• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.1
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• pp.147-154
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• 2002

The dynamic load caused by sloshing of internal fluid severely affects the structural and control stabilities of cylindrical liquid containers accelerating vertically. If the sloshing frequency of fluid is near the frequency of control system or the tank structure, large dynamic force and moment act on launching vehicles. For the suppression of such dynamic effects, generally flexible ring-type baffles are employed. In this paper, we perform the numerical analysis to evaluate the dynamic suppression effects of baffle. The parametric analysis is performed with respect to the baffle inner-hole diameter and two different baffle spacing types : equal spacing with respect to the tank and one with respect to the fluid height. The ALE (arbitrary Lagrangin-Eulerian) numerical method is adopted for the accurate and effective simulation of the hydrodynamic interaction between fluid and elastic structure.

• Journal of Korean Society of Steel Construction
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• v.18 no.5
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• pp.585-596
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• 2006

This study focuses on the seismic behavior of 3-, 9-, and 20-story steel moment resisting frame (MRF) structures designed in accordance with the 2000 International Building Code using different Response Modification factors (R factors), i.e., 8, 9, 10, 11, and 12. For a detailed case study, 30 different structures were evaluated for 20 ground motions representing the hazard level, which is equal to a 2% probability in 50 years (2% in 50 years). The results showed that the current R factors provide conservative designs for the 3- and 9-story buildings for the Collapse Prevention performance objective. the 20-story buildings, which were designed without using the minimum requirement of spectral acceleration CS prescribed in IBC 2000, did not satisfy the seismic performance for Collapse Prevention performance.

• Journal of the Korean Wood Science and Technology
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• v.33 no.6 s.134
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• pp.46-54
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• 2005

To make the composite panels of wood particles and recycled plastics, the recycled polypropylene was used. In the composite panels the sizes of wood particles were 1/32", 1/4" and 1/2" mesh, and the composition ratios of the recycled plastics were 10%, 30%, 50% and 70%. The physical and mechanical properties of the composite panels were investigated. As the composition ratio of wood particle increases, the density increases, while it decreases at the same composition ratio because the size of wood particle increases. As the composition ratio of recycled polypropylene increases from 10% to 30%, both thickness swelling and water adsorption significantly decrease. As the composition ratio of recycled polypropylene increases, the modulus of rupture in bending strength increases, but the modulus of elasticity in bending strength decreases. SEM shows that the dissolved recycled polypropylene penetrates into tracheid and pit, and bonds mechanically to other wood particle and matrix to increase the bonding strength and improve the physical and mechanical properties of composite panel.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.5
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• pp.35-43
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• 2008

In this study we confirmed for the cardiopulmonary ability improvement of the cycling exercise which uses a target heart beat. Consequently, we looked the resting systolic blood pressure down at 2.98% and THBI(Total Heart Beat Index) also decrements at 7.59%. But, increase of $VO_2$ max and PTT(Pulse Transit Time)were each point 24.60% and 4.92%. Increase of $VO_2$ max showed the growth of stroke volume by myocardial development. The increase of a stroke volume induces the decrease of Heart rate. The blood pressure was reduced also though the blood of many quantity was supplied at the artery. The reason is the phenomenon to be due to by an elasticity increase of the artery. We found out it through the decrease of PTT. So the cycling exercise to use consequently the target heart beat will become big aid at the health care.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.3
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• pp.59-65
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• 1991

Failure criteria for asphalt concrete pavements are developed combining the AASHTO design equation and the multi-layered elastic theory. Thickness range including typical layer thicknesses of four-layer Korea highway structures are employed for pavement structure models. Total of 2430 pavement models with different layer thicknesses and moduli are analyzed. Models with crushed stone and asphalt stabilized base courses are equally included in the analysis. Number of load repetition and the maximum tensile strain at the bottom of asphalt layer are computed from the AASHTO design equation with terminal PSI=2.5 and multi-layered elastic computer program, SINELA, respectively. Failure criteria are developed through the regression analysis. From the analysis, failure criteria for the asphalt concrete pavements with 50% and 95% reliability levels are developed. It is found that the failure criterion of 95% reliability level gives similar results with existing fatigue failure criteria whose terminal performance condition is crack development when compared in a graphical form an equation to estimate failure criterion for a specific reliability level is also proposed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.3 no.2
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• pp.31-44
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• 1983

This paper applies an optimization algorithm for the elastic truss structures. The acceleration technique utilized in this study is the geometric programming method developed by the Operation Research or the applied methematics. The applicability and the efficiency of the algorithm applied in this study are tested for four different trusses. Test results show that the optimum solutions are obtained after only one or seven iterations which is very small compared with other techniques and no oscillation is needed for the convergency. Test rusults also show that the Geometric Programming Method is also effective algorithm for the convergency of the Optimum Solution in case of only being compared with the number of iteration.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.4
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• pp.487-493
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• 2010

Most structural analyses are concerned with the deformations and stresses in a body subjected to external loads. However, in many fields, inverse problems have to be interpreted to determine surface tractions or internal stresses from displacements measured on a remote surface. In this study, the inverse processes are studied by using the finite element method for the evaluation of internal stresses. Small errors in the measured displacements often result in a substantial loss of stability of an inverse system. In order to improve the stability of the inverse system, the displacements on a section near the region of the unknown tractions are predicted by using orthogonal basis functions. We use the Gram-Schmidt orthogonal technique to determine two bases for the displacements on a section near the region of the unknown tractions. Advantages over previous methods are discussed by using numerical examples.

• Polymer(Korea)
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• v.24 no.6
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• pp.829-836
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• 2000

In order to recyle the FRP waste from SMC bathtubs and rock-crush sludge obtained as a byproduct of stones, the composite consisting of the FRP and rock-crush sludge and the unsaturated polyester matrix resin were prepared. To enhance the interfacial bonding force between the reinforcements and the matrix resin, the rock-crush sludge was treated with silane coupling agent, ${\gamma}$-methacryloxypropyltrimethoxysilane (${\gamma}$-MPS) and their mechanical properties and interface phenomena were examined. The flexural modulus of the composite containing 10 wt% rock-crush powder treated with 3 wt% silane coupling agent showed the maximum value. And also the initial thermal degradation temperature of composites were in the range of 352~359$^{\circ}C$. From these results, we observed that the weight loss of composites was almost constant regardless of the concentration of silane coupling agent. It is confirmed that the interface of the composites containing filler treated with ${\gamma}$-MPS was improved in that there were no pull-out phenomena between the reinforcement and matrix resin.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6C
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• pp.221-229
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• 2011

A core zone of a fill dam is an important part of a dam for cutoff of water. Therefore, the material properties and behavior characteristics of a core zone are very important factors in an analysis of dam stability. However, the investigation on material properties of actual dam core is extremely rare so far. The material properties have been acquired or estimated by indirect methods like a surface wave surveying or empirical equation. In this research, in-situ and laboratory tests were conducted during dismantling an existing dam directly to investigate characteristics of the core zone in terms of the depth and transient variation of properties after construction of the dam. Dynamic material properties like shear wave velocity and shear modulus were measured and compared to other existing empirical correlations. In addition, aging characteristics of dynamic material properties were investigated by a series of laboratory tests.

• Journal of the Korean Society for Advanced Composite Structures
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• v.2 no.1
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• pp.15-22
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• 2011

Pultruded fiber reinforced polymeric plastic (PFRP) structural members may be one of attractive alternatives of the structural members in the civil engineering applications because of its many advantageous mechanical properties. However, they have relatively low modulus of elasticity and also cross-sections of structural shapes are composed of thin plate components such as flange and web. Therefore, structural stability is an important issue in the design of pultruded structural compression members. For the design of pultruded structural member under compression, buckling and post-buckling strengths of plate components may be taken into account. In the structural steel design following AISC/LRFD, in addition to the buckling strength, the nonuniform stress distribution in the section is incorporated with a form factor. In this paper, the form factor for the design of PFRP structural member under compression is investigated through the analytical study. Furthermore, the process for the determination of the form factor is suggested.