• 건설안전기술
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• 통권38호
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• pp.79-87
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• 2006

Formwork is a temporary structure that supports its weight and that of freshly placed concrete as well as construction live loads. In constructions site, pipe supports are usually used as shores which are consisted of the stab formwork. The strength of a pipe support is decreasing as it is frequently being used at the construction site. Among the accidents and failures that occur during concrete construction, there are many formwork failures which usually happen at the time concrete is being placed. The objective of this study is to find out the strength change of used pipe support and unused pipe supports according to aging. In this study, 2857 pipe supports were prepared. Among these pipe supports, 2337 pipe supports were lent to the construction companies free of charge. 520 pipe supports were kept on the outside. Compressive strength was measured by knife edge test and plate test at each 3 month. Test results show that the strength of unused pipe supports as well as used pipe supports was decreasing according to age, use frequency and load carrier, and the strength of used pipe supports was lower than the strength of unused pipe supports at the same age. So, the strength of used pipe supports from 191 days to present day was not satisfied the specification of KSF 8001. In this study, the strength of pipe support according to age, use frequency and load carrier was predicted using SPSS 12.0. It was known that the strength of pipe support using for 5 years was reduced to 42.8%. According to these results, it shows that attention has to be paid to formwork design using used pipe supports. Therefore, the present study results will be able to provide a firm base to prevent formwork collapses.

• 한국안전학회지
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• 제1권1호
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• pp.51-59
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• 1986

This study was conducted to analyse the exact causes of occupational accidents in Korean construction industry and to contribute to the accident prevention programs. The results and conclusions of the field survey are as follows ： 1) The accidents caused by hazardous conditions are 96 percent, and those by unsafe acts are 97.3 percent. The accidents caused simultaneously by two categories are nore than 96 percent. 2) The injured workers who were employed less than 3 months are 71.1 percent. Safety training for newly recruited workers should be required. 3) More than 40 percent of all accidents were occurred in the morning and more than 30 percent were in summer. Required caution should be paid for the time and season. 4) Fracture, cut/laceration/puncture and multiple injuries in the lower extremeties, upper entremeties and head as well as many kinds of injuries by the fall from elevation mainly occurred. Safety. shoes, safety gloves, safety helmets, safety glasses, face shields and safity belts should be used 5) As the sources of injuries, each of building/structure and materials is one third of all sources, and machinery is a quarter. 6) The use of hazardous methods/procedures, defects of agencies and inadequate guarding of builing/structure, materials' and machinery mainly caused the accident types, such as s truck by, struck against, fall from elevation, and fall on same level. Such a hazardous conditiion should not be used and be correctet 7) The unsafe acts, such as improper use of hands or body parts, the operation or working at unsafe speed and improper use of equipment mainly caused accidents. Safety training for the control of such a unsafe acts should be strengthened.

• Smart Structures and Systems
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• 제24권6호
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• pp.769-781
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• 2019

Dynamic displacement response of civil structures is an important index for in-construction and in-service structural condition assessment. However, accurately measuring the displacement of large-scale civil structures such as high-rise buildings still remains as a challenging task. In order to cope with this problem, a vision-based system with the use of industrial digital camera and image processing has been developed for long-distance, remote, and real-time monitoring of dynamic displacement of supertall structures. Instead of acquiring image signals, the proposed system traces only the coordinates of the target points, therefore enabling real-time monitoring and display of displacement responses in a relatively high sampling rate. This study addresses the in-situ experimental verification of the developed vision-based system on the Canton Tower of 600 m high. To facilitate the verification, a GPS system is used to calibrate/verify the structural displacement responses measured by the vision-based system. Meanwhile, an accelerometer deployed in the vicinity of the target point also provides frequency-domain information for comparison. Special attention has been given on understanding the influence of the surrounding light on the monitoring results. For this purpose, the experimental tests are conducted in daytime and nighttime through placing the vision-based system outside the tower (in a brilliant environment) and inside the tower (in a dark environment), respectively. The results indicate that the displacement response time histories monitored by the vision-based system not only match well with those acquired by the GPS receiver, but also have higher fidelity and are less noise-corrupted. In addition, the low-order modal frequencies of the building identified with use of the data obtained from the vision-based system are all in good agreement with those obtained from the accelerometer, the GPS receiver and an elaborate finite element model. Especially, the vision-based system placed at the bottom of the enclosed elevator shaft offers better monitoring data compared with the system placed outside the tower. Based on a wavelet filtering technique, the displacement response time histories obtained by the vision-based system are easily decomposed into two parts: a quasi-static ingredient primarily resulting from temperature variation and a dynamic component mainly caused by fluctuating wind load.

• 방송공학회논문지
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• 제7권2호
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• pp.79-87
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• 2002

지난 10여년간의 디지털 비디오와 관련 멀티미디어처리 기술의 빠른 발전은 비디오 내용의 이해에 기반한 키프레임 기반의 내용요약과 같은 여러 가지의 비선형적 비디오 브라우징 방법들을 가능하게 하였다. 그러나 스토리보드나 목차와 같은 키프레임 기반의 사용자 인터페이스들은 텔레비전 환경에 익숙한 대다수의 일반 사용자들에게는 여전히 사용하기 어렵다는 단점이 있으며, 이러한 사용자 인터페이스의 구성 또한 실시간 처리를 지원하지 않고 있어 서비스 제공자를 배제한 일반 방송 환경에서 사용하기 어렵다는 단점을 가지고 있다. 본 논문에서는 이러한 단점들을 극복하며 동시에 사용자들이 사용하기 편리한 비선형적 비디오 브라우징 기술들을 제안하며, 이를 지원하기 위한 실시간 비디오 인덱싱 기술을 제안하고 있다. 즉 구조기반의 건너뛰기와 요약보기 기능은 실시간 비디오 인덱싱 기술에 기반하여, 사용자들이 기존의 비디오 레코더의 리모콘과 같은 간단한 사용으로 원하는 장면을 쉽게 찾아갈 수 있도록 하여 주며, 간단한 요약 기능을 제공하여 짧은 시간에 전체의 내용을 이해할 수 있도록 하여 준다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2006년도 학술발표회 논문집
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• pp.1191-1195
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• 2006

Now days, heavy storm occur to be continue. It is hard to use before frequency based on flood discharge for decision that design water pocket structure. We need to estimation of frequency based on flood discharge on the important basin likely city or basin that damage caused by flood recurrence. In this paper flood discharge calculated by Clark watershed method and SCS synthetic unit hydrograph method about upside during each minute of among time distribution method of rainfall, Huff method choosing Bocheong Stream basin that is representative basin of International Hydrologic Project (IHP) about time distribution of rainfall that exert big effect at flood discharge estimate to research target basin because of and the result is as following. Relation between probability flood discharge that is calculated through frequency analysis about flood discharge data and rainfall - runoff that is calculated through outward flow model was assumed about $48.1{\sim}95.9%$ in the case of $55.8{\sim}104.0%$, SCS synthetic unit hydrograph method in case of Clark watershed method, and Clark watershed method has big value overly in case of than SCS synthetic unit hydrograph method in case of basin that see, but branch of except appeared little more similarly with frequency flood discharge that calculate using survey data. In the case of Critical duration, could know that change is big area of basin is decrescent. When decide time distribution type of rainfall, apply upside during most Huff 1-ST because heavy rain phenomenon of upsides appears by the most things during result 1-ST about observation recording of target area about Huff method to be method to use most in business, but maximum value of peak flood discharge appeared on Huff 3-RD too in the case of upside, SCS synthetic unit hydrograph method during Huff 3-RD incidental of this research and case of Clark watershed method. That is, in the case of Huff method, latitude is decide that it is decision method of reasonable design floods that calculate applying during all $1-ST{\sim}4-TH$.

• Archives of Plastic Surgery
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• 제33권1호
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• pp.61-66
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• 2006

The purpose of this study is to introduce the method of palate repair that combines minimal hard palate dissection and radical retropositiong of levator musculature, which was presented by Sommerlad. As this method presents, additional use of the operating microscope enables atraumatic and radical dissection, and it might provide more improved speech function to the patients. A total of 17 patients with cleft palate underwent Sommerlad's method from December 2003 to August 2004. The mean follow-up period was 4.5 months. The use of a microscope provided high quality variable magnification and good illumination at the operating field. Repair was carried out through incisions at the margins of cleft with mucoperiosteal flap elevation. Muscles were rearranged and repaired properly. It was unable to evaluate the improvement of speech because the patients were too young to learn meaningful speech. Average operating time including anesthetic induction time, V-tube insertion and recovery from anesthesia was 2 hours 45 minutes which was not quite different from conventional method's operating time. Oronasal fistula developed in 2 patients of them. One of them was healed spontaneously. As meticulous and radical muscle dissection was possible with Sommerlad's method, we could minimize the trauma to the muscular and neurovascluar structure. In addition, we expect better faculty of speech as a result of this method although longer follow-up time was unavailable.

• Smart Structures and Systems
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• 제13권2호
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• pp.177-201
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• 2014

With the increased size and flexibility of the tower and blades, structural vibrations are becoming a limiting factor towards the design of even larger and more powerful wind turbines. Research into the use of vibration mitigation devices in the turbine tower has been carried out but the use of dampers in the blades has yet to be investigated in detail. Mitigating vibrations will increase the design life and hence economic viability of the turbine blades and allow for continual operation with decreased downtime. The aim of this paper is to investigate the effectiveness of Semi-Active Tuned Mass Dampers (STMDs) in reducing the edgewise vibrations in the turbine blades. A frequency tracking algorithm based on the Short Time Fourier Transform (STFT) technique is used to tune the damper. A theoretical model has been developed to capture the dynamic behaviour of the blades including the coupling with the tower to accurately model the dynamics of the entire turbine structure. The resulting model consists of time dependent equations of motion and negative damping terms due to the coupling present in the system. The performances of the STMDs based vibration controller have been tested under different loading and operating conditions. Numerical analysis has shown that variation in certain parameters of the system, along with the time varying nature of the system matrices has led to the need for STMDs to allow for real-time tuning to the resonant frequencies of the system.

• Earthquakes and Structures
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• 제14권5호
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• pp.411-424
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• 2018

This study explores the inelastic behavior of systems with flexible base. The use of a single degree of freedom system (ESDOF) with equivalent ductility to represent the response of flexible base systems is discussed. Two different equations to compute equivalent ductility are proposed, one which includes the contribution of rigid body components, and other based on the overstrength of the structure. In order to asses the accuracy of ESDOF approach with the proposed equations, the behavior of a 10-story regular building with reinforced concrete (RC) moment resisting frames is studied. Local and global ductility capacity and demands are used to study the modifications introduced by base flexibility. Three soil types are considered with shear wave velocities of 70, 100 and 250 m/s. Soil-foundation stiffness is included with a set of springs on the base (impedance functions). Capacity curves of the building are computed with pushover analysis. In addition, non linear time history analysis are used to asses the ductility demands. Results show that ductility capacity of the soil-structure system including rigid body components is reduced. Base flexibility does not modify neither yield and maximum base shear. Equivalent ductility estimated with the proposed equations is fits better the results of the numerical model than the one considering elastoplastic behavior. Modification of beams ductility demand due to base flexibility are not constant within the structure. Some elements experience reduced ductility demands while other elements experience increments when flexible base is considered. Soil structure interaction produces changes in the relation between yield strength reduction factor and structure ductility demand. These changes are dependent on the spectral shape and the period of the system with fixed and flexible base.

• Computers and Concrete
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• 제8권3호
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• pp.293-309
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• 2011

A long-term structural health monitoring (SHM) system comprising over 700 sensors of sixteen types has been implemented on the Guangzhou Television and Sightseeing Tower (GTST) of 610 m high for real-time monitoring of the structure at both construction and service stages. As part of this sophisticated SHM system, 48 temperature sensors have been deployed at 12 cross-sections of the reinforced concrete inner structure of the GTST to provide on-line monitoring via a wireless data transmission system. In this paper, the differential temperature profiles in the reinforced concrete inner structure of the GTST, which are mainly caused by solar radiation, are recognized from the monitoring data with the purpose of understanding the temperature-induced structural internal forces and deformations. After a careful examination of the pre-classified temperature measurement data obtained under sunny days and non-sunny days, common characteristic of the daily temperature variation is observed from the data acquired in sunny days. Making use of 60-day temperature measurement data obtained in sunny days, statistical patterns of the daily rising temperature and daily descending temperature are synthesized, and temperature distribution models of the reinforced concrete inner structure of the GTST are formulated using linear regression analysis. The developed monitoring-based temperature distribution models will serve as a reliable input for numerical prediction of the temperature-induced deformations and provide a robust basis to facilitate the design and construction of similar structures in consideration of thermal effects.

• 대한지리학회지
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• 제42권3호
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• pp.315-331
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• 2007

한국 불교 사찰을 대표하는 불국사는 활단층인 불국사(울산)단층선이 통과하는 한반도에서 지반이 가장 불안정한 곳에 입지 한다. 사찰이 조성된 선상지 지형면의 폭이 좁고 경사가 급하므로 건축자들은 불교의 상징세계를 완성하기 위하여 부지의 남쪽과 서쪽을 확장하였다. 인위적으로 넓힌 공간에는 이 지역의 지형적 특성을 고려하여 내진 구조를 고안하여 적용하였다. 건축미를 극대화하면서 중요한 목적인 내진 기능을 작동시키기 위하여 화강암을 목재처럼 가공하거나 자연석과 다듬은 석재를 이용하여 여러 장치들을 고안하였다. 불국사에 적용된 내진 구조는 그렝이법, 목조건축 기법을 적용한 석조구조(결구), 주두석(동틀돌, 첨차석)의 이용, 유공초석의 사용이다. 석축을 구성하고 있는 각 부분들은 나름대로 지진에너지를 흡수하는 특별한 역할을 하면서 전체적으로 균형과 조화를 이루고 있다. 복잡하고 세밀한 내진 구조들을 겉으로 드러내지 않고 석축 안에 감추면서 미학적으로 절정의 건축물을 만든 건축설계는 1250년 전 신라인들의 기술 수준을 짐작하게 한다. 기교에만 치우쳐 지나치게 치장한 것으로도 보일 수 있는 이 건축물의 진정한 미는 과학에 근거한 아름다움을 추구한 것이다.