• Journal of the Earthquake Engineering Society of Korea
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• v.25 no.1
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• pp.11-20
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• 2021

The seismic deformation method is conventionally used as a seismic design for a multi-utility tunnel in Korea. In the seismic deformation method, the soil ground's natural period is one of the most critical factors for calculating the ground displacement using cosine functions. Correction factors for the natural period and shear wave velocity have been used to consider the non-linearity of dynamic soil properties. However, the correction factors have been issued because the correction factors have not been sufficiently studied to consider Korea's regional conditions. This paper aims to evaluate the natural periods for the seismic deformation method considering Korea's ground conditions. Ground response analysis was performed using seven real earthquake records on twelve sites with different soil conditions where actual multi-utility tunnels are installed. As a result, natural periods of the sites were analyzed and new correction factors were proposed according to seismic performance and Korea's regional conditions.

• The Journal of Fisheries Business Administration
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• v.17 no.1
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• pp.1-17
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• 1986

Since the middle of the 70s, the countries with the marine resources declared the exclusive water zone of two hundred miles. As a result, our country lacked many foreign fishing grounds. This awakened our perception of fishing grounds. The fishing ground is an important factor in the economical effectiveness of fisheries. The fishing ground must have the following basic conditions. 1. It must be the place the fishery resources inhabit and wander. 2. Their catching or aquaculturing must be possible by the technical methods. 3. It must have economic worth in the management. The fishing ground that achieves the above basic conditions is affected by the following factors. This is the factor of the fishing ground location. A. Natural factor 1). Suitable climate 2).Abundant resources 3). Good quality of the sea-bottom 4). Not to be pollutted area B, Economic factor 1). Be adjacent to fishing port and fisheries market 2). Good working conditions 3). Be abundant of economical resources C. Social factor 1). Be possible to work legally 2). Be permitted in the political relations 3). Be acquainted with the customs of foreign countries The fishing ground location is mainly affected by the natural factor of the above factors. The abundance of resources depends on the natural resources. The resources in the fishing ground have the cycle of developing period, maturing period, and decaying period according to the fishing efforts. The point that we sustainably yield the maximum of fishery resources is the changing point of maturing period and decaying period. We call this point MSY, so the resources of fishing ground should be managed by the MSY. Therefore, when we select the fishing ground location. We should judge the natural factor, the economic factor and the social factor synthetically according to the situation and environment, so we can achieve the efficient management.

• Journal of the Earthquake Engineering Society of Korea
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• v.27 no.1
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• pp.1-12
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• 2023

Structures of high-rise buildings are less prone to earthquake damage. This is because the response acceleration of high-rise buildings appears to be small by generally occurring short-period ground motions. However, due to the increased construction volume of high-rise buildings and concerns about large earthquakes, long-period ground motions have begun to be recognized as a risk factor for high-rise buildings. Ground motion observed on each floor of the building is affected by the eigenmode of the building because the ground motion input to the building is amplified in the frequency range corresponding to the building's natural frequency. In addition, long-period components of ground motion are more easily transmitted to the floor or attached components of the building than short-period components. As such, high-rise buildings and non-structural components pose concerns about long-period ground motion. However, the criteria (ASCE 7-22) underestimate the acceleration response of buildings and non-structural components caused by long-period ground motion. Therefore, the characteristics of buildings' acceleration response amplification ratio and non-structural components were reviewed in this study through shake table tests considering long-period ground motions.

• Coupled systems mechanics
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• v.5 no.3
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• pp.223-234
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• 2016

The main purpose of current study is to find the soil effects on natural period of elevated tank. The coupled analytical method is used to assess in this study. The current study presented models which are capable to consider the soil dynamic stiffness changes and fluid- structure interaction effects on natural period of elevated tanks. The basic of mentioned models is extracted from elastic beam and lumped mass theory. The finite element is used to verify the results. It is observed that, external excitation can change the natural period of elevated tanks. Considering the increase of excitation frequency, the natural period will be decreased. The concluded values of natural period in case of soft and very soft soil are more affected from excitation frequency values. The high range of excitation frequency may reduce the natural period values. In addition it is observed that the excitation frequency has no significant effect on convective period compare with impulsive period.

• Atmosphere
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• v.15 no.2
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• pp.101-118
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• 2005

Atmospheric ozone changes temporally and spatially according to both anthropogenic and natural causes. It is essential to quantify the natural contributions to total ozone variations for the estimation of trend caused by anthropogenic processes. The aims of this study are to understand the intrinsic natural variability of long-term total ozone changes and to estimate more reliable ozone trend caused by anthropogenic ozone-depleting materials. For doing that, long-term time series for Seoul of monthly total ozone which were measured from both ground-based Dobson Spectrophotometer (Beck #124)(1985-2004) and satellite TOMS (1979-1984) are analyzed for selected period, after dividing the whole period (1979~2004) into two periods; the former period (1979~1991) and the latter period (1992~2004). In this study, ozone trends for the time series are calculated using multiple regression models with explanatory natural oscillations for the Arctic Oscillation(AO), North Atlantic Oscillation(NAO), North Pacific Oscillation(NPO), Pacific Decadal Oscillation(PDO), Quasi Biennial Oscillation(QBO), Southern Oscillation(SO), and Solar Cycle(SC) including tropopause pressure(TROPP). Using the developed models, more reliable anthropogenic ozone trend is estimated than previous studies that considered only QBO and SC as natural oscillations (eg; WMO, 1999). The quasi-anthropogenic ozone trend in Seoul is estimated to -0.12 %/decade during the whole period, -2.39 %/decade during the former period, and +0.10 %/decade during the latter period, respectively. Consequently, the net forcing mechanism of the natural oscillations on the ozone variability might be noticeably different in two time intervals with positive forcing for the former period (1979-1991) and negative forcing for the latter period (1992-2004). These results are also found to be consistent with those analyzed from the data observed at ground stations (Sapporo, Tateno) of Japan. In addition, the recent trend analyses for Seoul show positive change-in-trend estimates of +0.75 %/decade since 1997 relative to negative trend of -1.49 %/decade existing prior to 1997, showing -0.74 %/decade for the recent 8-year period since 1997. Also, additional supporting evidence for a slowdown in ozone depletion in the upper stratosphere has been obtained by Newchurch et al.(2003).

• Journal of the Earthquake Engineering Society of Korea
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• v.25 no.1
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• pp.33-42
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• 2021

The design response spectrum presented in the seismic design standard reflects the characteristics of the tectonic environment at a site. However, since the design response spectrum does not represent the ground motion with a specific earthquake magnitude or distance, input ground motions for response history analysis need to be selected reasonably. It is appropriate to use observed ground motions recorded in Korea for the seismic design. However, recently recorded ground motions in the Gyeongju (2016) or Pohang (2017) earthquakes are not compatible with the design response spectrum. Therefore, it is necessary to convert the recorded ground motion in Korea to a model similar to the design response spectrum. In this study, several approaches to adjust the spectral acceleration level at each period range were tested. These are the intrinsic and scattering attenuation considering the earthquake environment, magnitude, distance change by the green function method, and a rupture propagation direction's directivity effect. Using these variables, the amplification ratio for the representative natural period was regressed. Finally, the optimum condition compatible with the design response spectrum was suggested, and the validation was performed by converting the recorded ground motion.

• KCI Concrete Journal
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• v.11 no.3
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• pp.153-164
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• 1999

The objective of this research is to observe the actual response of a low-rise nonseismic moment-resisting masonry-infilled reinforced concrete frame subjected to varied levels of earthquake ground motions. The reduction scale for the model was determined as 1 : 5 considering the capacity of the shaking table to be used. This model was, then, subjected to the shaking table motions simulating Taft N2IE component earthquake ground motion, whose peak ground acceleration(PGA) was modified to 0.12g, 0.2g, 0.3g, and 0.4g. The g1oba1 behavior and failure mode were observed. The lateral accelerations and displacements at each story and local deformations at the critical portions of the structure were measured. Before and after each earthquake simulation test, free vibration tests and white noise tests were performed to find the changes in the natural period of the model. When the results of the masonry-infilled frame are compared with those of the bare frame, it can be recognized that masonry infills contribute to the large increase in the stiffness and strength of the g1oba1 structure whereas it also accompanies the increase of earthquake inertia forces. However, it is judged that masonry infills may be beneficial to the performance of the structure since the rate of increase in strength appears to be greater than that of the induced earthquake inertia forces.

• Structural Engineering and Mechanics
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• v.28 no.4
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• pp.357-372
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• 2008

This study investigates effect of uncertainty in natural vibration period on the seismic demand. It is shown that since this uncertainty affects the acceleration and displacement responses differently, two ratios, one relating peak acceleration responses and the other relating the peak displacement responses, are not equal and both must be employed in evaluating and defining the critical seismic demand. The evaluation of the ratios is carried out using more than 200 strong ground motion records. The results suggest that the uncertainty in the natural vibration period impacts significantly the statistics of the ratios relating the peak responses. By using the statistics of the ratios, a procedure and sets of empirical equations are developed for estimating the probability consistent seismic demand for both linear and nonlinear systems.

• Journal of the Korean Geotechnical Society
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• v.36 no.12
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• pp.77-86
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• 2020

In this study, the importance of implied strength correction for shallow depths at a region of moderate to low seismicity with primary focus on its effect upon site natural period and mean period of the ground motion is investigated. In addition to the most commonly used Modified Kondner-Zelasko (MKZ) model, this paper uses a quadratic/hyperbolic (GQ/H) model that can capture the stress - strain response at large strains as well as small strain stiffness dependence. A total of six site profiles by downhole tests are used and 1D site response analyses are performed using three input motions with contrasting mean periods. The difference between non-corrected and corrected analyses is conditional on the site period as well as mean ground motion period. The effect of periods is analyzed by correlating them with the effective peak ground acceleration, maximum shear strains and amplification factors. The comparative study reveals that the difference is more prominent in soft sites with long site periods. Insignificant differences are observed when soil profiles are subjected to ground motion with very short mean period.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1999.10a
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• pp.375-382
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• 1999

The fundamental vibration period of a shearwall apartments cannot estimate accurately by means of empirical formulas specified in present codes, The objective of this paper is to estimate the period of a shearwall apartments by microtremor measurement. A micretremor is the continuous small oscillation of the ground cause by traffic and operation machinery. Microtremors are extensively studied primarily in Japan to estimate conveniently subsurface structures of soil deposits and building vibrations. It is obtained the results that the fundamental periods estimated by microtremor measurement are shorter than those values by dynamic analysis of building.