In the actual sea, the additional resistance due to external force such as wind, current and wave is accompanied, and the required power is added in response to these resistance. Especially when the ship is sailing at low speed, the effects of wind and current have a great impact on the safe control of the ship. Likewise, it is thought that the effects of wind and current have a great impact on the trawl ship control since the towing speed of a bottom trawl ship is a low speed of 3 to 4 knots. If the reduce of ship speed and the increase of engine power due to the influence of wind and current can be identified, the safe towing power can be calculated based on a given engine output. Thus, the appropriate size of a fishing gear can be determined. In this study, a total of 20 trawl operations were conducted for seasonal maritime research in the same research area according to the operation mode of propeller. Based on navigation data, trawl fishing data, and engine performance data acquired during the towing fishing gear, and data of ship speed, hull resistance, fishing gear resistance, wind force and current force according to an incidence angle were estimated. The overall power for these loads was calculated and compared with the measured engine power, and the effects of wind force and current force on the engine power were investigated.

새만금 호의 수질 개선을 위하여 국가에서 해수 유통을 증가시킴에 따라 해수 유통 빈도 증가로 인한 새만금 호 내 염분과 저 층수 교환 변화를 알아보기 위하여, EFDC(Environmental Fluid Dynamics Code) 모델을 이용하였다. 갑문 개폐 횟수를 하루 1회에서 2회로 증 가했을 때, 새만금 호 내부 수위는 최대 약 0.7 m 상승하였다. 염분은 서측 방조제 근방에서 2.12 psu 증가하였으며, 담수 유입 부근에서는 1.18 psu 감소하였다. 입자추적을 이용하여 저층수 교환 정도 분석한 결과, 수심 5m 이하 입자 잔류율은 Case 2(1일 2회 개방)에서 Case 1(1 일 1회 개방)에 비해 2.52% 감소한 것으로 나타났다. 이는 수문 개폐 횟수를 증가시켰을 때, 저층수 교환이 더 활발해 질 수 있다는 것을 알 수 있다. 따라서 해수 유통 증가에 따른 염분 및 저층수 교환 증가로 새만금 호의 수질 개선이 될 수 있다고 판단된다.

This study was investigated in order to find composition and density of fisheries resource using bottom trawl in April, July, August, and November 2022 in the East China Sea. The average density of fisheries resource was estimated using the swept area method. As a result, 35 species were collected from the East China Sea. These included 21 fishes, six crustaceans, six cephalopods and two echinoderms. Seasonally, the average density of crustacean individuals per unit area were highest in November (692.1 inds./km 2 ), while cephalopod individuals per unit area were highest in August (39.4 inds./km 2 ). The average density of fish individuals per unit area were highest in August at 355.0 (inds./km 2 ).

The 2017 Pohang earthquake caused severe damage to low-rise piloti buildings. The damage was caused mainly by column shear failure, and some core walls were as well. The damaged piloti buildings in Pohang City could be relieved if they were designed correctly according to the standards at that time. However, the post-earthquake investigation revealed design, construction, and permission problems. To solve the problems, the Piloti Building Structure Design Guidelines that include strict specifications were published in 2018. Separately, KDS 41 17 00, the seismic design standard for buildings, was enacted in 2019 and it included the guideline contents. Therefore, at least after the publication of the guidelines, piloti buildings, designed by the standard and guidelines, can be expected to possess better seismic performance than existing piloti buildings. To confirm this, the probability of exceedance for several damage state thresholds was estimated for existing and designed piloti buildings. As a result, the probability of damage of designed piloti buildings was very low compared to existing ones. Consequently, it was confirmed that the guideline and standard adequately supplement the structural fragility of existing piloti buildings.

In this study, the seismic performance of a two-story unreinforced masonry (URM) building was assessed following the linear and nonlinear static procedures specified in the seismic evaluation guideline of existing buildings. First, the provisions to assess failure modes and shear strengths of URM walls and wall piers were reviewed. Then, a two-story URM building was assessed by the linear static procedure using m-factors. The results showed that the walls and wall piers with aspect ratios he /l (i.e., effective height-to-length ratio) > 1.5 were unsafe due to rocking or toe crushing, whereas the walls with he /l ≤1.5 and governed by bed-joint sliding mainly were safe. Axial stresses and shear forces acted upon individual masonry walls, and wall piers differed depending on whether the openings were modeled. The masonry building was reevaluated according to the nonlinear static procedure for a more refined assessment. Based on the linear and nonlinear assessment results, considerations of seismic evaluation for low-rise masonry buildings were given with a focus on the effects of openings.

Current seismic fragility functions for buildings were developed by defining damage state threshold based on story drift concerning foreign references and using the capacity spectrum method based on spectral displacement. In this study, insufficient details and dependence on the core location of piloti-type buildings were not reflected in the fragility function because it was developed before the Pohang earthquake. In order to develop an improved one for piloti-type buildings, several types of core were selected, damage state threshold was determined based on the capacity of structural members, and three-dimensional analyses were utilized. As a result, seismic fragility functions based on spectral acceleration were developed for various core locations and different shear strengths of the column stirrup. The fragility of piloti-type buildings significantly varied according to core location, an additional single wall, and whether the contribution of column stirrup was included or not. To estimate fragility more reasonably, it is necessary to prepare the parameters to reflect actual state well.

The Ministry of the Interior and Safety in Korea developed seismic fragility function for various building types in 2009. Damage states for most building types were determined by structural analyses of sample models and foreign references because actual cases damaged by earthquakes rarely exist in Korea. Low-rise, piloti-type buildings showed severe damage by brittle failure in columns due to insufficient stirrup details in the 2017 Pohang earthquake. Therefore, it is necessary to improve damage state criteria for piloti-type buildings by consulting actual outcomes from the earthquake. An analytical approach was conducted by developing analysis models of sample buildings reflecting insufficient stirrup details of columns to accomplish the purpose. The result showed that current spectral displacements of damage states for piloti-type buildings might be too large to estimate actual fragility. When the brittle behavior observed in the earthquake is reflected in the analysis model, one-fourth through one-sixth of current spectral displacements of damage states may be appropriate for existing low-rise, piloti-type buildings.

본 연구에서는 Aramid FRP와 모서리보강재로 구속한 엔지니어링플라스틱 보강을 통해 기둥의 횡구속 능력을 증대하여 콘크리트 피복 및 압괴 파괴를 지연시킴으로써 휨 항복 후 연성거동을 유도하여 기존 저층 필로티 건축물의 내진 성능을 확보하는 방법을 제시하고 저층 필로티 건축물의 내진취약요인을 분석하여 필요한 전단보강량을 산정, 제안공법의 목표전단보강을 설정하는 것을 목적으로 한다. 엔지니어링플라스틱을 활용한 기둥의 전단보강형상을 제안하고 필로티 구조의 내진취약요인 보강임계점 예측과 예제모델의 구조해석을 통해 제안공법의 목표전단보강량을 검증하였다. 구조해석 결과, 특별지진하중 적용 시, 휨-축력 내력 초과비율이 타 유형군에 비해 낮은 ST-A1(1축편심)을 기준으로 연면적 750m² 이하와 1축 편심 중심-강심편심율 18%이하에 해당될 경우에는 본 논문에서 제안하는 ‘고성능 복합섬유 패널 전단 보강법’을 적용할 수 있는 경계로 제한하고자 한다.

여러 센서를 이용한 구조물의 구조 응답을 모니터링하는 사례가 증가하고 있다. 그러나 비용과 관리 문제로 인해 제한된 센서만이 구조물에 설치되어 일부의 구조 응답만을 수집하는 경우가 대부분이다. 이는 구조물의 전체 거동을 분석하는데 장애요소로 작용하게 된다. 따라서 제한된 센서를 이용해 센서가 설치되지 않은 위치에서의 응답을 신뢰할 수 있는 수준으로 예측하는 기술이 필요하다. 본 연구에서는 제한된 정보를 이용해 저층 건물 구조물의 지진 응답을 예측하는 해석적 연구를 수행한다. 활용 가능한 응답 정보는 1층과 최상층의 가속도 응답만을 사용할 수 있다고 가정한다. 두 정보를 이용하면 구조물의 1차 고유진동수를 얻을 수 있다. 1층 가속도 정보는 구조물의 가력 정보로 활용한다. 최상층의 가속도이력응답에 대한 오차와 대상 구조물의 1차 고유진동수 오차를 최소화하는 구조물의 질량과 강성 정보를 유전자알고리즘을 이용해 예측하는 기법을 제시한다. 제약조건은 고려하지 않는다. 탐색공간을 의미하는 설계변수의 범위를 결정하기 위해 인공신경망 기반의 파라미터 예측기법을 제시한다. 또한 유전자알고리즘을 통해 얻게 되는 해를 개선시키기 위해 앞서 언급한 인공신경망을 활용한다. 제시한 기법을 검증하기 위해 5층 구조물 예제를 사용한다.

In this study, the results of an analytical investigation on the seismic behavior of two residential 4-story bearing wall buildings with pilotis, each of which has symmetric or unsymmetric wall arrangement at their piloti level, are presented. The dynamic characteristics and lateral resistance of the piloti buildings were investigated through linear elastic and nonlinear static analyses. According to the results, the analytical natural period of vibration of the piloti buildings were significantly shorter than the fundamental period calculated in accordance with KBC 2016. In the initial elastic behavior, the walls resisting in-plane shear contributed to the lateral stiffness and strength, while the contribution of columns resisting flexural moments in double curvature was limited. However, after the shear cracking and yielding of the walls occurred, the columns significantly contributed to the residual strength and ductility. Based on those investigations, design recommendations of low-rise bearing wall buildings with piloti configuration are given.