Woo-Sun Park

Damage Monitoring in Foundation-Structure Interface of Harbor Caisson Using Vibration-based Autoregressive Model

This study presents the damage monitoring method in foundation-structure interface of harbor caisson using vibration-based autoregressive (AR) model. In order to achieve the objective, the following approaches are implemented. Firstly, vibration-based AR model is selected to monitor the damage in foundation-structure interface of caisson structure. Secondly, finite element analysis on a caisson structure model is implemented to evaluate the vibration-based damage monitoring method. Finally, vibration test on a caisson structure model is performed to evaluate applicability of vibration-based AR model method for foundation-structure interface of caisson structure.

Evaluation of Vibration Characteristics of Caisson-Type Breakwater Using Impact Vibration Tests and Validation of Numerical Analysis Model

In this study, impact vibration tests are applied to analyze the vibration characteristics of caisson-type breakwater, and the results obtained from vibration tests are compared with numerical simulation results considering fluid-soil-structure interaction effects to verify the feasibility of a numerical analysis model. It is found that natural frequencies are reduced as amount of 1.7-4.3% after additional parapet structure is added to increase the height of breakwater, and the same results was observed from the numerical simulation study. Through the comparison, it was verified that the vibration tests and numerical simulation study can be applied to evaluate the vibration characteristics of caisson-type breakwater.

Evaluation of Vibration Characteristics of an Existing Harbor Caisson Structure Using Tugboat Impact Tests and Modal Analysis

Ambient and forced vibration tests are proposed to evaluate dynamic characteristics of a caisson-type breakwater, including natural frequencies and modal damping ratios. The feasibility of a numerical analysis model with fluid-structure-soil interaction effects, which play an important role in evaluating structural performance and safety, was investigated by comparing the numerical results with experimental results. The Oryukdo breakwater in Busan, Republic of Korea, was employed as the target structure. This breakwater was once heightened by installing additional parapet structures of about 4 m tall to improve the harbor tranquility in 2005. Vibration tests were carried out in 2000 (before heightening) and in 2011 (after heightening). Most caissons were tested in the first test, while only one caisson was tested in 2011. It was found that natural frequencies were reduced by 1.7%–4.3% after heightening, and similar results were observed from the numerical analysis. It was also found that forced vibration tests can yield more reasonable results than ambient vibration tests. Even though there is some discrepancy between experimental and numerical results, numerical analysis can be carried out to analyze dynamic characteristics and evaluate structural performance and safety.

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.

Proposal of Sliding Stability Assessment Formulas for an Interlocking Caisson Breakwater under Wave Forces

Recently, the possibility of abnormal waves of which height is greater than design wave height have been increased due to the climate change, and therefore it has been urgent to secure the stability for harbor structures. As a countermeasure for improving the stability of conventional caisson breakwaters, a method has been proposed in which adjacent caissons are interlocked with each other to consecutively resist the abnormal wave forces. In order to reflect this research trend, the reduction effect of the maximum wave force resulted from introducing a long caisson has been presented in the revision to the design criteria for ports and fishing harbors and commentary. However, no method has been proposed to evaluate the stability of interlocking caisson breakwater. In this study, we consider the effect of the phase difference of the oblique incidence of the wave based on the linear wave theory and apply the Goda pressure formula for considering design wave pressure distribution in the vertical direction. Sliding stability assessment formula of an interlocking caisson breakwater is proposed for regular, irregular, and multidirectional irregular wave conditions.

Elastic Buckling Behavior of Circular Steel Tube in Fire

화재의 위험이 높은 각종 산업시설 구조물, 물류창고 등 넒 은 공간의 건물은 철골 건물로 건설되고 있다. 이러한 철골구 조물은 고온에서 그 성능이 급격히 저하되어 화재 시 국부 및 전체 좌굴이 발생하여 대형 피해로 이어진다. 대표적으로, 지난 2015년 4월 부산 연제구 중고차 매매단지(부지면적 3166 m 2 )의 화재의 경우 부산소방안전본부에 따르면 차량 560대가 전소되어 약 35억의 재산피해를 가져왔으며 건축물 철거와 감식 작업이 끝났지만 화재 원인은 최종적으로 규명 되지 못했다(Fig. 1). 그러나 Fig. 1과 같이 화재로 인한 차량 의 전소는 내부의 휘발유와 경유로 인하여 일반적인 화재에 비하여 큰 강도의 화재로 이어진다. 본 화재의 경우 철골구조 로 되어 있어 화재가 집중된 중간부분에 원형강관기둥들이 좌굴이 발생함에 따라서 붕괴된 것으로 추정된다. 강재는 온 도에 따라서 급격하게 그 물성치가 변하기 때문에 강구조물 의 내화설계가 매우 중요하다. 강구조물의 경우 항복파괴도 중요하지만 화재에 의한 국부 혹은 전체의 탄성계수 감소에 Abstract

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.