• Journal of the Korean Society of Safety
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• v.31 no.5
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• pp.89-94
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• 2016

The objective of this study was to estimate the dynamic behavior of a personal rapid transit(PRT) track system using a rail of rectangular tube section and a rail joint of sliding type, and to compare the results with the normal rail and rail joint of a PRT track system by performing field measurements using actual vehicles running along the service lines. The measured vertical displacement of rail and sleeper, and vertical acceleration of rail for the normal rail and rail joint section were found to be similar, and the rail joint of sliding type satisfied the design specifications of the track impact factor for a conventional railway track. The experimental results showed that the overall dynamic response of the rail joint were found to be similar to or less than that of the normal rail, therefore the rail joint of sliding type for PRT track system was sufficient to ensure a stability and safety of PRT track system.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1995.10a
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• pp.111-121
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• 1995

In Extracting the dynamic parameters for estimating the load carrying capacity and integrity of bridges, both the instrumentation and the processing the data plays important role . When the fixed point can not be secured, it is difficult and expensive to measure dynamic displacements. Even if the displacement is obtained through the integration of the acceleration data, the results can be quite different from the real behavior, because the main frequency contents can be leaked during discretized data processing. The instrumentation is used for measurements, and every measurement involves error and uncertainty, such as systematic, conformance, environmental, observational, sampling, and ranmom error. Systematic and conformance error can be remedied through the proper sellection and installation of the instruments, but sampling and random errors could not have been corrected properly and it becomes the limitation for using acceleration data. In this paper, the errors which can be occurred in numerical processing of dynamic data are referred, and the method to sellect proper sampling rate for the structural frequency range are proposed. Using the proposed method, the displacement response of the structures can be economically obtained from the measured acceleration record, and this procedure can be used properly to estimate the integrity of the bridges and infrastructures subjected to dynamic loads.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.1
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• pp.1-8
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• 2015

Wind power systems have gained much attention due to the relatively high reliability, good infrastructures and cost competitiveness to the fossil fuels. Advances have been made to increase the power efficiency of wind turbines while less attention has been focused on structural integrity assessment of structural sub-systems such as towers and foundations. Among many parameters for integrity assessment, the most perceptive parameter may be the induced horizontal displacement at the hub height although it is very difficult to measure particularly in large-scale and high-rise wind turbine structures. This study proposes an indirect displacement estimation scheme based on the combined use of inclinometers and accelerometers for more convenient and cost-effective measurements. To this end, (1) the formulation for data fusion of inclination and acceleration responses was presented and (2) the proposed method was numerically validated on an NREL 5 MW wind turbine model. The numerical analysis was carried out to investigate the performance of the propose method according to the number of sensors, the resolution and the available sampling rate of the inclinometers to be used.

• Tunnel and Underground Space
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• v.25 no.1
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• pp.76-85
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• 2015

We have developed a software to predict failure time of the rock slope based on analysis of the data from real time displacement measurements with respect to time. The software consists of four modules that play roles in analytical methods such as inverse velocity method, log time-log velocity method, log velocity-log acceleration method and nonlinear least square method to estimate failure time. VisualBasic.NET on the MS Visual Studio platform was utilized as a development tool to efficiently implement the modules and the graphical user interface of the software. Displacement data obtained from laboratory physical model studies of plane sliding were used to explore the applicability of the software, and to evaluate the possibility of predicting potential slope failure. It seems possible to estimate failure time using developed software for sliding plane having exponential type of deformability.

• Journal of the Korean Geosynthetics Society
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• v.10 no.4
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• pp.49-59
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• 2011

In order to understand evaluation of the seismic stability of a reinforced earth retaining, we made chambers of 1:10 (the ratio of the miniature), considering the law of similarity based on drawings of representative cross sections. And we measured an increase in acceleration, earth pressure, and displacement after applying Hachinohe wave (long period), Ofunato wave (short period), and artificial wave, complying with the domestic standards, in order to evaluate the external stability of the reinforced earth retaining wall during earthquake based on the measurements. As a result, the unreinforced earth retaining wall collapsed at 2 g of seismic acceleration. But the reinforced earth retaining wall was evaluated to ensure proper stability as well, with respect to the earth pressure gauge, the increments of earth pressure tend to be raised significantly in the upper than the lower and showed a similar characteristic of behavior in previous theory.

• Coupled systems mechanics
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• v.1 no.4
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• pp.311-324
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• 2012

Previous investigations have demonstrated that strong earthquakes can cause severe damage or collapse to storage tanks. Theoretical studies by other researchers have shown that allowing the tank to uplift generally reduces the base shear and the base moment. This paper provides the necessary experimental confirmation of some of the numerical finding by other researchers. This paper reports on a series of experiments of a model tank containing water using a shake table. A comparison of the seismic behaviour of a fixed base system (tank with anchorage) and a system free to uplift (tank without anchorage) is considered. The six ground motions are scaled to the design spectrum provided by New Zealand Standard 1170.5 (2004) and a range of aspect ratios (height/radius) is considered. Measurements were made of the impulsive acceleration, the horizontal displacement of the top of the tank and uplift of the base plate. A preliminary comparison between the experimental results and the recommendations provided by the liquid storage tank design recommendations of the New Zealand Society for Earthquake Engineering is included. The measurement of anchorage forces required to avoid uplift under varying conditions will be discussed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.312-316
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• 2002

Recently, mixers are being widely used in the water purification plant in order to increase the filtration efficiency. It has been found that a severe vibration was being felt on a upper structure of a mixer facility during steady state operation. The cause of the excessive vibration of the structure to which the mixer's shaft is supported has been evaluated through modal analysis on the shaft and vibration measurements during operation. The fundamental natural frequency of the mixer's shaft is found to be around 1.8 Hz and the main vibratory frequency around 30 Hz. It has been tuned out that the main vibratory frequency, 30 Hz is coincident with the fundamental holding frequency of the upper structure, and that the acceleration signal of the upper structure and the displacement signal of the mixer's shaft showed highly coherent to each other. Accordingly, it reveals that the main cause of the excessive vibration is due not to the mixer's vibration but to the natural frequency of the upper structure excited by flow turbulence.

• The Journal of the Convergence on Culture Technology
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• v.7 no.4
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• pp.801-806
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• 2021

Rail corrugation is continuously increasing due to the lack of maintenance regulations for the amount of rail irregularities. Rail corrugation is causing various problems, such as a decrease in ride comfort and an increase in the amount of track maintenance. In this paper, the effect of rail corrugation on the track force was analyzed by measuring the rail irregularities before and after rail grinding and the track measurements (dynamic wheel load, displacement, and acceleration) for the section where the rail corrugation occurred. In addition, it was experimentally proven that the rail grinding performed to reduce the corrugation of the rail was very effective in reducing the additional forces on the track.

• Smart Structures and Systems
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• v.3 no.3
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• pp.281-298
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• 2007

The load carrying capacity of a bridge needs to be properly assessed to operate the bridge safely and maintain it efficiently. For the evaluation of load carrying capacity considering the current state of a bridge, static and quasi-static loading tests with weight-controlled heavy trucks have been conventionally utilized. In these tests, the deflection (or strain) of the structural members loaded by the controlled vehicles are measured and analyzed. Using the measured data, deflection (or strain) correction factor and impact correction factor are calculated. These correction factors are used in the enhancement of the load carrying capacity of a bridge, reflecting the real state of a bridge. However, full or partial control of the traffic during the tests and difficulties during the installment of displacement transducers or strain gauges may cause not only inconvenience to the traffic but also the increase of the logistics cost and time. To overcome these difficulties, an alternative method is proposed using an excited response part of full measured ambient acceleration data by ordinary traffic on a bridge without traffic control. Based on the modal properties extracted from the ambient vibration data, the initial finite element (FE) model of a bridge can be updated to represent the current real state of a bridge. Using the updated FE model, the deflection of a bridge akin to the real value can be easily obtained without measuring the real deflection. Impact factors are obtained from pseudo-deflection, which is obtained by double-integration of the acceleration data with removal of the linear components on the acceleration data. For validation, a series of tests were carried out on a steel plategirder bridge of an expressway in Korea in four different seasons, and the evaluated load carrying capacities of the bridge by the proposed method are compared with the result obtained by the conventional load test method.

• Ocean Systems Engineering
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• v.8 no.2
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• pp.223-246
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• 2018

In this paper the results of CFD simulations, that were carried out to study the impact pressures acting on a symmetric wedge during water entry under the influence of gravity, are presented. The simulations were done using a solver implementing finite volume discretization and using the VOF scheme to keep track of the free surface during water entry. The parameters such as pressure on impact, displacement, velocity, acceleration and net hydrodynamic forces, etc., which govern the water entry process are monitored during the initial stage of water entry. In addition, the results of the complete water entry process of wedges covering the initial stage where the impact pressure reaches its maximum as well as the late stage that covers the rebound process of the buoyant wedge are presented. The study was conducted for a few touchdown velocities to understand its influence on the water entry phenomenon. The simulation results are compared with the experimental measurements available in the literature with good accuracy. The various computational parameters (e.g., mesh size, time step, solver, etc.) that are necessary for accurate prediction of impact pressures, as well as the entry-exit trajectory, are discussed.