• 한국전산구조공학회논문집
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• 제20권5호
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• pp.653-660
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• 2007

강바닥판 포장에 사용될 수 있는 특수아스팔트 중의 하나인 구스아스팔트는 $240^{\circ}C$에서 $260^{\circ}C$의 고온 상태에서 시공되기 때문에 강바닥판에 예상하지 못한 열응력 및 열변형을 발생시킬 수 있다. 따라서 구스아스팔트의 타설 중에 강바닥판에 미치는 열영향을 시공조건을 고려하여 사전에 평가하고 그 영향의 최소화를 위해서는 열전달 및 열응력 수치해석을 실시하여야 하지만 구조해석에서 주로 사용되는 평판/보요소의 특성상 3차원 구조해석 모델에서 구현하기가 매우 어렵다. 본 연구에서는 강바닥판 교량의 열영향해석을 위하여 일반적인 구조해석모델에 직접 적용할 수 있는 등가열원(EHS) 산정방법을 제안하였다. 강바닥판 교량의 구스아스팔트에 의한 열영향을 정확히 평가하기 위하여 (1) 기존의 실험결과를 이용하여 열전달해석에 필요한 물리량을 검증하고, (2) 정밀해석을 통해 3차원 교량모델에 적합한 등가열원을 산정하였으며, (3) 이를 해석모델에 적용하여 산정한 등가열원에 의한 수치해석방법의 타당성을 검증하였다. 본 연구에서 제안된 등가열원은 실제 강교량의 3차원 열전달 및 열응력 해석에 즉각 활용될 수 있으며, 등가열원산정기법은 용접잔류응력해석, 교량의 화재 해석 등 열영향을 받는 다른 공학적 해석에 응용될 수 있을 것으로 기대된다.

• 한국강구조학회 논문집
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• 제16권4호통권71호
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• pp.463-470
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• 2004

본 연구에서는 중심축하중을 받는 각형강관기둥의 베이스플레이트의 지압응력의 분포와 설계에 대하여 조사하였다. 일반적으로 강구조 기둥의 베이스플레이트는 지압응력이 등분포하다고 가정하고 그 크기와 두께를 결정한다. 그러나 축하중이 적으면 베이스플레이트의 크기도 작아지고 두께도 얇아지며 지압응력은 등분포하게 되지 않으며 기둥단면의 하부에 집중된다. 본 연구에서는 실험적 방법과 해석적 방법으로 지압응력의 분포에 대하여 조사하고 그 결과를 이용하여 설계법을 검토하였다. 4개의 각형강관기둥 베이스플레이트 시험체를 제작하여 실험을 수행하였다. 또한 유한요소해석프로그램인 ANSYS를 이용하여 베이스플레이트의 지압응력의 분포를 해석하였다. 연구결과 축하중이 적은 경우 지압응력은 기둥단면의 하부에 집중되고 등분포하지 않으므로 유효폭의 개념을 이용하여 베이스플레이트를 설계하는 방법이 적절함을 나타내었다.

• Steel and Composite Structures
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• 제20권1호
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• pp.91-106
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• 2016

Two-dimensional elastoplastic finite element formulation is employed to investigate the load- carrying capacity degradation of reinforced concrete piers wrapped with steel plates due to occurrence of corrosion at the pier base. By comparing with experimental results, the employed finite element analysis method is verified to be accurate. After that, a series of parametric studies are conducted to investigate the effect of corrosion ratio and corrosion mode of steel plates located near the base of in-service pier P2 on load-carrying capacity of the piers. It is observed that the load-carrying capacity of the piers decreases with the increase in corrosion ratio of steel plates. There exists an obvious linear relationship between the load-carrying capacity and the corrosion ratio in the case of even corrosion mode. The degradation of load-carrying capacity resulted from the web's uneven corrosion mode is more serious than that under even corrosion mode, and the former case is more liable to occur than the latter case in actual engineering application. Finally, the failure modes of the piers under different corrosion state are discussed. It is found that the principal tensile strain of concrete and yield range of steel plates are distributed within a wide range in the case of slight corrosion, and they are concentrated on the column base when complete corrosion occurs. The findings obtained from the present study can provide a useful reference for the maintenance and strengthening of the in-service piers.

• Steel and Composite Structures
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• 제19권4호
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• pp.1035-1053
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• 2015

A genetic algorithm-based minimum weight design method is presented for steel frames containing composite beams, semi-rigid connections and column bases. Genetic Algorithms carry out optimum steel frames by selecting suitable profile sections from a specified list including 128 W sections taken from American Institute of Steel Construction (AISC). The displacement and stress constraints obeying AISC Allowable Stress Design (ASD) specification and geometric (size) constraints are incorporated in the optimization process. Optimum designs of three different plane frames with semi-rigid beam-to-column and column-to-base plate connections are carried out first without considering concrete slab effects on floor beams in finite element analyses. The same optimization procedures are then repeated for the case of frames with composite beams. A program is coded in MATLAB for all optimization procedures. Results obtained from the examples show the applicability and robustness of the method. Moreover, it is proved that consideration of the contribution of concrete on the behavior of the floor beams enables a lighter and more economical design for steel frames with semi-rigid connections and column bases.

• 한국응용과학기술학회지
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• 제25권4호
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• pp.485-494
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• 2008

The acrylic coating emulsions were prepared by the emulsion polymerization to protect the surface of steel plate from the corrosion chemicals like acid, base and salt water. MMA(methyl methacrylate), styrene, BA(butyl acrylate), and 2-HEMA(2-hydroxyethyl methacrylate) were used as monomer. KPS(potassium persulfate) and SBS(sodium bisulfite) as redox initiator and SDBS(sodium dodecylbenzene sulfonate) as emulsifier were used on the emulsion polymerization reaction. The most stable in-situ coating was obtained when 10% of MMA was added. Both particle size and quantity in emulsion were decreased as increasing the mount of SDBS. the most stable prepared coating emulsion with polyisocyanate crosslinker showed very high anticorrosion properties on the coated steel layer to salt water, whereas no significant improvement of anticorrosion property to acdic and basic condition it showed.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.505-510
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• 2008

The design of noncomposite construction for skew bridges with large skew angels has been often checked because composite construction may cause large stresses in the bridge deck. In this study, the analytical model considered dynamic behaviors for noncomposite skew bridges was proposed. Using the proposed analytical model, the effects of interactions between the concrete deck and steel girders such as composite construction, and noncomposite construction on the dynamic characteristics of simply supported skew bridges were investigated. A series of parametric studies for the total 27 skew bridges was conducted with respect to parameters such as girder spacing, skew angle, and deck aspect ratio. The slip at the interfaces between the concrete deck and steel girders may bring about longer vibration periods that result in the reduced total seismic base shear.

• 한국지진공학회논문집
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• 제21권6호
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• pp.311-322
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• 2017

In this study, the seismic performance of concrete-steel composite moment frame structures equipped with seismic retrofitting systems such as seismic reinforcement, base isolators, and bracing members, which are typical earthquake damage mitigation systems, is evaluated through nonlinear dynamic analyses. A total of five frame models were designed and each frame model was developed for numerical analyses. A total of 80 ground acceleration data were used to perform the nonlinear dynamic analysis to measure ground shear force and roof displacement, and to evaluate the behavioral performance of each frame model by measuring inter-story drift ratios. The analysis results indicate that the retrofitting device of the base isolator make a significant contribution to generating relatively larger absolute displacement than other devices due to flexibility provided to interface between ground and column base. However, the occurrence of the inter-story drift ratio, which is a relative displacement that can detect the damage of the structure, is relatively small compared with other models. On the other hand, the seismic reinforced frame model enhanced with the steel plate at the lower part of the column was found to be the least efficient.

• 열처리공학회지
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• 제8권1호
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• pp.53-64
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• 1995

A study was made to characterize the microstructures and mechanical properties of the base metal and the heat-affected zone(HAZ) in Cu-bearing HSLA-100 steel. The Gleeble thermal/mechanical simulator was used to simulated the weld HAZ. The relationship between microstructure and toughness of HAZ was studied by impact test, O. M, SEM, TEM, and DSC. The toughness requirement of military specification value was met in all test temperatures for the base metal. The decrease of HAZ toughness comparing to base plate is ascribed to the coarsed-grain and the formation of bainite. Obliquely sectioned Charpy specimens show that secondary crack propagate easily along bainite lath. Improved toughness(240J) at HAZ of $Tp_2=950^{\circ}C$ is due to the fine grain, and reasonable toughness(160~00J) in the intercritical reheated HZA is achieved by the addition of small amount of carbon which affects the formation of "M-A". Cu precipitated during ageing for increasing the strength of base metal is dissolved during single thermal cycle to $1,350^{\circ}C$ and is precipitated little on cooling and heating during subsequent weld thermal cycle. Thus, the decrease of toughness does not occur owing to the precipitation of Cu.

• Corrosion Science and Technology
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• 제6권3호
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• pp.96-102
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• 2007

The resistance of the linepipe steel to hydrogen-induced cracking (HIC) and sulfide stress cracking (SSC) is very important for steel to be used in sour oil/gas environments. Welding of steels is necessary to the construction of pipe-line transporting oil/gas. In this study, HIC and SSC resistance of an electric resistance welded (ERW) steel plate which belongs to API X70 grade was evaluated by using NACE TM0284-96A and NACE TM0177-96A methods. HIC and SSC fracturing behavior was investigated by observing fractured surfaces using optical microscopy (OM) and scanning electron microscopy (SEM). It was discussed in terms of metallurgical parameters such as the distribution of primary microstructure, second phases and inclusions. Results showed that the weld joint of ERW steel is more sensitive than base metal to HIC and SSC. This is due to difference in the contribution of metallurgical parameters to HIC and SSC nucleation and propagation.

• 한국표면공학회지
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• 제13권2호
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• pp.81-86
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• 1980

The mechanical properties of aluminized steel were investigated after the JIS SB 41 plates were dipped in molten aluminum bath. (1) The growth rate of iron-aluminum alloy layer was fast in early stage of alumizing, and then gradually decreased with increasing time. However, over the time period above 10 minutes the growth of alloy layer did not occur. (2) The constituent of alloy layer formed on the steel surface was identified to be intermetallic compound of $Fe_2\;Al_5$. (3) The ultimate tensile strength and elongation of aluminized steel showed a nearly constant value over all thickness below about 0.15 mm. However, both properties decreased rapidly in showed a nearly constant value over all thickness above about 0.20 mm. (4) In case of aluminized steel with greater thickness, crack was formed below yield point of base metal, which is considered to be attributed to the alloy layer failure.