• Journal of Korean Association for Spatial Structures
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• v.10 no.1
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• pp.75-84
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• 2010

According to the available study and experimental data about the long term behavior of CFT(Concrete Filled Tube) columns, the creep and of concrete in CFT columns are smaller than those of RC columns because of the confinement effect of outer steel columns. In this study, the uncertainties associated with assumed values for concrete properties such as strength, creep coefficients, and service load have been considered and analyzed for the prediction of time-dependent column shortening of CFT column. The CFT column shortening analysis using Monte Carlo method is proposed and an of a 37 story tall building with CFT columns is studied for illustration. According to the results obtained by the probability analysis with multi parameters, the effect of variation coefficient for 3 parameters is investigated considering confidence interval.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.6 s.261
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• pp.665-670
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• 2007

Alpha-phase alumina TGO(Thermally Grown Oxide) forms on the interface between zirconia top coat and bond coat of thermal barrier coating system for superalloys during exposure to high temperature over $1000^{\circ}C$. It is known to provide a good protection against hot corrosion and to cause surface failure such as rumpling and cracking due to difference in thermal expansion coefficient from the substrate metal and the lateral growth. Consequently, mechanical properties of the alumina TGO at the high temperature are the key parameters determining the integrity of TBC system. In this work, by using Fecralloy foils as the alumina forming substrate, creep tests and tensile tests have been performed with various TGO thicknesses$(h=0{\sim}4{\mu}m)$ and yttrium contents(0, 200ppm) at $1200^{\circ}C$. Displacement-time curves and load-displacement curves for each TGO thickness(h=1,2,..) were measured from the creep and tensile tests, respectively, and compared with the curves without TGO thickness(h=0). As the result, the intrinsic tensile and creep properties of TGO itself were determined.

• Korean Journal of Metals and Materials
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• v.48 no.9
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• pp.791-797
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• 2010

The creep crack growth rate (da/dt) of the Cr-Mo steels tested by pre-crack and the voltage (or resistance) variables were related into fracture parameter (Ct), crack growth coefficient (H), and an exponent (q) in the parts of Base, weld and HAZ. The fracture parameter (Ct) has various variables relating to the specimen and crack shape, applied stress, and creep strain curve. The H and q was inferred by OLS regression (ordinary least square method), and the H values were solved in statistics and probability assessment, which were attained fromPDF's distributions (probability density function). The HAZ part has the highest value of q by OLS regression and the widest distribution of H by PDF of WEIBULL, which means that the crack sensitivity of HAZ should be cautioned against the creep crack growth and failure.

• Journal of the Korean Wood Science and Technology
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• v.52 no.4
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• pp.375-382
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• 2024

The study focuses on evaluating the bending creep performance of laminated veneer lumber (LVL) formwork in timber concrete composite (TCC) structures. Timber-framed construction is highlighted for its environmental benefits and seismic resistance, but limitations such as poor tensile strength and brittle failure in bending hinder its use in high-rise buildings. Wood-concrete hybrid structures, particularly those using reinforced concrete slabs with TCC floors, emerge as a potential solution. The research aims to understand the time-dependent behavior of TCC components, considering factors like wood and concrete shrinkage and connection creep. The experiment was conducted in western Japan on the TCC floor designed for use in the Kama-city Inatsuki-higashi compulsory education school. The LVL formwork, measuring 9,000 mm by 900 mm, and concrete is loaded onto it for testing. The creep test periods are examined using concrete loading. It employs a comprehensive creep analysis, adhering to Japanese standards, involving deflection measurements and regression analysis to estimate the creep coefficient. Results indicate substantial deformation after shoring removal, suggesting potential reinforcement needs. The study recommends extending test periods for improved accuracy and recognizing regional climate impacts. Overall, the research provides valuable insights into the potential of LVL formwork in TCC structures, emphasizing safety considerations and paving the way for further experimentation under varied conditions to validate structural integrity.

• Journal of the Korea Institute of Building Construction
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• v.1 no.1
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• pp.151-159
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• 2001

This study was performed to investigate the effect of time-dependent creep on the deformation. In the analysis, modified Cam-Clay model was adopted to describe the elastic-plastic behavior of clayey soil. In order to consider effect of creep, the secondary coefficient of consolidation $\alpha$ was supplemented to modified Cam-Clay model. To examine the reliability of the program which is developed in this study, the estimated values by this program were compared with the experimental results. The results of the analysis were in good agreement with the observed values in the field.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.61-64
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• 2006

This paper presents experimental analysis of a friction-driven wheel responsible for generating wheel squeal. Squeal noise generating mechanism has been examined under the laboratory condition by the model rig. Creep characteristics and squeal noise were observed by varying relative velocity of the wheel with respect to the rail and friction coefficient. Computational radiating noise analysis was also performed based on the modal analysis and noise transfer function measurement of the object wheel.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.720-721
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• 2006

The new alloy$^{1)}$ is made from rapidly solidified Al-Ni-Zr-Ce aluminum alloy powder, and has the following unique mechanical characteristics:(1) The stress-strain curve shows a yield point; (2) The alloy shows high heat resistance; (3) Although the alloy is submicron particle diameter, it shows excellent creep resistance. We observed the micro structures of this new alloy, and it is thought that is based on the following reasons:(1) The dislocation strongly adheres to the alloy's many crystal boundaries;(2) The added alloying elements have a small diffusion coefficient in aluminum;(3) The tiny intermetallic compound particles crystallizing at the grain boundary.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.2A
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• pp.243-247
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• 2008

An analytical approach to calculate time-dependent stresses and strains in initially cracked reinforced concrete section with biaxial bending was proposed. The method utilized the aging coefficient approach of Bazant and the linear creep theory. The position of neutral axis and strain and stress distributions of cracked section after creep and shrinkage were determined from the requirements of strain compatibility and equilibrium of a section. With this proposed algorithm, examples were given for rectangular section and a comparative analysis for stress and strain was also made.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.3
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• pp.219-227
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• 2016

In this study, we have proposed a method of monitoring of bridges under construction in view of the long-term behavior of the prestress concrete bridge of which the Free Cantilever Method is applied. As a method to confirm the ability of the long-term behavior of the concrete box girder, temperature sensors and strain gauges were installed, and the measured data was used to calculate creep coefficient. Moreover, we have measured the stress of the concrete box girder during construction which was applied with creep coefficient and compared with the changes in temperature to analyze the vertical displacement along the segment. In conclusion, monitoring of the FCM bridge during construction in consideration of the long-term behavior can be analyzed efficiently by suing temperature and displacement data without the use of laser displacement meter or laser delfectometer.

• Journal of The Korean Society of Agricultural Engineers
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• v.66 no.2
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• pp.1-12
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• 2024

In order to integrate two consolidation theories of Terzaghi's consolidation theory and Mesri's secondary compression theory and to identify a model suitable for analyzing stress-strain behavior over time, numerical analysis on consolidation tests were conducted using a modified cam-clay model and a soft soil creep model and the following conclusions were obtained. The results of numerical analysis applying the theory that a linear proportional relationship is established between the void ratio at logarithmic scale and the permeability coefficient at logarithmic scale is better agreement with the result of oedometer test than the results of applying constant hydraulic conductivity. The modified cam-clay model is a model that does not include secondary compression, but the slope of the normal consolidation line corresponding to the compression index of the standard consolidation test includes secondary compression, so the actual settlement curve over time is lower than the predicted value through numerical analysis. It always gets smaller. Other previous studies that applied Terzaghi's consolidation theory to consolidation test analysis showed the same results and were cross-confirmed. The soft soil creep model, which includes secondary compression in the theory, showed good agreement in all sections including secondary compression in the consolidation test results. It was judged appropriate to use a soft soil creep model when performing numerical analysis of soft clay ground.