• Journal of the Korean Wood Science and Technology
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• v.39 no.1
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• pp.1-7
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• 2011

Recently, the visual grading rule of Korea Forest Research Institute (KFRI) was revised and it is necessary to investigate the distribution characteristics of visual graded lumber in accordance with the revised rule. Therefore, in this study, the distribution characteristics of bending strength was investigated with revised visual grading rule and changed prior rule, respectively. The size of specimens was $38{\times}140{\times}3,000$ (mm) and the species were $Larix$ $kaempferi$ and $Pinus$ $koraiensis$. The moisture content was under 18% and the specimens were tested in accordance with ASTM D-198. The number of No. 1 and 2 grades, suitable for structural lumber, was increased when the revised visual grading rule was applied. Moreover, the revised rule was more effective to distinguish sharply between No. 1 and 2 grades and below No. 3 grade. Meanwhile, the lower 5% exclusion limit and allowable stresses were generally decreased when revised visual grading rule had been applied. However, the announcement of Korea Forest Service, tested with small clear specimen, was much lower than the allowable stresses of this test, tested with structural lumber. Therefore, the revision of allowable design values should be considered for more exact use and effective structural design.

• Journal of Korean Society of Steel Construction
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• v.10 no.3 s.36
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• pp.383-391
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• 1998

Launching truss used for constructing the precast segmental concrete bridge has upper chord, lower chord and diagonal members. And the pin is used for connecting these members. From the field loading test carried out for investigating the actual behavior of launching truss, the great difference is analyzed between measured stress and calculated stress. Based on measured value, the structural analysis are carried out about assumed abnormal behavior of connection part. From the results of analysis, it is analyzed that the abnormal behavior of connection part greatly affect the structural behavior of launching truss. In addition, from the investigation of safety of launching truss, it is evaluated that the launching truss has enough safety with normal behavior of connection part.

• Journal of Korean Society of Steel Construction
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• v.20 no.3
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• pp.389-398
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• 2008

The current design practice of electric transmission tower is based on the allowable stress design. However, it is difficult to find the cause behind a transmission tower's collapse by the above design approach as the collapse is caused by large secondary deformations based on and geometrical nonlinear behavior.influence factor for the nonlinear behavior is mainly residual stress, initial imperfection and end restraints on members. In this study, the necessity of the nonlinear analysis is examined through the comparison between elastic ana the nonlinear analysis, a new analytical method (equivalent nonlinear analysis technique) is proposed. To confirm the reliability of the proposed method, the computed ultimate load of the transmission tower using the method was compared with that of the nonlinear finite element analysis. Effects of parameters, such as compressive force and the slenderness ratio of the brace member on the main post member, were investigated. The effective member length according to influential parameters was formulated in table form for practical purposes.

• Composites Research
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• v.18 no.4
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• pp.8-13
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• 2005

Rotating circular disks are widely used in data storage devices as well as in traditional industrial machines. Faster rotating speed is required in data storage devices for higher data transfer rate. In this Paper an application of composite materials to CD is proposed to increase critical speeds and the strength analysis was performed. A differential equation of displacement is derived for the analytic stress distribution of rotating polar orthotropic disk. The stress distributions for typical GFRP and CFRP disks and the maximum allowable speeds subjected to a constraint of tensile strength are presented in addition to polycarbonate disk. The results show that the application of CFRP to rotating disk can increase the maximum allowable rotating speed but this may not be applicable to GFRP disk.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.2
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• pp.129-136
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• 2017

This study aims to assess the damage tolerance of the wing structure of aged aircraft with long-term service through the fatigue crack growth analysis and tests. For the fatigue-critical locations (FCL) W2 and W4 in the wing structure, the fatigue stress spectrum was derived based on a previous study. Thereafter, a crack propagation analysis for the FCLs was conducted using the commercial software $NASGRO^{TM}$. The algorithm for the fatigue stress spectrum was verified. Fatigue crack growth tests were then performed for two types of specimens: Type #1 was extracted from the wing structure of aged aircraft, and Type #2 was made of the same material as the wing structure. By comparing the experimental results of these specimens, we assessed the damage tolerance of the wing structure of aged aircraft with service time.

• Journal of Korean Society of Disaster and Security
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• v.12 no.4
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• pp.43-52
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• 2019

To analyze the influence on the stability, resulting from application of upgrade pipe roof structure (UPRS) method to the structure existed under subway Station, physical properties of a ground, elasticity and elasto-plastic theories, including displacement analysis of finite elements, stress analysis of finite elements, displacement caused by steel pipe propulsion and internal excavation, and stress change in a steel pipe, were introduced. Then, the influence on structural stability when applying the UPRS method was compared and reviewed based on the construction management standard of the Ministry Land, Infrastructure and Transport and foreign sources, using numerical analysis with a model which assumes that each microelement divided into a structurally stable point consists of the connection of finite points. As a result of the finite element analysis, 7.21 mm maximum displacement, 1/3,950 angular displacement, 70.28 MPa bending compressive stress of steel pipe structure constructed with UPRS (non-excavation) method and 477.38 MPa maximum shear strength were within their allowable standards (25.00 mm, 1/500, 210.00 MPa and 120.00 MPa, respectively), and therefore, the results showed that the design and construction are stable.

• Journal of Bio-Environment Control
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• v.14 no.3
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• pp.166-173
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• 2005

This study was carried out to evaluate the structural stability in a non-heating greenhouse with a single cover for Citrus cultivation which was built up in Jeju on the basis of the drawing designed by Jejudo Agricultural Research & Extension Services and also to make use of the data for developing a standardized non-heating greenhouse in Jeju. The analysis of a structural stability was conducted by using CFX-5.7 and ANSYS under the design condition of a maximum accumulated snow-depth of 19.1 cm as well as an instantaneous maximum wind velocity of $36.6\;m{\cdot}s^{-1}$ which was set up on the basis of meteorological statistics in Jeju. As a result, the maximum von-Mises stress applied on pipes under the wind velocity of $36.6\;m{\cdot}s^{-1}$ showed a value of $250\;N{\cdot}mm^{-2}$ which was greater than the allowable stress of the pipe with a value of $235.4\;N{\cdot}mm^{-2}$ (=$2,400\;kg{\cdot}cm^{-2}$) and also $53.8\;N{\cdot}mm^{-2}$ under the snow-depth of 19.1 cm, respectively. This result suggested that the greenhouse be unstable under the design condition of an instantaneous wind velocity of $36.6\;m{\cdot}s^{-1}$ so that it was necessary for the greenhouse to be reinforced to secure the structural stability.

• Journal of the Korean Geosynthetics Society
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• v.16 no.4
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• pp.151-161
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• 2017

A TSL (Thin Spray-on Liner) has a higher initial strength and faster construction time than conventional cementitious shotcrete. Because of its high adhesion and tensile strength, the TSL reinforced concrete show a characteristic like composite materials. In this study, to consider an application to the conventional design method, ASD (allowable stress design), numerical study was used. In the numerical analysis, material and contact properties were adopt from previous studies. Then a thickness of concrete in the tunnel was evaluated with the TSL reinforced case by the ASD concept. In other words, bending compressive stress, bending tensile stress and shearing force of the concrete were considered to determine a thickness of concrete lining by the given boundary conditions. From the numerical analysis, there was no tendency to show by the ASD because the ASD is based on the elastic theory while the TSL typically contributes to reinforcement after yielding.

• Journal of the Korean Geotechnical Society
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• v.15 no.1
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• pp.5-13
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• 1999

Maximum stress in pile is developed when it is driven. If the stress is greater than allowable stress of the pile, the pile will be damaged and result in stability problem. Therefore, the stress should be estimated correctly beforehand and overstress should be prevented during pile driving. There are many methods to estimate compressive stresses in concrete piles when they are driven. Nowadays, computer analysis on wave equation offers a satisfactory results. But. under certain circumstances, application of this method is difficult. Then, estimation of the stress utilizing simple formulae might be practical. In this study, relatively reasonable formulae were selected and the stresses which were measured in situ and calculated from the formulae were compared and analysed. The results show that the calculated values from Uto and Huyuki's formula were reasonably accurate and more accurate values were acquired if the values are modified by multiplying the reduction factors according to ground and construction conditions.

• Journal of Korean Society of Steel Construction
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• v.22 no.5
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• pp.435-443
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• 2010

The current design practice of an electric transmission tower is based on the allowable stress design. Design strengths of the electric transmission tower's compression member are determined by buckling the strength of the member itself without considering joint strength. There is a possibility of a joint failure prior to the buckling of a member. Therefore, in this study, joint strength is calculated for various member forces, and the shape of joint and database of strength were established. These data was compared with the member strength obtained from previous research studies based on an equivalent nonlinear analysis technique. Finally, practical evaluation and design method to distinguish failure mode in an electric transmission tower member is proposed.