최근 국내에서는 고층 벽식 아파트 건설 시, 하부 주차공간과 공용공간 확보를 위하여 RC 전이슬래브 시스템을 사용하는 경우가 증가하고 있다. 하지만 두께가 얇은 RC 무량판 슬래브를 위해 개발된 설계방법 및 구조성능평가 방법을 두께가 매우 두꺼운 전이슬래브 구조설계에 그대로 사용하고 있다는 문제점이 있다. 따라서 합리적인 전이슬래브의 구조설계를 위해서는 RC 전이슬래브 시스템의 2면 전단거동 양상에 대한 명확한 분석이 필요하다. 이에 따라 본 연구에서는 전이슬래브의 두께, 콘크리트 강도, 전단경간비, 철근비 등 다양한 설계변수에 따라 비선형 FEM을 이용하여 전이슬래브의 2면 전단거동을 분석 하였다. 또한 비선형 FEM 해석결과와 기존의 2면 전단강도 평가식으로 예측한 전단강도를 비교분석하여 기존 평가식의 전이슬래브 2면 전단강도 평가 유효성을 검토하였다.

In this paper, we analyzed the safety on static and dynamic characteristics of a top-down evacuation instrument fixed on the exterior walls of a building using finite element analysis. For this purpose, the stress distribution characteristics of the H-beam structure were analyzed and the equivalent stress distribution, deflection displacement and natural frequency characteristics of the overall structure of the evacuation instrument were analyzed. The structures were applied with the materials of SS440 and SUS304. The static analysis results showed the elastic behavior with safety coefficients from 2.4 to 2.9, by confirming the structural safety. In addition, the analysis of the natural frequency characteristics confirmed that the vibration characteristics were higher than the external conditions of 20Hz.

PURPOSES: The objective of this study was to develop an asphalt pavement response model for a subsurface cavity section using the 3D finite element method and a statistical approach. METHODS: It is necessary to analyze the structural behavior of asphalt pavement with a subsurface cavity to evaluate the degree of risk for a road cave-in. A 3D finite element model was developed to simulate the subsurface cavity underneath asphalt pavement and was verified using the ILLIPAVE program. Finite element analysis was conducted for asphalt pavement sections with different asphalt layer thickness/modulus, and cavity depth and length, to generate the artificial pavement response database. The critical pavement response considered in this study was the tensile strain at the bottom of the asphalt layer because fatigue cracking is the main cause of road cave-in. The relationship between the critical pavement response and influencing factors was investigated using the pavement response database. The statistical regression approach was adopted to develop the asphalt pavement response model for predicting the critical pavement response of asphalt pavement with a subsurface cavity. RESULTS : It was found from the sensitivity analysis that the asphalt layer thickness or modulus, and cavity depth or length, are the major factors affecting road cave-in incidents involving asphalt pavement. The asphalt pavement response model showed high accuracy in predicting the tensile strain at the bottom of asphalt layer. It was found from the verification study that the R square value between finite element model and pavement response model were 0.969 and 0.978 in the cavity and intact sections, respectively. CONCLUSIONS: The work reported in this paper was intended to figure out the pavement structural behavior and to develop a pavement response model for the occurrence of cavities underneath asphalt pavement using 3D finite element analysis. In the future, critical pavement response will be utilized to establish the criteria of risk of road cave-in based on various different conditions.

본 연구에서는 옹벽 구조물의 내진성능 평가를 위해 2차원 유한요소 해석을 수행하였다. 2차원 유한요소 모델은 실제로 시공된 옹벽 구조를 기반으로 2차원 평면변형 요소로 모델링되었으며, 지반은 각각 유한요소와 무한요소로 모델링 하였다. 지진하중은 총 38개의 인공 지진을 생성하여 사용하였고, 생성된 인공 지진파를 11개의 PGA로 나누어 총 418회의 시간이력해석을 수행하였다. 수치해석 결과를 바탕으로 옹벽 구조물의 지진에 대한 취약도를 분석하였다. 취약도 분석 결과 콘크리트 및 철근의 취약도 곡선이 낮은 PGA 수준에서 급격히 변하는 것을 관찰할 수 있었다. 유한요소 해석 결과를 바탕으로 실제 현장의 옹벽 구조에서 상대적으로 낮은 수준의 지진파가 발생하더라도 높은 파괴확률로 인해 지진에 상대적으로 취약함을 확인하였다.

UHPFRC 15 M 분절형 박스거더에 대한 비선형 재료 및 비선형 기하학적 유한요소해석을 수행하였다. UHPFRC의 인장 및 압축 영역에서의 구성방정식은 공시체 시험을 기반으로 하였고, 체적 대비 강섬유 혼입률이 각각 1.0%, 1.5% 및 2.0%에 대해 해석을 수행하였다. UHPFRC를 위한 3차원 8 node hexahedron brick model과 1차원 embedded steel element를 기반으로 모델링하였다. UHPFRC 박스거더 단면에서 하부플랜지에 14개, 24개, 32개의 15.2mm 강연선을 모델링하여 실험결과와 비교하였다. 하중과 변위관계, 선형거동에서 비선형거동으로 변하는 시점에서 하중 및 중립축 변화 과정이 실험결과와 비교해 볼 때 정확하게 산출되었다. 따라서, 압축 및 인장구역에서 구성방정식을 반영한 재료적 비선형해석, UHPFRC 분절형 박스의 기하학적 비선형 해석이 유효함을 알 수 있다.

범용유한요소프로그램인 Abaqus의 확장유한요소법(XFEM)의 사용성 검증을 위하여 2차원 모델에 적용하여 수치해석을 수행하였다. 기존의 연구에 많이 사용되었던 응집요소(cohesive element) 모델은 균열 경로를 예측하고 요소를 삽입하여야 하는 단점 때문에 실제 균열을 모사하는데 한계가 있다. 이러한 이유로 응력의 방향성 및 특이성을 바탕으로 균열의 경로를 예측하는 확장유한요소법(XFEM)이 균열 해석에 있어서 더 발전된 방법으로 이용되어 왔다. 이번 연구에서는 균열의 경로가 자명한 2차원 모델에 사용하여 응집요소해석과 XFEM에 응집요소의 물성을 적용한 해석을 비교하고 XFEM 적용의 타당성을 확인하였다. 수치해석으로 균열 발생 직전의 응력분포 및 응력 특이성을 확인하고 실제 균열 발생경로와의 비교를 한다. 본 연구를 바탕으로 몇 가지의 한계를 극복하면 실제 복잡한 모델의 실제 균열진전해석을 수행하여 균열을 모사할 수 있을 것으로 기대된다.

Recently, the incidence and magnitude of earthquakes have been continuously increasing. NFPA 13 requires that hydroponics fire extinguishing system pipelines apply seismic isolation. Stainless steel joints have been newly developed to replace these seismic isolation joints. Therefore, in this study, a nonlinear finite element model of a pipeline with Stainless Power Joint was developed based on experimental data, and finite element analysis was performed by applying hydrostatic pressure and cyclic loading.

In this study, finite element (FE) analysis was performed to evaluate the seismic performance of the water treatment plant, which is a major state of the art water treatment plant, to predict tensile cracks and compressive failure. The FE model simulation for two facilities of the water purification plant was made considering the initial conditions, boundary conditions and water effect. For the nonlinear dynamic analysis, seismic analysis was performed using ground acceleration. Tensile cracks and compressive failure are analyzed and the effects on the structures are analyzed. As a result of the analysis, tensile cracks can be predicted to occur in the main structure.

Construction of irregular-shaped concrete structures requires a lot of time and money. To reduce the cost and time, the F3D(Free-Form Formwork 3D Printer) technology was adopted in manufacturing EPS(Expanded Polystyrene) formwork for irregular-shaped concrete structure. To design EPS formwork precisely, lateral pressure acting on irregular-shaped formwork and deformation of EPS form liner should be evaluated. However, in current Korean formwork standard, there are no standards for irregular-shaped formwork as it includes a lot of complex variables. For this reason, several researchers developed 3-dimensional finite element analysis model to calculate lateral pressure exerted by fresh concrete. In this study, deformation of irregular-shaped EPS formwork and lateral pressure acting on formwork was examined using finite element analysis model.

비선형 유한요소해석 결과를 이용하여 철근콘크리트 부재를 설계를 하고자 할 경우 위험단면에서의 휨모멘트를 산정하여 야 한다. 본 논문에서는 연속체 요소를 사용한 철근콘크리트 유한요소해석 결과를 이용한 휨 모멘트 계산식을 제시하고 유한요소의 변위 함수의 차수에 따른 최적의 요소 크기를 제안하였다. 해석으로부터 산출된 응력을 적분하여 구한 휨 모멘트 와 정역학적 평형 조건을 이용하여 계산한 휨 모멘트를 비교하였다. 응력을 적분하는 방법에서는 철근에 의한 응력과 콘크 리트의 응력을 모두 고려하였다. 또한 유한요소해석으로 산출된 응력의 정확도에 영향을 주는 여러 요인들을 분석하고 적용 요소의 변위 함수와 요소 크기를 다르게 설정하여 그 영향을 확인하였다. 해석의 목적이 부재의 거동을 대략적으로 살펴보 는 목적이라면 1차 변위 함수를 사용하고 요소 크기가 해석 모델의 단면 높이의 25%정도라도 적절하다고 판단된다. 정확도가 높은 부재의 내력을 도출해야 할 경우에는 2차 변위 함수를 사용하고 요소 크기를 12.5%로 할 것을 제안한다.

The F3D(Free-Form Formwork 3D Printer) technology that manufactures EPS(Expanded Polystyrene) formworks for irregular-shaped concrete structures by 3D printers was developed to reduce the cost and time. Because of weak strength and low elastic modulus of the EPS, structural performance including lateral pressure by fresh concrete of the formwork that consisted of EPS should be investigated. In order to calculate lateral pressures acting on formwork, several variables including sizes, shapes of formwork, tangential force(fricition) between fresh concrete and formwork, and material properties of fresh concrete should be considered. However, current regulations have not considered the properties of concrete, only focused on vertical formwork. Galleo introduced 3-dimensional finite element analysis models to calculate lateral pressure on formwork. Thus, proposed finite element analysis model based on previous studies were verified for vertical formwork and irregular-shaped formwork. The test results were compared with those by FEM analysis. As a result, the test agrees well with the analysis.

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.

A strain-gradient crystal plasticity finite element method(SGCP-FEM) was utilized to simulate the compressive deformation behaviors of single-slip, (111)[101], oriented FCC single-crystal micro-pillars with two different slip-plane inclination angles, 36.3o and 48.7o, and the simulation results were compared with those from conventional crystal plasticity finite element method(CP-FEM) simulations. For the low slip-plane inclination angle, a macroscopic diagonal shear band formed along the primary slip direction in both the CP- and SGCP-FEM simulations. However, this shear deformation was limited in the SGCP-FEM, mainly due to the increased slip resistance caused by local strain gradients, which also resulted in strain hardening in the simulated flow curves. The development of a secondly active slip system was altered in the SGCP-FEM, compared to the CP-FEM, for the low slip-plane inclination angle. The shear deformation controlled by the SGCP-FEM reduced the overall crystal rotation of the micro-pillar and limited the evolution of the primary slip system, even at 10% compression.

Although most of the automobile bodies are made of steel, the application of aluminum alloy sheet with high strength is under consideration for the development of environmentally friendly lightweight body for fuel economy improvement and carbon dioxide emission reduction. In the case of some inner plates, application of magnesium alloy sheet is examined. TRB plate has been studied mainly for weight reduction and rigidity reinforcement of steel plate parts. Recently, research on aluminum TRB rolled plate for light and environment friendly automobile application has been started, It is expected that the development of eco - friendly TRB rolling material made of light alloy will increase as the importance of light weight body for future energy efficiency increases. Therefore, in this study, we tried to obtain the technology to improve the quality of the product by pre - verifying the cooling performance of the hot forming process through the heat flow analysis and evaluating the cooling performance through the temperature distribution analysis. As a result, it was found that the temperature distribution through the flow velocity problem and the flow of the cooling channel can influence the quality of the final product through different heat distribution and cooling time depending on the shape of the mold and the product.

This paper uses finite element analysis to analyze the equivalent stress and fatigue duration distributed in the timing belt pulley of the rotating part. The pulley structure used for analysis was categorized into one body type and separate axis type and their characteristics were analyzed when materials S45C and SCM440-870C were applied. A static structural analysis and durability analysis show that when external forces are applied to the pulley, the separate axis structure is structurally safer and more favorable in terms of fatigue, compared to the one body. In addition, the separate axis structure using SCM440-870C material was found to have the best safety factor at 10.4 and infinite fatigue life. These findings are expected to be useful when manufacturing timing belt pulleys.

PURPOSES : The piezoelectric energy road analysis technology using a three-dimensional finite element method was developed to investigate pavement behaviors when piezoelectric energy harvesters and a new polyurethane surface layer were installed in field conditions. The main purpose of this study is to predict the long-term performance of the piezoelectric energy road through the proposed analytical steps. METHODS: To predict the stresses and strains of the piezoelectric energy road, the developed energy harvesters were embedded into the polyurethane surface layer (50 mm from the top surface). The typical type of triaxial dump truck loading was applied to the top of each energy harvester. In this paper, a general purpose finite element analysis program called ABAQUS was used and it was assumed that a harvester is installed in the cross section of a typical asphalt pavement structure. RESULTS : The maximum tensile stress of the polyurethane surface layer in the initial fatigue model occurred up to 0.035 MPa in the transverse direction when the truck tire load was loaded on the top of each harvester. The maximum tensile stresses were 0.025 MPa in the intermediate fatigue model and 0.013 MPa in the final fatigue model, which were 72% and 37% lower than that of the initial stage model, respectively. CONCLUSIONS : The main critical damage locations can be estimated between the base layer and the surface layer. If the crack propagates, bottom-up cracking from the base layer is the main cracking pattern where the tensile stress is higher than in other locations. It is also considered that the possibility of cracking in the top-down direction at the edge of energy harvester is more likely to occur because the material strength of the energy harvester is much higher and plays a role in the supporting points. In terms of long-term performance, all tensile stresses in the energy harvester and polyurethane layer are less than 1% of the maximum tensile strength and the possibility of fatigue damage was very low. Since the harvester is embedded in the surface layer of the polyurethane, which has higher tensile strength and toughness, it can assure a good, long-term performance.

고준위폐기물 처분용기를 처분장에서 처분 시 사고로 운송차량에서 추락낙하 하여 지면과 충돌하는 경우 처분용기에 가 해지는 충격력에 의해 처분용기에 응력이 발생한다. 본 논문에서는 고준위폐기물 처분용기의 구조안전성 설계과정의 일환으 로 이와 같은 충격력에 의하여 여러 가지 처분용기 모델에 발생하는 응력에 대한 비교연구를 수행하였다. 연구의 주된 내용 은 이와 같은 비교연구를 통하여 구조적으로 건전한 처분용기의 설계에 관한 것이다. 처분장에서 운반차량으로 처분용기 운 반 중 사고로 추락낙하 하여 지면과의 충돌 시에 처분용기에 가해지는 충격력은 기구동역학해석 상용 컴퓨터코드인 RecurDyn으로 구하였다. 이렇게 구한 충격력에 의하여 여러 가지 처분용기 모델에 발생하는 응력 및 변형은 유한요소해석 상용 컴퓨터코드인 NISA를 이용하여 구하였다. 이 응력과 변형 값들의 비교 검토를 통하여 구조적으로 건전한 처분용기에 대한 연구를 수행하였다. 연구결과 처분용기 내부 고준위폐기물 다발을 감싸는 외곽 벽의 두께가 두꺼워 질수록 또는 처분 용기의 직경이 커질수록 처분용기에 발생하는 응력이 커지는 것을 알 수 있었다. 그러나 처분용기에 가해지는 충격력도 처 분용기의 직경이 커짐에 따라 증가하였다. 그럼에도 불구하고, 단위 충격력 당 발생하는 변형의 크기는 직경이 증가함에 따 라 감소하였다. 따라서 결론적으로 직경이 증가할수록 처분용기는 구조적으로 건전함을 알 수 있었다.