• Proceedings of the Computational Structural Engineering Institute Conference
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• 1997.04a
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• pp.192-199
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• 1997

The purpose of this paper is to get a powerful tool for response analysis of a spherical dome subjected to dynamic excitation based on mathematically analytical method, i. e., the Galerkin procedure in modal analysis, with sufficient accuracy and practicality. At first, this paper provides an approximate solution of eigen modes, which has sufficient accuracy and praticallity for response analysis in symmetric and antisymmetric state. In the second stage of this paper, response analysis of a dome subjected to horizontal earthquakes is executed as the application of these approximate modes. Many important response characteristics may manifest themselves through parametric survey of material and geometric properties.

• Journal of the Korean Society of Safety
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• v.18 no.4
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• pp.57-63
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• 2003

Thermal degradation of Acrylonitrile butadiene rubber(NBR), which is used for O-ring material as elastomeric sealed diaphragm value in the nuclear power plants, is examined. The thermal degradation is accelerated at 130$^{\circ}C$ by Arrhenius exploit method using the activation energy calculated by thermogravimetric analysis. The weight loss temperature and glass transition temperature are verified for thermally aged NBR. The relationship between dynamic mechanical properties and elongation at break are also investigated. The threshold alue of thermally aged NBR is a ten year in the change of elongation at break.

• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.4
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• pp.430-434
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• 2013

In this paper, we have investigated deformation of cup for EFI detonator in high velocity impact test. The experimental result shows that STS cup deformed 0.170 mm with the bulged shape. The numerical simulation result with static/dynamic material properties of SUS304 shows 0.166 mm of deformation. The main parameters to decrease the deformation of cup are stength, thickness and density of cup. The initial condition of SUS304 cup was strength of 215 MPa and thickness of 0.12 mm. As strength increases to 500 MPa, deformation of cup converges to 0 mm, and as thickness increases to 0.18 mm, deformation of cup converges to 0 mm. If the density of cup decreases from 8 to 2.7 g/cc, the deformation of cup decreases to 0.141 mm.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.1242-1248
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• 2001

In this paper, the process of development of resilient sleepers, which improves the train safety, passenger comport and reduces the noise and vibration, is presented. To determine the required material properties of elastic pad, static and dynamic simulations are performed and is applied in manufacturing. Lateral resistance and durability characteristics of the resilient sleepers are experimentally investigated. From the experiment results, it is investigated that the displacement is less for sleeper with elastic pad than that in ordinary PC form. However, the lateral resistance is investigated little less -for sleeper with elastic pad than ordinary PC form. These results indicate that the elastic pad can reduce possibility of rail-corrugations and thus resulting in the reduction of maintenance costs.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2006.03a
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• pp.597-604
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• 2006

The seismic safety of the prestressed concrete containment building was evaluated by the seismic fragility analysis based on the nonlinear dynamic time-history analyses. Four kinds of earthquake ground motions were used for the seismic fragility analysis of the containment building to consider the potential earthquake hazard. The conventional seismic fragility analysis of the safety related structures in nuclear pouter plant have been performed by using the linear elastic analysis results for the seismic design. In this study, the displacement based seismic fragility analysis method was proposed.

• Bulletin of the Korean Chemical Society
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• v.19 no.6
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• pp.625-628
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• 1998

The dynamic mechanical properties of the unclustered cesium neutralized poly(methyl methacrylate-co-methacrylic acid) ionomers plasticized with three different plasticizers of low molecular weight were investigated. It was found that the effectiveness of the plasticization followed the order: glycerol (Gly) 4-decylaniline (4DA) >dioctyl phthalate (DOP). For the ionomer plasticized with Gly, the only effect was a significant decrease in the Tg. Thus it is concluded that the polar plasticizer not only increases the mobility of the ionomer but also dissolves the ionic groups. In the case of the 4DA-plasticized ionomer, both a drastic decrease in the Tg and the appearance of a second glass transition were observed. Therefore, it is suggested that the nonpolar 4DA molecules partition evenly in the poly(methyl methacrylate) matrix and cluster phases via hydrogen bonding between the aniline group of the plasticizer and the carbonyl groups of the ionomer. As a result, the Tg is lowered, multiplets can form, and the material behaves like a clustered ionomer.

• Proceedings of the KSR Conference
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• 1998.11a
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• pp.398-404
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• 1998

The acoustic power reduction methods of the vibrating structures are valid to design the quite structure. To calculate the acoustic power, the dynamic responses have to be determined. It is not easy to analyse the structure composed of the corrugated panels. Because of the structural complexity and the many analysing times. To make up for these defects, the equivalent orthogonal panel is presented. Also the acoustic power prediction method of the vibrating structures is proposed. As examples, the equivalent material properties of the corrugated plates are obtained and the acoustic powers of the floor structure are calculated at several frequency regions for KHST.

• Advances in concrete construction
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• v.5 no.1
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• pp.1-15
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• 2017

This research project aimed at evaluating experimentally the effect of natural perlite powder as an alternative supplementary cementing material (SCM) on the performance of fiber reinforced self-consolidating repair mortars (FR-SCRMs). For this purpose, four FR-SCRMs mixes incorporating 0%, 10%, 20%, and 30% of natural perlite powder as cement replacements were prepared. The evaluation was based on fresh (slump flow, flow time, and unit weight), hardened (air-dry unit weight, compressive and flexural strengths, dynamic modulus of elasticity), and durability (water absorption test) performances. The results reveal that structural repair mortars confronting the performance requirements of class R4 materials (European Standard EN 1504-3) could be designed using 10%, 20%, and 30% of perlite powder as cement substitutions. Bonding results between repair mortars containing perlite powder and old concrete substrate investigated by the slant shear test showed good interlocking justifying the effectiveness of these produced mortars.

• Earthquakes and Structures
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• v.17 no.1
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• pp.31-37
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• 2019

This work presents a free vibration analysis of functionally graded beams by employing an original high order shear deformation theory (HSDBT). This theory use only three unknowns, but it satisfies the stress free boundary conditions on the top and bottom surfaces of the beam without requiring any shear correction factors. The mechanical properties of the beam are assumed to vary continuously in the thickness direction by a simple power-law distribution in terms of the volume fractions of the constituents. In order to investigate the free vibration response, the equations of motion for the dynamic analysis are determined via the Hamilton's principle. The Navier solution technique is adopted to derive analytical solutions for simply supported beams. The accuracy and effectiveness of proposed model are verified by comparison with previous research.

• Smart Structures and Systems
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• v.22 no.6
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• pp.711-725
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• 2018

Most of the practical engineering structures exhibit nonlinearity due to nonlinear dynamic characteristics of structural joints, nonlinear boundary conditions and nonlinear material properties. Hence, it is highly desirable to detect and characterize the nonlinearity present in the system in order to assess the true behaviour of the structural system. Further, these identified nonlinear features can be effectively used for damage diagnosis during structural health monitoring. In this paper, we focus on the detection of the nonlinearity present in the system by confining our discussion to only a few selective time-frequency analysis and multivariate analysis based techniques. Both damage induced nonlinearity and inherent structural nonlinearity in healthy systems are considered. The strengths and weakness of various techniques for nonlinear detection are investigated through numerically simulated two different classes of nonlinear problems. These numerical results are complemented with the experimental data to demonstrate its suitability to the practical problems.