• 국제강구조저널
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• 제18권4호
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• pp.1191-1199
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• 2018

Concepts of submerged floating tunnels (SFTs) for land connection have been continuously suggested and developed by several researchers and institutes. To maintain their predefined positions under various dynamic environmental loading conditions, the submerged floating tunnels should be effectively moored by reasonable mooring systems. With rational mooring systems, the design of SFTs should be confirmed to satisfy the structural safety, fatigue, and operability design criteria related to tunnel motion, internal forces, structural stresses, and the fatigue life of the main structural members. This paper presents a feasibility study of a submerged floating tunnel moored by an inclined tendon system. The basic structural concept was developed based on the concept of conventional cable-stayed bridges to minimize the seabed excavation, penetration, and anchoring work by applying tower-inclined tendon systems instead of conventional tendons with individual seabed anchors. To evaluate the structural performance of the new type of SFT, a hydrodynamic analysis was performed in the time domain using the commercial nonlinear finite element code ABAQUS-AQUA. For the main dynamic environmental loading condition, an irregular wave load was examined. A JONSWAP wave spectrum was used to generate a time-series wave-induced hydrodynamic load considering the specific significant wave height and peak period for predetermined wave conditions. By performing a time-domain hydrodynamic analysis on the submerged floating structure under irregular waves, the motional characteristics, structural stresses, and fatigue damage of the floating tunnel and mooring members were analyzed to evaluate the structural safety and fatigue performance. According to the analytical study, the suggested conceptual model for SFTs shows very good hydrodynamic structural performance. It can be concluded that the concept can be considered as a reasonable structural type of SFT.

• 한국안전학회지
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• 제21권3호
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• pp.67-72
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• 2006

This study is to investigate the related materials such as domestic law regulation, research paper, research report, and the other material, and to suggest suitable counter measures, to find out hazard degree for its works of workers and work place through direct survey, in order to determine risk score of each hazardous work which is designated by the Government, without consideration of labour's consciousness against risk level at a site. Therefore, a new questionnaire survey related to the decision of risk level are made and distributed to find out what risk level each worker recognizes. Also, the authors tried to approach reasonable conclusions after discussing reasonability of qualification standard and improving ideas of worker at hazardous work places with worker, faculty member, H&S manager, labour union. And the results show hazard degrees by each work kind of the above: 3.75 for working with machinery, 3.7 for steel structure, 3.5 for operation of tower crane, 3.51 for retaining wall, 3.85 for form work, 3.46 for scaffolding are obtained. This quantified risk can be applied to establishing a reasonable system to keep safe against hazardous works.

• 한국안전학회지
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• 제21권5호
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• pp.53-59
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• 2006

Standard safety management costs can not be applied to each site with same rate, it is very difficult, because it depends on the experience, work method, work kind, work progress schedule, and hazard level of each construction company. Therefore, this study is to find out hazard level of each work kinds through questionnaire and interview and investigate analyze the status which standard safety management costs have been used. Also, this study is to show reasonable rates of standard safety management costs in construction industry and to set up countermeasures against those problem after reviewing its status in korea with in Japan and Europe. The domestic system of standard safety management costs is not considered in the foreign country, while only related subjective items have been investigated and evaluated for this study. This study is to investigate eleven project kinds of domestic system, first, and to investigate eleven items of apartment bldg, office, civil work such as bridge, tunnel, dam, plant etc, secondly. Additionally, three items of gymnasium, railway, particular steel tower are investigated in this study. Also this study is to investigate and analyze performed costs of presently processing worker finished work so that it shows a new reasonable rate against standard safety management costs in construction industry, in order to make basial data and material to be systemized.

• 한국조경학회지
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• 제33권3호
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• pp.43-55
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• 2005

Since 1990s, increasing number of public arts have been installed in housing projects in Korea. Most of them were made of granite, bronze and stainless steel and were sculptures as well. Then it resulted in monotony. New technology and community need various Dials in material and genre of Public art. The author wonders if people really want granite sculpture, so started the study of public arts in housing projects. Unfortunately most of people related public art wanted granite sculpture. But there were some hope in survey. They wanted the other genre and material like ceramic wall, art fountain and landmark tower. This means that they care about real world like vandalism and Product Liability, but also want more fantastic and beautiful world in the second step. Recently, the facades of apartments are changing rapidly as more diverse materials in their forms, textures, and colors. And landscape designs are changing their clothes in every second as well. According to these flows public arts in apartments needs more diversified trial within genres and materials to avoid monotonous outdoor.

• 전기의세계
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• 제18권1호
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• pp.24-29
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• 1969

This is preliminary study concerning the future construction and operation of 345KV power transmission line in Korea which will be added to the existing 161KV power system by the end of 1970 in order to increase the power carrying capacity between Seoul and Pusan area; 350 kilo meters aparts, in accordance with the ambitious second five years power development schedule of Korea Electric Company. The result of this study says that an intermidiate switching station should be installed at the middle position of the line to improve the transient stability of the system, considerable amount of capacitors or synchronous condenser are to be installed to reduce the voltage drop at receving end of line during the heavy load hours, and also in some measure to avoid the voltage rise by self-excitation of power generators during the light load hours and while energizing the line. This is the first attempt to realize the EHV power transmission line in Korea so that the additional study is necessary on the kind and size of conductors, the necessary number of insulators and the suitable clearance distances between conductor and steel tower or earth from the technical and economical view points. These are necessary steps to be taken by the writer before getting into the calculation on the transient stablity of the power system.

• Structural Engineering and Mechanics
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• 제44권3호
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• pp.379-403
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• 2012

In recent years, the need for optimal design of structures under time-history loading aroused great attention in researchers. The main problem in this field is the extremely high computational demand of time-history analyses, which may convert the solution algorithm to an illogical one. In this paper, a new framework is developed to solve the size optimization problem of steel truss structures subjected to ground motions. In order to solve this problem, the covariance matrix adaptation evolution strategy algorithm is employed for the optimization procedure, while a generalized regression neural network is utilized as a meta-model for fitness approximation. Moreover, the computational cost of time-history analysis is decreased through a wavelet analysis. Capability and efficiency of the proposed framework is investigated via two design examples, comprising of a tower truss and a footbridge truss.

• 복합신소재구조학회 논문집
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• 제2권3호
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• pp.42-47
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• 2011

임의의 단면과 지점을 갖고 임의의 하중을 받는 보나 탑의 진동해석 방법이 발표된 바가 있다. 이러한 진동해석을 위하여 처짐의 영향을 고려한 다양한 방법이 검토되었다. 본 연구에서 얻은 결과를 보 이론과 비교하였다. 이러한 목적으로 본 논문에서는 유한차분법을 사용하였다. 고유진동수에 대한 $D_{22}$ 탄성계수의 영향을 철저히 검토하였다. 본 논문에서는 구조부재의 고유진동수와 적용 하중의 크기에 대한 관련성을 연구하였으며 그 결과를 제시하였다. 본 논문에서는 특별직교이방성 판이론 이용하여 강교량과 철근콘크리트 슬래브 교량에 적용하여 을 해석하였으며 그 결과를 제시하였다.

• Structural Engineering and Mechanics
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• 제15권1호
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• pp.115-134
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• 2003

The Ting Kau Bridge in Hong Kong is a cable-stayed bridge comprising two main spans and two side spans. The bridge deck is supported by three towers, an end pier and an abutment. Each of the three towers consists of a single reinforced concrete mast which reduces its section in steps, and it is strengthened by transverse cables and struts in the transverse vertical plane. The bridge deck is supported by four inclined planes of cables emanating from anchorages at the tower tops. In view of the threat from typhoons, the dynamic behaviour of long-span cable-supported bridges in the region is always an important consideration in their design. This paper is devoted to the ambient vibration measurements of the bridge for evaluation of dynamic characteristics including the natural frequencies and mode shapes. It also describes the modelling of the bridge. A few finite element models are developed and calibrated to match with the field data and the results of subsequent structural health monitoring of the bridge.

• Coupled systems mechanics
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• 제3권2호
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• pp.171-193
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• 2014

The dynamic characterization is important in making accurate predictions of the seismic response of the hybrid structures dominated by different damping mechanisms. Different damping characteristics arise from the construction of hybrid structure with different materials: steel for the upper part; reinforced concrete for the lower main part and interaction with supporting soil. The process of modeling damping matrices and experimental verification is challenging because damping cannot be determined via static tests as can mass and stiffness. The assumption of classical damping is not appropriate if the system to be analyzed consists of two or more parts with significantly different levels of damping. The dynamic response of structures is critically determined by the damping mechanisms, and its value is very important for the design and analysis of vibrating structures. A numerical algorithm capable of evaluating the equivalent modal damping ratio from structural components is desirable for improving seismic design. Two approaches are considered to explore the dynamic response of hybrid tower of cable-stayed bridges: The first approach makes use of a simplified model of 2 coupled lumped masses to investigate the effects of subsystems different damping, mass ratio, frequency ratio on dynamic characteristics and equivalent modal damping; the second approach employs a detailed numerical step-by step integration procedure.

• 한국안전학회지
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• 제37권6호
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• pp.25-31
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• 2022

In this study, the spill and leak system is developed to provide real-time remote monitoring of industrial complexes where chemical accidents have been occurring every year. The spill and leak monitoring system uses IR-RCD equipment mounted on a 70m-high steel tower to detect chemical substances, thereby detecting chemical accidents such as leaks, fires, and explosions in real time. If IR-RCD equipment can actually detect chemical substances at a long distance, accurate and rapid initial response can be expected. Therefore, in order to confirm that IR-RCD equipment can detect chemical leakage accidents occurring at a long distance, acetone was selected as the experimental substance and a detection experiment was designed. The experiment was conducted using the acetone pool evaporation method at the wharf which was located 1.5 km away from IR-RCD equipment, and it was confirmed whether IR-RCD equipment could detect acetone in real time through the control monitor.