• 한국구조물진단유지관리공학회 논문집
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• 제10권4호
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• pp.183-193
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• 2006

본 연구는 탄소섬유시트로 보강된 철근콘크리트 보에 정적하중과 반복하중이 작용할 때의 거동을 다루고 있다. 탄소섬유시트로 보강된 RC보의 정적실험 결과를 기준으로 반복하중 실험을 수행하였다. 반복하중 실험의 변수는 탄소섬유시트 겹수, 단부 U밴드 유무, 반복하중 재하속도 등이 있다. 실험결과를 통해 단조증가하중과 반복하중 하에서의 에너지 소산량과 휨 강성의 변화, 연성특성, 강도특성, 휨 거동 등을 고찰하며, 또한 탄소섬유시트의 파단변형률을 평가하였다. 본 연구에서는 반복하중 실험 결과를 바탕으로 탄소섬유시트로 보강된 RC보의 정적 및 동적 휨 보강 해석 및 설계에 필요한 기초자료를 제시하고자 한다.

• Wind and Structures
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• 제37권3호
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• pp.229-243
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• 2023

This study analyzes the response of a tall building with an H-shaped cross-section when subjected to wind loading generated by the same H-shape. As normative standards usually adopt regular geometries for determining the wind loading, this paper shows unpublished results which compares results of the dynamic response of H-shaped buildings with the response of simplified section buildings. Computational Fluid Dynamics (CFD) is employed to determine the steady wind load on the H-shaped building. The CFD models are validated by comparison with wind tunnel test data for the k-ε and k-ω models of turbulence. Transient wind loading is determined using the Synthetic Wind Method. A new methodology is presented that combines Stochastic and CFD methods. In addition, time-history dynamic structural analysis is performed using the HHT method for a period of 60 seconds on finite element models. First, the along-wind response is studied for wind speed variations. The wind speeds of 28, 36, 42, and 50 m/s at 0° case are considered. Subsequently, the dynamic response of the building is studied for wind loads at 0°, 45°, and 90° with a wind speed of 42 m/s, which approximates the point of resonance between gusts of wind and the structure. The response values associated with the first two directions for the H-shaped building are smaller than those for the R-shaped (Equivalent Rectangular Shape) one. However, the displacements of the H-shaped building associated with the latter wind load are larger.

• 한국지진공학회논문집
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• 제6권2호
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• pp.21-28
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• 2002

Ductile behavior and strength of concrete-filled steel(CFS) piers was supported by many quasi-static cyclic loading tests. This test method, however, only estimates the member′s deformation capacity under escalating and repetitive displacement and ignores dynamic and random aspects of an earthquake load. Therefore, to understand complete seismic behavior of the structure against an earthquake, dynamic tests such as shaking table test and pseudo-dynamic tests are required as well as quasi-static tests. In this paper, following "Seismic Performance of Concrete-Filled Steel Piers Part I : Quasi-Static Cyclic Loadint Test", the seismic behavior of CFS and steel piers designed for I-Soo overpass in Seoul in investigated by the pseudo-dynamic test. In addition, the residual strength of both piers after an earthquake is estimated by the quasi-static test. The results show that both piers have satisfactory ductility and strength against well-known EI Centro earthquake although the CFS pier has better strength and energy dissipation than the steel pier.

• 대한토목학회논문집
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• 제32권4A호
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• pp.245-253
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• 2012

본 연구에서는 장대터널이나 지하차도 등에 시공되는 횡류식 환기시스템을 구성하는 내화패널이 부착된 프리캐스트 풍도슬래브의 구조성능을 평가하기 위해서 실물모형 구조실험을 수행하였다. 또한, 내화패널의 휨강도와 Pull-off test를 통하여 내화패널과 슬래브의 부착성능 등의 기초성능을 우선적으로 확인하였다. 실물모형시험은 내화패널과 프리캐스트 PSC 슬래브의 정적 휨성능과 차량의 통행 시 발생하는 표면압력 이상의 하중에 대한 동적피로부착성능을 평가하였다. 동적피로하중 시험에서 내화패널과 PSC 슬래브 사이의 탈락이나 손상은 발생하지 않았으며, 정적재하시험에서도 매우 안정적인 거동을 보였으며, 하부에 부착된 내화패널의 탈락은 발생하지 않았다. 따라서 시공 중이나 시공 후 외부하중에 의해 내화패널의 탈락은 발생하지 않을 것으로 판단된다.

• 한국철도학회논문집
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• 제7권1호
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• pp.32-36
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• 2004

Aluminum carbody for rolling stocks is light and perfectly recycled, but includes severe defects which are very dangerous to fatigue strength. Static load test has been performed up to date to assess structural safety of the carbody. However, static load test is not sufficient to evaluate fatigue strength of the carbody, because fatigue failure is caused by dynamic load. In this study, the established load test methods for carbody are described and the characteristics of the methods are discussed. Also, a testing method to simulate dynamic loading condition is proposed for evaluation of fatigue strength of the carbody. The results by the proposed testing method are compared with the results by the static load test and new findings are discussed.

• Composites Research
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• 제27권4호
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• pp.135-140
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• 2014

발포 폴리우레탄의 변형거동을 설명하기 위해 제안된 구성방정식을 발포 폴리프로필렌에 적용하였다. 이 방정식은 7개의 매개변수를 갖고 있으며, 그중 5개의 변수는 기준 변형률속도에서 준정적 압축시험을 하여 얻은 결과를 커브 피팅하여 구하고, 나머지 두 변수는 변형률 속도를 다르게 한 준정적 압축시험으로부터 얻은 결과를 커브 피팅하여 구한다. 이렇게 구한 응력-변형률 방정식이 높은 변형률속도에서도 유효한지 알기 위해 충격시험으로부터 얻은 결과와 비교하였으며 30배와 40배로 발포된 폴리프로필렌 폼 시편에 대하여 각각 시행하였다.

• 대한기계학회논문집
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• 제17권7호
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• pp.1772-1782
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• 1993

The characteristics of metal matrix composite under dynamic tension at high strain rates up to the order of $10^3/sec$ is studied by using newly developed apparatus. The composite material processed in this research is aluminum-alumina metal matrix composites, arid fabricated by compocasting with the fiber volume fraction from 5 to 20%. The whisker and matrix material used in this paper were ${\delta}-Al_2O_3$ and Al-6061, respectively. The mechanical tests performed in this research are low and high strain rate tensile test. At low strain-rate tensile test, the modulus of elasticity and the ultimate tensile strength of the composites were improved about 77 pct. and 55 pct., respectively comparing with the unreinforced materials. At strain-rate from $10^{-3}\;to\;10^3/s$, the effect of strain-rate on the modulus, ultimate strength, flow stress is determined. Also the effect of strain rate on the modulus, ultimate tensile strength, flow stress and elongation to failures were investigated.

• 한국지반공학회논문집
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• 제19권4호
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• pp.265-275
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• 2003

본 연구에서는 매립지에서 사용되고 있는 토목섬유 (지오멤브레인, 지오텍스타일, 토목섬유 점토 차수재) 사이의 동적 접촉 마찰 특성을 평가하기 위해서 진동대 실험을 실시하였다. 동적 하중하에서 진동대와 하부에 토목섬유가 부착된 상자의 가속도, 이들 사이의 상대적 변위를 측정하였으며, 연직응력, 진동 주파수, 건조/수침 상태가 접촉면의 동적 거동 특성에 미치는 영향도 알아보았다. 실험 결과를 통해 동적하중이 감쇠없이 토목섬유 사이를 통과하는 한계 가속도가 존재함을 확인하였으며, 이를 이용하여 토목섬유 사이의 동적 접촉 마찰각을 산정할 수 있었다. 접촉면에서의 상대 변위는 접촉면의 형태와 건조/수침 상태에 따라 다르게 측정되었다. 각 토목섬유 접촉면에 대한 최대 상대변위는 무차원으로 정규화시켜, 가속도와 최대 미끄러짐 사이의 관계식을 구하였다. 이 식을 이용하면 주어진 가속도와 주파수에서, 토목섬유 사이를 따라 발생되는 최대 미끄러짐의 크기를 예측할 수 있다.

• 한국안전학회지
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• 제31권6호
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• pp.52-57
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• 2016

In this study, a restoring viscous damper is introduced for X-type damper system which is designed for the seismic response control of large spatial structures. A nonlinear numerical model for its behavior is developed using the result of dynamic loading tests. The X-type damper system is composed of restoring viscous dampers and connecting devices such as adjustable wire bracing, where the damping capacity of the system is controllable by changing the number of the dampers. The restoring viscous damper is devised to exert main damping force in tension direction, which is effective to prevent the buckling of bracing subjected to compressive axial force. To evaluate the performance of the proposed damper, dynamic cyclic loading tests are performed by using manufactured dampers at full scale. In order to construct the numerical model of the damper system, its model parameters are first identified using a nonlinear curve fitting method with the test data. The numerical simulations are then performed to validate the accuracy of the numerical model in comparison with the experimental test results. It is expected that the proposed system is effectively applicable to various building structures for seismic performance enhancement.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.590-599
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• 2006

In this study, Liquefaction characteristics of saturated sand under various dynamic loadings such as sinusoidal loading, increasing wedge loading, and real earthquake loading were investigated focusing on the dissipated energy. From the results of cyclic triaxial test, liquefaction resistance strength was calculated by the concept of energy according to the type of input loading. Liquefaction resistance strength was expressed in accumulated dissipated energy calculated from stress-strain curve(hysteresis loop). The dissipated energy according to loading type was compared and the energy-based evaluation was proposed. The procedures are presented in terms of normalized energy demand(NED), normalized energy capacity(NEC), and factor of safely, where NED is the load imparted to the soil by the loading(both amplitude and duration), NEC is the demand required to induce liquefaction, and factor of safely is defined as the ratio of NEC and NED.