• 한국철도학회:학술대회논문집
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• 한국철도학회 2006년도 추계학술대회 논문집
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• pp.1354-1363
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• 2006

Until now, NATM(New Austrian Tunneling Method) has been increasingly developed based on concept of making use of ground as support. Also, NATM in its essence is a method of risk based on monitoring behaviour of tunnel. This Monitoring is irreplaceable for the quality construction of tunnel, and safety of tunnel itself. Pre-reinforcement ahead of a tunnel face using long steel pipes in NATM, known as the RPUM(Reinforced Protective Umbrella Method), is the auxiliary method to sustain the stability of a tunnel face and reduce the ground settlements. Since design of RPUM has been dependent on the empirical design, it is necessary to develop the improved design methods. In this study, to understand behaviour of steel pipes, it is monitored displacement of tunnel crown, axial force of rock bolt, displacement and axial stress of steel pipes. Also, in order to clarify the mechanical behaviour and RPUM effects, 3-Dimensional numerical analysis is performed that various cases of different parameter combinations including original length and repeated length of steel pipes, installation width and angle, repeated length of steel. In the results of comparison monitoring with analysis, it is suggested more economical and efficient design technique than empirical design methods.

• 한국강구조학회 논문집
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• 제19권4호
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• pp.403-411
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• 2007

CFT(Concrete filled steel tube)기둥은 콘크리트와 강관의 이질적인 성질을 상호보완 할 수 있는 구조체 일뿐만 아니라 시공적인 측면에서도 공기단축으로 인한 공사원가 절감으로 인해 최근 널리 사용되고 있다. 그러나 기존CFT기둥은 강관의 항복이후 일정지점의 국부좌굴을 생기는 단점을 지니고 있다. 이를 개선하고자 본 연구에서는 예상국부좌굴위치에 탄소섬유쉬트로 보강을 한 TR(Tranversely reinforced) -CFT기둥에 대해 실험을 수행하였다. 실험변수는 콘크리트강도와 탄소섬유쉬트보강량이며 CFT실험체와 TR-CFT실험체의 이력곡선, 초기강성, 내력, 소성변형능력, 흡수에너지를 각각 비교분석하였다.

• 대한금속재료학회지
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• 제50권1호
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• pp.13-22
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• 2012

Forged and flat-bar rolled STD11 tool steel shows anisotropic dimensional change during heat treatment. The dimensional change in the rolling direction is larger than that in the transverse direction. The cause of the anisotropic dimensional change is that the steel is anisotropic in composition, microstructure and other properties. The decrease of anisotropic distortion in tool steel is important for making better precision cold working dies. In this study, the effect of ingot weight and hot rolling reduction ratio on the anisotropic dimensional change of STD11 during heat treatment has been studied. Dimensional change was evaluated by simulating a real heat treatment process, including gas quenching and tempering. Experimental results showed that all the rolled flat-bar products had anisotropic distortion to some degree, but the anisotropic distortion was reduced as hot rolling ratio increased. Ingot weight had a little effect on anisotropic distortion. Microstructural observation showed that the anisotropic dimensional change of STD11 tool steel was closely related to the amount, shape and distribution of coarse carbides.

• Computers and Concrete
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• 제22권6호
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• pp.527-538
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• 2018

Buckling of longitudinal bars is a brittle failure mechanism, often recorded in reinforced concrete (RC) structures after an earthquake. Studies in the literature highlights that it often occurs when steel is in the post elastic range, by inducing a modification of the engineered stress-strain law of steel in compression. A proper evaluation of this effect is of fundamental importance for correctly evaluating capacity and ductility of structures. Significant errors can be obtained in terms of ultimate bending moment and curvature ductility of an RC section if these effects are not accounted, as well as incorrect evaluations are achieved by non-linear static analyses. This paper presents a numerical investigation aiming to evaluate the engineered stress-strain law of reinforcing steel in compression, including second order effects. Non-linear FE analyses are performed under the assumption of local buckling. A role of key parameters is evaluated, making difference between steel with strain hardening or with perfectly plastic behaviour. Comparisons with experimental data available in the literature confirm the accuracy of the achieved results and make it possible to formulate recommendations for design purposes. Finally, comparisons are made with analytical formulations available in the literature and based on obtained results, a modification of the stress-strain law model of Dhakal and Maekawa (2002) is proposed for fitting the numerical predictions.

• Earthquakes and Structures
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• 제26권5호
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• pp.363-382
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• 2024

In India's north-eastern region, low-strength autoclaved aerated concrete (AAC) blocks are widely used for constructing masonry structures, making them susceptible to lateral forces due to their low tensile and shear strengths and brittleness nature. The absence of earthquake-resistant attributes further compromises their resilience during seismic events. An economically viable solution to enhance the structural integrity of these masonry structures involves integrating steel wire mesh within the masonry mortar joints. This study investigates the in-plane shear behaviour of AAC masonry by employing two approaches: incorporating steel wire mesh within the masonry bed joint "BJ" and the masonry bed and head joint "BHJ". These approaches aim to augment strength and ductility, potentially serving as earthquake-resistant attributes in masonry structures. Three distinct variations of steel wire mesh and three reinforcing arrangements, i.e. (-), (L) and (Z) arrangement were employed to reinforce the two approaches. The test result reveals a significant enhancement in structural performance upon inclusion of steel wire mesh in both reinforcing approaches, with the "BHJ" approach outperforming the "BJ" approach and the unreinforced masonry, along with increase in capacity as the wire mesh size increases. Furthermore, the effectiveness of the reinforcing arrangement is ranked with the (Z) arrangement showing the largest performance, followed by the (L) and (-) arrangement.

• 자원리싸이클링
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• 제26권6호
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• pp.45-49
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• 2017

반도체 산업의 실리콘(Si) 제조과정에서 실리콘과 실리콘 카바이드(SiC)를 포함하는 폐 슬러리가 발생하게 된다. 폐 슬러리는 단순히 시멘트로 고형화하여 보관하거나 매립하는 방법이 있지만, 본 연구에서는 제강공정의 부원료인 승온제로 사용하는 방안이 제시되었다. 폐 슬러리를 정제하여 분말을 만들어 SiC계 슬러지 브리켓으로 재활용하였다. SiC계 슬러지 브리켓은 화학적 성분을 분석하고 투입시기와 투입량에 따른 승온제 특성을 관찰하였다. 이 결과 SiC계 슬러지 브리켓은 제강공장에서 저비용과 고효율로 용강온도를 높이는 효과가 있었다.

• 한국강구조학회 논문집
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• 제21권5호
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• pp.515-526
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• 2009

콘크리트 충전강관에 사용되는 강관의 제작법은 재단된 4장의 플레이트를 모서리에서 용접하는 일반강관 제작법과, ㄷ형으로 절곡성형과정을 거쳐 2-Seam으로 용접하는 제작방법, 그리고 원형강관을 압축하여 4각형태로 만드는 방법등이 일반적으로 사용되며, 강관제작에 사용되는 용접방법과 용접량의 선택은 강관 제작비용에 큰 부분을 차지하고 있다. 새로운 제작형식으로 개발된 각형강관은 4장의 플레이트를 ㄱ형으로 절곡성형한 후 강관 폭의 중앙에서 4-Seam Flare 용접하는 방식이다. 본 연구에서는 새로운 제작형식의 CFT 각형 기둥에 대하여 용접량 평가를 위한 실험방법을 제시하고, 강관 제작법, 강관두께 및 용접량을 변수로 총 6개의 실험체를 제작하여 구조실험 및 해석을 수행하여 강관내부의 수압에 따른 강관의 거동을 평가하였다.

• 산업경영시스템학회지
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• 제40권2호
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• pp.51-59
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• 2017

Due to the rapid change of global business environment, the growth of China's steel industry and the inflow of cheap products, domestic steel industry is faced on downward trend. The change of business paradigms from a quantitative growth to a qualitative product is needed in this steel industry. In this environment, it is very important for domestic steel distribution companies to secure their competitiveness by selecting good supply companies through a efficient procurement strategy and effective method. This study tried to find out the success factors of steel distribution industry based on survey research from experts. Weighted values of each factors were found by using AHP (analytic hierarchy process) analysis. The weighted values were applied to DEA(data envelopment analysis) model and eventually the best steel supply company were selected. This paper used 29 domestic steel distribution firms for case example and 5 steps of decision process to select good vendors were suggested. This study used quality, price, delivery and finance as a selection criteria. Using this four criterions, nine variable were suggested. Which were product diversity, base price, discount, payment position, average delivery date, urgency order responsibility and financial condition. These variables were used as a output variable of DEA. Sales and facilities were used as an input variable. Pairwise comparison was conducted using these variables. The weighted value calculated by AHP pairwise comparison were used for DEA analysis. Through the analysis of DEA efficiency process, good DMU (decision making unit) were recommended as a steel supply company. The domestic case example was used to show the effectiveness of this study.

• Structural Engineering and Mechanics
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• 제84권3호
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• pp.311-321
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• 2022

In the buildings with long spans and high floors, such as logistics warehouses and semiconductor factories, it is difficult to install supporting posts under beams during construction. Therefore, the size of structural members becomes larger inevitably, resulting in a significant increase in construction costs. Accordingly, a prestressed hybrid wide flange (PHWF) beam with hollowed steel webs was developed, which can reduce construction costs by making multiple openings in the web of the steel member embedded in concrete. However, since multiple openings exist and prestress is introduced only into the bottom flange concrete, it is necessary to identify the shear resistance mechanism of the PHWF beam. This study presents experimental shear tests of PHWF beams with hollowed steel webs. Four PHWF beams with cast-in-place (CIP) concrete were fabricated, with key variables being the width and spacing of the steel webs embedded in the concrete and the presence of shear reinforcing bars, and web-shear tests were conducted. The shear behavior of the PHWF beam, including crack patterns, strain behavior of steel webs, and composite action between the prestressed bottom flange and CIP concrete, were measured and analyzed comprehensively. The test results showed that the steel web resists external shear forces through shear deformation when its width is sufficiently large, but as its width decreased, it exerted its shear contribution through normal deformation in a manner similar to that of shear reinforcing bars. In addition, it was found that stirrups placed on the cross section where the steel web does not exist contribute to improving the shear strength and deformation capacity of the member. Based on the shear behavior of the specimens, a straightforward calculation method was proposed to estimate the web-shear strength of PHWF beams with CIP concrete, and it provided a good estimation of the shear strength of PHWF beams, more accurate than the existing code equations.

• Structural Engineering and Mechanics
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• 제50권3호
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• pp.323-347
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• 2014

This paper proposes a Particle Swarm Optimization (PSO) algorithm, which is improved by making use of the Harmony Search (HS) approach and called HS-PSO algorithm. A computer code is developed for optimal sizing design of non-linear steel frames with various semi-rigid and rigid beam-to-column connections based on the HS-PSO algorithm. The developed code selects suitable sections for beams and columns, from a standard set of steel sections such as American Institute of Steel Construction (AISC) wide-flange W-shapes, such that the minimum total cost, which comprises total member plus connection costs, is obtained. Stress and displacement constraints of AISC-LRFD code together with the size constraints are imposed on the frame in the optimal design procedure. The nonlinear moment-rotation behavior of connections is modeled using the Frye-Morris polynomial model. Moreover, the P-${\Delta}$ effects of beam-column members are taken into account in the non-linear structural analysis. Three benchmark design examples with several types of connections are presented and the results are compared with those of standard PSO and of other researches as well. The comparison shows that the proposed HS-PSO algorithm performs better both than the PSO and the Big Bang-Big Crunch (BB-BC) methods.