• 소성∙가공
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• 제25권1호
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• pp.36-42
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• 2016

Fiber metal laminates (FMLs) are well known for improved fatigue strength, better impact resistance, superior damage tolerance and slow crack growth rate compared to traditional metallic materials. However, defects and loss of strength of a composite material can occur due to the vertical load from the punch during the joining with a dissimilar material using a conventional clinching method. In the current study, tapered-hole clinching was an alternative process used to join Al 5052 and FMLs. The tapered hole was formed in the FML before the joining. For the better understanding of static and dynamic characteristics, a clinched joining followed by a tensile-shear test was numerically simulated using the finite element analysis. The design parameters were also evaluated for the geometry of the tapered hole by the Taguchi method in order to improve and compare the lateral joining strength of the clinched joint. The influence of the neck thickness and the undercut were evaluated and the contribution of each design parameter was determined. Then, actual experiments for the joining and tensile-shear test were conducted to verify the results of the numerical simulations. In conclusion, the appropriate combination of the design parameters can improve the joining strength and the cross-sections of the tapered-hole clinched joint formed in the actual experiments were in good agreement with the results of the numerical simulations.

• 콘크리트학회논문집
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• 제12권6호
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• pp.75-82
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• 2000

Flexural behaviors of two typical architectural precast beam sections ; inverted tee and rectangular - were compared and investigated. The heights of web in inverted tee beams are generally less than half of beam depth in building structures to accomodate the nib of double-tee where the total building height limited considerably. The inverted-tee beams are designed for parking live load - 500kgf/$\m^2$ and market - 1,200kgf/$\m^2$ according to the currently used typical shape in the domestic market building site in Korea. The bottom dimension and area of rectangular beams are same to those of inverted tee beams to compare the flexural behaviors of two beams. These two beams are also reinforced for similar strength. Four flexural tests are performed on two beams. Following results are obtained from the tests; 1) The rectangular beam is simpler in production, transportation, and election, and more economic than the inverted tee beam for these two beams with same dimension and similar strength. 1) The estimations of flexural strength of two beams by Strength Design Method and Strain Compatibility Method is fully complied with the result of tests. However, Strain Compatibility Method is slightly ore accurate than Strength Design Method. 2) Overall deflections of two type beam under the service loads are less than those of the allowable limit in ACI Code provision. 3) The rectangular beam is failed in large deflection (average 12.56mm large) than those of inverted tee beams. 4) The rectangular and inverted tee beams with 6m span develop initial flexural crackings under the 88% of full service loading even though they designed to satisfy the ACI tensile stress limit provisions.

• 한국지반공학회논문집
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• 제35권5호
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• pp.5-19
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• 2019

암반으로 구성되어 있는 급경사($65^{\circ}{\sim}85^{\circ}$)비탈면이 장기간 안정한 상태로 유지되고 있는 자연현상을 고려할 때, 설계 및 초기 시공 단계에서 위와 유사한 지반 상태로 이루어진 깎기 암반비탈면에 대해 1:0.5(발파암 경사 기준)보다 급한 경사를 적용할 수 있을 것이다. 급경사로 설계 가능한 양호한 연속체 암반비탈면의 안정성을 검토하는 과정에서, 설계실무 측면에서 범용적인 암반강도정수 산정방법이 필요하게 되었다. Hoek 등(2002)이 수정 보완하여 발표한 Hoek-Brown 파괴기준과 GSI분류는 불연속구조의 영향을 충분히 고려한 암반특성화 시스템으로 평가되었으며, 응력변화에 따라 등가 Mohr-Coulomb 강도정수(등면적법)를 산출하는 방법을 제안하였다. 비탈면에서는 등가 M-C 강도정수가 최대구속응력(${{\sigma}^{\prime}}_{3max}$ 또는 수직응력)변화에 따라 민감하게 변화하므로 실무적으로 활용하기에 어려운 점이 있다. 이 연구에서는 양호한 연속체 암반비탈면에 대해 최대구속응력 범위이내에서 범용적으로 적용할 수 있는 강도정수산정방법(등각분할법)을 H-B 파괴기준을 응용하여 제안한다. 등각분할법 강도정수(A)의 타당성 및 적용성을 평가하기 위해, 연구대상 암반비탈면을 기존 실시설계 현장 인근에 있는 급경사 비탈면에서 암석종류별(화성암, 변성암, 퇴적암)로 선정하고, Hoek이 제시한 등가 M-C 강도정수(등면적법)들과 비교 분석하였다. 등면적법 및 등각분할법 등가 M-C 강도정수는 기본적인 자료인 기존 실시설계 현장의 실내 암석 삼축압축시험과 연구대상 암반비탈면의 불연속구조의 특성조사(Face Mapping)를 통해 RocLab 프로그램(H-B 파괴기준을 기본으로 전산화된 지반정수 산정 소프트웨어)을 활용하여 산정하였다. 산정된 등면적법 등가 M-C 강도정수는 상호 연동되어 점착력과 내부마찰각이 아주 크거나($45^{\circ}$ 이상) 작게 나타났다. 등각분할법 등가 M-C 강도정수는 등면적법 등가 M-C 강도정수의 중간 정도이며, 내부마찰각은 $30^{\circ}{\sim}42^{\circ}$의 범위를 보인다. 연구대상 암반비탈면의 등각분할법 강도정수(A)와 기존 실시 설계 현장에서 연구대상 암반비탈면과 유사한 암반상태(동일 등급 RMR)에 적용한 강도정수(B)와 비교 분석하고, 이 지반정수들로 적용한 비탈면 안정해석(한계평형해석과 유한요소해석) 결과를 통해 제안한 등각분할법의 적용성을 간접적으로 평가하였다. A와 B의 강도정수 차이는 10% 정도이다. 한계평형해석 결과(우기 기준), A적용 안전율(Fs)=14.08~58.22(평균 32.9), B적용 안전율(Fs)=18.39~60.04(평균 32.2)이며, 각 동일한 암석종류에 따라 상호 유사하게 나타났다. 유한요소 해석 결과, A적용 변위=0.13~0.65mm(평균 0.27mm), B적용 변위=0.14~1.07mm(평균 0.37mm)으로 매우 유사하다. H-B 파괴기준을 응용하여 등각분할법으로 산출한 지반 정수를 실무적인 전단강도로 적용할 수 있는 적용성 평가에서 유의미한 결과를 확인할 수 있었다.

• 한국지진공학회논문집
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• 제8권1호
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• pp.17-27
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• 2004

본 연구에서는 할선강성을 사용하여 반복계산을 수행하는 새로운 내진설계법을 개발하였다. 개발한 설계법은 탄성해석을 수행하므로 수치해석의 안정성과 용이성을 갖추고 있으며, 동시에 반복계산으로 구조물의 비탄성 거동을 해석할 수 있으므로 각 부재의 강도 및 연성 요구량을 정확히 예측할 수 있다. 본 연구에서는 제안된 설계법의 절차를 정립하였고, 이를 고려한 컴퓨터 해석/설계 프로그램을 개발하였다. 또한, 제안된 설계법을 사용한 설계예제를 제시하였고, 탄성 혹은 비탄성 해석을 이용한 기존 설계법과의 비교를 통하여 그 장점을 검증하였다. 해석과 설계를 통합적으로 수행하는 제안된 설계법은 설계자의 의도에 따라 부재의 강도 및 연성능력, 강기둥-약보 등과 같은 내진설계전략을 효과적으로 구현할 수 있으며, 초기설계단계에서 각 부재의 크기만이 가정된 구조물에 대하여 반복계산을 수행함으로써 주어진 설계전략을 만족하는 비탄성 강도 및 연성 요구량을 직접적으로 계산할 수 있으므로, 경제적이고 안전한 내진설계가 가능하다.

• International Journal of Aeronautical and Space Sciences
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• 제15권4호
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• pp.383-395
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• 2014

According to the requirement of wing weight estimation and frequent adjustments during aircraft conceptual design, a wing weight estimation method considering the constraints of structural strength and stiffness is proposed to help designers make wing weight estimations rapidly and accurately. This method implements weight predictions on the basis of structure weight optimization with stiffness constraints and strength constraints, which include achievement of wing shape parametric modeling, rapid structure layout, finite element (FE) model automated generation, load calculation, structure analysis, weight optimization, and weight computed based on modeling. A software tool is developed with this wing weight estimation method. This software can realize the whole process of wing weight estimation with the method and the workload of wing weight estimation is reduced because much of the work can be completed by the software. Finally, an example is given to illustrate that this weight estimation method is effective.

• Steel and Composite Structures
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• 제12권1호
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• pp.73-92
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• 2012

The effect of element interaction and material nonlinearity on the ultimate capacity of stainless steel plated cross-sections is investigated in this paper. The focus of the research lies in cross-sections failing by local buckling; member instabilities, distortional buckling and interactions thereof with local buckling are not considered. The cross-sections investigated include rectangular hollow sections (RHS), I sections and parallel flange channels (PFC). Based on previous finite element investigations of structural stainless steel stub columns, parametric studies were conducted and the ultimate capacity of the aforementioned cross-sections with a range of element slendernesses and aspect ratios has been obtained. Various design methods, including the effective width approach, the direct strength method (DSM), the continuous strength method (CSM) and a design method based on regression analysis, which accounts for element interaction, were assessed on the basis of the numerical results, and the relative merits and weaknesses of each design approach have been highlighted. Element interaction has been shown to be significant for slender cross-sections, whilst the behaviour of stocky cross-sections is more strongly influenced by the material strain-hardening characteristics. A modification to the continuous strength method has been proposed to allow for the effect of element interaction, which leads to more reliable ultimate capacity predictions. Comparisons with available test data have also been made to demonstrate the enhanced accuracy of the proposed method and its suitability for the treatment of local buckling in stainless steel cross-sections.

• 한국강구조학회 논문집
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• 제22권5호
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• pp.435-443
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• 2010

현행 송전강관철탑의 경우 허용응력 설계개념을 도입한 철탑설계기준을 적용하여 설계, 제작되고 있다. 이 철탑설계기준의 압축재의 설계 강도 결정은 압축재의 허용좌굴응력에 의하여 결정되고 있으나 이는 접합부의 내력을 고려치 않은 값이다. 부재가 압축좌굴내력에 도달하기 전에 접합부의 변형으로 인하여 국부변형에 의한 접합부 파괴가 발생할 수 있다. 따라서 본 연구에서는 접합부의 보강형태별로 접합부내력을 산출하고 이를 데이터베이스화한 후 지난 연구에서 도출한 등가비선형해석기법의 부재내력과의 상호 비교를 통하여 부재파괴와 접합부파괴의 선행 여부를 판별할 수 있는 실용적인 평가 및 설계 기법을 제시하였다.

• Steel and Composite Structures
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• 제7권4호
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• pp.321-337
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• 2007

The investigation on the behaviour of cold-formed stainless steel non-slender circular hollow section columns is presented in this paper. The normal strength austenitic stainless steel type 304 and the high strength duplex materials (austenitic-ferritic approximately equivalent to EN 1.4462 and UNS S31803) were considered in this study. The finite element method has been used to carry out the investigation. The columns were compressed between fixed ends at different column lengths. The geometric and material nonlinearities have been included in the finite element analysis. The column strengths and failure modes were predicted. An extensive parametric study was carried out to study the effects of normal and high strength materials on cold-formed stainless steel non-slender circular hollow section columns. The column strengths predicted from the finite element analysis were compared with the design strengths calculated using the American Specification, Australian/New Zealand Standard and European Code for cold-formed stainless steel structures. The numerical results showed that the design rules specified in the American, Australian/New Zealand and European specifications are generally unconservative for the cold-formed stainless steel non-slender circular hollow section columns of normal and high strength materials, except for the short columns and some of the high strength stainless steel columns. Therefore, different values of the imperfection factor and limiting slenderness in the European Code design rules were proposed for cold-formed stainless steel non-slender circular hollow section columns.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2022년도 봄 학술논문 발표대회
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• pp.247-248
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• 2022

3D printer-based self-healing capsules have been proposed to heal cracks by enabling various structural designs, repeatable fabrication, and strength analysis of the capsules. The Fusion Deposition Modeling (FDM) method was used to design, analyze, and produce new self-healing capsules that are widely used at low cost. However, PLA extruded from FDM has low interlayer adhesion energy, and thus strength varies depending on the angle of load applied to the laminated layer and the concrete structure, thereby degrading the performance of the self-healing capsule. Therefore, in this paper, the structure of the capsule manufactured by the FDM PLA method has isotropic strength was designed. In addition, the fracture strength in the x, y, and z directions of the load applied through the compression test was analyzed. As a result, it was confirmed that the newly proposed capsule design has an isotropic fracture strength of 1400% in all directions compared to the existing spherical thin-film capsule.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.862-870
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• 2010

This thesis has been researched on optimized design method for the total cross section of embankment considering the fact that the size of embankment cross section is directly related with economic efficiency when dam designing. In general, embankment cross section of fill dam is either determined by cohesion and angle of internal friction, a strength parameter of embankment materials or by permeability of embankment. Therefore the size of embankment cross section depending on strength parameter of embankment materials was determined by using MIDAS-GTS program through stress-seepage coupled analysis at the time of fill dam design. As a result, determination of embankment cross section was more affected by the size of central core and permeability rather than by slope stability by shear strength and it was revealed that in case of embankment height being over 20m, stability against infiltration and slope action could be secured only when embankment slope is at least over 1:2.5. In addition, it was also revealed that in case of making the size of central core exceeding specification standard, total cross section of embankment could be reduced considerably and at the time of embankment design, adequate size and appropriateness of embankment cross section could be determined with referring the table suggested by this study.