• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.12
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• pp.1250-1256
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• 2012

Resilient materials are used to reduce the floor impact sound in apartment buildings. Since an on-dol layer is installed in the resilient materials' upper part, thickness deformation can be occur in the resilient material. It is necessary to check a thickness deformation grade for a long period of time. In this research, we measured thickness deformation over 400th day to the resilient materials(EPP, EPS, EVA) which is used in Korea. Although there was a difference according to the kind of measurement test specimens, it became clear that thickness was decreases as to time increased. The thickness deformation grade of ten years after was calculated based on the thickness measurement result. Compare with the calculated result and result of ISO 20392. Larger thickness deformation occurred in the measurement result of these research findings compare with the ISO standard.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.843-846
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• 2004

Cavity tone is generated due to the feedback between flow and acoustic wave. It is recognized that the period is determined by the time required for the flow convection in one direction, the time required for the acoustic propagation in the other direction and the time for phase shift depending on the flows and mode. Most of the phenomena have been investigated by experiments and a simple but fundamental theory. But the cause of the phase shift and the correctness of the theory have not been clearly explained so far. In this paper, the phenomena are calculated numerically to obtain detail information of flow and acoustic wave to explain the mechanism including the phase. High order high resolution scheme of optimized high order compact is used to resolve the small acoustic quantities and large flow quantities at the same time. The data are reduced using cross correlation function in space and time and cross spectral density function which has phase information. Abrupt change in pressure near corner in cavity is observed and is relate to phase variation. The time required for the feedback between the flow and acoustic wave is calculated after the numerical simulation f3r various modes. The periods based on the time calculated using the above method and direct observation from the acoustic waves generated and propagated in the numerical simulation are compared. It is found that no phase shift is required if we examine the time required carefully. Rossiter's formula for the cavity tone used for quick estimation needs to be modified far some modes.

• The Journal of Engineering Geology
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• v.1 no.1
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• pp.109-120
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• 1991

Applications of microtremor to geological engineering are widely reviewed and observed microtremors are processed to show evidences of close relationship between the predominant periods of microtremor and underground structure. The ground vibrates continuously at all times and the elastic vibration is called microtremor (0.5-20Hz) or microseisms (0.01-0.1Hz) according to their frequency range. The vibration is believed to have propagative nature like those of the dispersive surface waves or multireflected shear waves. Microtremors were recorded at selected thress places of which subsoil structures are well distinguished in the Kyongsang Sedimentary Basin. It is found that the underground structures estimated from microtremor analysis coincide well with the known structures. The microtremor analysis of the long period range can be an inexpensive and effective tool in geological engineering for the evaluation of the underground structure, site-specific reponse spectrum, and seismic microzonations.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.5
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• pp.424-431
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• 2004

An implicit direct-time integration method for obtaining transient responses of general dynamic systems is described. The conventional Newmark method cannot be directly applied to state-space first-order differential equations, which contain no explicit acceleration terms. The method proposed here is the state-space Newmark method that incorporates the average velocity concept, and can be applied to an analysis of general dynamic systems that are expressed by state-space first-order differential equations. It is also readily coded into a program. Stability and accuracy analyses indicate that the method is numerically unconditionally stable like the conventional Newmark method, and has a period error of 2nd-order accuracy for small damping and 4th-order for large damping and an amplitude error of 2nd-order, regardless of damping. In addition, its utility and validity are confirmed by two application examples. The results suggest that the proposed state-space Newmark method based on average velocity be generally applied to the analysis of transient responses of general dynamic systems with a high degree of reliability with respect to stability and accuracy.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.1 s.71
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• pp.39-46
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• 2006

This paper analyzes the continuous Galerkin method for the space-time discretization of wave equation. The method of space-time finite elements enables the simple solution than the usual finite element analysis with discretization in space only. We present a discretization technique in which finite element approximations are used in time and space simultaneously for a relatively large time period called a time slab. The weighted residual process is used to formulate a finite element method for a space-time domain. Instability is caused by a too large time step in successive time steps. A stability problem is described and some investigations for chosen types of rectangular space-time finite elements are carried out. Some numerical examples prove the efficiency of the described method under determined limitations.

• Explosives and Blasting
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• v.34 no.2
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• pp.18-30
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• 2016

A drill & blasting method using explosives is the most efficient way to break the rock in the urban projects. However, the blasting method cause vibration, noise and fly-rock as blast pollutions so that blasting wroks are restricted by adjacent structures such as apartment and residence houses. To conduct blasting works at near structures, the numbers of blast-holes a blast and the size of the blast are limited by kinds of detonators and initiation methods. So, the production rate is reduced and the construction period should be increased. Therefore, in this case the deck-charge blasting methods using available detonators in domestic market were designed and evaluated in order to confirm the application possibilities in specific urban sites.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1212-1217
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• 2006

This study is concerned with static and sinusoidal disturbance rejection for a single periodic input disturbance with known period. In the area of active elimination of a disturbance force, the control input should have two different kinds of gains: one is to deliver a stable control and the other is a force component to cancel the external disturbance force. In this paper we employ a simple state feedback control law to make the balance beam stable and employ a linear observer to estimate the states which represent the external disturbance force components. Simulation results verify our proposed control method to reject a static and sinusoidal disturbance force.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.6
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• pp.503-511
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• 2004

In this study, for estimating responses of a controlled structure and determining the maximum control force of velocity-dependent damping devices, three estimation models such as Fourier envelope convex model, probability model, and Newmark design spectrum are used. For this purpose, a procedure is proposed for estimating actual velocity using pseudo-velocity and this procedure considers the effects of damping ratio increased by the damping device. Time history results indicate that actual velocity should be used for estimating accurate maximum control force of damping device and Newmark design spectrum modified by the proposed equation gives the best estimation results for over all period structures.

• Advances in concrete construction
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• v.12 no.5
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• pp.377-389
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• 2021

Reinforced concrete vertical silos are universal structures that store large amounts of granular materials. Due to the asymmetric structure, heavy load, uneven storage material distribution, and the difference between the storage volume and the storage material bulk density, the corresponding earthquake is very complicated. Some scholars have proposed the calculation method of horizontal forces on reinforced concrete vertical silos under the action of earthquakes. Without considering the effect of torsional effect, this article aims to reveal the expansion factor of the silo group considering the torsional effect through experiments. Through two-way seismic simulation shaking table tests on reinforced concrete column-supported group silo structures, the basic dynamic characteristics of the structure under earthquake are obtained. Taking into account the torsional response, the structure has three types of storage: empty, half and full. A comprehensive analysis of the internal force conditions under the material conditions shows that: the different positions of the group bin model are different, the side bin displacement produces a displacement difference, and a torsional effect occurs; as the mass of the material increases, the structure's natural vibration frequency decreases and the damping ratio Increase; it shows that the storage material plays a role in reducing energy consumption of the model structure, and the contribution value is related to the stiffness difference in different directions of the model itself, providing data reference for other researchers; analyzing and calculating the model stiffness and calculating the internal force of the earthquake. As the horizontal side shift increases in the later period, the torsional effect of the group silo increases, and the shear force at the bottom of the column increases. It is recommended to consider the effect of the torsional effect, and the increase factor of the torsional effect is about 1.15. It can provide a reference for the structural safety design of column-supported silos.

• Structural Engineering and Mechanics
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• v.81 no.6
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• pp.691-703
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• 2022

To obtain the seismic response of lead-cored rubber, shape memory alloy (SMA)-rubber isolation Plate-shell Integrated Concrete Liquid-Storage Structure (PSICLSS), based on a PSICLSS in a water treatment plant, built a scale experimental model, and a shaking table test was conducted. Discussed the seismic responses of rubber isolation, SMA-rubber isolation PSICLSS. Combined with numerical model analysis, the vibration characteristics of rubber isolation PSICLSS are studied. The results showed that the acceleration, liquid sloshing height, hydrodynamic pressure of rubber and SMA-rubber isolation PSICLSS are amplified when the frequency of seismic excitation is close to the main frequency of the isolation PSICLSS. The earthquake causes a significant leakage of liquid, at the same time, the external liquid sloshing height is significantly higher than internal liquid sloshing height. Numerical analysis showed that the low-frequency acceleration excitation causes a more significant dynamic response of PSICLSS. The sinusoidal excitation with first-order sloshing frequency of internal liquid causes a more significant sloshing height of the internal liquid, but has little effect on the structural principal stresses. The sinusoidal excitation with first-order sloshing frequency of external liquid causes the most enormous structural principal stress, and a more significant external liquid sloshing height. In particular, the principal stress of PSICLSSS with long isolation period will be significantly enlarged. Therefore, the stiffness of the isolation layer should be properly adjusted in the design of rubber and SMA-rubber isolation PSICLSS.