• 대한토목학회논문집
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• 제3권2호
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• pp.31-44
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• 1983

본연구(本硏究)에서는 OR이나 응용수학분야(應用數學分野)에서 개발(開發)된 기하적(幾何的) 계획법(計劃法)을 탄성이론(彈性理論)에 의(依)한 트러스구조물(構造物)의 최적화(最適化)에 도입(導入)하여 최적화(最適化) 알고리즘으로 적용(適用)하였다. 최적화(最適化) 문제형성(問題形成)에서 목적함수(目的函數)는 중량함수(重量函數), 제약조건식(制約條件式)으로는 축응력(軸應力), 좌굴응력(挫屈應力), 변위(變位), 설계변수(設計變數) 한계제약조건식(限界制約條件式)을 취하였다. 트러스구조물(構造物)의 최적설계(最適設計)에 이 알고리즘을 적용(適用)할 수 있는지의 적용가능성(適用可能性)과 그 효율성(効率性)을 검토(檢討)하기 위하여 절점수(節點數), 부재수(部材數), 극하조건수(戟荷條件數), 설계변수(設計變數)의 초기치(初期値)를 달리한 4종류(種類)의 트러스구조물(構造物)의 최적설계(最適設計)를 실시(實施)하고 그 결과(結果)를 분석(分析)하였다. 연구결과(硏究結果) 최적설계과정(最適設計過程)의 반복회수(反復回數)를 중심(中心)으로 분석(分析)할 때 본연구(本硏究)의 알고리즘은 1~7회(回) 반복과정(反復過程)만으로 Oscillation현상(現像)없이 안정성(安定性)있게 최적해(最適解)에 수감(收歛)하고 있어 본연구(本硏究)의 방법(方法)도 반복회수(反復回數)만을 비교(比較)할 경우 효율적이라는 결론(結論)을 얻었다.

• 한국건설관리학회:학술대회논문집
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• 한국건설관리학회 2001년도 학술대회지
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• pp.214-221
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• 2001

인천국제공항 교통센터의 Great Hall은 3차원의 입체적 곡면 Truss로 구성되어 있고, Great Hall Roof Truss는 최대 경간162m, 480Ton인 Truss을 포함한 13개의 Main Steel Truss로 구성되어 있다. Great Hall Roof Truss는 총 중량 6,300Ton, 9,600 Pieces로 1개의 절점당 최대 13개의 다른 부재가 접합하게 되어 있고, 12개의 Fabric 기초에 의해 지지된다. 경제적인 효과와 공기적 측면을 고려하여 기존 재래식(가설 Bent) 공법보다 Block화 공법 및 Sliding공법을 채택하였다. Roof 구조물은 3,550Ton과 2,700Ton 중량인 두 Block으로 나누고 구조물 외부에 설치 된 Giant Sleigh에 선 조립 후 Tandem Pulling Jack과 Strand를 이용하여 181m를 Sliding하여 본 구조물의 위치에 설치되었다.

• Structural Engineering and Mechanics
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• 제43권5호
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• pp.607-621
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• 2012

The Expo Culture Centre is one of the permanent buildings at the World Expo 2010 in Shanghai, China. The main structure has an oval shape and consists of 36 radial cantilever steel trusses with different lengths and inner frames made of concrete-filled rectangular steel tube members. Tuned mass dampers are used to reduce the excessive vibrations of the sixth floor that are caused by human-induced resonance. A three-dimensional analytical model of the system is developed, and its main characteristics are established. A series of field tests are performed on the structure, and the test results show that the vertical vibration frequencies of most structural cantilevers are between 2.5 Hz and 3.5 Hz, which falls in the range of human-induced vibration. Twelve pairs of tuned mass dampers weighing 115 tons total were installed in the structure to suppress the vibration response of the system. These mass dampers were tuned to the vertical vibration frequency of the structure, which had the highest possibility of excitation. Test data obtained after the installation of the tuned mass dampers are used to evaluate their effectiveness for the reduction of the vibration acceleration. An analytical model of the structure is calibrated according to the measured dynamic characteristics. An analysis of the modified model is performed and the results show that when people walk normally, the structural vibration was low and the tuned mass dampers have no effect, but when people run at the structural vibration frequency, the tuned mass dampers can reduce the floor vibration acceleration by approximately 15%.

• Journal of the Korean Wood Science and Technology
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• 제27권3호
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• pp.23-30
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• 1999

경골 목조 트러스를 접합하는데 가장 널리 사용되는 메탈 플레이트 접합부의 거동을 해석하기 위한 연구가 많이 수행되어왔다. 유한요소법을 사용한 해석은 그 연구들중의 하나이다. 선형 모델을 사용한 유한요소법은 하중-변위 곡선의 초기 경사를 예측하는데는 유효하게 사용될 수 있다. 하지만, 하중이 증가할수록 예측된 변위는 실험치에 비해 과예측이 된다. 따라서 선형 모델을 비선형부분을 예측하는데는 사용할 수 없다. 실제 거동을 더욱 정확하게 예측하기 위해, 본 연구에서는 비선형 항을 유한요소 모델에 첨가시켰다. EA와 AA 형태에서는 예측치와 실험치간에 고도의 유사성을 보여주었다. 하지만, EE와 AE 형태에서는 곡선의 비선형 부분에서 실험치와 예측치가 약간의 차이를 보여주었다. 이러한 결과는 슬립의 효과를 충분히 반영하지 못한 것에 기인한 것으로 추측된다. 결과적으로 메틸플레이트 접합부의 거동에 있어서 비선형 해석의 정확도를 증진시키기 위해서는 반드시 슬립의 효과가 고려되어야 할 것이다.

• Steel and Composite Structures
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• 제28권2호
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• pp.233-250
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• 2018

Back-to-back built-up cold-formed steel un-lipped channel sections are used in cold-formed steel structures; such as trusses, wall frames and portal frames. In such built-up columns, intermediate fasteners resist the buckling of individual channel-sections. No experimental tests or finite element analyses have been reported in the literature for back-to-back built-up cold-formed steel un-lipped channel sections and specially investigated the effect of screw spacing on axial strength of such columns. The issue is addressed in this paper. The results of 95 finite element analyses are presented covering stub to slender columns. The finite element model is validated against the experimental tests recently conducted by authors for back-to-back built-up cold-formed steel lipped channel sections. The verified finite element model is then used for the purposes of a parametric study to investigate the effect of screw spacing on axial strength of back-to-back built-up cold-formed steel un-lipped channel sections. Results are compared against the built-up lipped channel sections and it is shown that the axial strength of un-lipped built-up sections are 31% lesser on average than the built-up lipped channel sections. It was also found that the American Iron and Steel Institute (AISI) and the Australian and New Zealand Standards were over-conservative by around 15% for built-up columns failed through overall buckling, however AISI and AS/NZS were un-conservative by around 8% for built-up columns mainly failed by local buckling.

• 한국전산구조공학회논문집
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• 제14권3호
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• pp.339-348
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• 2001

상용 구조해석 프로그램을 이용한 구조물의 최적설계에서는 최적화 프로그램과 구조해석 프로그램의 연결 및 두 프로그램 사이의 데이터 교환이 용이하지 못하다. 최근 많은 구조물 설계자들은 근사 최적화 기법을 이용하여 이와 같은 문제들을 해결하고 있다. 일반적으로 최적실계 문제의 설계변수에 대한 설계영역은 아주 작은 값에서 아주 큰 값으로 범위가 정해진다. 이렇게 넓은 설계영역에서 생성된 시스템 응답 근사식의 정확도는 떨어지게 되며, 이는 근사 최적해에 지배적인 영향을 미친다. 따라서, 본 연구의 목적은 넓은 설계영역에서 정확도가 높은 근사식 생성을 위한 순차 설계영역법 개발에 있다. 순차 설계영역에서의 근사식은 반응표면법을 이용하여 구성하고, 반응표면법에 필요한 실험방법으로는 직교 배열표를 사용한다. 본 연구에서는 순차 설계영역법의 신뢰도 검증을 위하여 3부재 및 10부재 트러스 구조물을 수치예제로 선정한다.

• 콘크리트학회논문집
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• 제17권4호
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• pp.513-520
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• 2005

현재 유럽 및 일본의 경우 기둥 및 보 부재에 대한 전단 설계에 있어, 전단기구로서 전단보강근과 주철근의 부착작용을 필요로 하지 않는 아치기구와 전단보강근과 주근의 부착 작용을 필요로 하는 트러스기구를 고려하여, 양자의 합으로 전단내력을 평가하는 방식을 취하고 있다. 이러한 설계 방법은 매우 명료하고, 또한 힘의 평형 조건에 기초하여, 단적으로 부착의 좋고 나쁨 및 전단보강근 양의 대소로 정해지는 상한 값으로 전단 내력을 평가하는 것이 특징이다. 본 연구에서는, 역대칭 휨 모멘트를 받는 철근콘크리트 보 부재에서 단부의 텐션쉬프트 영역 사이를 대상으로 한 주철근의 축 방향 응력(압축, 인장) 및 주근의 직경, 부착길이의 상이함에 기인하는 부착거동의 차이와 트러스 기구와의 관계를 명확히 하는 것을 목적으로, 트러스기구만이 재현 가능한 모델 실험법을 제안하고, 전단보강근의 양, 부재의 축압축 응력의 크기 및 부착 영역 양단의 주철근에 가하는 힘의 크기를 실험 변수로 한 부재 실험을 실시하였다. 실험에서 얻은 결과에 기초하여, 양단부 주철근에 가한 힘의 차이로 인해 발생하는 부착응력 분포의 차이를 고려한 일정 트러스 기구와 부채형 트러스기구를 중첩한 복합 트러스 모델을 제안하였다.

• Steel and Composite Structures
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• 제33권4호
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• pp.595-614
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• 2019

In cold-formed steel (CFS) structures, such as trusses, transmission towers and portal frames, the use of back-to-back built-up CFS unequal angle sections are becoming increasingly popular. In such an arrangement, intermediate welds or screw fasteners are required at discrete points along the length, preventing the angle sections from buckling independently. Limited research is available in the literature on axial strength of back-to-back built-up CFS unequal angle sections. The issue is addressed herein. This paper presents an experimental investigation on both the welded and screw fastened back-to-back built-up CFS unequal angle sections under axial compression. The load-axial shortening and the load verses lateral displacement behaviour along with the deformed shapes at failure are reported. A nonlinear finite element (FE) model was then developed, which includes material non-linearity, geometric imperfections and modelling of intermediate fasteners. The FE model was validated against the experimental test results, which showed good agreement, both in terms of failure loads and deformed shapes at failure. The validated FE model was then used for the purpose of a parametric study to investigate the effect of different thicknesses, lengths and, yield stresses of steel on axial strength of back-to-back built-up CFS unequal angle sections. Five different thicknesses and seven different lengths (stub to slender columns) with two different yield stresses were investigated in the parametric study. Axial strengths obtained from the experimental tests and FE analyses were used to assess the performance of the current design guidelines as per the Direct Strength Method (DSM); obtained comparisons show that the current DSM is conservative by only 7% on average, while predicting the axial strengths of back-to-back built-up CFS unequal angle sections.

• Steel and Composite Structures
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• 제33권1호
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• pp.37-66
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• 2019

In cold-formed steel structures, such as trusses, wall frames and portal frames, the use of back-to-back built-up cold-formed stainless-steel lipped channels as compression members are becoming increasingly popular. The advantages of using stainless-steel as structural members are corrosion resistance and durability, compared with carbon steel. The AISI/ASCE Standard, SEI/ASCE-8-02 and AS/NZS do not include the design of stainless-steel built-up channels and very few experimental tests or finite element analyses have been reported in the literature for such back-to back cold-formed stainless-steel channels. Current guidance by the American Iron and Steel Institute (AISI) and the Australian and New Zealand (gAS/NZS) standards for built-up carbon steel sections only describe a modified slenderness approach, to consider the spacing of the intermediate fasteners. Thus, this paper presents a numerical investigation on the behavior of back-to-back cold-formed stainless-steel built-up lipped channels. Three different grades of stainless steel i.e., duplex EN1.4462, ferritic EN1.4003 and austenitic EN1.4404 have been considered. Effect of screw spacing on the axial strength of such built-up channels was investigated. As expected, most of the short and intermediate columns failed by either local-global or local-distortional buckling interactions, whereas the long columns, failed by global buckling. All three grades of stainless-steel stub columns failed by local buckling. A comprehensive parametric study was then carried out covering a wide range of slenderness and different cross-sectional geometries to assess the performance of the current design guidelines by AISI and AS/NZS. In total, 647 finite element models were analyzed. From the results of the parametric study, it was found that the AISI & AS/NZS are conservative by around 10 to 20% for cold-formed stainless-steel built-up lipped channels failed through overall buckling, irrespective of the stainless-steel grades. However, the AISI and AS/NZS can be un-conservative by around 6% for all three grades of stainless-steel built-up channels, which failed by local buckling.

• Wind and Structures
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• 제28권3호
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• pp.181-190
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• 2019

Light-frame wood structures have the ability to carry gravity loads. However, their performance during severe wind storms has indicated weakness with respect to resisting uplift wind loads exerted on the roofs of residential houses. A common failure mode observed during almost all main hurricane events initiates at the roof-to-wall connections (RTWCs). The toe-nail connections typically used at these locations are weak with regard to resisting uplift loading. This issue has been investigated at the Insurance Research Lab for Better Homes, where full-scale testing was conducted of a house under appropriate simulated uplift wind loads. This paper describes the detailed and sophisticated numerical simulation performed for this full-scale test, following which the numerical predictions were compared with the experimental results. In the numerical model, the nonlinear behavior is concentrated at the RTWCs, which is simulated with the use of a multi-linear plastic element. The analysis was conducted on four sets of uplift loads applied during the physical testing: 30 m/sincreased by 5 m/sincrements to 45 m/s. At this level of uplift loading, the connections exhibited inelastic behavior. A comparison with the experimental results revealed the ability of the sophisticated numerical model to predict the nonlinear response of the roof under wind uplift loads that vary both in time and space. A further component of the study was an evaluation of the load sharing among the trusses under realistic, uniform, and code pressures. Both the numerical model and the tributary area method were used for the load-sharing calculations.