• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.140-144
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• 1997

Although the cone type venturi flow meter is superior to another differential pressure type flow meter in precision, the venturi is installed at the pipe as an L beam, so that the dynamic load due to drag force and flow-induced force is generated in the flow meter. In this paper we propose a methodology to evaluate this dynamic load directly by using stain-gages attached on the venturi and we discuss about the dynamic characteristics on the basis of flow-induced vibration theory.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.175-178
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• 2010

동하중의 영향을 받는 구조물의 효율적인 구조 해석 및 최적화 수행을 위해 동하중을 등가정하중으로 변환하는 방법이 요구된다. 이 때 적절한 자유도를 선정하여 등가정하중을 부여하는 것이 중요하다. 기존방법에서는 시스템 축소기법을 통해 일정 개수 이상의 주자유도를 선택하여 등가정하중을 부여하고 그 결과 변위가 동하중 하에서의 변위와 같도록 하였다. 그러나 보수적인 결과를 얻기 위한 제한 조건의 지배적인 성격으로 인하여 등가정하중 하에서의 변위가 지나치게 크게 나타나 그 효율성이 떨어지게 되었다. 본 연구에서는 등가정하중의 변환에 있어서 효율성을 높이는 방안을 제안한다. 제안기법은 보수적 결과를 얻는 범위 내에서 과도응답해석 결과와의 오차를 크게 줄일 수 있다. 수치예제를 통해 제안기법의 결과를 기존 기법의 결과와 비교해본다.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.16 no.1
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• pp.1-6
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• 2008

Role of landing gear is to absorb energy which is generated by aircraft ground maneuvering and landing. Generally, in order to absorb the impact energy, oleo-pneumatic type shock absorber is used in aircraft landing gear. Oleo-pneumatic type shock absorber has a good energy absorption efficiency and is light in weight because structure of oleo-pneumatic type shock strut is relatively simple. In this study, dynamic load analysis for swinging arm type landing gear was performed to predict landing loads. Modeling of landing gear was conducted with MSC.ADAMS, and dynamic landing loads were analyzed based on ADS-29. Optimum landing loads were generated through adjustment of damping orifice and the analysis results were presented with various aircraft attitude.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.2
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• pp.43-54
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• 1992

For shallow arches with large dynamic loading, linear analysis is no longer considered as practical and accurate. In this study, a method is presented for the dynamic analysis of shallow arches in which geometric nonlinearity must be considered. A program is developed for the analysis of the nonlinear dynamic behavior and for evaluation of critical buckling loads of shallow arches. Geometric nonlinearity is modeled using Lagrangian description of the motion. The finite element analysis procedure is used to solve the dynamic equation of motion and Newmark method is adopted in the approximation of time integration. A shallow arch subject to radial step loads is analyzed. The results are compared with those from other researches to verify the developed program. The behavior of arches is analyzed using the non-dimensional time, load, and shape parameters. It is shown that geometric nonlinearity should be considered in the analysis of shallow arches and probability of buckling failure is getting higher as arches are getting shallower. It is confirmed that arches with the same shape parameter have the same deflection ratio at the same time parameter when arches are loaded with the same parametric load. In addition, it is proved that buckling of arches with the same shape parameter occurs at the same load parameter. Circular arches, which are under a single or uniform normal load, are analyzed for comparison. A parabolic arch with radial step load is also analyzed. It is verified that the developed program is applicable for those problems.

• Tunnel and Underground Space
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• v.16 no.1 s.60
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• pp.58-72
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• 2006

In recent years, not only the occurrences but the magnitude of earthquakes in Korea are on an increasing trend and other sources of dynamic events including large-scale construction, operation of hi띤-speed railway and explosives blasting have been increasing. Besides, the probability of exposure fir rock joints to free faces gets higher as the scale of rock mass structures becomes larger. For that reason, the frictional behavior of rock joints under dynamic conditions needs to be investigated. In this study, a shaking table test system was set up and a series of dynamic test was carried out to examine the dynamic frictional behavior of rock joints. In addition, a computer program was developed, which calculated the acceleration and deformation of the sliding block theoretically based on Newmark sliding block procedure. The static friction angle was back-calculated by measuring yield acceleration at the onset of slide. The dynamic friction angle was estimated by closely approximating the experimental results to the program-simulated responses. As a result of dynamic testing, the static friction angle at the onset of slide as well as the dynamic friction angle during sliding were estimated to be significantly lower than tilt angle. The difference between the tilt angle and the static friction angle was $4.5\~8.2^{\circ}$ and the difference between the tilt angle and the dynamic friction angle was $2.0\~7.5^{\circ}$. The decreasing trend was influenced by the magnitude of the base acceleration and inclination angle. A DEM program was used to simulate the shaking table test and the result well simulated the experimental behavior. Friction angles obtained by shaking table test were significantly lower than basic friction angle by direct shear test.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2001.02a
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• pp.40-46
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• 2001

• Proceedings of the Korean Nuclear Society Conference
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• 2001.10a
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• pp.191-191
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• 2001

• Proceedings of the Korean Nuclear Society Conference
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• 1999.10a
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• pp.135.1-135
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• 1999

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.4
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• pp.642-651
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• 1988

The present paper develops finite element procedures to calculate displacements, strains and stresses in initially stressed elastic solids subjected to static or time-dependent loading conditions. As a point of departure, we employ Hamilton's principle to obtain nonlinear equations of motion characterizing the displacement in a solid. The equations of motion reduce to linear equations of motion if incremental stresses are assumed to be infinitesimal. In the case of linear problem, finite element solutions are obtained by Newmark's direct integration method and by modal analysis. An analytic solution is referred to compare with the linear finite element solution. In the case of nonlinear problem, finite element solutions are obtained by Newton-Raphson iteration method and compared with the linear solution. Finally, the effect of the order of Gauss-Legendre numerical integration on the nonlinear finite element solution, has been investigated.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.1
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• pp.40-48
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• 2017

RC flat plates may be governed by a serviceability as well as a strength condition, and a construction sequence and its impact on the distributions of gravity loads among slabs tied by shores are decisive factors influencing short and long term behaviors of flat plate. Over-loading and tensile cracking in early-aged slabs significantly increase the deflection of a flat plate system under construction, and a reshoring work may be helpful in reducing slab deflections by controlling the vertical distributions of loads in a multi-shored flat plate system. In this study, a effect of reshoring works on short and long term deflections of flat plate systems are analyzed. The slab construction loads with various reshoring schemes and slab design and construction conditions are defined by a simplified method, and the practical calculation of slab deflections with considering construction sequences and concrete cracking and long term effects is applied. From parametric studies, the reshoring works are verified to reduce slab deflections, and the optimized conditions for the reshoring works and slab design and constructions are discussed.