Sang-Hun Han

Vibration Characteristics of Gravity-Type Caisson Breakwater Structure with Water-Level Variation

Vibration characteristics of gravity-type caisson breakwater structures which have water-level variations are experimentally examined by using wave load excitations. To achieve the objective, the following approaches are implemented. Firstly, vibration analysis methods are selected to examine the dynamic characteristics of the lab-scale caisson. Secondly, vibration test on a lab-scale caisson which is installed in a two-dimensional wave flume is performed under several excitation sources and water levels. Thirdly, the compatibility of the wave-induced vibration responses is evaluated by comparison with the impact vibration responses, and the appropriate vibration analysis method is selected. Finally, the water-level effects on the caisson breakwater are examined based on the modal parameters which are experimentally measured for the 2D wave flume tests.

Wave-Induced Vibration Monitoring for Stability Assessment of Harbor Caisson

Up-to-date structural health monitoring (SHM) studies have been focused mostly on in-land structures such as bridge and building. Only a few research efforts have been made for harbor structures such as caisson-type breakwater. For stability assessment of harbor caisson structures, it is very essential to monitor vibration responses with limited accessibility, to analyze the vibration features, and to specify the sensitive motions with respect to damage in the caisson-foundation’s interface. In this paper, a wireless sensing system for SHM of harbor caisson structures is presented. To achieve the objective, the following approaches were implemented. First, a wave-induced vibration sensing system was designed for global structural health monitoring. Second, global SHM methods which are suitable for damage monitoring of caisson structures were selected to alarm the occurrence of unwanted behaviors. Third, a SHM scheme was designed for the target structure by implementing the selected SHM methods. Operation logics of the SHM methods were programmed based on the concept of the wireless sensor network. Finally, the performance of the proposed system was globally evaluated for a field harbor caisson structure for which a series of tasks were experimentally performed by the wireless sensing system.

Evaluation of Material Properties of Concrete Harbour Facilities Using Nondestructive Testing Methods

Recently harbor remodeling projects are seriously considered to enhance the loading and unloading capability of old container terminals and to make decrepit ports as eco-friendly harbor and waterfront spaces in many countries. In such a case, quantitative and qualitative evaluations on concrete harbor facilities are mandatory to determine the current structural integrity condition of aged materials. Once the remodeling project is determined to be carried out, the reusability of individual structural members and facilities including caissons, cell-blocks, and tetra-pods need to be decided based on the simple and economic visual inspection and/or nondestructive testing. In this study, the systematic quantitative evaluation procedure for determining the structural integrity condition and the reusability is studied based the nondestructive testing and evaluation methods. Conventional methods including Schmidt hammer test and ultrasonicpulse velocity methods and elastic wave based methods including impact echo test and surface wave test are applied to the old harbor facilities in five different sites. The compressive tests are also carried out to determine the elastic modulus and compressive strength of concrete materials.

Section performance of submerged floating tunnel using steel composite hollow RC structure

Submerged floating tunnel (SFT) has been considered as an interesting structure to connect the banks separated by a narrow and deep sea. Reinforced concrete (RC) tunnels have been suggested as SFT structures. Because the governing load of a SFT is bending moment, a structure with enhanced stiffness and ductility will be useful for a SFT. Therefore, new-type structures which have superior stiffness and ductility were proposed for the SFT using steel composite Hollow RC member. In this study, the application of steel composite RC structure for SFT was investigated by analysis method. To evaluate the section performance of new type SFT, bending analyses were carried out by using an exclusive program with the considerations of material nonlinearity and confining effect of concrete. Furthermore, module connection for new type SFT was proposed, its performance was evaluated by analysis method.

Damage Rate of Reinforced Concrete Submerged Floating Tunnels Under Fire Scenarios

최근 대륙 간 연결 사업의 추진이 증대되고 있는 가운데 우 리나라 주변에는 한-중 및 한-일 철도 또는 도로 연결에 대한 논의가 진행되고 있다. 이 때 적용 가능한 기술에는 해중터널, 해저터널, 침매터널 등이 있으며, 여기서 해중터널이란 부력 에 의하여 수중에 부유하거나 지지보가 자중을 부담하여 수 중에 잔교식의 형태로 건설되는 터널의 형식을 말하며, 이는 Fig. 1과 같이 일반적인 교량, 침매터널 및 해저터널의 보완구 조물 혹은 대체구조물로 건설 가능하다. Fig. 1은 강 또는 바다를 통해 대륙을 횡단하는 방법을 나타 낸 것으로 1은 일반적인 횡단방법인 교량을 나타내는 것이 고 2는 해중터널 3은 침매터널, 그리고 4는 해저터널을 나 타내고 있다. 일반적인 해중터널의 구조 형태는 부력과 자중 의 관계에 따라 4가지로 나눌 수 있다(Håvard Østlid, 2010). 부력이 자중보다 큰 경우에는 텐션레그 형태의 구조물이 되 Abstract

Key Technologies for Construction of Seabed Base

By the exhaustion of natural resources and the aggravation of the food situation, many countries are going ahead with development of the ocean space and ocean resources. To expand the border of human life, it is necessary to develop the underwater space. To perform these objectives, it is required to construct and secure a seabed base. The construction of a seabed base will also be the motive power for economy growth in the future. The key technologies to construct a seabed base under high pressure and low temperature conditions are the extreme engineering technologies and they are some parts of space engineering. They are also key technologies to survive when a worldwide-huge disaster attacks the earth. In this study, the necessary technologies for the construction of seabed base were surveyed. And the surveyed technologies were categorized by phase 1 and phase 2, which were defined by construction depth and size, and possible time. The surveyed results showed that it is necessary to construct a seabed base and develop a new constructional material and energy supplying method.

Evaluation of Chloride Ion Penetration Characteristics for Concrete Structures at Coastal Area

A major source of durability problems in concrete structures is the corrosion of steel by the damage of passivity layer around steel bars. As chloride ion penetration is major cause of the destruction of passivity layer, evaluation of depth and concentration profile of chloride ion is the essential factor for the service-life estimation of concrete structure. To estimate chloride ion penetration characteristics, this paper on the basis of in-situ experimental data investigated the depth and concentration profile of chloride ion penetration. The core specimens are obtained at air-zone, splash zone, and tidal zone in Wando, Masan, Incheon, Gwangyang, and donghae harbors. Colorimentric method measured the chloride ion penetration depth and ASTM C 114 evaluated the concentration profile of chloride ion. Based on experimental data, the influence of harbor location and exposure condition on chloride ion penetration is evaluated.