• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6A
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• pp.399-409
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• 2012

The flexural behavior of HSB plate girder with a non-slender web, due to inelastic lateral-torsional buckling, under uniform bending was investigated by the nonlinear finite element analysis. Both homogeneous sections fabricated from SM570-TMC, HSB600 or HSB800 steel and hybrid sections with HSB800 flanges and SM570-TMC web were considered. The flanges and web of selected noncomposite I-girders were modeled as thin shell elements and the geometrical and material nonlinear finite element analysis was performed by the ABAQUS program. The steel was assumed as an elasto-plastic strain hardening material. Initial imperfections and residual stresses were taken into account and their effects on the inelastic lateral-torsional buckling behavior were analyzed. The flexural strengths of selected sections obtained by the finite element analysis were compared with the nominal flexural strengths from KHBDC LSD, AASHTO LRFD, and Eurocode and the applicability of these codes in predicting the inelastic lateral torsional buckling strength of HSB plate girders with a non-slender web was assessed.

• Journal of Korean Society for Geospatial Information Science
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• v.16 no.3
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• pp.105-110
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• 2008

The cross-section data are generally used for hydraulic and hydrologic modeling. However, when the detailed data of river channel are required, it is not available to use because of too wide distance of the offset between cross-sections. Also, the actual form of river channel cannot be reflected with the general interpolation methods which is considering straight line between acquired points. The aim of this paper is to present an algorithm which is to interpolate point using bilinear method and to estimate random cross-section between two surveyed cross-section data. And it is supposed that the proposed algorithm can be able to offer available data for hydraulic and hydrologic modeling.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.1
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• pp.123-134
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• 2019

This paper proposed a new design equation for the inelastic lateral torsional buckling (LTB) of singly symmetric stepped I-beams with non-compact flange sections. The proposed equation was generated using a finite element program, ABAQUS, and a statistical program, MINITAB. The parameters used were the stepped beams parameters; ${\alpha}$, ${\beta}$, and ${\gamma}$ and the length-to-height ratio ($L_b/h$) of the beam. The proposed equation was further validated by means of experimental test, where beams were subjected to four-point bending and supported by roller and lateral braces near the end supports. In addition, finite element models were simulated using the same parameters used in the experimental test to verify the results of the test conducted. It was proved that LTB capacity calculated from the proposed equation is accurate and conservative in comparison with the yielded values from the FEM and actual test, making it a reliable and safe approach in calculating the buckling capacities of singly symmetric stepped beams with non-compact flange sections.

• Journal of the Korea Institute of Military Science and Technology
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• v.2 no.2
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• pp.234-241
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• 1999

본 논문에서는 얇은 직사각형 단면 형상을 가지는 세 가지 서로 다른 유동로 안에서 움직이는 공기버블의 변형 거동에 대한 실험을 수행하였다. 압력 차이로 유체는 유동되며, 유동장을 따라서 변형하는 버블의 정상상태 모양을 관찰하였다. 벽면효과를 알아보기 위해 세 종류의 얇은 사각단면을 사용하였으며, 두 가지 종류의 작동 유체, 버블의 초기 크기, 작동 유체의 유량 등을 변화시켰을 때 이에 대한 공기 버블의 변형을 체계적으로 관찰하고 이들의 관계를 고찰하였다. 실험데이타를 정량화하여 캐필러리 수에 대한 버블의 무차원 속도비와의 관계를 상세하게 고찰하였다. 글리세린의 경우는 항상 버블 선단부의 곡률이 후단의 곡률보다 더 작게 나타났으며 실리콘 오일의 경우와 반대 경향이 관찰되었다. 두 경우 모두 캐필러리 수에 대한 속도비와 세장비 값은 1 보다 큰 값을 가졌다. 실리콘 오일의 경우는 주어진 Ca 수에 대하여 속도비가 글리세린의 경우보다 더 크게 나왔으며 버블 크기에 따른 속도비 분산도가 더 조밀하게 나타났다. 사각 단면 폭이 감소할수록 벽면 효과는 증대되었으며 같은 폭에 대해서는 버블 변형이 축소관의 경우가 가장 크게 나타났다.

• Journal of Korean Society of Steel Construction
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• v.24 no.2
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• pp.217-231
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• 2012

The flexural behavior of HSB I-girder with a non-slender web attributed to inelastic lateral-torsional buckling under uniform bending was investigated using nonlinear finite element analysis of ABAQUS. The girder was assumed to have a compact or noncompact web in order to prevent premature bend-buckling of the web. The unbraced length of the girder was selected so that inelastic lateral-torsional buckling governs the ultimate flexural strength. The compression flange was also assumed to be either compact or noncompact to prevent local buckling of the elastic flange. Both homogeneous sections fabricated from HSB600 or HSB800 steel and hybrid sections with HSB800 flanges and SM570-TMC web were considered. In the FE analysis, the flanges and web of I-girder were modeled as thin shell elements. Initial imperfections and residual stresses were imposed on the FE model. An elasto-plastic strain hardening material was assumed for steel. After establishing the validity of the present FE analysis by comparing FE results with test results in existing literature, the effects of initial imperfection and residual stress on the inelastic lateral-torsional buckling behavior were analyzed. Finite element analysis results for 96 sections demonstrated that the current inelastic strength equations for the compression flange in AASHTO LTFD can be applied to predict the inelastic lateral torsional buckling strength of homogeneous and hybrid HSB I-girders with a non-slender web.

• Journal of Korean Society of Steel Construction
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• v.25 no.2
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• pp.141-151
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• 2013

In this paper, lateral-torsional buckling(LTB) strength of HSB800 steel plate girder under uniform bending moment was estimated by the nonlinear analysis. Doubly symmetric sections with slender, noncompact and compact webs were considered and the LTB strength in the inelastic range was estimated by taking initial imperfection and residual stress into account. For the numerical analysis, single-panel model and three-panel model were considered and analysis of SM490 steel plate girder was performed to judge the validity of the constructed models by comparing the results with AASHTO, AISC, Eurocode and KHBDC(LSD) codes. By using the same models, LTB strength of HSB800 girder was evaluated and it was acknowledged that the current codes can be applied to HSB800 girders with doubly symmetric section in the inelastic LTB range.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.524-524
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• 2023

하천 내 식생의 분포는 흐름저항의 증가와 수위상승에 큰 영향을 미치는 요소 중 하나이다. 동일한 단면정보를 가졌더라도 식생이 분포하는 하도는 식생이 없는 하도에 비해 흐름저항으로 인해 유속이 현저히 느려져 홍수위 상승을 유발하기 때문이다. 따라서 식생의 종류, 크기, 분포 형태, 잎의 밀도 등에 따라 흐름저항계수를 정량화하며 흐름을 정확히 예측하는 것이 필요하다. 본 연구에서는 2019년 한국건설기술연구원 하천실험센터에서 진행된 식생하도에 대한 실규모 실험의 조건과 지형정보를 HEC-RAS(Hydrologic Engineering Center's River Analysis System) 1차원 수치모형에 입력하고, 식생 패치의 분포를 고려한 Manning's n의 공간적 분포 및 적용방식에 따른 수면 경사 재현 정확도에 대한 민감도 분석을 수행하였다. 실험은 상단 폭 11 m, 경사 1:2(V:H)의 사다리꼴 단면을 가진 실규모 수로에서 70 m 길이의 구간을 대상으로 진행되었다. 실험 구간 내 6개의 압력식 수위계를 설치해 수위 측정 및 수면 경사 산정을 실행하였다. 실험 조건으로 적용된 인공 식생패치의 분포 및 밀도 조건은 3가지로 큰 패치와 작은 패치로 구성된 조밀한 조건, 단일 패치로 구성된 조밀한 조건, 단일 패치로 구성된 성긴 조건이었으며, 모두 정수(emergent)상태로 진행되었다. 적용된 패치의 형상은 내성천에서 조사된 자연 형태의 식생패치 형태를 참고하였으며, 버드나무 종을 모사하였다. 실험 조건에 따라 유량은 각각 평균 1.5 cms와 2.7 cms로 공급하였으며, 평균 수심은 약 1 m로 측정되었다. 위 실험 내용을 바탕으로 수치모의를 위한 경계조건과 지형정보를 수립하였으며 모의 케이스는 크게 두 가지로, 수로 내 식생의 분포를 종방향으로 고려한 케이스와 횡방향으로 고려하여 조도계수를 적용한 케이스로 분류하였다. 모의에 적용된 조도계수는 실험에서 획득한 데이터와 베르누이 방정식을 활용하여 산정되었으며, 두 케이스에 대한 모의 결과는 실험에서 관측된 수위와 비교하였다. 본 연구에 따르면 여러 개의 식생패치가 정수상태로 존재하는 하천에 대한 1차원 수치모의 시 식생의 분포를 종방향으로 고려하여 하나의 구간조도계수를 적용하는 방식이 종횡단면의 식생패치 위치를 고려한 조도계수를 세분화하여 적용하는 방식에 비해 수위 계산 정확도가 상대적으로 높은 것으로 나타났다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.10a
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• pp.143-150
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• 1999

The LRFD Specification defines two sets of limiting width-to-thickness ratios. On the basis of these limiting values, steel sections we subdivided into three categories: compact, noncompact, and slender sections. A compact section is capable of developing a fully plastic stress distribution (plastic moment), and can sustain rotations approximately three times beyond the yield before the possibility of local buckling arises. Noncompact sections can develop the yield stress before local buckling occurs. They may not, however, resist local buckling at the strain levels required to develop the fully plastic stress distribution. In this paper, 1-Type girders of a 2 span continuous steel bridge are divided into compact and non-compact sections and analyzed. In the design process, an optimization skill was adopted and ADS, a Fortran program for Automated Design Synthesis, was used.

• Journal of Korean Society of Steel Construction
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• v.17 no.1 s.74
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• pp.63-71
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• 2005

There were already several studies conducted on the steel-concrete (SC) composite column, which was developedcomplement the weaknesses and maintain the advantages of previous composite columns. The axial compressive capacity of the SC composite column was estimated by the tests in previous studies, but the experiments for the large-scale column could not be performed because of the limitation with the laboratory's capacity. In this study, the analytical study was performed using the general finite element analysis program to reflect the interaction of concrete and steel and the local buckling of steel flange composed of the non-compact section. The appropriateness of the analytical model was verified by the comparison between experimental and analytical results. The nonlinear behavior of full-scale SC composite column was analyzed using the verified analytical model. From these analytical studies, it was concluded that the width-to-thickness ratio of the steel cross-section of the SC composite column should not exceed 25:0. The section area of the link is best when it is over 0.025 dt, and the link distance is to be less than D/2 or 300mm.

• Korean Journal of Food Science and Technology
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• v.44 no.2
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• pp.162-167
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• 2012

Edible biopolymer films were developed from hijiki ($Hizikia$ $fusiforme$), using a high-pressure homogenization (HPH). Effects of pressure and pass number of HPH on color, tensile, moisture barrier properties, flavor profiles, and microstructure of hijiki films were investigated. A hydrocolloid of hijiki was processed by HPH at 69, 103, or 152 MPa with 1, 2, or 3 passes. A hijiki-base film was formed by drying a film-forming solution which was prepared by mixing of the HPH-processed suspension with glycerol and Polysorbate 20. Tensile strength and elastic modulus increased with increasing HPH pressure. Uniformity of the films increased as the pressure of HPH with 1 pass increased and the number of pass increased at 152 MPa. Water vapor permeability ($2.1-3.3g{\cdot}mm/kPa{\cdot}h{\cdot}m^2$) and water solubility (0.4-1.0%), which are relatively low compared to those of many other edible films, show the potential that hijiki-base films are applied to the range of low to intermediate moisture food as wrapping or coating.