• 한국정밀공학회지
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• 제18권2호
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• pp.186-191
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• 2001

A crack with electrically impermeable surfaces in an electrostrictive material subjected to uniform electric loading is analysed. The effect of electric yielding on stress intensity factor is investigated by using a small scale yielding model and a strip yield zone model. Complete forms of electric fields and elastic fields are derived by using complex function theory. The electrical yield zone shapes for two models are different each other. The two models, however, predict similar yield zone sizes under the small scale yielding conditions. It is found that the influence of electric yielding on the stress intensity factor is insensitive to the modeling of the electrical yield zone shape.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 가을 학술발표회 논문집
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• pp.533-540
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• 2002

Tubular joints having a large diameter are reinforced using internal ring stiffener in order to increase the load carrying capacity. In this study, the static strengths of Internally ring-stiffened tubular T-joints subjected to compressive brace loading are assessed. Nonlinear finite element analyses are used to compute the behavior of unstiffened and ring-stiffened T-joints. From the numerical results, Internal ring stiffener is found to efficient in improving the ultimate capacity, and reinforcement effect are calculated. The influence of geometric parameters for members and ring is evaluated. Based on the FE results, regression analysis is performed considering practical sizes of ring stiffener, finally strength estimation formulae for ring-stiffened T-joints are proposed.

• Steel and Composite Structures
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• 제39권2호
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• pp.159-170
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• 2021

Concrete filled steel tubes (CFSTs) are extensively used in a variety of structures due to their structural and economic advantages over other types of structures. Considerable research has been conducted with regards to their short-term behaviour, and very limited studies have focused on their long-term behaviour. In this study, a series of tests were carried out on high strength squat (short) CFSTs and concrete cylinders under controlled conditions of temperature and humidity to better understand their time dependent behaviour. A number of parameters were investigated including the influence of steel and concrete bond, confinement, level of sustained load and sizes of specimens. The results revealed that creep strains increased by more than 40% if there was no bonding between steel tube and concrete core. As expected, creep and shrinkage of concrete inside a steel tube were significantly less than those developed in exposed concrete. At the end of a creep period of six months, all the specimens were tested to failure to observe the influence of sustained loads on the ultimate strength. It was found that creep does not have a major effect on the strength of short CFSTs in the specific experimental study conducted here, which was less than 2.5%.

• Structural Engineering and Mechanics
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• 제19권3호
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• pp.337-346
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• 2005

The paper reports on a study of bond strength between reduced-water-content concrete and tensile reinforcement in spliced mode. Three different diameters (12, 16 and 22 mm) of tensile steel were spliced in the constant moment zone, where there were two bars of same size in tension. For each diameter of reinforcement, a total of nine beams ($1900{\times}270{\times}180mm$) were tested, of which three beams were with no axial force (positive bending) and the other six beams were with axial force (combined bending). The splice length was selected so that bars would fail in bond, splitting the concrete cover in the splice region, before reaching the yield point. It was found that there was a considerable size effect in the experimental results, i.e., as the diameter of the reinforcement reduced the bond strength and the deflection recorded at the midspan increased significantly, whilst the stiffness of the beams reduced. It was also found for all reinforcement sizes that higher bond strength and stiffness were obtained for beams tested in combined bending than that of the beams tested in positive bending only.

• 한국식품과학회지
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• 제11권2호
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• pp.81-85
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• 1979

1. Gram Quality Analyzer로 측정한 단백질과 Kjeldahi치와는 곡종에 관계없이 고도의 상관(상관계수 $0.97{\sim}0.98$)을 나타내었으며 반복 측정시 의미있는 차이를 보이지 않았다. 2. 밀의 경우 경연질별로 큰 차이가 없었으나 보리의 경우 겉보리가 쌀보리보다 상관계수가 약간 낮았고 반복간 오차도 컸다. 3. 측정시료의 입자크기는 단백질 측정치에 직접 영향은 없었으나 입자크기가 작을수록 측정오차가 작았다. 4. 측정 cell에 충진하는 시료는 12 g 정도가 적합하였으며 시료를 많이 넣는 경우 적외선 reflectance가 많아 단백질 측정치는 다소 증가하였으며, 8 g 이하로 넣는 경우 오차가 컸다.

• Steel and Composite Structures
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• 제46권4호
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• pp.525-538
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• 2023

This paper focuses on the energy absorption of lattice core sandwich structures of different configurations. The diamond lattice unit cell, which has been extensively investigated for energy absorption applications, is the starting point for this research. The energy absorption behaviour of sandwich structures with an expanded metal sheet as the core is investigated at low-velocity impact loading. Numerical simulations were carried out using ABAQUS/EXPLICIT and the results were thoroughly compared with the experimental results, which indicated desirable accuracy. A parametric analysis, using a Box-Behnken design (BBD), as a method for the design of experiments (DOE), was performed. The samples fabricated in three levels of parameters include 0.081, 0.145, and 0.562 mm² Cell sizes, and 0, 45, and 90-degree cell orientation, which were investigated. It was observed from experimental data that the angle of cells orientation had the highest degree of influence on the specific energy absorption. The results showed that the angle of cells orientation has been the most influential parameter to increase the peak forces. The results from using the design expert software showed the optimal specific energy absorption and peak force to be 1786 J/kg and 26314.4 N, respectively. The obtained R2 values and normal probability plots indicated a good agreement between the experimental results and those predicted by the model.

• Structural Engineering and Mechanics
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• 제89권6호
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• pp.601-615
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• 2024

Effect of ring and straight stiffeners in the buckling as well as vibration characteristics of metal-ceramic functionally graded plates with cutout subjected to various uniaxial and localized in-plane compressive edge loadings was explored in the present work. In the current work, the distinguishing characteristics of metal and ceramic are merged in a single volume, and power law was used for estimating the material composition throughout thickness. Buckling and free vibration characteristics were studied initially for unstiffened Al/SiC functionally graded plates with cutout. Subsequently, the influence of cutout ratio on buckling load as well as natural frequency for different power law indices was discussed. The functionally graded plate was stiffened by three different stiffener patterns, namely; ring stiffener, straight stiffener, as well as a combination of the ring and the straight stiffener, to enhance the buckling as well as vibration characteristics. The effect of stiffener depth ratio for different stiffener patterns was also presented for functionally graded plates having different cutout sizes under various loading conditions. Such studies on functionally graded material have potential applications in a variety of technological fields including the aerospace and defense sectors.

• Structural Engineering and Mechanics
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• 제76권6호
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• pp.687-708
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• 2020

Openings in steel plate shear walls (SPSWs) are usually used for decorative designs, crossing locations of multiple utilities and/or structural objectives. However, earlier studies showed that generating an opening in an SPSW has a negative effect on the cyclic performance of the SPSW. Therefore, this study proposes tripling or doubling the steel-sheet-plate (SSP) layer and stiffening the opening of the SPSW to provide a solution to undesirable opening effects, improve the SPSW performance and provide the infill option of potential strengthening measures after the construction stage. The study aims to investigate the impact of SSP doubling with a stiffened opening on the cyclic behaviour, expand the essential data required by structural designers and quantify the SPSW performance factors. Validated numerical models were adopted to identify the influence of the chosen parameters on the cyclic capacity, energy dissipation, ductility, seismic performance factors (SPF) and stiffness of the suggested method. A finite Element (FE) analysis was performed via Abaqus/CAE software on half-scale single-story models of SPSWs exposed to cyclic loading. The key parameters included the number of SSP layers, the opening size ratios corresponding to the net width of the SSP, and the opening shape. The findings showed that the proposed assembly method found a negligible influence in the shear capacity with opening sizes of 10, 15, 20%. However, a deterioration in the wall strength was observed for openings with sizes of 25% and 30%. The circular opening is preferable compared with the square opening. Moreover, for all the models, the average value of the obtained ductility did not show substantial changes and the ultimate shear resistance was achieved after reaching a drift ratio of 4.36%. Additionally, the equivalent sectional area of the SSP in the twin and triple configuration of the SPSWs demonstrated approximately similar results. Compared with the single SSP layer, the proposed configuration of the twin SSP layer with a stiffened opening suggest to more sufficiency create SSP openings in the SPSW compared to that of other configurations. Finally, a tabular SPF quantification is exhibited for SPSWs with openings.

• Steel and Composite Structures
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• 제36권5호
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• pp.553-568
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• 2020

Steel-concrete composite structures have been extensively used in building, bridges, and other civil engineering infrastructure. Shear stud connectors between steel and concrete are essential in composite members to guarantee the effectiveness of their behavior in terms of strength and deformability. This study focuses on investigating the shear stiffness of headed studs embedded in several types of concrete with wide range of compressive strength, and their effects on the elastic behavior of steel-concrete composite girders were evaluated. Firstly, totally 206 monotonic push-out tests from the literature were reviewed to investigate the shear stiffness of headed studs embedded in various types of concrete (NC, HPC, UHPC etc.). Shear stiffness of studs is defined as the secant stiffness of the load-slip curve at 0.5V_u, and a formulation for predicting defined shear stiffness in elastic state was proposed, indicating that the stud diameter and the elastic modulus of steel and concrete are the main factors. And the shear stiffness predicted by the new formula agree well with test results for studs with a diameter ranging from 10 to 30 mm in the concrete with compressive strength ranging from 22.0 to 200.0MPa. Then, the effects of shear stiffness on the elastic behaviors of composite girders with different sizes and under different loading conditions were analyzed, the equations for calculating the stress and deformation of simply supported composite girders considering the influence of connection's shear stiffness were derived under different loading conditions using classical linear partial-interaction theory. As the increasing of shear stiffness, the stress and deflection at the most unfavorable section under partial connected condition tend to be those under full connected condition, but the approaching speed decreases gradually. Finally, the connector's shear stiffness was recommended for fully connection in composite girders with different dimensions under different loading conditions. The findings from present study may provide a reference for the prediction of shear stiffness for headed studs and the elastic design of steel-concrete composite girder.

• 터널과지하공간
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• 제26권4호
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• pp.316-326
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• 2016

본 연구는 화강암에 존재하는 결 이방성이 간접인장강도에 미치는 영향을 평가하였다. 표준 간접인장시험 및 3개의 서로다른 중공 크기에 대한 중공 간접인장시험을 수행하였다. 2차원 개별요소 수치해석을 통해 간접인장시험에서의 파괴 과정 및 메커니즘을 고찰하였다. 간접인장강도는 화강암의 결에 따라 하드웨이, 그레인, 리프트 면의 순으로 감소하였다. 중공 간접인장강도는 일반 간접인장강도에 비해 2.5~6.4배 정도 크게 나타났으며, 중공 크기가 클수록 크게 나타났다. 중공 시편에 대한 간접인장 파괴 유형은 중공 크기 및 결과 하중방향 각도에 영향을 받는 것으로 나타났다.