• Computers and Concrete
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• 제10권2호
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• pp.121-133
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• 2012

Structures suffer from damages in their lifetime due to time-dependant effects, such as fatigue, creep and shrinkage, which can be expressed by concrete strains. These processes could be seen in the context of strain estimation of pre-stressed structures in two phases by using numerical methods. Their aim is checking and validating existing code procedures in determination of deformations of pre-tensioned girders by solving a system of nonlinear equations with strains as unknown parameters. This paper presents an approach based on the Newton-Raphson method for obtaining the stresses and strains in middle span section of pre-stressed girders according the equilibrium state.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1996년도 가을 학술발표회 논문집
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• pp.258-266
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• 1996

The purpose of this study is to make a reasonable correction in construction stage through exact prediction of long-time differential column shortening that occurs in the high-rise RC building. For this, a self-developed program adopted PCA code is used to predict differential column shortening with sequential loading process. Using this program, the amount of the different column shortening of Amatapura Apartment in Indonesia is predicted and the effect is analyzed. From the result, the major factor affecting the shortening amount in columns is elastic strain and the effect of shrinkage is very small rather than creep. And maximun differential column shortening is appeared near the middle of the building.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2011년도 추계 학술논문 발표대회
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• pp.181-183
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• 2011

This study was carried out about construction management plan to reduce water leakage of underground parking lot in the apartment housing. To minimize effect of upper working load, installation position of jack support and paving with rubble on the top of underground parking lot were studied. By calculation shrinkage strain of underground parking lot scale, water leakage risk in design of level difference was studied. In this study, the basic data about construction management was provided to reduce water leakage of underground parking lot in the apartment housing.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2010년도 춘계 학술대회 제22권1호
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• pp.105-106
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• 2010

본 연구에서는 대구 사장교 건설현장에 FBG 온도센서와 변형률 센서를 설치하여 콘크리트 타설 초기의 온도와 변형률을 모니터링을 실시하였으며, 이 연구에서 사용된 모니터링 기법은 매우 유용한 방법으로 실용화 될 수 있을 것으로 기대된다.

• 한국생산제조학회지
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• 제20권5호
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• pp.659-665
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• 2011

Recently, the plastic resin such as PC, ABS are widely used in IT market. Especially, in most cases the keypads mounted on the mobile phone are the dual-injection-plated type. Environmental regulation is based on the quality of injection-molded products and the minimum process steps are required to avoid the plating defects. Various parameters to produce the injection-molded plastic products make it difficult to obtain the desired stability. However, the past experience and the use of CAE analysis make it possible to predict the problems occurred in injection molding process. Especially, the problems of the weld lines such as runner balancing, bending, deformation and forming defects can be solved systematically and minimized by CAE analysis. Through this study, the non-uniform volumetric shrinkage and the difference in temperature distribution induce the deformation and the high value of stress causes the problems such as crack.

• Steel and Composite Structures
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• 제7권1호
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• pp.71-85
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• 2007

This study suggests modular composite profile beams, where the prefab concept is applied to existing composite profile beams. The prefab concept produces a beam of desired size having two types of profile: side module and bottom module. Module section will improve construction efforts because it offers several benefits : reduction of deflections due to creep and shrinkage, which might be found in existing composite profile beams; increase in span/depth ratio; and free prefabrication of any required beams. Based on the established analysis theory of composite profile beams, an analysis theory of modular composite profile beams was suggested, and analysis values were compared with experimental ones. The behavior of individual modules with increase of load was measured with a strain gauge, and the shear connection ratio between modules was analyzed by using the measured values. As a result of experiment, it was found that theoretical flexural strength on condition of full connection was 57%-80% by connection of modules for each specimen, and it is expected that flexural strength will approximate the theoretical levels through further module improvement.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.427-432
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• 2003

An analytical method to predict the flexural behavior of composite girder is presented in which the early-age properties of concrete are specified including maturing of elastic modulus, creep and shrinkage. The time dependent constitutive relation accounting for the early-age concrete properties is derived in an incremental format by expanding the total form of stress-strain relation by the first order Taylor series with respect to the reference time. The sectional analysis calculates the axial and curvature strains based on the force and moment equilibriums. The deflection curve of the box girder approximated by the quadratic polynomial function is calculated by applying to the proper boundary conditions in the consecutive segments. Numerical applications are made for the 3-span double composite steel box girders which is a composite bridge girder filled with concrete at the bottom of the steel box in the negative moment region. The one dimensional finite element analysis results are compared with those of the three dimensional finite element analysis and the analytical method based on the sectional analysis. Close agreement is observed among the three methods.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.463-468
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• 2003

A finite element formulation to predict the flexural behavior of composite girder is presented in which the early-age properties of concrete are specified including maturing of elastic modulus, creep and shrinkage. The time dependent constitutive relation accounting for the early-age concrete properties is derived in an incremental format by expanding the total form of stress-strain relation by the first order Taylor series with respect to the reference time. The total potential energy of the flexural composite member is minimized to derive the time dependent finite element equilibrium equation. Numerical applications are made for the 3-span double composite steel box girders which is a composite bridge girder filled with concrete at the bottom of the steel box in the negative moment region. The numerical analysis with considering the variation of concrete elastic modulus are performed to investigate the effect of it on the early-age behavior of composite structures. The one dimensional finite element analysis results are compared with the analytical method based on the sectional analysis. Close agreement is observed among the two methods.

• 한국세라믹학회지
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• 제28권11호
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• pp.926-934
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• 1991

The effect of aggregates on the forming and sintering behaviors of BaTiO3 was studied. Aggregates and deaggregates of fine crystallite were obtained by thermal decomposition of oxalate coprecipitates and subsequently crushing them with a press, respectively. Large voids formed by packing of aggregates were not easily eliminated despite the successive destruction of aggregates with increasing forming pressure. As a result, compacts of aggregates showed inhomogeneity with larger mid-pore size and broader pore size distribution with respect to those of deaggregates. This inhomogeneity caused differential shrinkage and consequental internal stress, which retarded densification. The differential sintering increased the size of mid-pores in the initial stage, and formed duplex structure composed of dense region with abnormally grown grains and porous region with fine grains. The driving force of this abnormal grain growth shown in the specimens of aggregates was attributed to the minimization of the elastic strain energy due to internal stress.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.607-612
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• 2000

A slitter, also called a roll slitter or rewinding machine, is a sort of machinery to cut sheet materials in rolls continuously in the longitudinal direction. Recently slitter line users have requiring higher wuality and precision in products in addition to high productivity. In this paper, on effect of clearance on shear planes in slitting of S.K.B(shrinkage Bnad) is performed by using finite element method. The results obtained are as follows: (1)Load stroke curves show decreasing maximum force when increasing the clearance. (2)Effective strain decreases when the clearance increases. (3)Deformation is concentrated along the very narrow shear band.