• Journal of Advanced Marine Engineering and Technology
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• v.25 no.2
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• pp.409-409
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• 2001

해양구조물은 점점 대형화되어 가고 있는 추세에 있으며 또한 이들 구조물의 대형화에 따른 구조물의 보수, 유지관리가 매우 중요한 사안으로 등장하게 되었다. 뿐만 아니라, 이러한 구조물 등이 손상또는 파괴되었을 경우는 그에 따른 인적, 경제적 손실 또한 막대할 것으로 사료되며 이러한 구조물의 파괴사례중 상당 부분이 용접부의 부식문제 및 수소취화와 관련된 사고인것으로 보고되고 있다. 한편 용접은 급속가열, 급속냉각의 공적으로 인한 경도와 열적, 조직적 변화를 일으켜 용접부 각 미세부위별 전위차가 발생하게 되며, 이로 인해 갈바낙부실을 일으키는 것으로 보고 있다. 그리고 갈바닉 부식에 의한 용접부의 부식성을 억제하기 위해 용접후열처리(post weld heat treatment PWHT)를 시행하여 내식성을 향상시키는 경우도 있다. 본 연구에서는 고장력강인 RE36강 시험편을 전기화학적 측면에서 최적의 용접후열처리 온도를 규명하였으며, 용접방법(FCAW, SMAW), 용접후 열처리 유무에 따른 용접부위의 저변형을 인장실험을 통한 기계적 특성, 전기화학적 특성 및 수소취화 감수성을 등을 규명하였다. 따라서 본 연구 결과는 해양구조물 선박의 설계시공시에 용접부 주위의 기계적. 전기화학적 특성 평가 및 수소취화 방지대책에 좋은 참고자료가 될 것으로 기대된다.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.121-124
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• 2008

Fast construction of bridge substructures is a new trend of bridge design. A precast pier system with bonded prestressing bars was proposed. In this paper, quasi-static tests on precast prestressed piers were conducted to evaluate the seismic behavior of the precast piers with bonded prestressing bars. In order to strengthen the shear strength of the joints between column segments, steel tubes filled with mortar were used. Displacement ductility and energy dissipation capacity of the precast piers were evaluated. The suggested precast pier system showed better seismic performance than the required ductility. Based on the research results, an example bridge pier for light-railway lines was designed and design considerations were discussed.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1251-1258
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• 2008

The purpose of this research is to introduce the new temporary earth retaining wall system using landslide stabilizing piles. This system is a self-supported retaining wall(SSR) without installing supports such as tiebacks, struts and rakers. The SSR is a kind of gravity structures consisting of twin parallel lines of piles driven below dredge level, tied together at head of soldier piles and landslide stabilizing piles by beams. There are three types of excavation wall structures: standard method for medium retained heights(<8.0m), internal excavation method and slope excavation method for deep-excavation applications(>8.0m). In the present study, the measured data from seven different sites which the SSR was used for excavation were collected and analyzed to investigate the characteristic behavior lateral wall movements associated with urban excavations in Korea.

• The Journal of Engineering Geology
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• v.30 no.2
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• pp.185-198
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• 2020

High-density rapid expansion material is a method that increases the solid volume of injection materials due to hydration and foam reactions at the same time as spraying. It is an effective method for securing ground stability, restoring subsidence, and loading during construction of structures. In this regard, through the mechanical experiments of injection materials, the stability of the foundation ground of the structure and the effect of increasing the endurance using site construction were analyzed. The results of the experiment showed that the unit weight of soil decreased by 10.5% after injection of the filling material, and the allowable support for the structure was deemed safe, and the subsidence by each section after ground improvement was determined to be safe at 2.28, 1.55 and 0.46 cm, respectively, with an acceptable subsidence of less than 5 cm. After the field test, five inclinometers were installed on the top floor of the target building to measure the displacement of the X and Y axes. As a result of the measurement, no displacement related to the phenomenon of inequality or subsidence cracks of the structure was measured for about 16 months (509 days) after construction. This can be judged to be a sufficient increase in the stability of the ground after the injection of rapid expansion.

• Journal of the Korea Concrete Institute
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• v.27 no.1
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• pp.55-63
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• 2015

Prefabrication technologies are making bridge construction safer and less disruptive to the environment and traveling public, making bridge designs more constructible and, improving the quality and durability by shifting site work to a more controllable environment. Modular bridge substructures with concrete-filled steel tube (CFT) piers and composite pier caps were suggested to realize accelerated bridge construction. The precast segmental pier cap consists of a composite pier table and precast prestressed segments on the table. The pier table has embedded steel section to mitigate stress concentration at the connection by small tubes. Each bridge pier has four or six CFT columns which connect to the pier cap. Shear strength of the pier cap was obtained by extending vertical reinforcing bars from the table to the precast segment. Transverse prestressing was introduced to control tensile stresses by service loadings. Structural performance of the proposed modular system was evaluated by static tests. Design requirements of the composite pier cap were satisfied by continuous reinforcing bars and prestressing tendons. Standardized modular substructures can be effectively utilized for the fast replacement or construction of bridges.

• Fire Science and Engineering
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• v.31 no.3
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• pp.79-87
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• 2017

Sandwich panels which are having the both sides are bonded with a heat insulating material with an iron plate are used as factories, warehouse structures as advantages of convenience in construction at economic efficiency of material cost. However, in a panel structure constructed by continuous joining of sandwich panels, a joint portion where a panel and a panel are connected is generated. The joint part is a part which is easily vulnerable to fire because flames easily flow into the melting and deformation of the iron plate during fire. The flames flowing into the panel induce diffusion of fire by rapid burning, causing damage of human life and property. In this research, we developed a flame spread prevention plate to prevent spreading of sandwich panel. This is an improvement of the workability by the anti-spreading construction method of the existing previous research, it can be applied independently to the connecting part where the panel and the panel are coupled, designed to prevent inflow and spreading of flame did. The actual fire test of the test method of KS F ISO 13784-1 of the sandwich panel specimen was conducted and the burning behavior corresponding to the presence or absence of application of the flame spread prevention plate was grasped at the panel connection part and its effect was measured. Inserting a fire spreading plate into the test result panel connecting part is measured by delaying the flashover, prevention of collapse of the specimen, and temperature rise of the opening, effectively improving the fire safety of the panel structure It was confirmed as a method that can be secured. It is judged that panel structure will contribute to ensuring fire safety by applying the fire spread prevention construction method of various methods ensuring the workability and economy of panel connection vulnerable to fire.

• Journal of the Korea Institute of Building Construction
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• v.21 no.5
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• pp.483-493
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• 2021

Urban overcrowding has created an explosive supply and demand for high-rise buildings. High-rise buildings are contributing to enhancing the image of the city by serving as focal points, but due to the stack effect, malfunction of elevator doors, difficulties in opening and closing the doors and windows of the outer wall, smoke and odors spreading to the upper floors, noise, energy loss, fire and pollutants have been causing various unexpected problems such as rapid spread of fire. This study classified high-rise buildings according to their vertical zoning, analyzed the causes of and solutions to the stack effect, and derived design and construction methods. Through the initial plan to block the outside air and securing airtightness through precise construction, we sought ways to secure the airtightness inside and outside the building by actively blocking the airflow from the lower floors. In addition, the facility solution can be a measure to reduce the specific phenomena caused by the stack effect, but it should only be applied to the minimum extent because the potential for secondary damage is high. This study emphasized the need for systematic stack effect management by suggesting design and construction measures for each vertical zoning of the causes and countermeasures of the stack effect. It is expected that this study will be helpful not only for design and construction, but also for building maintenance.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.6
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• pp.1707-1721
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• 2014

Half-depth panels were developed with the merits of CIP (Cast In Place) decks and precast decks for constructability and fast construction. In this paper, details of half-depth panels with pre-tensioning were suggested. For evaluation of structural performance, five half-depth panel specimens were fabricated and static tests were conducted. The cross-sections of these specimens were composed of pre-tensioned half-depth panels and pre-tensioned two-span half-depth panels. Test parameters were the amount of the prestressing force and the longitudinal reinforcements. Static tests on simply-supported slabs showed that ultimate strength was 1.55 times greater than calculated nominal strength. The flexural strength was only 10 % increased and the influence on crack width control was negligible when the member of tendons was increased twice. For two-span continuous specimens, the ultimate strength increased 1.2 times and 1.38 times respectively as the reinforcement was additionally provided. The verified half-depth panels by this research can be effectively utilized for the fast replacement or construction of bridges.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.6D
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• pp.623-629
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• 2010

Recently, the Shield TBM (Tunnel Boring Machine) construction method is used gradually to increase at the Tunnel Constructin site. However the design and application of the Shield TBM were carried out without sufficient investigation of the ground conditions in the construction site. Due to insufficient understanding to the corresponding equipment is frequently occurring unexpected construction cost and extension of a construction period. The most suitable alternative construction method was determined by analyzing tunneling rate, duration, construction cost of shield machine and tunneling data of alternative method. The result of the case study is suggested as follows. First, the accurate soil exploration on the construction site should be preceded to prevent from tunneling stoppage and schedule delay. Second, the most suitable selection of the shield machine to the ground conditions of the construction site should be executed based on the investigation. Third, the best alternative method for boring of hard rock section is 'hard rock blasting after open cut and cover method'.

• Journal of Korean Society of Steel Construction
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• v.22 no.2
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• pp.161-171
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• 2010

Bridges have undergone distinctive development in accordance of the introduction of new materials and structural types. The importance on rapid construction technology is currently attracting more and more attention worldwidely as well as domestically because its effectiveness in reducing the overall construction cost. While a wide ranges of previous researches on rapid construction of super structures are available, the studies on substructures are quite limited. The development of the precast segmental internally confined hollow CFT piers are briefly introduced herein and design formulas are presented for pier segment joints, Also, a extensive parametric studies are carried out for the effect of the constitutive elements of the joints. Finally, the design formulas are verified throughout a series of extensive finite element analyses.