• 한국기계가공학회지
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• 제10권4호
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• pp.44-49
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• 2011

The crawler crane, which consists of a lattice boom, a driving system, and movable vehicle, is widely used in a construction site. It needs to be installed an overload limiter to prevent the overturning accident and the fracture of structure. This research is undertaken to provide the relation formula for designing the overload limiter as follows: First the relation formulas between the wire-rope tension and the hoisting load or the overturning ratio according to the luffing angle and length of a lattice boom are established. Secondly the derived formulas are corrected by using the compensated angle considering the deflection of boom through the finite element analysis. The stiffness analysis is carried out for 30-kinds of models as a combination of 6-kinds of luffing angle and 5-kinds of length of boom. Finally the shape design of a stick type load cell, which is the device to measure the wire-rope tension, is performed. 5-kinds of notch radius and 5-kinds of center hole radius are adopted as the design parameter for the strength analysis of the load cell.

• 한국자동차공학회논문집
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• 제7권6호
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• pp.144-155
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• 1999

An occupant analysis code SAFE (Safety Analysis For occupant crash Environment) is utilized to simulate and improve the crash performance of an energy absorbing steering system. The safety standard FMVSS 203 is simulated and used for design evaluations . Segments and contact elliposids are utilized to model the bod blocks and the components of the steering system with SAFE. Spring-damper elements and force-deflection characteristics are utilized to model the energy absorbing components such as the plate and the polyacetal molding. The plate absorbs the impact energy through tensile deformation . Whereas, the polyacetal molding absorbs the impact energy through compression. the body block test is carried out to validate tie simulation model, and real component tests are performed to extract the force-deflection curves . After the model is validated , the parameter study is carried out to evaluate the crash performance of the energy absorbing components. A performance measure is defined for the parameter study. Using the results of the parameter study and managing the orthogonal arrays, optimum design values of energy absorbing components are determined to minize the occupant injury.

• Structural Engineering and Mechanics
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• 제58권6호
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• pp.949-966
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• 2016

The second order analysis taking place due to non-linear behavior of the structures under the mechanical and geometric factors through implementing exact and approximate methods is an indispensible issue in the analysis of such structures. Among the exact methods is the slope-deflection method that due to its simplicity and efficiency of its relationships has always been in consideration. By solving the differential equations of the modified slope-deflection method in which the effect of axial compressive force is considered, the stiffness matrix including trigonometric entries would be obtained. The complexity of computations with trigonometric functions causes replacement with their Maclaurin expansion. In most cases only the first two terms of this expansion are used but to obtain more accurate results, more elements are needed. In this paper, the effect of utilizing higher order terms of Maclaurin expansion on reducing the number of required elements and attaining more rapid convergence with less error is investigated for the Bernoulli beam with various boundary conditions. The results indicate that when using only one element along the beam length, utilizing higher order terms in Maclaurin expansion would reduce the relative error in determining the critical buckling load and kinematic parameters in the second order analysis.

• 한국도로학회논문집
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• 제19권1호
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• pp.73-80
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• 2017

PURPOSES : This paper presents a comparison study between dynamic and static analyses of falling weight deflectometer (FWD) testing, which is a test used for evaluating layered material stiffness. METHODS: In this study, a forward model, based on nonlinear subgrade models, was developed via finite element analysis using ABAQUS. The subgrade material coefficients from granular and fine-grained soils were used to represent strong and weak subgrade stiffnesses, respectively. Furthermore, the nonlinearity in the analysis of multi-load FWD deflection measured from intact PCC slab was investigated using the deflection data obtained in this study. This pavement has a 14-inch-thick PCC slab over fine-grained soil. RESULTS: From case studies related to the nonlinearity of FWD analysis measured from intact PCC slab, a nonlinear subgrade model-based comparison study between the static and dynamic analyses of nondestructive FWD tests was shown to be effectively performed; this was achieved by investigating the primary difference in pavement responses between the static and dynamic analyses as based on the nonlinearity of soil model as well as the multi-load FWD deflection. CONCLUSIONS : In conclusion, a comparison between dynamic and static FEM analyses was conducted, as based on the FEM analysis performed on various pavement structures, in order to investigate the significance of the differences in pavement responses between the static and dynamic analyses.

• 한국농공학회지
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• 제41권4호
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• pp.104-112
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• 1999

Tensile behavior in concrete has been neglected until recently. However, the effect of tensile stresses in concrete must be considered where the member primarily carries tensile forces or when ultimate strength is affected by the cracking history. In this paper, a series of experiments were performed with a reinforced rectangular beams of 15 specimens in order to investigate the effect of tension stiffening into the nonlinear analysis and cracking behavior. The experimental results were analyzed in terms of load-deflection curves and strain fracture energy with respect to the main experimental variables such as types of specimen, strength of concrete and steel ration. The results from experiments and finite element analysis were compared in terms of load-deflection relationship and cracking pattern. The results are as follows ; The tension stffening effects of reinforced concrete beams were observedc up to yielding of members after cracking showing strain energy difference of 35 % at the beam of 0.57% steel ratio compared with that of beam ignoring the tension stiffening effect. The tension stiffening of concrete strength 400kgf/$\textrm{cm}^2$ and 600kgf/$\textrm{cm}^2$ increased by 8% and 13%, respectively, compared with that of concrete strength 200kgf/$\textrm{cm}^2$. The tension stiffening effects were greater at a ductile member rather than a brittle one. The load-deflection results of finite element analysis showed very similar results from experiment. The crack growth and pattern might be predicted from the nonlinear finite element analysis considering concrete stiffening.

• 한국전산구조공학회논문집
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• 제28권1호
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• pp.39-46
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• 2015

본 연구에서는 프리스트레스트 콘크리트 보의 처짐 예측을 위해 재료비선형이 고려된 콘크리트 및 철근, 강연선의 거동을 고려할 수 있는 구성모델을 조합하여 적층 쉘 요소를 사용한 유한요소해석 모델에 적용하였다. 이를 기존 연구자들의 실험 결과와 비교함으로써 모델의 타당성을 검증하였고, 스팬-깊이비, 편심 그리고 프리스트레싱 크기에 대한 처짐을 해석하고 이를 수계산 결과와 비교하였다. 그 결과, 스팬-깊이비가 커질수록, 편심이 작아질수록, 프리스트레싱 크기가 작아질수록 처짐이 증가하는 것을 확인하였다. 또한, 편심이 매우 작을 경우와 프리스트레싱 크기가 매우 작을 경우에는 수계산이 처짐을 과대평가한다는 것을 확인하였다.

• 한국항공우주학회지
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• 제35권6호
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• pp.503-508
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• 2007

본 연구에서는 대변형 보이론을 이용하여 무베어링 로터 시스템의 공력탄성학적 안정성 해석을 수행하였다. 무베어링 로터 시스템의 유연보, 토오크 튜브, 그리고 메인 블레이드를 각각 탄성 운동을 하는 보로 가정하고, 1차원 보 요소로 모델링을 하였다. 외력으로는 2차원 준-정상 공기력 모델을 적용하였으며, 보의 유한 요소 지배방정식은 헤밀턴 원리(Hamilton's Principle)를 이용하여 얻었다. 공력탄성학적 안정성 해석을 수행하기 위하여 정지 비행시는 모달 접근법을, 전진 비행시는 주기적인 특성을 갖는 비선형 정적 트림해를 얻기 위해 동체 평형을 고려한 연계 평형 해석을 통한 완전 유한요소 방정식을 이용하였다. 본 연구에서 구한 결과를 기존의 적정변형 보이론에 모달 접근법을 이용한 무베어링 로터 시스템의 결과와 비교하였다.

• KIEAE Journal
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• 제14권6호
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• pp.93-97
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• 2014

Curtain wall system of office buildings has recently become very common in Korea. As the multi-layer curtain glazing is exposed to outdoor environment, it is very subjected to direct environmental impact. Consequently, breakage and cracks of glazing due to heat expansion is frequently observed. This study explores various causes and aspects for destruction of multi-layer glazing. A sensitivity analysis was performed on the basis that thermal changes causes damage to the multi-layer glazing. Air temperature in air cavity within the multi-layer glazing was examined to find its effect on multi-layer glazing breakage. Analysis showed high deflection to depth ratio of 1:1.8 and that higher the aspect ratio, smaller is the deflection. Allowable pressure showed that the weakest value is for aspect ratio of 1:2.9. Sensitivity analysis by the area of the glazing showed that as area of glazing becomes higher, allowable pressure and deflection-depth ratio becomes smaller. For allowable pressure and allowable deflection-depth within air cavity, the glazing breakage occurred at least $107^{\circ}C$. The results from glazing breakage by thermal factor shows that it is hard to break the glazing with only an increase in air cavity temperature in multi-layer glazing applied in buildings.

• 한국전산구조공학회논문집
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• 제27권6호
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• pp.525-532
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• 2014

본 연구에서는 프리스트레스트 콘크리트 일방향 슬래브의 사용성 평가를 위한 처짐을 분석하기 위하여 유한요소법에 기반한 해석적 연구를 수행하였다. 유한요소 상용 프로그램을 이용한 해석결과와 실험결과를 비교하여 모델링의 타당성을 검증하였으며, 비교적 유사한 결과를 나타내었다. 또한, 콘크리트 압축강도, 편심 거리, 활하중, 그리고 긴장재의 배치형태에 따른 처짐을 분석하여 수계산 결과와 비교하였고, 회귀분석을 통해 변수들과 처짐 사이의 상관관계를 확인하였다. 그 결과, 콘크리트 압축강도가 클수록, 편심 거리가 클수록, 활하중이 작을수록 처짐이 감소하는 것을 확인하였으며, 직선형태의 처짐이 가장 작고 절곡형태의 처짐이 가장 큰 것을 확인하였다. 또한 회귀분석을 통해 콘크리트 압축강도와 편심 거리가 솟음값에 미치는 영향을 분석하였다.

• Structural Engineering and Mechanics
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• 제28권2호
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• pp.207-220
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• 2008

The shear lag has been studied for many years. Nevertheless, existing research gives a variety of stress concentration factors. Unlike the elementary beam theory, the application of load is not unique in reality. For example, concentrated load can be applied as point load or distributed load along the height of the web. This non-uniqueness may be a reason for the discrepancy of the stress concentration factors in the existing studies. The finite element method has been often employed for studying the effect of the shear lag. However, not many researches have taken into account the influence of the finite element mesh on the shear lag phenomenon, although stress concentration can be quite sensitive to the mesh employed in the finite element analysis. This may be another source for the discrepancy of the stress concentration factors. It also needs to be noted that much less studies seem to have been conducted for the shear lag effect on deflection while some design codes have formulas. The present study investigates the shear lag effect in a simply supported box girder by the three-dimensional finite element method using shell elements. The whole girder is modeled by shell elements, and extensive parametric study with respect to the geometry of a box girder is carried out. Not only stress concentration but also deflection is computed. The effect of the way load is applied and the dependency of finite element mesh on the shear lag are carefully treated. Based on the numerical results thus obtained, empirical formulas are proposed to compute stress concentration and deflection that includes the shear lag effect.