• 한국해양공학회지
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• 제34권3호
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• pp.194-201
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• 2020

In this study, an optical-fiber sensor was used to measure loads that could act in an environment similar to the loading conditions that exist in an actual pipe. The structure and the installation method of the optical-fiber strain sensor were applied considering the actual large pipe and the buried pipe environment. Load tests were performed using a displacement sensor and sandbags to determine the deflection of the pipe according to the external load, and the linear measurement results were verified. Considering the conditions that could exist in the actual pipe, the test method was presented, and the strain of the buried pipe generated at this time was measured.

• Advances in nano research
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• 제14권5호
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• pp.475-493
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• 2023

In the context of nonclassical nonlocal strain gradient elasticity, this article studies the free and forced responses of functionally graded material (FGM) porous nanoplates exposed to thermal and magnetic fields under a moving load. The developed mathematical model includes shear deformation, size-scale, miscorstructure influences in the framework of higher order shear deformation theory (HSDT) and nonlocal strain gradient theory (NSGT), respectively. To explore the porosity effect, the study considers four different porosity models across the thickness: uniform, symmetrical, asymmetric bottom, and asymmetric top distributions. The system of quations of motion of the FGM porous nanoplate, including the effects of thermal load, Lorentz force, due to the magnetic field and moving load, are derived using the Hamilton's principle, and then solved analytically by employing the Navier method. For the free and forced responses of the nanoplate, the effects of nonlocal elasticity, strain gradient elasticity, temperature rise, magnetic field intensity, porosity volume fraction, and porosity distribution are analyzed. It is found that the forced vibrations of FGM porous nanoplates under thermal and live loads can be damped by applying a directed magnetic field.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.933-943
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• 2009

Axial loads and shaft resistances can be calculated by load transfer analysis using strain data with load level. In load transfer analysis, the elastic modulus of concrete is a one of the most important parameters to consider. The elastic modulus, $E_{50}$, suggested by ACI (American Concrete Institute), has been commonly used. However, elastic modulus of concrete shows nonlinear stress-strain characteristic, so nonlinearity should be considered in load transfer analysis. In this paper, a load transfer analysis was performed by using data obtained from bi-directional pile load tests for four cases of drilled shafts. For consideration of nonlinearity, elastic modulus was calculated by both the Fellenius method and the nonlinear method, assuming the stress-strain relation of concrete to be a quadratic function, and then, the calculated elastic modulus was applied to the estimation of shaft resistance. The calculated shaft resistances were compared with the result obtained using the constant elastic modulus of ACI code. It was found that the f-w curves are similar to each method, and elastic modulus and shaft resistances decreased as strain increased. Moreover, shaft resistances estimated from elastic modulus considering nonlinearity were 5~15% different than those obtained using the constant elastic modulus.

• Computers and Concrete
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• 제2권4호
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• pp.249-266
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• 2005

In the present paper a transient three-dimensional thermo-mechanical model for concrete is presented. For given boundary conditions, temperature distribution is calculated by employing a three-dimensional transient thermal finite element analysis. Thermal properties of concrete are assumed to be constant and independent of the stress-strain distribution. In the thermo-mechanical model for concrete the total strain tensor is decomposed into pure mechanical strain, free thermal strain and load induced thermal strain. The mechanical strain is calculated by using temperature dependent microplane model for concrete (O$\check{z}$bolt, et al. 2001). The dependency of the macroscopic concrete properties (Young's modulus, tensile and compressive strengths and fracture energy) on temperature is based on the available experimental database. The stress independent free thermal strain is calculated according to the proposal of Nielsen, et al. (2001). The load induced thermal strain is obtained by employing the biparabolic model, which was recently proposed by Nielsen, et al. (2004). It is assumed that the total load induced thermal strain is irrecoverable, i.e., creep component is neglected. The model is implemented into a three-dimensional FE code. The performance of headed stud anchors exposed to fire was studied. Three-dimensional transient thermal FE analysis was carried out for three embedment depths and for four thermal loading histories. The results of the analysis show that the resistance of anchors can be significantly reduced if they are exposed to fire. The largest reduction of the load capacity was obtained for anchors with relatively small embedment depths. The numerical results agree well with the available experimental evidence.

• 대한치과보철학회지
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• 제43권3호
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• pp.322-330
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• 2005

Statement of problem. In distal extension removable partial denture, the preservation of health of abutment teeth is very important, but abutment teeth are subjected to unfavorable stress. Purpose. The purpose of this study was to investigate the biomechanical effects of mandibular removable partial dentures with various prosthetic designs using strain gauge analysis. Material and methods. Artificial teeth of both canines were anchored bilaterally in a mandibular edentulous model made of resin. Bilateral distal extension removable partial dentures with splinted and unsplinted abutments were fabricated. Group 1 : Clasp-retained mandibular removable partial denture with unsplinted abuhnents Group 2 : Clasp-retained mandibular removable partial denture with splinted abutments by 6-unit bridge Group 3 : Bar-retained mandibular removable partial denture Strain gauges were bonded on the labial plate of the mandibular resin model, approximately 2 mm close to the abutments. Two vertical experimental loadings (100N and 200N) were applied subsequently via two miniature load cells that were placed at mandibular first molar regions. Strain measurements were performed and simultaneously monitored from a computer connected to data acquisition system. For within-group evaluations, t-test was used to compare the strain values and for between-group comparisons, a one-way analysis of variance (ANOVA) was used and Duncan test was used as post hoc comparisons. Results. Strain values increased as the applied load increased from 100N to 200N for all groups (p<.05). The strain values of group 1 and 2 were tensile under loadings. In contrast, strain values of group 3 were compressive in nature. Under 100N loading, group 1 showed higher strain values than group 3 in absolute quantity (p<.05). Under 200N loading, group 3 showed higher strain values than group 1 and 2 in absolute quantity (p<.05). Group 1 showed higher strain values than group 2 (p<.05). Conclusion. Splinting of two isolated abutments by bridge reduced the peri-abutment strain in comparison with unsplinted abutments. Strain of bar-retained removable partial denture increased much more as applied load increased, but was compressive in nature.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1992년도 가을 학술발표회 논문집
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• pp.82-87
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• 1992

In this thesis, the fatigue tests were performed on a series of SFRC (steel fiber reinforced concrete)to investigate the flexural tensile behavior of SFRC varying with the steel fiber contents and the steel fiber aspect ratios. Beam specimens of 10$\times$10$\times$60cm are used. the specimen series are classified according to the steel fiber contents varying 0.5. 1.0, 1.5%, and to the steel fiber aspect ratios varying 60, 80, 100. The three point loading system was used in the fatigue tests. The minimum value of repeated loading was fixed at 10.0kgf and maximum value was 75% to static ultimate strength for periodically using concrete strain gages located at the lower end of the mid-span, and the stress-strain curves were drawn for each specimens, respectively. From the tests result, it was found that the larger steel fiber content and the smaller the steel fiber aspect ratio is , the tensile strain of SFRC under fatigue load proportionally increases. By the regression analysis on these results, the empirical formulae to predict the tensile strain of SFRC were suggested. In comparison of the tensile elastic modulus under fatigue load, it was also found that the larger steel fiber content and the smaller steel fiber aspect ratio is , the smaller decreasing rate of the stiffness of SFRC under fatigue load decreased.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.293-294
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• 2006

The conventional strain measuring device is costly and complicated - it is not simple to understand its structure. Hence, strain gage and the A/D converter are assembled to come up with a load and a strain measuring device. The device was tested for measuring the strain in a loaded specimen and the experimental results were compared to those obtained by a commercial strain indicator.

• 한국농공학회지
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• 제44권1호
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• pp.93-102
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• 2002

Steel fiber and polymer are used widely for reinforcement material of RC structures because of its excellences of the durability, serviceability as well as mechanical properties. The purpose of this study is to investigate the shear behavior of polymer cement high strength concrete beams mixed with steel fiber. The compressive strength of concrete was based on the 100$\times$200 mm cylinder specimens. The compressive strength of concrete are 320$kgf/cm^2$, 436 $kgf/cm^2$ and 520 $kgf/cm^2$ in the 28 days. The static test was carried out to measure the ultimate load, the initial load of flexural and diagonal cracking, crack patterns and fracture modes. Also, load-strain and load-deflection examined. During the test cracks were sketched against the load values according to the growth of crack. result are as follows; (1) The failure modes of the specimens are increased in rigidity and durability with mixing steel fiber and polymer. (2) The load of initial crack was similar a theory of shear-crack strength. (3) The deflection and strain at failure load of Polymer-steel fiber high strength concrete beams were increased, improving the brittleness of the high strength concrete.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.385-389
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• 2004

Test facilities for the wind turbine performance monitoring and mechanical load measurements are installed in Vestas 100 kW wind turbine in Wollyong test site, Jeju island. The monitoring system consists of Garrad-Hassan T-MON system, telemetry system for blade load measurement, various sensors such as anemometer, wind vane, strain gauge, power meter, and etc. The experimental procedure for the measurement of wind turbine loads, such as edgewise(lead-lag) bending moment, flapwise bending moment, and tower base bending moment, has been established. Strain gauges are on-site calibrated against load cell prior to monitoring the wind turbine loads. Using the established monitoring system, the wind turbine is remotely monitored. From the measured load data, the load analysis has been performed to obtain the load power spectral density and the fatigue load spectra of the wind turbine.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회논문집(I)
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• pp.601-608
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• 2000

Steel fiber and Polymer are used widely for the reinforcement material of RC structures because of its excellence of durability, serviceability as well as mechanical properties. Polymer-Steel fibrous high strength concrete beam's input ratio are 1.0%. The shear span-to-depth ratio are 1.5, 2.8 and 3.6, compressive strength of specimens 320kg/㎠, 436kgf/㎠ and 520kgf/㎠ in 28 days. The static test was carried out to measure the ultimate load, the initial load of flexural crack and of diagonal crack, from which crack patte군 and fracture modes are earned. Also, stress-strain, load-strain and load-deflection are examined during the test cracks(shear crack, flexural crack, and diagonal tension crack), when the load values are sketched according to the growth of crack. Result are as follows; (1) The failure modes of the specimens increase in rigidity and durability in accordance with the increase of mixing steel fiber and polymer. (2) The load of initial crack was the same as the theory of shear-crack strength (3) Polymer-Steel fibrous high strength concrete beams have increased the deflection and strain at failure load, improving the brittleness of the high strength concrete. (4) In this result of study, an additional study need to make a need formular because the study is different from ACI formular and Zsutty formular.