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박연수,전동호,서병철,김욱,최동호,Park, Yeon Soo,Jeon, Dong Ho,Suh, Byoung Chal,Kim, Wook,Choi, Dong Ho 한국강구조학회 2003 韓國鋼構造學會 論文集 Vol.15 No.4
본 연구에서는 강부재에서의 손상지수를 제시하여 반복하중재하를 받는 각형강관 기둥의 파괴에 이르는 과정을 손상지수를 이용하여 규명하였다. 이를 위해 유한요소 프로그램을 이용하여 비선형 해석을 수행하였고 이에 대한 손상과정을 비교 분석하였다. 재료시험을 실시하여 재료물성치와 강종별 변형률특성을 구하였으며 이를 바탕으로 강종과 하중재하조건의 변수를 주어 이 인자들이 부재의 손상에 미치는 영향을 비교하였다. 각 변수에 따른 변형률 특성과 누적소성변형률 이력곡선을 바탕으로 하는 하중조건과 강종이 손상에 미치는 영향을 정량적으로 파악할 수 있었다. This study proposed a damage index for steel members and examined a process where steel square tubular columns under cycle loading failed to meet the damage index. A nonlinear analysis was carried out and a damage process analyzed using a finite element program. Material properties and strain characteristics were obtained from material testing. The effect on the damage of members was analyzed according to varying kinds of steels and conditions of loading based on material testing results. According to strain characteristics and cumulative plastic strain of each variable, the effect of conditions of loading and kinds of steels on the damage could be estimated quantitatively.
박연수,한석열,서병철,Park, Yeon Soo,Han, Suk Yeol,Suh, Byoung Chal 한국강구조학회 2003 韓國鋼構造學會 論文集 Vol.15 No.5
본 연구는 선형탄성 파괴역학적 방법을 사용하여 피로 손상을 평가할 수 있는 해석모델을 개발하는데 있다. 트럭 한 대가 교량상부를 통과할 때 부재에 발생하는 응력이력을 블록하중이라 정의하고 하중상호작용효과를 설명하는 균열닫힘 모델 이론을 적용한다. 블록하중에 대해 사하중 응력과 균열개구응력을 고려하여 응력범위빈도해석을 수행하였다. 여기서 구한 응력범위빈도분포에 확률적 방법을 적용하여 응력범위빈도분포의 확률분포 파라미타를 추 정하였다. 확률분포의 확률변수를 발생시키는 Monte Carlo Simulation 실행을 하여 파괴블럭수와 확률분포를 구한다. 이로부터 부재의 파로파괴가 발생하지 않는 피로신뢰성을 계산한다. 또한 파괴블럭수를 일평균 트럭교통량으로 나누면 예상잔존수명을 구할 수 있다. 제안된 피로신뢰성 해석모델을 사용하여 강상자형교 가로보와 수직보강개의 용접부에 피로신뢰성 해석을 수행 한 결과, 피크해석방법 결과와 잔존수명이 3.8% 정도 차이가 있었다. 이는 제안된 모델이 균열닫힘 현상이나 균열지연 형상을 고려하고 있음을 알 수 있었다. This study developed an analysis model of estimating fatigue damage using the linear elastic fracture mechanics method. Stress history occurring to an element when a truck passed over a bridge was defined as block loading and crack closure theory explaining load interaction effect was applied. Stress range frequency analysis considering dead load stress and crack opening was done. Probability of stress range frequency distribution was applied and the probability distribution parameters were estimated. The Monte Carlo simulation of generating the probability various of distribution was performed. The probability distribution of failure block numbers was obtained. With this the fatigue reliability of an element not occurring in failure could be calculated. The failure block number divided by average daily truck traffic remains the life of a day. Fatigue reliability analysis model was carried out for the welding member of cross beam flange and vertical stiffener of steel box bridge using the proposed model. Consequently, a 3.8% difference was observed between the remaining life in the peak analysis method and in the proposed analysis model. The proposed analysis model considered crack closure phase and crack retard.
박연수 ( Park Yeon-soo ),김병하 ( Kim Byoung-ha ),한상호 ( Han Sang-ho ),박선준 ( Park Sun-joon ),서병철 ( Suh Byoung-chal ) 한국구조물진단유지관리공학회 2003 한국구조물진단유지관리공학회 논문집 Vol.7 No.1
In this research, multiple corrosion factors of buried environments were measured in order to establish a formula for the corrosion character of corrugated steel structures in domestic environments. By substituting corrosion factors for each predicting formula, the durable lifetime was measured, and the measured lifetime was compared with the estimated lifetime by applying existing thickness-measuring techniques. A new usage standard was proposed with these results, in order to create the conclusion below. There are known differences in the soil factors used as variables in estimating the duration caused by the seasonal effects of rainfall and temperature. Comparing the durable lifetime estimated by each predicting formula, the findings show that the California technique is conservative. This study demonstrates that the error range of the AISI technique, which is mostly used as a duration technique, is a very narrow predicting technique as compared with many other countries. Considering that there is on average, a 13% error margin in this study, a proposed safety factor of 0.87 could be used to more accurately predict the duration. The laying time in the California technique is not longer than the whole durability, and as a result, this error margin exists. It is concluded that this study on the open area has been overdue. Based on these findings, it's proposed that this error margin should be applied to the domestic environment through periodic observation, in order to establish the predicting techniques of durable lifetime.