• 한국산학기술학회논문지
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• 제18권6호
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• pp.389-394
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• 2017

선체구조의 보강재로서 비대칭 단면재인 L 형강재가 대칭 단면재인 T형 조립부재(built-up T)에 비해 단면 비틀림 현상 등 다소 불리한 강도 특성에도 불구하고 오랜 관습과 자재 구입의 용이성 등으로 널리 사용되어 왔다. 그러나 근래 선박이 대형화 되어감에 따라 보강재의 형태는 압출 형강재의 사용이 줄고 다양한 설계 치수를 반영하여 용접을 통해 직접 제작하는 조립부재의 적용이 늘어가는 추세이다. 본 연구의 목적은 점차 사용량이 증대되고 있는 조립형 보강재의 효율적인 적용을 위한 최적설계 프로그램을 개발하는데 있다. 최적화 알고리즘으로는 선박 및 해양구조물의 최적설계에 많이 적용되고 있는 진화전략 기법을 선정하였다. 최적설계 결과의 실용성을 위해 부식여유를 고려한 총두께 개념을 설계변수와 목적함수에 도입하였고, 제한조건에는 최근 발효된 통합공통구조규칙(HCSR, Harmonized Common Structural Rules)을 적용하였다. 개발된 최적화 프로그램을 이용하여 최근 수주된 300K VLCC와 158K COT의 실선 설계를 수행한 결과 각각 144톤, 60톤의 중량 절감 효과를 얻었으며 대형 선박일수록 중량 절감 효과가 크게 나타남을 확인하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.259-264
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• 1995

Recently, in order to achieve high flexibilty, monitoring and control strategies of a new type have been developed. This paper investigates the fesability of using scoustic emission signal analysis for the detection of built-up edge during machining. Results for maching SM45C steel show that the presence of a built-up edge can significantil affect the generation of acoustic emission in metal cutting. When the cutting speed comes to the conditions conducive to development of built-up edge, it is shown that the slope of curve-fitted AErms signal undergoes a change. The fesability of utilizing AErms in built-up edge sensing is sugested.

• 한국정밀공학회지
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• 제14권7호
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• pp.67-72
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• 1997

Recently, in order to achieve high flexibility of manufacture, monitoring and control strategies of a new type have been developed. Since the generation of built-up edge on the cutting tool damages the surface finish of the workpiece, the monitoring system of built-up edge is an important process monitoring. In this study, the analyzing methods of cutting force signal to detect the built-up edge during cutting process are described. The cutting force signals are analyzed using the mean, standard deviation and mean to standard deviation of this cutting signals. We can obtain the guide to detect the built-up edge during turning process.

• Steel and Composite Structures
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• 제38권6호
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• pp.617-635
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• 2021

This paper numerically investigated the behavior of built-up square concrete-filled steel tubular (CFST) columns under combined preload and axial compression. The finite element (FE) models of target columns were verified in terms of failure mode, axial load-deformation curve and ultimate strength. A full-range analysis on the axial load-deformation response as well as the interaction behavior was conducted to reveal the composite mechanism. The parametric study was performed to investigate the influences of material strengths and geometric sizes. Subsequently, influence of construction preload on the full-range behavior and confinement effect was investigated. Numerical results indicate that the axial load-deformation curve can be divided into four working stages where the contact pressure of curling rib arc gradually disappears as the steel tube buckles; increasing width-to-thickness (B/t) ratio can enhance the strength enhancement index (e.g., an increment of 1.88% from B/t=40 to B/t=100), though ultimate strength and ductility are decreased; stiffener length and lip inclination angle display a slight influence on strength enhancement index and ductility; construction preload can degrade the plastic deformation capacity and postpone the origin appearance of contact pressure, thus making a decrease of 14.81%~27.23% in ductility. Finally, a revised equation for determining strain εscy corresponding to ultimate strength was proposed to evaluate the plastic deformation capacity of built-up square CFST columns.

• Structural Engineering and Mechanics
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• 제74권3호
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• pp.381-394
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• 2020

The structural performance of cold-formed steel (CFS) built-up battened columns were numerically investigated in this paper. The built-up column sections were formed by connecting two-lipped channels back-to-back, with a regular spacing of battens plates, and have been investigated in the current study. Finite element models were validated with the test results reported by the authors in the companion paper. Using the validated models, the parametric study was extended, covering a wider range of overall slenderness to assess the accuracy of the current design rules in predicting the design strengths of the CFS built-up battened columns. The parameters viz., overall slenderness, different geometries, plate slenderness (b/t ratio) and yield stress were considered for this study. In total, a total of 228 finite element models were analyzed and the results obtained were compared with current design strength predicted by Effective Width Method of AISI Specifications (AISI S100:2016) and European specifications (EN1993-1-3:2006). The parametric study results indicated that the current design rules are limited in predicting the accuracy of the design strengths of CFS built-up battened columns. Therefore, a design equation was proposed for the AISI and EC3 specifications to predict the reliable design strength of the CFS Built-up battened columns and was also verified by the reliability analysis.

• Steel and Composite Structures
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• 제18권6호
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• pp.1451-1464
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• 2015

Recently, in recognition of their outstanding structural performance, the use of Concrete Filled Steel Tube (CFT) columns has been increased. New shape welded built-up square tube was developed by the authors for broader usability using thin steel plates which were bent to be L-shaped (Channel) and each unit members were welded to form square steel tube as an cost-efficient use of expensive steel. In addition, since the rib placed at the center of the tube width acts as an anchor; higher load capacity of buckling is achievable. In order to apply the new shape built-up square columns, the structural behavior and stress distribution with parameter width of thickness (b/t), with and without rib were predicted. The New shape welded built-up square tube effectively delayed the local buckling of the steel tube, which led to a greater strength and ductility than regular HSS.

• 한국강구조학회 논문집
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• 제30권1호
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• pp.13-23
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• 2018

단면을 자유롭게 제작할 수 있는 Built-up H형강(BH)의 사용이 점점 증대하고 있다. 본 연구는 BH의 규격화를 위한 기초연구로 SM490, SM520 강재의 항복강도, 인장강도, 연신율, 샤르피 흡수에너지 등의 소재특성을 확인하였다. 또한 single-SAW 및 tandem-SAW를 활용하여 6개의 BH 공시체를 제작하였으며, 공시체에서 매크로시험편, T바 인장실험체를 채취하여 용접성능을 확인하였다. 소재특성시험 결과 국내산 SM490, SM520 강재의 특성은 모두 KS를 만족하였으며, 용접성능실험 결과 BH의 용접부는 충분한 용접성능을 갖추었다고 판단할 수 있다. 따라서 본 연구에서 사용된 국내산 SM490, SM520 강재는 BH의 소재로 적합한 것으로 판단되며, single-SAW, tandem-SAW는 충분한 용접성능을 발휘하는 것으로 사료된다.

• Steel and Composite Structures
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• 제34권3호
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• pp.347-359
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• 2020

The objective of this study is to experimentally scrutinize the axial performance of built-up concrete filled steel tube (CFT) columns composed of steel plates. In this case, the main parameters cross section types, compressive strength of filled concrete, and the effect of welding lines. Welded built-up steel box columns are fabricated by connecting two pieces of cold-formed U-shaped or four pieces of L-shaped thin steel plates with continuous penetration groove welding line located at mid-depth of stub column section. Furthermore, traditional square steel box sections with no welding lines are investigated for the comparison of axial behavior between the generic and build-up cross sections. Accordingly, 20 stub columns with thickness and height of 2 and 300 mm have been manufactured. As a result, welding lines in built-up specimens act as stiffeners because have higher strength and thickness in comparison to the plates. Subsequently, by increasing the welding lines, the load bearing capacity of stub columns has been increased in comparison to the traditional series. Furthermore, for specimens with the same confinement steel tubes and concrete core, increment of B/t ratio has reduced the ductility and axial strength.

• 한국강구조학회 논문집
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• 제20권5호
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• pp.645-653
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• 2008

용접조립 각형강관은 얇은 강판을 L형으로 절곡한 4개의 단위 부재를 플레어 용접으로 용접한 강관으로 용접조립 각형강관이 CFT 기둥으로 사용될 경우 콘크리트와 강관 폭의 중앙에 설치된 리브가 국부좌굴을 방지하는 역할을 하며 강관은 내부의 콘크리트의 구속하여 콘크리트의 구조내력을 향상시키는 역할을 한다. 본 연구에서는 용접조립 각형강관기둥의 제작방법을 소개하고 용접조립 각형강관과 용접조립 각형CFT 기둥 의 구조성능을 평가하기 위해 강관의 형상(용접조립 각형강관, 일반강관)과 폭두께비(B/t=50, 58, 67), 콘크리트의 강도(f'c=, 10MPa, 40MPa) 를 변수로 총 15개의 실대형 실험체를 제작하여 구조실험을 수행하였으며 용접조립 각형강관의 단면효율과 구조내력의 우수성을 확인하였다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2006년 추계학술발표대회 개요집
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• pp.54-56
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• 2006