• Steel and Composite Structures
• /
• 제9권3호
• /
• pp.255-274
• /
• 2009

This paper presents an experimental study of a newly developed composite floor system, built up from thin-walled C-profiles and upper concrete deck. Trapezoidal sheeting provides the formwork and the fastening of the sheet transmits the shear forces between the C-profiles and the deck. The modified formation of the standard self-drilling screw in the beam-to-sheet connection is applied as shear connector. Push-out tests are completed to study the composite behaviour of the different connection arrangements. On the basis of the test results the behaviour is characterized by the observed failure modes. The design values of the connection stiffness and strength are calculated by the recommendation of Eurocode 4. In the next phase of the experimental study six full-scale composite beams are tested. The global geometry is based on the proposed geometry of the developed floor system. The applied shear connections are selected as the most efficient arrangements obtained from the push-out tests. The experimental behaviour of the composite beams are discussed and evaluated. As a conclusion of the experimental study the Eurocode 4 plastic design method is validated for the developed composite floor.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2006년도 춘계학술대회논문집
• /
• pp.850-853
• /
• 2006

This paper presents a primary study for a new method of enhancing measurement using impedance analysis method, which is widely used for structure health monitoring. Many of skyscrapers, bridges, tunnels, which have been built up several years, and nearly reached their operating life due to aging crack, material deterioration, and so on. therefore, the health monitoring technique has obtained considerable attention. The usage of the PZT sensor is proposed, and the coupling torque of bolt-connection overlapping beam is assumed. By using the torque wrench, it is easy to apply torque of different values to each bolt. The coupling torque is adjusted gradually from $3N{\cdot}m\;to\;0N{\cdot}m$ with the decrement of $1N{\cdot}m$. Simultaneously, the impedance peak variation is measured. The peak frequency variation can be determined through the change of bolt coupling torque.

• Earthquakes and Structures
• /
• 제9권1호
• /
• pp.195-219
• /
• 2015

A partial (hybrid) seismic isolation scheme for precast girder bridges in the form of a "buffer-gap-elastomeric bearings" system has been endorsed in the literature as an efficient seismic design system. However, no guides exist to detail an optimal gap size for different configurations. A numerical study is established herein for different scenarios according to Euro code seismic requirements in order to develop guidelines for the selection of optimal buffer-gap arrangements for various design cases. Various schemes are hence designed for ductile and limited ductility behavior of the bridge piers for different seismic demand levels. Seven real ground records are selected to perform incremental dynamic analysis of the bridges up to failure. Bridges with typical short and high piers are studied; and different values of initial gaps at piers are also investigated varying from a zero gap (i.e., fully locked) condition up to an initial gap at piers that is three quarters the gap left at abutments. Among the main conclusions is that the as-built initial gaps at piers (and especially large gap sizes that are ${\geq}1/2$ as-built gaps at abutments) do not practically reduce the seismic design demand and do not affect the reserve capacity of the bridge against failure for bridges featuring long piers, especially when these bridges are designed a priori for ductile behavior. To the contrary, the "buffer-gap-elastomeric bearings" system is more effective for the bridge schemes with short piers having a large difference between the stiffness of the bearings and that of their supporting (much stiffer) squat piers, particularly for designs with limited ductility. Such effectiveness is even amplified for the case of larger initial as-built gap sizes at piers.

• 임산에너지
• /
• 제25권2호
• /
• pp.34-41
• /
• 2006

본 연구에서는 국산 중소경재를 보다 효과적으로 활용하기 위한 목적으로 제재 수율이 높은 대형요소를 이용하여 구조용으로 사용될 수 있는 공학목재를 개발하였다. 중소경 원목으로부터 생산된 상대적으로 큰 단면의 Flitch재를 이용하여 세 가지 기계적 접합방법을 적용한 구조용 대단면 공학목재를 개발하고 휨시험을 통해 그 성능을 평가하였다. 개별 요소를 접합하기 위한 기계적 접합방법으로는 강철 볼트와 목재 다우얼, 철제 래그 볼트가 각각 검토되었다. 개발된 공학목재의 휨성능을 평가한 결과, 강철 볼트를 적용한 경우에 MOR은 평균 $514kgf/cm^2$, MOE는 $129,000kgf/cm^2$ 대표적인 구조용 공학목재인 집성재에 비해 조금 낮거나 유사한 경향을 나타내었다. 목재 다우얼과 철제 래그 볼트를 적용한 경우에는 하중이 증가함에 따라 층재가 분리되어 개별적으로 하중에 저항함으로써 MOR과 MOE 모두가 절반정도로 감소되었다. 본 연구의 결과로부터 대형요소의 기계적 접합으로 제조되는 공학목재의 휨성능은 개별 요소의 접합 성능에 의해 가장 크게 영향 받음을 알 수 있었다.

• 한국음향학회지
• /
• 제21권1호
• /
• pp.73-81
• /
• 2002

본 논문에서는 중고주파영역에서의 진동해석기법인 파워흐름해석 법을 보와 평판이 연성된 구조물에 적용하기 위하여 무한보가 무한평판을 수직으로 투과하는 구조물에서의 파워투과반사계수를 파동전달법을 이용하여 구하였다. 이러한 파워투과반사계수를 실제 구조물에 적용하기 위해서는 파워흐름유한요소법으로의 활용이 필요하다. 이를 위해 본 논문에서는 파워투과반사계수를 이용하여 보 평판구조물을 위한 연결요소행렬식을 정립하였으며, 또한 보와 평판요소를 각각 해석할 수 있는 파워흐름유한요소해석 프로그램을 구성하고, 여기에 정립된 보와 평판간의 연결요소 행렬식을 대입하여 보와 평판이 연성된 구조물까지 해석이 가능한 프로그램으로 개발하였다. 이 프로그램을 이용하여 이상화한 선박의 선미부 구조물을 해석한 결과, 선박구조물에서 진동에너지분포를 구할 수 있었고, 진동 인텐시티를 통하여 구조물에서의 파워전달경로를 예측할 수 있었다.

• 한국강구조학회 논문집
• /
• 제20권6호
• /
• pp.711-722
• /
• 2008

기존 콘크리트충전 각형강관(CFT) 구조에 사용하는 각형강관은 4개의 판을 용접하여 제작하는 박스칼럼이 일반적이다. 그러나 이러한 강관은 제작효율이 저하되며, 또한 기둥-보 접합부에는 내측 다이아프램과 관통 다이아프램을 용접하는데 특수한 용접기술이 필요하다. 따라서, 얇은 강판을 절곡하는 방식으로 응력집중 위치의 용접을 피하고, 단면효율이 극대화된 내부앵커 돌출형의 각형강관을 개발하게 되었다. 본 연구에서는 이 개발된 강관의 기둥-보 접합부로 외다이아프램형식을 채택하고. 보 플랜지의 응력 전달을 명확히 하기 위한 기둥-보 접합부 상세를 확 정하고자 이 접합부에 대한 단순인장 실험체를 제작하여 성능평가 실험을 수행하였다. 이 실험을 통해 콘크리트충전 기둥-보 접합부의 기둥-보 플랜지 용접 유무, 기둥-다이아프램 용접량, 콘크리트 충전유무, 다이아프램 설치 기둥과 일반기둥의 비교 등에 따른 인장영역 응력분포 및 내력평가를 진행하고 내부 앵커와 콘크리트 사이의 합성효과를 파악하였다.

• Advances in concrete construction
• /
• 제11권5호
• /
• pp.429-445
• /
• 2021

With regard to economic efficiency, composite fix beams are widely used to pass longitudinal shear forces across the interface. The current knowledge of the composite beam load-slip activity and shear capability are restricted to data from measurements of push-off. Modelling and analysis of the composite beams based on Euro-code 4 regarding to shear, bending, and deflection under differing loads were carried out using Finite Element through an efficient computer simulation and the final loading and sections capacity based on the failure modes was analysed. In bending, the section potential was increased by an improvement of the strength in both steel and concrete, but the flexural and compressive resistance growth is very weak (3.2% 3.1% and 3.0%), while the strength of the concrete has increased respectively from 25 N/mm² to 30, 35, and 40 N/mm² compared to the increment of steel strength by 27% and 21% when it was raised from 275 to 355 and 460 N/mm², respectively. It was found that the final flexural load capacity of fix beams was declined with increase in the fix beam span for both three steel strength. The shear capacity of sections was remained unchanged at constant steel strength and different length, but raised with final yield strength increment of steel sections by 29%, and 67% when it was raised from 275 N/mm² to 355 N/mm² and 460 N/mm², respectively.

• 한국화재소방학회논문지
• /
• 제23권4호
• /
• pp.59-66
• /
• 2009

본 연구는 합성구조에 사용되는 스터드커넥터의 화재시 성능에 대한 연구이다. 스터드커넥터는 전단연결재로 가장 폭넓게 사용되고 있으며, 콘크리트와 강재를 일체화시켜 합성 성능을 확보한다. 스터드커넥터에 대한 상세 내화성능은 아직 명확한 자료가 없으며, 향후 성능설계에서 무피복 합성보 등에 대한 설계 자료로 요구 된다. 본 실험의 스터드커넥터 성능시험은 푸시 아웃 실험을 변형하여 특수 전기로와 결합 ISO 표준온도곡선을 기본으로 거동 성능실험을 수행하였으며, 화재 조건의 파괴 형상을 기반으로 성능 분석 방법을 제안하였다.

• 한국광학회:학술대회논문집
• /
• 한국광학회 2000년도 하계학술발표회
• /
• pp.3-3
• /
• 2000

Adaptive Optical (AO) technology can compensate for wave-front errors in real-time to improve image and beam quality. The research and development on AO in China began in 1979. In 1980, the first laboratory on AO in China was established in Institute of Optics and Electronics (IOE), Chinese Academy of Sciences (CAS). Since then several AO systems have been built in this Laboratory. The 19-element system is the first AO system in the world ever used in inertial confinement fusion (ICF) facility in our knowledge. It corrects the static error of this large laser engineering. The 21-element system was firstly tested at the 1.2m telescope of Kunming Observatory in 1990 and then up-dated as an IR AO system installed at the 2.16m telescope of Beijing Observatory. The 37-element system was used with a turbulence cell in Laboratory on Atmospheric Optics in Hefei to conduct elementary research on Atmospheric Optics. The 61-element system for astronomical observation is newly developed. It has been successfully installed at the 1.2m telescope of Kunming Observatory and a laser guide star system will be integrated with the system. A compact AO system using our newly developed miniature DM for high resolution ophthalmic imaging of retina is also being built. The key elements of these AO systems, deformable mirrors and fast-steering mirrors, are all developed in this Laboratory. In this talk, the main configurations of these AO systems, some test results as well as the specifications of these active mirrors will be presented.

• 동력기계공학회지
• /
• 제12권3호
• /
• pp.66-71
• /
• 2008

Diamond-like-carbon (DLC) coatings could be good candidates as solid lubricants for cutting tools in dry machining of aluminum alloy. In this work, DLC thin films were produced as a friction reduction coating for WC-Co insert tip using the plasma immersion ion beam deposition (PIIED) technique. DLC coatings were also coated on $Al_2O_3$ specimens and high temperature wear tested up to $400^{\circ}C$ in dry air to observe the survivability of the DLC coating in simulated severe cutting conditions using a pin-on-disc tribotester with Hertzian contact stress of 1.3GPa. It showed reduced friction coefficients of minimum 0.02 up to $400^{\circ}C$. And cutting performance of DLC coated WC-Co insert tips to Al 6061 alloy were conducted in a high speed machining center. The main problems of built-up edge formation in aluminum machining are drastically reduced with improved surface roughness. The improvements were mainly related to the low friction coefficient of DLC to Al alloy and the anti-adhesion of Al alloy to WE due to the inertness of DLC.