• 한국압력기기공학회 논문집
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• 제4권2호
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• pp.50-56
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• 2008

The tubes in heat exchanger are typically made of copper alloy, stainless steel, carbon steel, titanium alloy material. Type-439 ferritic stainless steel is ferromagnetic material, and furnish higher heat transfer rates than austenitic stainless steels and higher resistance to corrosion-induced flaws. Ferritic stainless steel can be found in low-pressure(LP) feedwater heaters and moisture separator reheaters(MSRs) in turbine system. LP feedwater heaters generally utilize thin wall Type-439 stainless steel tubing, whereas MSRs typically employ a heavier wall tubing with integral fins. Service-induced damage can occur on the O.D(outside diameter) surface of Type-439 ferritic stainless steel tubing which is employed for MSRs tubing, and the most typical damage mechanism is vibration-induced tube-to-TSP(tube support plate) wear and fatigue cracking. The wear has been reported that occurs mainly on the OD surface. Accordingly, in this study, we have evaluated the flaw sizing capability of magnetic saturation eddy current technique using magnetic saturation probe and flawed specimen.

• Steel and Composite Structures
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• 제35권4호
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• pp.509-525
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• 2020

Steel-concrete composite slabs with profiled steel sheeting are widely used in the execution of floors in steel and composite buildings. The rapid construction process, the elimination of conventional replaceable shuttering and the reduction of temporary support are, in general, considered the main advantages of this structural system. In slabs with the spans currently used, the longitudinal shear resistance commonly provided by the embossments along the steel sheet tends to be the governing design mode. This paper presents an innovative reinforcing system that increases the longitudinal shear capacity of composite slabs. The system is constituted by a set of transversal reinforcing bars crossing longitudinal stiffeners executed along the upper flanges of the steel sheet profiles. This type of reinforcement takes advantage of the high bending resistance of the composite slabs and increases the slab's ductility. Two experimental programmes were carried out: a small-scale test programme - to study the resistance provided by the reinforcing system in detail - and a full-scale test programme to test simply supported and continuous composite slabs - to assess the efficacy of the proposed reinforcing system on the global behaviour of the slabs. Based on the results of the small-scale tests, an equation to predict the resistance provided by the proposed reinforcing system was established. The present study concludes that the resistance and the ductility of composite slabs using the reinforcing system proposed here are significantly increased.

• Earthquakes and Structures
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• 제7권1호
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• pp.101-117
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• 2014

This paper presents a reliability-based analysis on seismic performance of timber-steel hybrid shear wall systems. Such system is composed of steel moment resisting frame and infill wood frame shear wall. The performance criteria of the hybrid system with respect to different seismic hazard levels were determined through a damage assessment process, and the effectiveness of the infill wood shear walls on improving the seismic performance of the hybrid systems was evaluated. Performance curves were obtained by considering different target non-exceedance probabilities, and design charts were further established as a function of seismic weight. Wall drift responses and shear forces in wood-steel bolted connections were used as performance criteria in establishing the performance curves to illustrate the proposed design procedure. It was found that the presence of the infill wood shear walls significantly reduced the non-performance probabilities of the hybrid wall systems. This study provides performance-based seismic evaluations on the timber-steel hybrid shear walls in support of future applications of such hybrid systems in multi-story buildings.

• 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.

• Earthquakes and Structures
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• 제27권1호
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• pp.31-39
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• 2024

The reliability-based seismic design of steel frames is a complex process that incorporates seismic demand with a structural capacity to attain safe buildings aligned with specified constraints. This paper introduces an efficient base shear force formulation to support the reliability-based design process of steel frames. The introduced base shear force equation combines the seismic demand statistics with the reliability objective to calculate a fictitious base shear force for linear static analysis. By concentrating on the seismic demand and promising to meet a certain level of reliability, the equation converts the reliability-based seismic design problem to a deterministic one. Two code-compliant real-size steel moment frames are developed according to different reliability objectives to demonstrate the competency of the proposed formula. The nonlinear dynamic analysis method is used to assess the seismic reliability of the constructed frames, and the numerical results validate the credibility of the suggested formulation. The base shear force calculation method regarding seismic reliability is the main finding of this study. The ease of use makes this approach a potent tool for design professionals and stakeholders to make rapid risk-informed decisions regarding steel moment frame design.

• 열처리공학회지
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• 제23권4호
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• pp.198-204
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• 2010

Modified 9Cr-1Mo steels possess excellent high-temperature mechanical properties and are widely used in energy conversion industries. However, in-service materials degradation, such as softening, carbide-induced embrittlement, temper embrittlement, etc., can take place during long-term operation. Evolution of microstructure due to service exposure to high temperature has a strong effect on the performance of heat resistant steels. In case of modified 9Cr-1Mo steels, precipitation of $Fe_2Mo$-type laves phases and coarsening of $M_{23}C_6$-type carbides are the primary cause of degradation of mechanical properties such as toughness, hardness, tensile strength and creep resistance. This study was aimed at finding reliable parameter for assessing the integrity of modified 9Cr-1Mo steels. Characteristic parameters were attained between mechanical and ultrasonic properties.

• 한국강구조학회 논문집
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• 제21권5호
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• pp.471-481
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• 2009

본 연구는 SSC(Stiffened Steel Plate-Concrete) 구조와 NSC(Non-Stiffened Steel Plate-Concrete) 구조의 압축거동 특성을 비교 분석하여 SSC 구조의 구조적 성능 향상 효과를 파악하는데 그 목적이 있다. 여기서, SSC 구조는 강판에 리브(H형강)을 사용하여 선지지하고 스터드로 점지지하여 콘크리트와 일체화 시킨 구조이다. 한편 NSC 구조는 강판에 스터드로 점지지하여 콘크리트와 일체화 시킨 구조이다. 실험을 통해 다음과 같은 결과를 얻었다. SSC 구조가 NSC 구조에 비해 시험체의 강판좌굴 억제 및 급격한 콘크리트의 취성파괴를 방지하는 것으로 나타났다. 또한 SSC 구조가 NSC 구조에 비해 약 5%~28%정도 최대압축강도가 증가한 것으로 나타났다.

• Steel and Composite Structures
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• 제49권2호
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• pp.143-159
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• 2023

Recently, the design of scaffolding systems has garnered considerable attention due to the increasing number of scaffold collapses. These incidents arise from the underestimation of imposed loads and the site-specific conditions that restrict the application of lateral restraints in scaffold assemblies. The present study is committed to augmenting the buckling resistance of vertical support members, obviating the need for supplementary lateral restraints. To achieve this objective, experimental and computational analyses were performed to assess the axial load buckling capacity of steel props, composed of two hollow steel pipes that slide into each other for a certain length. Three full-scale steel props with various geometric properties were tested to construct and validate the analytical models. The total unsupported length of the steel props is 6 m, while three pins were installed to tighten the outer and inner pipes in the distance they overlapped. Finite Element (FE) modeling is carried out for the three steel props, and the developed models were verified using the experimental results. Also, theoretical analysis is utilized to verify the FE analysis. Using the FE-verified models, a parametric study is conducted to evaluate the effect of different inserted pipe lengths on the steel props' axial load capacity and lateral displacement. Based on the results, the typical failure mode for the studied steel props is global elastic buckling. Also, the prop's elastic buckling strength is sensitive to the inserted length of the smaller pipe. A threshold of minimum inserted length is one-third of the total length, after which the buckling strength increases. The present study offers a prop with enhanced buckling resistance and introduces an equation for calculating an equivalent effective length factor (k), which can be seamlessly incorporated into Euler's buckling equation, thereby facilitating the determination of the buckling capacity of the enhanced props and providing a pragmatic engineering solution.

• Wind and Structures
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• 제18권2호
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• pp.117-134
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• 2014

It is believed that offshore wind farms may satisfy an increasing portion of the energy demand in the next years. This paper presents a comparative study of the fatigue performances of tripod and jacket steel support structures for offshore wind turbines in waters of intermediate depth (20-50 m). A reference site at a water depth of 45 m in the North Atlantic Ocean is considered. The tripod and jacket support structures are conceived according to typical current design. The fatigue behavior is assessed in the time domain under combined stochastic wind and wave loading and the results are compared in terms of a lifetime damage equivalent load.

• 터널과지하공간
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• 제3권1호
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• pp.40-49
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• 1993

In this study, the indirect estimation method of the support load which is based upon the integrated measuring technique suggested by Kovari was applied to the calculation of support load in the mine roadway. Four test supports were installed in the area where they had to be replaed. Two of those were GI-130 rigid supports and the others were U-26 yieldable supports. The vibrating wire strain gages which were attached inpairs on the steel arch support were used to provide an accurate measurement. Bending moments and normal forces obtained from strain gage pairs were used to calculate the support load. This method was also verified by laboratory bending tests. The results obtained from the back-calculction method showed relatively good agreement with the measured convergence for each crossection.