• Title/Summary/Keyword: Punching Process

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Stability Analysis and Application Evaluation of the Pretensioned Soil Nailing Systems (프리텐션 쏘일네일링 시스템의 안정해석 및 적용성 평가)

  • Kim, Hong-Taek;Park, Si-Sam
    • Proceedings of the Korean Geotechical Society Conference
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    • 2004.03b
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    • pp.783-790
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    • 2004
  • In this study, a newly modified soil nailing technology named as the PSN(pretensioned soil nailing) system, is developed to reduce both facing displacements and ground surface settlements in top-down excavation process as well as to increase the global stability. Up to now, the PSN system has been investigated mainly focusing on an establishment of the design procedure. In the present study, the analytical procedure and design technique are proposed to evaluate maximum pretension force and stability of the PSN system. Also proposed arc techniques to determine the required thickness of a shotcrete facing and to estimate probability of a failure against the punching shear. Based on the proposed procedure and technique, effects of the radius of a influence circle and dilatancy angle on the thickness of a shotcrete facing, bonded length and safety factors arc analyzed. In addition, effects of the reduction of deformations expected by pretensioning of the soil nails are examined in detail throughout an illustrative example and $FLAC^{2D}$ program analysis. And a numerical approach is further made to determine a postulated failure surface as well as a minimum safety factor of the proposed PSN system using the shear strength reduction technique with the $FLAC^{2D}$ program. Global minimum safety factors and local safety factors at various excavation stages computed in case of the PSN system arc analyzed throughout comparisons with the results expected in case of the general soil nailing system. The efficiency of the PSN system is also dealt with by analyzing the wall-facing deformations and the adjacent ground surface settlements.

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FPCB Cutting Process using ns and ps Laser (나노초 및 피코초 레이저를 이용한 FPCB의 절단특성 분석)

  • Shin, Dong-Sig;Lee, Jae-Hoon;Sohn, Hyon-Kee;Paik, Byoung-Man
    • Laser Solutions
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    • v.11 no.4
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    • pp.29-34
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    • 2008
  • Ultraviolet laser micromachining has increasingly been applied to the electronics industry where precision machining of high-density, multi-layer, and multi material components is in a strong demand. Due to the ever-decreasing size of electronic products such as cellular phones, MP3 players, digital cameras, etc., flexible printed circuit board (FPCB), multi-layered with polymers and metals, tends to be thicker. In present, multi-layered FPCBs are being mechanically cut with a punching die. The mechanical cutting of FPCBs causes such defects as burr on layer edges, cracks in terminals, delamination and chipping of layers. In this study, the laser cutting mechanism of FPCB was examined to solve problems related to surface debris and short-circuiting that can be caused by the photo-thermal effect. The laser cutting of PI and FCCL, which are base materials of FPCB, was carried out using a pico-second laser(355nm, 532nm) and nano-second UV laser with adjusting variables such as the average/peak power, scanning speed, cycles, gas and materials. Points which special attention should be paid are that a fast scanning speed, low repetition rate and high peak power are required for precision machining.

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Design Automation of Slab System by the Finite Element Method (유한요소법을 이용한 슬래브 시스템의 설계자동화)

  • 이성우
    • Computational Structural Engineering
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    • v.4 no.4
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    • pp.79-89
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    • 1991
  • New design method of R/C slab system based on finite element method has been presented. The proposed method can substitute inaccurate existing method, which has limitation in its application, and provide accurate and efficient design results for any type of slab system. Isoparametric plate element used in the slab design has been efficiently formulated to save computational time. Reinforcement has been determined by strength design method and compared with code minimum values. Graphical output through comprehensive contour map for resulting moments and designed steel areas has considerably facilitated design process. Accurate shear results from isoparametric plate element enabled to check punching shear in a proper manner. In addition to strength design criteria, serviceability has also been checked by utilizing newly developed inelastic deflection multiplier method. An example for circular slab with opening showed that the proposed method could be applied to design of irregular slab without any difficulty.

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Optimal Mix Design of High-Performance, Low-Heat Self-Compacting Concrete (고성능 저발열 자기충전 콘크리트의 최적 배합설계)

  • Kim, Young-Bong;Lee, Jun-Hae;Park, Dong-Cheon
    • Journal of the Korea Institute of Building Construction
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    • v.22 no.4
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    • pp.337-345
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    • 2022
  • The foundation of high-rise concrete building in coastal areas generally must be installed in an integrated manner, not separately, in order to prevent defects caused by stress on the upper and lower parts of the mounting surface and to manage the process smoothly. However, when performing integrated punching, there is a concern that temperature stress cracks may occur due to hydration heat. Due to the large member size, it is difficult to make a sufficient commitment, so it is necessary to mix concrete with high self-charging properties to ensure workability. In this research, the amount of high-performance spray and admixture used was adjusted as experimental variables to satisfy this required performance. Through the analysis of the results for each blending variable, it was found that the unit quantity was 155kg/m3 and the cement ratio in the binder was 18%, and the target values of the pre-concrete properties and compressive strength were satisfied. A four-component binder(18% cement, 50% slag fine powder, 27% fly ash, 5% silica fume) was used.

Adhesive Strength and Electrochemical Properties of Li(Ni0.5Co0.2Mn0.3)O2Electrodes with Lean Binder Composition (바인더 함량에 따른 Li(Ni0.5Co0.2Mn0.3)O2 전극의 접착력 및 전기화학 성능에 관한 연구)

  • Roh, Youngjoon;Byun, Seoungwoo;Ryou, Myung-Hyun;Lee, Yong Min
    • Journal of the Korean Electrochemical Society
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    • v.21 no.3
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    • pp.47-54
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    • 2018
  • To maximize the areal capacity($mAh\;cm^{-2}$) of $LiNi_{0.5}Co_{0.2}Mn_{0.3}O_2$(NCM523) electrode with the same loading level of $15mg\;cm^{-2}$, three NCM523 electrodes with 4, 2, and 1 wt% poly(vinylidene fluoride)(PVdF) binder content are fabricated. Due to the delamination issue of electrode composite at the edge during punching process, the 1 wt% electrode is excluded for further evaluation. When the PVdF binder content decreases from 4 to 2 wt%, both adhesion strength and shear stress decrease from 0.4846 to $0.2627kN\;m^{-1}$ by -46% and from 3.847 to 2.013 MPa by -48%, respectively. Regardless of these substantial decline of mechanical properties, their initial electrochemical properties such as initial coulombic efficiency and voltage profile are almost the same. However, owing to high loading level, the 2 wt% electrode not only exhibits worse cycle performance than the 4 wt% electrode, but also cannot maintain its mechanical integrity only after 80 cycles. Therefore, if the binder content is reduced to increase the area capacity, the mechanical properties as well as the cycle performance must be carefully evaluated.

Field Application of a Precast Concrete-panel Retaining Wall Adhered to In-situ Ground (원지반 부착식 판넬옹벽의 현장 적용성 평가)

  • Min, Kyoung-Nam;Lee, Jae-Won;Lee, Jung-Gwan;Kang, In-Kyu;Ahn, Tae-Bong
    • The Journal of Engineering Geology
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    • v.26 no.1
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    • pp.51-61
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    • 2016
  • New building methods are needed to aid increased inner-city redevelopment and industrial construction. A particular area of improvement is the efficient use of cut slopes, with the minimization of associated problems. A retaining wall of precast panels can resist the horizontal earth pressure by increasing the shear strength of the ground and reinforcing it through contact with the panels. Precast panels allow quick construction and avoid the problem of concrete deterioration. Other problems to be solved include the digging of borrow pits, the disposal of material cut from the slope, and degradation of the landscape caused by the exposed concrete retaining wall.This study suggest the methods of improvement of an existing precast panel wall system by changing the appearance of the panels to that of natural rock and improving the process of adhering the panel to a vertical slope. The panels were tested in the laboratory and in the field. The laboratory test verified their specific strength and behavior, and the field test assessed the panels' ground adherence at a vertical cutting. Reinforcement of the cutting slope was also measured and compared with the results of 3D numerical analysis. The results of laboratory test, identified that the shear bar increase the punching resistance of panel. And as a results of test construction, identified the construct ability and field applicability of the panel wall system adhered to in-situ ground. In addition to that, extended measurement and numerical analysis, identified the long-term stability of panel wall system adhered to in-situ ground.

Shear Performance of Post and Beam Construction by Pre-Cut Process (프리컷 방식을 적용한 기둥-보 공법의 수평전단내력)

  • Hwang, Kweonhwan;Park, Joo-Saeng;Park, Moon-Jae
    • Journal of the Korean Wood Science and Technology
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    • v.35 no.6
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    • pp.1-12
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    • 2007
  • For the purpose of effective utilization of domestic second-grown larch as structural members, post and beam construction applying traditional construction to Japanese larch glulam members was adopted with processing by machine pre-cut method. In general, horizontal shear test by KS F 2154 is conducted to assess the horizontal shear properties of the wooden structure by post and beam construction. The frame was consisted of post and beam member with appropriate fasteners, and members have their own processed parts (notch, hole, etc.) that can be well-connected each other. The shear wall was consisted of the frame with screw-nail sheathed panel (OSB). The results of horizontal shear loading tests without vertical loads conducted on the frame and the shear wall structures, the maximum strengths were about 1.9 kN/m and about 9.7 kN/m, the shear rigidities were about 167 kN/rad, 8198 kN/rad, respectively. The strength proportion of the frame specimen was about 20% of the wall's and about 2% in initial stiffness. Nail failures are remarkable on the shear wall specimen with punching shears and shear failures. The shear load factor for the shear wall specimen by the method of Architectural Institute of Japan was 1.5, which was obtained by the bi-linear method. Loading method should be considered to obtain smooth load-deformation relationship. For the better shear performance of the structures, column base and post and beam connections and sheathed panel should be further examined as well.

Behavior of Bearing Capacity for Shallow Foundation on a Sand overlying Clay Depending on Bearing Capacity Ratio (점토층 위 모래지반의 지지력비에 따른 얕은 기초의 지지력 거동)

  • Jung, Min Hyung;Shin, Hyo Hee;Lee, Song
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.15 no.1
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    • pp.198-208
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    • 2011
  • When a structure which has relatively low load constructs on soft clay, the bearing capacity of the ground will be improved by sand overlying clay. In this condition, verifying the bearing capacity is difficult from the P.B.T etcetera in the in-situ. So, it is needed to estimate precise bearing capacity in the design process. In this study, 2-dimensional chamber tests and FEM analyses are conducted to evaluate behavior of bearing capacity for shallow foundations on a sand overlying clay. Because depth ratio H/B and bearing capacity ratio $q_c/q_s$ are selected as main factors, height of a sand, undrained shear strength of a clay and width of a loading are designated as variables. Results from chamber tests are very similar with those of FEM analyses. And it shows that punching shear mechanism is more suitable than the equation of Okamura et al.(1998). To make continual application of load spread mechanism, the equivalent load spread angle is proposed for H/B and $q_c/q_s$. Also, the linear regression equation of critical depth ratio Hf is suggested for $q_c/q_s$.