• Journal of the Earthquake Engineering Society of Korea
• /
• v.27 no.6
• /
• pp.265-273
• /
• 2023

This study proposes a methodology for the regional seismic risk assessment of structural damage to buildings in Korea based on evaluating individual buildings, considering inconsistency between the administrative district border and grid lines to define seismic hazard. The accuracy of seismic hazards was enhanced by subdividing the current 2km-sized grids into ones with a smaller size. Considering the enhancement of the Korean seismic design code in 2005, existing seismic fragility functions for seismically designed buildings are revised by modifying the capacity spectrum according to the changes in seismic design load. A seismic risk index in building damage is defined using the total damaged floor area considering building size differences. The proposed seismic risk index was calculated for buildings in 29 administrative districts in 'A' city in Korea to validate the proposed assessment algorithm and risk index. In the validation procedure, sensitivity analysis was performed on the grid size, quantitative building damage measure, and seismic fragility function update.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.23 no.8
• /
• pp.759-769
• /
• 2013

Electronic equipment has been applied to virtually every area associated with commercial, industrial, and military applications. Specifically, electronics have been incorporated into avionics components installed in aircraft. This equipment is exposed to dynamic loads such as vibration, shock, and acceleration. Especially, avionics components installed in a helicopter are subjected to simultaneous sine and random base excitations. These are denoted as sine on random vibrations according to MIL-STD-810F, Method 514.5. In the past, isolators have been applied to avionics components to reduce vibration and shock. However, an isolator applied to an avionics component installed in a helicopter can amplify the vibration magnitude, and damage the chassis, circuit card assembly, and the isolator itself via resonance at low-frequency sinusoidal vibrations. The objective of this study is to investigate the dynamic characteristics of an avionics component installed in a helicopter and the structural dynamic modification of its tray plate without an isolator using both a finite element analysis and experiments. The structure is optimized by dynamic loads that are selected by comparing the vibration, shock, and acceleration loads using vibration and shock response spectra. A finite element model(FEM) was constructed using a simplified geometry and valid element types that reflect the dynamic characteristics. The FEM was verified by an experimental modal analysis. Design parameters were extracted and selected to modify the structural dynamics using topology optimization, and design of experiments(DOE). A prototype of a modified model was constructed and its feasibility was evaluated using an FEM and a performance test.

• Journal of the Korean Society of Radiology
• /
• v.11 no.3
• /
• pp.123-129
• /
• 2017

Compton suppression apparatus using the Compton scattering response, by inhibiting part of the spectrum Compton continuum Compton continuum in the area of the peak analysis of the gamma rays that enables a clearer device. In order to find out the geometry structure of high-purity germanium detector(HPGe) -NaI(TI) and to optimize the effect of movement, Monte Carlo simulation was used to grasp the behavioral characteristics of Compton suppression and compare several layout structures. And applied to the cylinder beaker used for the environmental measurement by using the efficiency according to the distance. For the low-energy source such as 81 keV, the Compton continuum is scarcely developed and the suppression effect is also insignificant because the scattering cross-section of the Compton effect is relatively low. In the spectrum for the remaining energy, it can be seen that the Compton continuum part is suppressed in a certain energy range. Compton suppression effect was not significantly different from positional shift. average reduction factor(ARF) value was about 1.08 for 81 keV and about 1.23 for 1332.4keV energy at the highest value. It can be seen that suppression over the Compton continuum region of the energy spectrum is a more appropriate arrangement. Therefore, it can be applied to various environmental sample measurement through optimized structure.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.29 no.3
• /
• pp.209-218
• /
• 2016

Recently, Wind-turbine electronic generator become popular. Wind-Turbine is free to cost for purchase and noise problem. For this reason, trend is shifting from Wind-turbine on land to offshore. Research and Development for offshore Wind-turbine has been conducted by various research institution. However, There is no solid design code for offshore Wind-turbine even in domestic as well as foreign. In this paper, conduct seismic analysis and compare results using design codes Korea Bridge Design Codes, Korea Harbor and Marina Design Codes, and DNV OS. Time-History analysis conducted for checking time dependent effect. The Added-Mass Method applied to consider water-structure effects and compared for w/ water and w/o water condition.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.17 no.2
• /
• pp.183-192
• /
• 2004

New dynamic analysis procedures lot the vertically drilled sea water pile are suggested and demonstrated by the typical design Problem. Pile structure submerged in the sea water as well as forces by the ocean waves and tidal currents are modeled and formulated by finite element method. To obtain wave forces for the finite element equation, Airy's wave theory is tested and selected among others. Lateral lifting forces induced by the vortex shedding of current flow is simply based on the harmonic function with the Strouhal frequency and lifting coefficient. Natural frequencies and frequency responses for the pile are calculated by NASTRAN using the results of the formulation. Dynamic displacement and stress results obtained by these procedures are shown to be applicable to predict the dynamic behaviors of the ocean pile by the wave and lifting forces as a preliminary design analysis.

• Nuclear Engineering and Technology
• /
• v.54 no.6
• /
• pp.2023-2030
• /
• 2022

A novel pulse fitting analysis (PFA) method is presented for the acquisition of nuclear spectra. The charging process of the feedback capacitor in the resistive feedback charge-sensitive preamplifier is equivalent to the impulsive pulse, and its impulse response function (IRF) can be obtained by non-linear fitting of the falling edge of the nuclear pulse. The integral of the IRF excluding the baseline represents the energy deposition of the particles in the detector. In addition, since the non-linear fitting process in PFA method is difficult to achieve in the conventional architecture of spectroscopy system, a new multi-channel analyzer (MCA) based on Zynq SoC is proposed, which transmits all the data of nuclear pulses from the programmable logic (PL) to the processing system (PS) by high-speed AXI-Stream in order to implement PFA method with precision. The linearity of new MCA has been tested. The spectrum of ¹³⁷Cs was obtained using LaBr₃(Ce) scintillator detector, and was compared with commercial MCA by ORTEC. The results of tests indicate that the MCA based on PFA method has the same performance as the commercial MCA based on pulse height analysis (PHA) method and excellent linearity for γ-rays with different energies, which infers that PFA method is an effective and promising method for the acquisition of spectra. Furthermore, it provides a new solution for nuclear pulse processing algorithms involving regression and iterative processes.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.24 no.6
• /
• pp.17-24
• /
• 2020

In this study, series of nonlinear seismic analysis were performed on a reinforced concrete intake tower surrounded by water. To consider the fluid effect around the structure, analysis models were composed using an added mass and CEL approach. At this time, the implicit method was used for the added mass model, and the explicit method was used for the fluid structure interaction model. The input motions were scaled to correspond to 500, 1000, and 2400 years return period of the same artificial earthquake. To estimate the counteractivity of the fluid coupled model, models without fluid effect were constructed and used as a reference. The material models of concrete and reinforcement were selected to consider the nonlinear behavior after yielding, and analysis were performed by ABAQUS. As results, in the acceleration response spectrum of the structure, it was found that the influence of the surrounding fluid reducing the peak frequency and magnitude corresponding to the fundamental frequency of the structure. However, the added mass model did not affect the peak value corresponding to the higher mode. The sectional moments were increased significantly in the case of the added mass model than those of the reference model. Especially, this amplification occurred largely for a small-sized earthquake response in which linear behavior is dominant. In the fluid structure interaction model, the sectional moment with a low frequency component amplifies compared to that of the reference model, but the sectional moment with a high requency component was not amplified. Based in these results, it was evaluated that the counteractivity of the additive mass model was greater than that of the fluid structure interaction model.

• Steel and Composite Structures
• /
• v.37 no.3
• /
• pp.291-306
• /
• 2020

The noise from the elevated lines of rail transit has become a growing problem. This paper presents a new method for the rapid prediction of the structure-borne noise from steel or composite bridges, based on the receptance and Statistical Energy Analysis (SEA), which is essential to the study of the generation mechanism and the design of a low-noise bridge. First, the vertical track-bridge coupled vibration equations in the frequency domain are constructed by simplifying the rail and the bridge as an infinite Timoshenko beam and a finite Euler-Bernoulli beam respectively. Second, all wheel/rail forces acting upon the track are computed by taking a moving wheel-rail roughness spectrum as the excitation to the train-track-bridge system. The displacements of rail and bridge are obtained by substituting wheel/rail forces into the track-bridge coupled vibration equations, and all spring forces on the bridge are calculated by multiplying the stiffness by the deformation of each spring. Then, the input power to the bridge in the SEA model is derived from spring forces and the bridge receptance. The vibration response of the bridge is derived from the solution to the power balance equations of the bridge, and then the structure-borne noise from the bridge is obtained. Finally, a tri-span continuous steel-concrete composite bridge is taken as a numerical example, and the theoretical calculations in terms of the vibration and noise induced by a passing train agree well with the field measurements, verifying the method. The influence of various factors on wheel/rail and spring forces is investigated to simplify the train-track-bridge interaction calculation for predicting the vibration and noise from steel or composite bridges.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.4 no.4
• /
• pp.319-332
• /
• 2002

Domestic masonry railroad tunnel lining consists of red bricks or granite stone blocks and mortar. It is necessary to evaluate the behaviour of the masonry tunnel lining during an earthquake because the lining was constructed without the consideration of seismic loads. In this study, a methodology to evaluate the seismic resistant capacity of masonry tunnel linings was proposed, i.e. material property evaluation and seismic analysis technique. The red brick masonry tunnel lining is arrayed with multi-layers composed of 3 to 5 bricks depending on ground conditions and each brick is attached with mortar. Equivalent property concept was adopted to consider the stiffness difference among the red brick material itself and joints between bricks. Response spectrum analysis was performed by considering ground-structure interactions. A parametric study was performed to figure out the effect of relative stiffness between the lining and rock mass on the seismic behavior. A resonable countermeasure to minimize the earthquake-induced damage was also proposed.

• Journal of Applied Reliability
• /
• v.17 no.4
• /
• pp.280-288
• /
• 2017

Purpose: PBA buried in underwater requires high reliability because of its mission critical characteristic and harsh operational environment during its life cycle. Therefore, various reliability improvement activities are necessary. The defect on PBA manufacturing process have been studied, as a result, many activities and standards have been presented. However, there are less studies regarding failure pattern on physical features based on design. In this paper, we studied a possible failure patten based on physical features that is related with manufacturing process of PBA. And reliability improvement design based on PoF (Physical of Failure) were intruduced in this paper. Methods: A reliability prediction simulation were performed on the components A and B of the H system using Sherlock Software which is a PoF commercial tool from DFR solution. Solder fatigue and PTH fatigue analysis based on thermal cycling profiles and random vibration was analyzed on three earthquake response spectrum. Result: It was validated that life time and reliability improvement design through solder fatigue and PTH fatigue analysis in case of component. For compoenet B, random vibration fatigue was additionally analyzed and validated reliability for earthquakes profile. Conclusion: In design stage prior to manufacturing, PoF can be analyzed, and it is possible to make a reliability improvement/validated design using design data. This study can be applied in every design step and contribute to make more stable development product.