배추는 국내 생산 엽채류 중 재배면적 및 생산량이 가장 높은 비중을 차지하는 중요한 작물이다. 농촌인구 감소 및 고령화는 농촌 노동력 부족으로 이어지고 이는 배추 생산력 감소의 원인이 되고 있다. 배추 수확은 대부분 인력에 의존하고 있으며, 노동력 절감과 생산성 향상을 위한 관리 및 수확을 위한 배추 수확기가 개발되고 있다. 본 논문의 목적은 견인형 자주식 배추 수확기 견인 고리 설계단계에서 구조해석을 실시하여 최대 응력, 변형량, 안전계수를 도출하여 안정성을 높이는 데 있다. 수집부에 배추가 최대 적재 시 발생하는 하중을 기준으로 하중의 각도, 견인 고리의 높이를 변경하여 구조해석을 실시하였다. 수집부 부착 견인 고리의 경우 최소 높이에서 최대 응력 608.38 MPa, 최대 변형량 3.14e-3 mm, 최소 안전계수 0.78이 도출되었으며, 배추 수확기 부착 견인 고리의 경우 최소 높이에서 최대 응력 835.76 MPa, 최대 변형량 4.74e-3 mm, 최소 안전계수 0.48이 도출되었다. 마지막으로 힌지핀의 경우 중간 높이에서 최대 응력 373.46 MPa, 최대 변형량 2.12e-3 mm, 최소 안전계수 1.23이 도출되었다. 최대 응력 지점을 제외한 대부분은 안전계수가 1보다 높았다. 따라서 제작 단계에서는, 최대 응력 지점을 보강하여 견인 고리에 대한 구조적 안정성을 높일 필요성이 있다.

In this study, a finite element analysis was used to analyze the stress state and vibration characteristics generated by continuous contact between wheels and rails when driving urban railway vehicles. The rails applied to the analysis were divided into straight and curved shapes, and three-dimensional modeling was performed to analyze the changes in structural characteristics of wheels and rails when driving on straight and curved rails. As a result of the analysis, the stress characteristics were up to 6.5 MPa on a straight rail and 9.81 MPa on a curved rail, and it is believed that this increase in stress will increase noise due to an increase in friction at the interface. The vibration characteristics of the wheels and rails showed similar behavior from the 3rd mode to the 9th mode of the rail to the intrinsic vibration characteristics from the 4th mode to the 6th mode of the wheel.

This paper presents the effect on the inelastic behavior and structural performance of concrete and filled steel pipe through a numerical method for reliable judgment under various load conditions of the CJS composite structural system. Variable values optimized for the CJS synthetic structural system and the effects of multiple variables used for finite element analysis to present analytical modeling were compared and analyzed with experimental results. The Winfrith concrete model was used as a concrete material model that describes the confinement effect well, and the concrete structure was modeled with solid elements. Through geometric analysis of shell and solid elements, rectangular steel pipe columns and steel elements were modeled as shell elements. In addition, the slip behavior of the joint between the concrete column and the rectangular steel pipe was described using the Surface-to-Surface function. After finite element analysis modeling, simulation was performed for cyclic loading after assuming that the lower part of the foundation was a pin in the same way as in the experiment. The analysis model was verified by comparing the calculated analysis results with the experimental results, focusing on initial stiffness, maximum strength, and energy dissipation capability.

Tomb of King Muryeong, located in Sonsan-ri, was found vulnerable due to leakages during since the summer of 2016. This research aims to evaluate structural safety of the Tomb under the tumulus. Site surveys were conducted to find vulnerable inner parts. Structural safety assessment is presented based on both site survey results and analytical results obtained through FEM analysis using the ANSYS program. The underground structure was explicitly modeled to focus on two types of loadings: design loads and actual gravity loads. In general, the tomb does not show any critical deflection increase or damage through the analytical investigation. However, maintenance through continuous monitoring is necessary to prevent severe deflections and stress concentrations since the rigidity of the tomb materials are very vulnerable and likely to be reduced due to prolonged weathering and continuous rain leakage.

This study was carried out to standardize the material properties of roll-over protective structure (ROPS) for agricultural tractor. The material properties which were obtained from stress-strain curve, a result of tensile test stress, were used to apply to the virtual test and varied from one production lot to the other and from one manufacturer to the other. And the finite element analysis was performed on the ROPS according to the OECD code. The results show that the load-displacement curves of virtual test were approximately equal to the actual test curves. The manufacturer or lot has been shown to have little effect on the properties of the material. Therefore, it is expected that the representative values that can be used in the finite element analysis can be determined by averaging the property values.

Subsurface cavities in the asphalt pavement which can cause road depression and cave-in accidents influence on the safety of pedestrians and vehicle drivers in the urban area. The existence of subsurface cavity can increase the tensile strain at the bottom of asphalt layer which is an indicator of fatigue cracking potential, and leads to the weakening of the pavement structural capacity. In this study, the finite element (FE) analysis was conducted to examine the relationship between the critical pavement responses and influencing factors, such as cavity depth and size, asphalt layer thickness, and asphalt concrete modulus. The surface deflections and tensile strains calculated from the ABAQUS FE program were compared to those from ILLIPAVE. It is found from this comparison that there are a good relationship between two analysis results. A three dimensional finite element model which is essential to simulate the hexahedral cavity were used to generate the synthetic database of critical pavement responses. To validate the developed model, the deflection data obtained from field Falling Weight Deflectometer (FWD) testing in four different locations were compared to FE deflections. It is found that the center deflections obtained from the FWD testing and FE analysis are similar to each other with an error values of 2.7, 4.4, 5.5, and 11.9 % respectively. The FE model developed in this study seems to be acceptable in simulating actual field cavity condition. On the basis of the data in the database, various analyses were conducted to estimate the effect of influencing factors on the critical pavement responses. It was found that the tensile strain at the bottom of asphalt layer is affected by all the factors but the most affected by the cavity depth and asphalt concrete modulus. Further studies are recommended to properly account for the effect of cavity’s geometry to pavement response.

PURPOSES: In this study, a three-dimensional nonlinear finite element analysis (FEA) model for airport concrete pavement was developed using the commercial program ABAQUS. Users can select an analysis method and set the range of input parameters to reflect actual conditions such as environmental loading.METHODS : The geometrical shape of the FEA model was chosen by considering the concrete pavement located in the third-stage construction site of Incheon International Airport. Incompatible eight-node elements were used for the FEA model. Laboratory test results for the concrete specimens fabricated at the construction site were used as material properties of the concrete slab. The material properties of the cement-treated base suggested by the Federal Aviation Administration(FAA) manual were used as those of the lean concrete subbase. In addition, preceding studies and pavement evaluation reports of Incheon International Airport were referred for the material properties of asphalt base and subgrade. The kinetic friction coefficient between the concrete slab and asphalt base acquired from a preceding study was used for the friction coefficient between the layers. A nonlinear temperature gradient according to slab depth was used as an input parameter of environmental loading, and a quasistatic method was used to analyze traffic loading. The average load transfer efficiency obtained from an Heavy falling Weight Deflectomete(HWD) test was converted to a spring constant between adjacent slabs to be used as an input parameter. The reliability of the FEA model developed in this study was verified by comparing its analysis results to those of the FEAFAA model.RESULTS : A series of analyses were performed for environmental loading, traffic loading, and combined loading by using both the model developed in this study and the FEAFAA model under the same conditions. The stresses of the concrete slab obtained by both analysis models were almost the same. An HWD test was simulated and analyzed using the FEA model developed in this study. As a result, the actual deflections at the center, mid-edge, and corner of the slab caused by the HWD loading were similar to those obtained by the analysis.CONCLUSIONS : The FEA model developed in this study was judged to be utilized sufficiently in the prediction of behavior of airport concrete pavement.

PURPOSES : Nowadays, cavity phenomena occur increasingly in pavement layers of downtown areas. This leads to an increment in the number of potholes, sinkholes, and other failure on the road. A loss of earth and sand from the pavement plays a key role in the occurrence of cavities, and, hence, a structural-performance evaluation of the pavement is essential. METHODS: The structural performance was evaluated via finite-element analysis using KPRP and KICTPAVE. KPRP was developed in order to formulate a Korean pavement design guide, which is based on a mechanical-empirical pavement design guide (M-EPDG). RESULTS: Installation of the anti-freezing layer yielded a fatigue crack, permanent deformation, and international roughness index (IRI) of 13%, 0.7 cm, and 3.0 m/km, respectively, as determined from the performance analysis conducted via KPRP. These values satisfy the design standards (fatigue crack: 20%, permanent deformation: 1.3 cm, IRI: 3.5 m/km). The results of FEM, using KICTPAVE, are shown in Figures 8~12 and Tables 3~5. CONCLUSIONS: The results of the performance analysis (conducted via KPRP) satisfy the design standards, even if the thickness of the anti-freezing layer is not considered. The corresponding values (i.e., 13%, 0.7 cm, and 3.0 m/km) are obtained for all conditions under which this layer is applied. Furthermore, the stress and strain on the interlayer between the sub-grade and the anti-freezing layer decrease gradually with increasing thickness of the anti-freezing layer. In contrast, the strain on the interlayer between the sub-base and the anti-freezing layer increases gradually with this increase in thickness.

The purpose of this study is to analyze the structural stability of pavement due to water infiltration at the road with infiltration trench as using the FEM(finite element analysis). Five cases for FEM is divided considering the amount of rainfall and rain duration time. The results of FEM show that the more rainfall in a short period time is faster the change of moisture content. Also, it is the proportional relationship between and changing area of moisture content of more than 40% due to rainfall. Case 3 and 4 are necessary to check the installation of infiltration trench because of moisture content of more than 40%, recovery time of initial moisture content, and changing area of more than 40%. Case 1,2, and 5 have no a significant effect on road pavement structure due to lower moisture content and shorter duration time of higher moisture content.

본 논문에서는 케이블 지지구조물의 비선형 정적해석과 동적해석에 사용할 수 있는 개선된 유한요소가 제시되었다. 케이블의 모델화를 위해 등가탄성계수를 사용하고 처짐곡선을 현수선함수로 가정한 케이블요소가 제안되었다. 프레임 부재에 사용되는 안정함수는 수치적으로 안정한 해를 얻기 위하여 수정되었다. 본 논문에서 제안한 요소의 유용성과 효율성을 검토하기 위하여 다양한 검증문제에 대한 수치해석이 수행되었다. 해석결과 본 논문에서 제시한 유한요소는 케이블 지지구조물의 모델화에 매우 유용하고 효율적으로 사용될 수 있을 것으로 판단된다.

본 연구에서는 유한요소 구조해석을 위한 전후처리 통합운영 시스템을 개발하였다. 이 시스템은 구조해석, 전처리 및 후처리가 윈도우즈 환경에서 통합운영될 수 있도록 설계되었는데, 다중처리, 객체연결 및 결합 기법 등을 사용한 다중 윈도우상에서 대화식 입출력 기능과 여러가지 입출력 결과의 동시표현 등으로 더 향상된 그래픽 사용자 접속장치 환경을 제공한다. 따라서 메뉴, 대화상자, 다중 윈도우상에서의 단계별 자동입력 등을 통하여 자료의 입력이 용이해졌고, 동일 화면상에서 입력자료와 출력결과를 동시에 나타낼 수 있게 되었다. 본 시스템의 타당성과 효율성을 검증하기 위하여 여러가지 구조물에 대한 정적 및 자유진동해석을 수행하였다.

The purpose of the analysis is the numerical simulation of structures strained to the limit loads. The finite element calculations and experiments with cracked structures have been carried out yielding over limit strains between 10% and 15% by single peak load. Load versus displacement-diagrams and J-diagrams up to the limit load are calculated. By this way the influence of geometric parameters may be assessed in the post yield region. It is proposed to use such calculations to correlate experiments carried out with small specimens to experiments simulating the true dimensions of the design structure.

지하구조물의 주위지반은 일반적으로 퇴적층의 형성 또는 지각의 변동에 의해 다층구조를 가지게 되므로, 구조물 및 주위지반의 거동을 정확히 예측하기 위해서는 해석에 다층구조의 영향을 반영해야 한다. 본 연구에서는 다층으로 구성된 지하구조계를 대상으로 하여 구조물과 그 주변에는 비선형 유한요소를 사용하고, 비선형성이 상대적으로 미약한 주변 다층지반에는 선형 경계요소를 사용하여 재료의 비선형성과 비균질성을 고려한 효율적인 조합해석방법을 개발하고자 한다. 반무한영역에 설정되는 다층구조계를 경계요소로 해석할 경우 그 기본해가 제한되어 있으므로, 본 연구에서는 기존의 무한기본해를 이용하는 방법을 사용하였다. 무한기본해를 이용하는 내부영역문제의 경우 각각의 균질한 층을 부영역(subdomain)으로 분할하고 계방정식을 구성한 뒤에 접합면에 대하여 평형조건과 적합조건을 만족시켜 주는 방법을 사용하여 비균질성을 고려한다. 부영역으로 층을 분할한 내부영역문제의 경계요소해석 결과는 선형 유한요소해석 결과와 비교하여 검증하였고, 검증된 경계요소 프로그램을 비선형 유한요소 프로그램과 조합하였다. 조합해석 결과, 굴착부 주변의 응력집 중부에는 비선형 유한요소를 사용하고, 비선형의 영향이 미소한 주변의 다층지반에 대해서는 부영역에 의한 선형 경계요소를 사용하는 조합해석방법이 합리적이고 효율적임을 알 수 있었다.

This pa야r 15 an attempt to aα:ount for the uncertainty of the residual strength in the reliability analysis of structural systems. For this purpose the stochastic finite element meth여(SFEM) is li띠<ed to the system reliability analysis pr'∞edure. The stochastic finite element is known to be able to a more explicitly ∞nsider the effect of uncerainties of material and g∞metric variables on those of load effects in structural analysis prlα:edure. The method has been applied to system as well as comφnent reliability analysis of a plane structure. Comparison of the results by the present approach is made with the method in which the residual strength of f려led ∞mponent is treated as deterministic variable. Several case studies have been carriE최 to show the effect of uncertainty in residual strength of a member after failure. Is has been ∞nform어 that reidual strength very much affect the system reliability level. It can be, hence, ∞ncluded that the uncertainties in the αlSt-ultimate behaviour may have to be t혀<en mto account in the system reliability analy의s for a better a s않ssment of the system reliability especially for a struct파e of which member behaviour is m여ell어 as asemi-brittle model.And then the sto .:hastic finite element method can efh디ently evaluate the system reliability.

강판콘크리트구조 설계기준(KEPIC SNG)에서 RC-SC구조 이종부재 접합방식은 기계적이음방법인 베이스플레이트형 접합 방식과 미겹침이음 접합방식을 제시하고 있다. RC구조간의 동일부재 접합부는 설계기준에서 철근의 직경에 따라 이음방식 을 별도로 규정하고 있지만, RC-SC구조 접합부는 철근의 직경에 따른 접합방식이 설계기준에 별도 구분되어 있지 않기 때문에 대구경 철근에 대해서도 미겹침이음 접합방식을 적용할 수 있을 것으로 예상된다. 베이스플레이트형 접합방식의 경우, RC-SC접합부 구조가 복잡하여 향후 적용성 측면에서 불리할 것으로 예상된다. 그러나, 미겹침이음 접합방식은 구조가 단순하여 적용성 측면에서 유리할 것으로 판단되나, 추가 실증실험과 전산해석을 통해 적용성 확보가 필요한 상황이다. 본 연구에서는 미겹침이음 접합방식의 주요 설계변수인 타이바와 철근정착의 구조거동을 분석하였으며, 철근의 정착성능을 강화할 수 있는 방안을 도출 및 적용하여 구조거동분석을 수행하였다.

본 연구는 경부고속철도(대구~부산) 도심통과 노반신설 공사중 기존 부산지하철 1호선 및 부산지하철 2호선 구간에 대한 안정성에 관한 연구로서 현장조사를 실시하여 대상시설물의 외관상태, 품질상태 및 내구성능 등을 평가하고 MIDAS/GTS를 이용한 수치해석을 통해 대상시설물 및 본선터널의 안정성을 검토하는데 그 목적이 있다. 지하수위 하에서 터널이 시공되는 기본 메카니즘과 3차원 유한요소해석 응력-간극수압 연계해석을 수행한 후 라이닝 작용하중, 막장안정성, 지표침하 등 지하수와 터널굴착의 상호관계를 고찰하였다. 수치해석의 결과 1, 2호선의 최대침하, 부등침하, 라이닝응력 등은 허용치 이내이며 손상정도는 무시할 수 있는 정도의 경미한 것으로 나타나고 있다. 그러나 실제 터널 시공시 막장거동을 최소화하기 위하여 필요시 Pre-Grouting을 시행하여 터널 굴착시 터널내 유출수를 최소화하는 것이 필요할 것으로 판단된다.