 위치시키고 인장에 강한 FRP를 하부에 위치시켜, FRP와 콘크리트가 갖는 장점을 극대화시킴으로서 내구성, 안전성 등을 두루 향상시킨 새로운 개념의 구조이다. 그러나 서로 다른 재질의 두 재료를 합성시키기 위한 방안으로서 연구 초기에 적용된 규사코팅 공법 외에 수직부착력을 향상시킬 수 있는 기계적 합성 방안을 고안하였다. 이렇게 고안한 합성 방안이 적용된 실제 사이즈의 바닥판 실험체를 제작하여 정적 및 피로반복실험을 수행하였다. 정적실험 결과 이 연구에서 제안한 합성 방안이 적용된 바닥판이 처짐 및 균열 등에 대해서 설계기준을 충분히 만족시켜 매우 우수한 성능을 나타내고 있었으며, 피로실험 결과 파괴하중의 50%로 200만회 가력한 후에도 처짐 및 균열 등에 대해 설계기준을 만족하고 있어 충분한 피로내구성을 확보하고 있는 것으로 나타났다. 이에 이 연구에서 제시한 규사코팅과 기계적 합성 방안을 동시에 적용한 합성 방안은 FRP-콘크리트 합성 바닥판에 대해 충분한 적용성을 갖고 있으며, FRP-콘크리트 합성 바닥판 설계시 제시한 설계조건들이 적절하게 이용될 수 있음을 확인하였다.

박용재료(舶用材料)의 반복경화(反復硬化) 및 저(低)싸이클 피로특성(疲勞特性)에 관한 연구 (A Study on the Cyclic Hardening Property and the Low Cycle Fatigue Behavior of Marine Materials)

  • 조상명;굴천조보
    • 대한조선학회논문집
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    • 제28권1호
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    • pp.108-116
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    • 1991
  • 선용재료중(船用材料中)에는 정적하중(靜的荷重)에 의한 정적거동(靜的擧動)(응력-변형률관계)과 반복하중(反復荷重)에 의한 반복거동(反復擧動)(응력진폭-변형률진폭관계)이 상이(相異)하게 되는 경우가 많다. 특히 탄소성(彈塑性) 응력집중부(應力集中部)에서 진전(進展)하는 초기의 짧은 피로균열(疲勞龜裂)은 재료(材料)의 반복거동(反復擧動)에 크게 의존하여 성장하므로 재료(材料)의 정적(靜的) 및 반복거동(反復擧動)의 비교, 검토가 요구된다. 본 연구에서는 2종류의 철강재료(鐵鋼材料)(SS41, HT80)와 5종류의 Al합금(合金)(A5083-O, A6N01-T5, A7N01-T4, A7016-T6, A7178-T6)에 대하여 정적(靜的) 및 반복하중(反復荷重)에 의한 재료(材料)의 응력-변형율(應力-變形率) 관계(關係)를 비교, 검토하였고, 각(各) 재료상수(材料常數)를 구하였다. 또한 응력집중부(應力集中部)에 일정 진폭의 반복하중(反復荷重)이 작용(作用)하여 탄소성(彈塑性) 변형(變形)할 때 그 선단(先端)의 응력(應力)과 변형률(變形率) 진폭(振幅)의 변화(變化)에 미치는 재료(材料)의 반복(反復) 경화특성(硬化特性)의 영향에 대하여 Neuber법칙(法則)과 중앙(中央)노치재(材의) 실험(實驗)에 의하여 고찰(考察을 행하였다.

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Steel Strap으로 횡구속된 무철근 바닥판의 정적 및 피로거동 특성 연구 (A Study on Static and Fatigue Behavior of Restrained Concrete Decks without Rebar by Steel Strap)

  • 조병완;김철환
    • 한국구조물진단유지관리공학회 논문집
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    • 제16권5호
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    • pp.137-147
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    • 2012
  • 무철근 교량 바닥판은 콘크리트 내부의 철근을 없애고 거더를 Strap으로 횡구속시켜 Arching action을 극대화시킨 교량 바닥판이다. 본 연구에서는 무철근 바닥판의 균열제어를 목적으로 FRP bar의 배치량을 변수로 하여 내하력과 균열, 연성도, 파괴시 응력수준 등을 판단하여 FRP bar 최소 배치량을 제시하였다. 실험결과 Steel strap 무철근 바닥판은 최소 0.15% FRP 보강근만 배치하여도 내하력과 연성이 확연히 향상됨을 확인하였다. FRP bar를 보강한 무철근 바닥판에 대하여 피로실험을 수행하였으며 200만회 반복하중 재하후 균열, 잔류 처짐 등에서 장기 사용성에 문제가 없음을 확인하였다. 교량 바닥판은 대체로 펀칭전단 파괴를 하며 2방향 슬래브의 전단강도식을 적용할 수 있으나 ACI, AASHTO 등에서는 바닥판의 비선형 파괴형상과 횡구속에 의한 Arching 효과를 명확히 고려하지 못하기 때문에 실제 파괴강도보다 과소평가 한다. 본 연구에서는 Steel strap 바닥판의 실제 파괴형상과 Strap에 의한 횡구속도를 고려한 펀칭전단강도식을 제안하였으며 이는 실험결과와도 비교적 잘 일치하는 결과를 보여주었다.

반복 하중이 Full veneer crown의 유지력에 미치는 영향에 관한 연구 (THE EFFECT OF CYCLIC LOADING ON THE RETENTIVE STRENGTH OF FULL VENEER CROWNS)

  • 김기연;이선형;정헌영;양재호;허성주
    • 대한치과보철학회지
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    • 제38권5호
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    • pp.583-594
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    • 2000
  • Dislodgement of a crown or extension bridge and the loosening of a retainer of a bridge is a serious clinical problem in fixed restoration. Generally these problems are considered to be associated with deformation of the restoration. During biting, the restoration is subjected to complex forces and deforms considerably within the limit of its elasticity. Deformation of the restoration under the occlusal force induces excessive stress in the cement film, which then leads to the cement fracture. Such a fracture may eventually cause loss of the restoration. Because most of the past retention tests for full veneer crown were done without fatigue loading, they were not exactly simulating intraoral environment. And the purpose of this study was to evaluate the effect of cyclic cantilever loading on the retentive strength of full veneer crowns depending on different type of cements and taper of prepared abutment. Steel dies with $8^{\circ}\;or\;16^{\circ}$ convergence angle were fabricated through milling and crowns with the same method. These dies and crowns were divided into 8 groups. Group 1 : $16^{\circ}$ taper die, cementation with zinc phosphate cement, without loading Group 2 : $16^{\circ}$ taper die, cementation with zinc phosphate cement, with loading Group 3 : $8^{\circ}$ taper die, cementation with zinc phosphate cement, without loading Group 4 : $8^{\circ}$ taper die, cementation with zinc phosphate cement, with loading Group 5 : $16^{\circ}$ taper die, cementation with Panavia 21, without loading Group 6 : $16^{\circ}$ taper die, cementation with Panavia 21, with loading Group 7 : $8^{\circ}$ taper die, cementation with Panavia 21 without loading Group 8 : $8^{\circ}$ taper die, cementation with Panavia 21, with loading After checking the fit of die and crown, the luting surface of dies and inner surface of crowns were air-abraded for 10 seconds. The crowns were cemented to the dies, with cements mixed according to the manufacturer's recommendations. A static load of 5kg was then applied for 10 minutes with static loading device. Twenty-four hours later, group 1, 3, 5, 7 were only thermocycled, group 2, 4, 6, 8 were subjected to cyclic loading after thermocycling. Retentive tests were performed on the Instron machine. From the finding of this study, the following conclusions were obtained 1. Panavia 21 showed significantly higher retentive strength than zinc phosphate cement for all groups (p<0.05). 2. There was a significant difference in the retentive strength between $8^{\circ}\;and\;16^{\circ}$ taper for zinc phosphate cement(p<0.05), but no significant difference for Panavia 21 (p>0.05). 3. Cyclic loading significantly decreased the retentive strength for all groups(p<0.05). 4. For zinc phosphate cement, there was 35% reduction of the retentive strength after loading in the $16^{\circ}$ taper die, 25% in the $8^{\circ}$ taper die, and for Panavia 21, 21% in the $16^{\circ}$ taper die, 18% in the $8^{\circ}$ taper die.

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