• 한국공간구조학회논문집
• /
• 제20권2호
• /
• pp.31-38
• /
• 2020

U-flanged truss beam is composed of u-shaped upper steel flange, lower steel plate of 8mm or more thickness, and connecting lattice bars. Upper flange and lower plate are connected by the diagonal lattice bars welded on the upper and lower sides. In this study, the details of delayed buckling of lattice members were developed through reinforcement of the end section, in order to improve structural capacity of U-flanged Truss Steel Beam. To verify the effects of these details, the simple beam experiment was conducted. The maximum capacity of all the specimens were determined by the buckling of the lattice. The vertical reinforced details of the ends with steel plates, rather than the details reinforced with steel bars, are confirmed to be a valid method for enhancing the structural capacity of the U-flanged Truss beam. In addition, U-flanged Truss Steel Beam with reinforced endings with steel plates can exhibit sufficient capacity of the lattice buckling by the formulae according to Korean Building Code (KBC, 2016) and Eurocode 3.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
• /
• pp.832-834
• /
• 2017

본 논문에서는 고유진동수 시험을 통해 복합재 격자구조체의 유한요소모델을 검증하였다. 복합재 격자구조체의 유한요소모델은 빔, 쉘 그리고 솔리드 요소를 사용하여 생성하였다. 고유진동수는 자유 경계조건 하에서 충격시험법을 사용하여 측정하였다. 쉘과 솔리드 요소의 유한요소해석 결과, 고유진동수 시험과 잘 일치하는 것을 확인하였다. 빔 요소는 섬유 비교차부의 물성저하를 고려하지 못하여 오차가 발생된 것으로 판단된다.

• 한국공간구조학회논문집
• /
• 제18권4호
• /
• pp.113-121
• /
• 2018

U-flanged truss beam is composed of u-shaped upper steel flange, lower steel plate of 8mm or more thickness, and connecting lattice bars. Upper flange and lower plate are connected by the diagonal lattice bars welded on the upper and lower sides. In this study the structural experiments on the U-flanged truss beams with various shapes of upper flange were performed, and the flexural and shear capacities of U-flanged truss beam in the construction stage were evaluated. The principal test parameters were the shape of upper flange and the alignment space of diagonal lattice bars. In all the test specimens, the peak loads were determined by the buckling of lattice bar regardless of the upper flange shape. The test results have shown that the buckling of lattice bar is very important design factor and there is no need to reinforce the basic u-shaped upper flange. However, the early lattice buckling occurred in the truss beam with upper steel bars because of the insufficient strength and stiffness of upper chord, and the reinforcement in the upper chord is necessary. The formulae of Eurocode 3 (2005) have presented more exact evaluations of lattice buckling load than those of KBC 2016.

• 한국구조물진단유지관리공학회 논문집
• /
• 제24권5호
• /
• pp.143-149
• /
• 2020

본 연구에서는 금속 적층 제조로 출력한 격자 구조체의 내부 공극에 반응성 아크릴 화합물을 충진시켜, 밀도 제어가 가능한 밀실 복합 격자 구조체를 제작하는 것을 목표로 한다. 또한 본 격자 구조체를 건설분야에 적용하기 위하여 반응성 아클릴 화합물에 보통 포틀랜드 시멘트를 첨가함으로써 콘크리트와의 부착성능을 향상시킨 부착력 증진 반응성 아크릴 화합물을 검토하였다. 최종적으로 제조한 부착력 증진 반응성 아크릴 화합물을 격자 구조체 내부에 충진하여 밀도 제어형 기능성 복합 격자 구조체(Hybrid Lattice structure)의 비중, 흡수율 및 부착강도를 검토하였다. 그 결과, 밀도 제어 가능, 흡수율 1.0 % 이하 및 재령 1일 부착강도 1.78 MPa ~ 1.98 MPa의 결과물을 도출하였다.

• Steel and Composite Structures
• /
• 제31권2호
• /
• pp.133-148
• /
• 2019

This paper reports on the energy absorption characteristics of a lattice-web reinforced composite sandwich cylinder (LRCSC) which is composed of glass fiber reinforced polymer (GFRP) face sheets, GFRP lattice webs, polyurethane (PU) foam and ceramsite filler. Quasi-static compression experiments on the LRCSC manufactured by a vacuum assisted resin infusion process (VARIP) were performed to demonstrate the feasibility of the proposed cylinders. Compared with the cylinders without lattice webs, a maximum increase in the ultimate elastic load of the lattice-web reinforced cylinders of approximately 928% can be obtained. Moreover, due to the use of ceramsite filler, the energy absorption was increased by 662%. Several numerical simulations using ANSYS/LS-DYNA were conducted to parametrically investigate the effects of the number of longitudinal lattice webs, the number of transverse lattice webs, and the thickness of the transverse lattice web and GFRP face sheet. The effectiveness and feasibility of the numerical model were verified by a series of experimental results. The numerical results demonstrated that a larger number of thicker transverse lattice webs can significantly enhance the ultimate elastic load and initial stiffness. Moreover, the ultimate elastic load and initial stiffness were hardly affected by the number of longitudinal lattice webs.

• 한국반도체및디스플레이장비학회:학술대회논문집
• /
• 한국반도체및디스플레이장비학회 2007년도 춘계학술대회
• /
• pp.234-237
• /
• 2007

We fabricated nano-structures of the anodic aluminum oxides on sapphire substrates. Two processes of nano-structured sapphire surface have present: the one is the template mask and the other is the anodic oxidized aluminum deposited on sapphire substrate. The formation of nano-structures has investigated by FE-SEM measurement. The etched surface by the template showed periodic lattice but the deposited surface showed the randomly distributed phase of nanoholes instead of the periodic lattice.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2004년도 봄 학술발표회 논문집
• /
• pp.463-469
• /
• 2004

This paper discusses 2D lattice models of beams for simulating the fracture of brittle materials. A simulation of an experiment on a connote beam subjected to bending, in which two overlapping cracks occur, is used to study the effect of individual beam characteristics and different arrangements of the beams in the overall lattice. It was found that my regular orientation of the beams influences the resulting crack patterns. Methods to implement a wide range of poisson's ratios are also developed, the use of the lattice to study arbitrary micro-structures is outlined The crack pattern that n obtained with lattice m in good agreement with the experimental results. Also, numerical simulations of the tests were performed by means of a lattice model, and non-integer dimensions were measured on the predicted lattice damage patterns.

• Wind and Structures
• /
• 제30권1호
• /
• pp.29-35
• /
• 2020

This paper presents a comparative structural analysis of lattice hybrid tower with six legs with conventional tubular steel tower for an onshore wind turbine using finite element method. Usually a lattice hybrid tower will have a conventional industry standard 'L' profile section for the lattice construction with four legs. In this work, the researcher attempted to identify and analyze the strength of six legged lattice hybrid tower designed with a special profile instead of four legged L profile. And to compare the structural benefits of special star profile with the conventional tubular tower. Using Ansys, a commercial FEM software, both static and dynamic structural analyses were performed. A simplified finite element model that represents the wind turbine tower was created using Shell elements. An ultimate load condition was applied to check the stress level of the tower in the static analysis. For the dynamic analysis, the frequency extraction was performed in order to obtain the natural frequencies of the tower.

• 한국공간구조학회논문집
• /
• 제12권4호
• /
• pp.109-118
• /
• 2012

The large-space single-layer lattice dome is relatively simpler in terms of the arrangement of the various framework members and of the design of the junction than the multi-layered lattice dome, can reduce the numbers and quantity of the framework members, and has the merit of exposing the beauty of the framework as it stands. The single-layer lattice dome, however, requires a stability investigation of the whole structure itself, along with an analysis of the stress of the framework members, because an unstable phenomenon called "buckling" occurs when its weight reaches critical levels. Many researchers have systematically conducted researches on the stability evaluation of the single-layer lattice dome. No construction case of a single-layer lattice dome with a 300-m-long span, however, has yet been reported anywhere in the world. The large-space dome structure is difficult to erect due to the gigantic span and higher ceiling compared with other common buildings, and its construction cost is generally huge. The method of erecting a structure causes major differences in the construction cost and period. Therefore, many researchers have been conducting various researches on the method of erecting such structure. The step-up method developed by these authors can reduce the construction cost and period to a great extent compared with the other general methods, but the application of this method inevitably requires the development of system supports in the center section as well as pre-existing supports in the boundary sections. In this research, the safety during the construction of a single-layer lattice dome with 300-m-long span using pre-existing materials was examined in the aspect of structural strength, and the basic data required for manufacturing the supports in the application of the step-up method developed by these authors during the erection of the roof structure were obtained.

• Journal of the Optical Society of Korea
• /
• 제18권3호
• /
• pp.207-216
• /
• 2014

In this work, we report detailed numerical analysis of the near-elliptic core index-guiding triangular-lattice and square-lattice photonic crystal fiber (PCFs); where we numerically characterize the birefringence, single mode, cut-off behavior and group velocity dispersion and effective area properties. By varying geometry and examining the modal field profile we find that for the same relative values of $d/{\Lambda}$, triangular-lattice PCFs show higher birefringence whereas the square-lattice PCFs show a wider range of single-mode operation. Square-lattice PCF was found to be endlessly single-mode for higher air-filling fraction ($d/{\Lambda}$). Dispersion comparison between the two structures reveal that we need smaller lengths of triangular-lattice PCF for dispersion compensation whereas PCFs with square-lattice with nearer relative dispersion slope (RDS) can better compensate the broadband dispersion. Square-lattice PCFs show zero dispersion wavelength (ZDW) red-shifted, making it preferable for mid-IR supercontinuum generation (SCG) with highly non-linear chalcogenide material. Square-lattice PCFs show higher dispersion slope that leads to compression of the broadband, thus accumulating more power in the pulse. On the other hand, triangular-lattice PCF with flat dispersion profile can generate broader SCG. Square-lattice PCF with low Group Velocity Dispersion (GVD) at the anomalous dispersion corresponds to higher dispersion length ($L_D$) and higher degree of solitonic interaction. The effective area of square-lattice PCF is always greater than its triangular-lattice counterpart making it better suited for high power applications. We have also performed a comparison of the dispersion properties of between the symmetric-core and asymmetric-core triangular-lattice PCF. While we need smaller length of symmetric-core PCF for dispersion compensation, broadband dispersion compensation can be performed with asymmetric-core PCF. Mid-Infrared (IR) SCG can be better performed with asymmetric core PCF with compressed and high power pulse, while wider range of SCG can be performed with symmetric core PCF. Thus, this study will be extremely useful for designing/realizing fiber towards a custom application around these characteristics.