• 한국군사과학기술학회지
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• 제25권4호
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• pp.355-363
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• 2022

Development of supersonic flying vehicle is one of the most latest issue in modern military technology. Specifically, structural integrity of supersonic flying vehicle can be verified by high temperature structural test. High temperature structural test is required to consider thermal load caused by aerodynamic heating while applying structural load simultaneously. Tubular quartz lamps are generally used to generate thermal load by emitting infrared radiation. In this study, modified heat flux model of tubular quartz lamp is proposed based on existing model. Parameters of the proposed model are optimized upon measured heat flux in three dimensions. Finally, thermal load of plate specimen is designed by the heat flux model. In conclusion, it is possible to predict heat flux applied on plate specimen and desired thermal load of high temperature structural test can be obtained.

• Structural Engineering and Mechanics
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• 제89권2호
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• pp.171-179
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• 2024

The market of the floating solar photovoltaic system is rapidly growing around the world with the rise of renewable energy that can replace fossil energy. While the floating solar photovoltaic system is operating and being installed in several countries, the system is exposed to the risk in terms of structural safety due to the absence of the proper design guideline. In this paper, design loads suitable for the floating solar photovoltaic system are presented. Utilizing the existing reliable design standards such as ASCE 7-16 (ASCE 7-16 2016) and DNV-RP-C205 (DNV-RP-C205 2010), the appropriate design loads for the floating solar photovoltaic system are presented. The proper load combinations are also presented by putting wave load based on DNV standards (DNV-OS-C101 2015 and DNV-OS-C201 2015) into the load combinations in ASCE standards (ASCE 7-16 2016). We present the load combinations for the allowable stress design and load and resistance factor design, respectively.

• Advances in concrete construction
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• 제3권4호
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• pp.295-316
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• 2015

A bridge widening technology using steel-concrete composite system was developed and is presented in this paper. The widened superstructure system consists of a newly built composite steel-concrete girder with concrete deck and steel diaphragms attached to the existing concrete girders. This method has been applied in several bridge widening projects in China, and one of those projects is presented in detail. Due to the higher stiffness-to-weight ratio and the rapid erection of composite girders, this widening method reveals benefits in both mechanical performance and construction. As only a few methods for the design of bridges with different types of girders are recommended in current design codes, a more accurate analytical method of estimating live load distribution on girder bridges was developed. In the analytical model, the effects of span length, girder pacing, diaphragms, concrete decks were considered, as well as the torsional and flexural stiffness of both composite box girders and concrete T girders. The study shows that the AASHTO LRFD specification procedures and the analytical models proposed in this paper closely approximate the live load distribution factors determined by finite element analysis. A parametric study was also conducted using the finite element method to evaluate the potential load carrying capacities of the existing concrete girders after widening.

• 한국안전학회지
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• 제15권4호
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• pp.139-149
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• 2000

This study aims to review and assess the existing postural classification schemes used for evaluating postural loads in industry. The schemes can be classified into three categories: self-report, observational and instrument-based techniques depending upon how to record working postures. Of the three techniques, this study was mainly focused on the observational methods. The observational technique is most widely used in the industrial sites because it does not interfere with work, and is easy and simple to use and cost-effective without requiring the use of expensive equipment for estimating the angular deviation of a body segment from the neutral position. In spite of the usefulness and applicability, the techniques have some problems: 1) The existing observational techniques lack the consistency in the class limits of the motion categories in each body segment; 2) Most of them do not provide the post-analysis criteria needed to judge whether or not any posture is acceptable in view point of the postural load; and 3) They can not precisely evaluate the postural load for a given posture because the external loads and dynamic factors including acceleration, moment and force were not taken into consideration.

• Steel and Composite Structures
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• 제5권6호
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• pp.459-484
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• 2005

In recent years, the use of steel tube confined concrete (STCC) columns has been the interests of many structural engineers. The present study is an attempt to study the monotonic and cyclic behaviours of STCC columns. For the monotonic behaviours, a series of tests on STCC stub columns (twenty one), and beam-columns (twenty) were carried out. The main parameters varied in the tests are: (1) column section types, circular and square; (2) tube diameter (or width) to thickness ratio, from 40 to 162, and (3) load eccentricity ratio (e/r), from 0 to 0.5. For the cyclic behaviours, the test parameters included the sectional types and the axial load level (n). Twelve STCC column specimens, including 6 specimens with circular sections and 6 specimens with square sections were tested under constant axial load and cyclically increasing flexural loading. Comparisons are made with predicted column strengths and flexural stiffness using the existing codes. It was found that STCC columns exhibit very high levels of energy dissipation and ductility, particularly when subjected to high axial loads. Generally, the energy dissipation ability of the columns with circular sections was much higher than those of the specimens with square sections. Comparisons are made with predicted column strengths and flexural stiffness using the existing codes such as AIJ-1997, AISCLRFD- 1994, BS5400-1979 and EC4-1994.

• 한국정밀공학회지
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• 제32권11호
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• pp.997-1005
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• 2015

In this study, modal analysis and equivalent static load analysis for valve supports of 26" gas piping in gas stations were conducted and the existing straight and inclined types of valve supports were compared using seismic performance testing. Also, a new valve support shape was suggested by optimizing position of fastener holes, width and thickness of the support, and size of bracket. Improvement in seismic performance by design optimization was verified through equivalent static load analysis. The seismic performance of the newly proposed valve support was greatly improved and the maximum displacement and maximum stress of the seismic load was about 20% lower than those of the existing valve support.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2020년도 봄 학술논문 발표대회
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• pp.10-11
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• 2020

Currently, the most used forms, such as euro form and aluminum form, has many problems. There are issues with noise of construction site because of existing forms' material and issues with safety because of heavy weight. To solve these problems, there are many researches on using plastic and composite materials on the formwork. However, plastic has lower tensile strength than the steel and aluminum and composite materials are expensive. Therefore, constructors are avoid to use the forms with new materials. The purpose of this study is to develop light-weight plastic form to solve these existing problems by using ABS with optimized design. To verify, the study measured the amount of deflection from developed form through a load test. The test result showed a deflection of 1.15mm when 1.4ton was loaded in the middle of form. The result of the study verified that the usage of ABS and optimized design effectively reduced the weight and noise. Also, it's performance was verified through the load test.

• 한국압력기기공학회 논문집
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• 제12권2호
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• pp.58-65
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• 2016

Since, in case of high energy piping, steam jets ejected from the rupture zone may cause damage to nearby structure, it is necessary to design it into consideration of nuclear power plant design. For the existing nuclear power plants, the ANSI / ANS 58.2 technical standard for high-energy pipe rupture was used. However, the US Nuclear Regulatory Commission (USNRC) and academia recently have pointed out the non-conservativeness of existing high energy pipe fracture evaluation methods. Therefore, it is necessary to develop a highly reliable evaluation methodology to evaluate the behavior of steam jet ejected during high energy pipe rupture and the effect of steam jet on peripheral devices and structures. In this study, we develop a method for analyzing the impact load of a jet by high energy pipe rupture, and plan to carry out an experiment to verify the evaluation methodology. In this paper, the basic data required for the design of the jet impact load experiment equipment under construction, 1) the load change according to the jet distance, 2) the load change according to the jet collision angle, 3) the load variation according to structure diameter, and 4) the load variation depending on the jet impact position, are numerically obtained using the developed steam jet analysis technique.

• 한국지반공학회논문집
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• 제19권4호
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• pp.95-105
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• 2003

암반에 근입된 현장타설말뚝의 지지력 산정을 위하여 제안된 기존의 설계기준과 경험식들의 대부분은 재하시험의 결과에 일관되지 않은 파괴기준을 적용해서 얻어진 극한지지력에 근거해서 얻어졌다. 그 결과 이들산정식들은 동일한 조건에 설치된 말뚝에 대해서도 서로 다른 예측치를 제공하게 된다. 본 연구에서는 암반에 근입된 현장타설말뚝의 지지력을 합리적으로 산정할 수 있는 최적의 지지력산정식을 결정하기 위하여 기존의 지지력산정식들에 대하여 정확도를 조사하였다. 이를 위해서 11개의 재하시험 결과에 동일한 파괴기준을 적용함으로써 말뚝의 극한선단지지력과 극한주면마찰력을 결정하였으며, 이들은 기존 산정식으로부터 계산된 예측치의 정확도 조사에 이용되었다. 예측치와 측정치를 비교한 결과 Zhang과 Einstein의 제안식과 NAVFAC의 설계기준에 의해 계산된 극한선단지지력이 실측치에 가장 근접한 것으로 나타났다. 그리고 극한주면마찰력의 경우에는 Rosenberg와 Journeaux의 제안식이 만족스러운 예측치를 제공하였다.

• 한국전자통신학회논문지
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• 제18권6호
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• pp.1087-1094
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• 2023

빅데이터, 클라우드, IoT, AI 등 기술의 발전으로 인해 높은 데이터 처리율이 요구되고 있으며 네트워크의 유연성과 확장성에 대한 중요성이 증가하고 있다. 하지만 기존 네트워크 체계는 벤더와 장비에 종속되어 앞선 요구를 충족하기에는 한계가 존재한다. 이에 소프트웨어 중심의 유연한 네트워크를 구성할 수 있는 SDN 기술이 주목받고 있으며 특히 SDN을 기반의 부하 분산 방식은 방대한 트래픽을 효율적으로 처리하여 네트워크 성능을 최적화할 수 있다. 기존 SDN 환경에서 부하 분산 연구들은 서버와 컨트롤러 간 불필요한 트래픽이 발생하거나 서버가 임계치에 도달한 후에야 부하 분산이 이루어지는 제한사항이 존재한다. 본 논문에서는 이를 해결하기 위해 서버 부하에 따라 단계적으로 서버에 가중치를 부여하는 방식을 통해 불필요한 트래픽을 최소화하고 서버가 과부화 되기 전에 적절한 부하 분산이 이루어질 수 있는 방식을 제안한다.