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비규격 스틸커튼월 부재의 적용을 위한 로봇 레이저용접 성능에 관한 연구
나상호 ( Na¸ Sangho ),이장현 ( Lee¸ Janghyun ),박영미 ( Park¸ Youngmi ),김성진 ( Kim¸ Sungjin ) 한국건축시공학회 2021 한국건축시공학회 학술발표대회 논문집 Vol.21 No.2
In irregular curtain walls, the nominal stress required for each member varies greatly depending on the shape, so it is inefficient to design members based on the maximum required stress. Then, built-up members are absolutely necessary, but built-up members manufactured by Manpower-welding cannot be constructed in an irregular curtain wall building because it' not precise. In order to address the problems, this paper presents why Robotic-laser-welding should be used in irregular curtain walls using Gwanggyo Galleria Department Store involving 3D printing as an example. Results verify the performance of Robot-Laser-Welding as an efficient solution for precise steel curtain wall members.
Pure rate effect on the concrete compressive strength in the split Hopkinson pressure bar test
Lee, Sangho,Kim, Kyoung-Min,Park, Jamin,Cho, Jae-Yeol Elsevier 2018 International journal of impact engineering Vol.113 No.-
<P><B>Abstract</B></P> <P>The dynamic increase factor (DIF) has been widely used to consider the rate effect in the analysis and design of concrete structures that are subject to impact loads. A variety of DIFs have been proposed by many researchers based on the results of dynamic material tests such as the split Hopkinson pressure bar (SHPB) test. These DIFs have been adopted in authoritative design guidelines and model codes such as the ACI 349–13, ACI 370R-14, fib MC2010, and UFC 3-340-02. However, previous studies did not properly consider the strain acceleration and the geometrical characteristics of the test specimens that cause the axial and radial inertia forces which influence the test results. For this reason, predictions can become non conservative when these DIFs are used in the analysis and design of concrete structures that are subject to impact or impulsive loads. In this study, to overcome the limitations of existing DIFs, a new concrete DIF that excludes inertia effects by considering the strain acceleration and geometry of the specimens has been proposed based on SHPB test results. The proposed DIF was numerically validated using finite element analyses. Compared with other existing DIFs, the results show improved predictions of the enhancement of the concrete compressive strength due to rate effect.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Strain acceleration and geometry of a specimen lead to inertia effects in SHPB test. </LI> <LI> Concrete SHPB tests were performed. </LI> <LI> DIF considering the pure rate effect was proposed. </LI> <LI> Proposed DIF provided an accurate prediction for the apparent dynamic strength. </LI> </UL> </P>
<tex> $W$</tex>-Band Multichannel FMCW Radar Sensor With Switching-TX Antennas
Lee, Seokchul,Joo, Joungmyoung,Choi, Junhyeok,Kim, Wansik,Kwon, Hosang,Lee, Sangho,Kwon, Youngwoo,Jeong, Jinho IEEE 2016 IEEE SENSORS JOURNAL Vol.16 No.14
<P>In this paper, a multichannel frequency-modulated continuous wave (FMCW) radar sensor with switching-transmit (TX) antennas is developed at W-band. To achieve a high angular resolution, a uniform linear array consisting of 5 switching-TX and 12 receive (RX) antennas is employed with the digital beamforming technique. The overall radar front-end module comprises a W-band transceiver and TX/RX antennas. A multichannel transceiver module consists of 5 up-conversion and 12 down-conversion channels, where one of the TX channels is sequentially switched ON. The developed radar sensor generates multiple digital beams with high gain, low side lobe level, and narrow beamwidth. The design of each component in the radar module is described with the measurement results. The assembled FMCW radar sensor exhibits a measured angular resolution of less than 2 degrees, and a field of view of approximately 60 degrees.</P>