• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.10
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• pp.127-133
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• 2019

Damage to high-rise buildings caused by earthquakes is less frequency due to small distribution of high-rise buildings and low transmissibility of seismic motion to high-rise buildings. However, demand for high-rise buildings is increasing for development of construction technology and efficient land use. In addition, if high-rise buildings are constructed on soft ground such as landfill, transmissibility of seismic motion due to long-periodization of seismic waves is likely to increase. Thus, with development of technology, buildings are required to expand range of seismic design such as safety for long-period seismic waves. Therefore, in this study, dynamic experiments were performed to evaluate response characteristics of high-rise buildings according to period characteristics of seismicwaves and time history analysis was performed to verify them.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.3
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• pp.117-123
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• 2016

One of the major characteristics of the swell-like high waves, which occur in the East Sea mostly in winter with large height and long period, is its suddenness associated with the rapid development of high waves from a calm state of sea. To represent such suddenness, in this study, the term sudden high waves is introduced. To propose the criterion of sudden high waves, comparisons were made between the wave measurement data at Gangneung and Wangdolcho for eight years from 2005 and the record of marine accidents and property damage on the coast of Gangwon-do Province and Gyeongsangbuk-do Province during the same period. It was found that most of the accidents occurred when ${\Delta}(H^2L)/{\Delta}t$ was approximately greater than the top 20% or $88.6m^3/hr$, which is therefore proposed as the criterion of sudden high waves. The used variable represents the rate of increase of the wave energy in one wavelength, including not only height and period but also suddenness of high waves.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.14 no.1
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• pp.51-64
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• 2002

To investigate long-period wave responses in Sokcho Harbor and Cheongcho lagoon, field measurements were made for long-and short-period waves and current velocities using a Directional Waverider, a ultrasonic-type wave gauge, four pressure-type wave gauges, and a current meter. From the data analysis, it was found that the Helmholtz resonant periods of Sokcho Harbor and Cheongcho lagoon are about 13.6 and 54.5 minutes, respectively, and the dominant period of wave induced current in the passage between Sokcho Harbor and Cheongcho lagoon is about 55.2 minutes which depends on Helmholtz resonant condition of the Cheongcho lagoon. It was also found that the energy level of the far-infra-gravity waves during storm conditions is very high compared with that during calm sea conditions. To investigate relationships between far-infra-gravity waves and short-period waves at offshore station, regression analyses were carried out especially for 1) heights, 2) periods, 3) direction and height, 4) height and period between short-and far-infra-gravity waves, respectively. The results showed that the long-period wave height is highly correlated with the short-period wave height. However, no special trend was found for the other relations. In the future far-infra-gravity wave heights on return period around Sokcho Harbor region can be suggested by using extreme value analyses of long term measured data.

• Journal of Ocean Engineering and Technology
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• v.16 no.4
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• pp.7-12
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• 2002

This study is aimed to find the scouring mechanism at the toe of rubble mound structures. To investigate the characteristics of scouring in front of the structure, experiments were performed with regular waves in a 2-D flume. The results of this study are as follows. 1) It can be said the characteristics of incident wave causes rolling and sliding of armour block. The difference of wave pressure on the slope, internal flow as well as settlement of armour block due to the weight cause scouring. 2) It is observed that scouring depth at the toe increased when wave height or period increased. The location of ultimate scouring and deposition depth moved seaward when wave period increased. 3) The failure of rubble mound structure was caused by waves or scouring. Failure by erosion increased with high waves and long waves. 4) Using surf-similarity parameter including characteristics of incident waves and structure, scouring and deposition pattern were found and their limit was formulated.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.13 no.3
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• pp.209-229
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• 2001

Simultaneous field measurements of short-period and long-period waves were made at five stations inside or outside Okkye Harbor, which is located in the east coast of Korea. Based on the measured data, spacial and temporal variations of the long-period wave energy were examined. Three smoothing methods were examined for the spectral estimates: fixed interval averaging method, incremental interval averaging method, and moving averaging method. It was shown that a proper smoothing method should be chosen depending on the period of first resonant mode and the length of data being used. By comparing the results obtained using the long-term data with those obtained using two-day data, we showed that it is necessary to analyze the data of calm seas and storm seas separately. The Helmholtz resonant period in Okkye Harbor was found to be about 9.6 minutes with its relative amplification ratio of 9 to 10, and local amplifications were apparent at the periods of 1.2 to 1.3 minutes and 0.7 minute. During calm seas, both at the harbor entrance and inside the harbor the energy of the waves of 9 minutes or longer period was larger than the infra-gravity wave energy by more than 100 times. However, during storm seas the energy level was very high all over the period band, and local amplification was larger than that during calm seas by more than 100 times, especially inside the harbor, Finally it was shown that the energies of the Helmholtz resonant mode and the infra-gravity waves of 1 to 2 minutes are proportional to the storm wave height.

• Journal of Ocean Engineering and Technology
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• v.19 no.6 s.67
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• pp.22-28
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• 2005

We investigated the characteristics of the overflow/wave overtopping, induced by the storm surge and high waves in Masan bay and Busan Coast during Typhoon 'Maemi', which landed at the southeast coast of the Korean peninsula on September, of 2003, causing a severe inundation disaster. Characteristics of the water level, increase by the overflow / wave overtopping, were discussed in two patterns. One is the increase of water level in the region, located inside of a bay, like Masan fishing port, and the waves are relatively small. The other is in the open sea, in which the waves act directly, as on the seawall in Suyong bay. In the former region, the water level increase was affected by the storm surge, as well as the long period oscillation and waves. In Masan fishing port, about $80\%$ of the water level increase on the quay wall was caused by the storm surge. In the latter one, it was greatly affected by the wave run-up. In Suyong bay, about $90\%$ of the water level increase on the seawall was caused by the wave run-up.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.5
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• pp.366-371
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• 2012

High swell has been known for the one of the main causes of beach erosion in the east coast of Korea. In this study, coastal topography changes due to high swells are simulated to find its effect on the backshore by using movable bed experiments and numerical experiments. Sea bottom topographical changes due to various incident waves were investigated using CSHORE model in the numerical experiments. Furthermore, the mechanism and the phenomena of beach erosion due to waves and high swells on the foreshore and backshore were analyzed and compared with movable bed hydraulic experiments.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.9 no.1
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• pp.24-34
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• 1997

To find the causes of the downtime problems in Pohang New Harbor, extensive field measurements of short- and long-period waves for 1.5 months and their analyses were made taking into account of wind and downtime records. Measured wave height ratios inside the harbor are appeared to be slightly larger than predicted ones using numerical methods in the previous studies. It is shown that the major causes of the downtime are the wind wave (or swell) higher than loading criteria and also swell with even smaller wave height but longer period(more than 10 sec). Waves of long-period components[0(min)] were recorded as 20 cm high in case of dominant seiche phenomena but they might not be related with the downtime problems.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.10
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• pp.956-961
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• 2007

We propose a new distance measurement method and local positioning system for the autonomous mobile robots localization. The distance measurement method is able to measure long-range distances with a high accuracy by using ultrasonic sensors. The time of flight of the ultrasonic waves include various noises is calculated accurately by the proposed period detecting method. The proposed local positioning system is composed of four ultrasonic transmitters and one ultrasonic receiver. The ultrasonic transmitter and receiver are separated but they are synchronized by RF (Radio frequency) signal. The proposed system using ultrasonic waves is represented as USAT(Ultrasonic Satellite System). USAT is able to estimate the position using the least square estimation. The experimental results show that the proposed local positioning system enables to estimate the absolute position precisely.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.21 no.6
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• pp.462-469
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• 2009

This study suggests a general formula of non-cohesive sediment transport rates for waves and currents which is also valid for wave only or current only condition. On-offshore sediment transport rates with the second order Stokes wave in the shallow water are calculated as the pickup rate times the distance. The formula depicts reasonably that high waves move material offshore, and low waves move material onshore. Also the formula, as is the case the waves with long period tend to move material onshore, shows good results.