• Structural Engineering and Mechanics
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• 제64권1호
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• pp.109-120
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• 2017

The behavior of moment resistant steel structures depends on both the beam-column connections and columns foundations connections. Obviously, if the connections can meet the adequate ductility and resistance against lateral loads, the seismic capacity of these structures will be linked practically to the performance of these connections. The shape memory alloys (SMAs) have been most recently used as a means of energy dissipation in buildings. The main approach adopted by researchers in the use of such alloys is firstly bracing, and secondly connecting the beams to columns. Additionally, the behavior of these alloys is modeled in software applications rarely involving equivalent torsional springs and column-foundation connections. This paper attempts to introduce the shape memory alloys and their applications in steel structural connections, proposing a new steel column-foundation connection, not merely a theoretical model but practically a realistic and applicable model in structures. Moreover, it entails the same functionality as macro modeling software based on real behavior, which can use different materials to establish a connection between the columns and foundations. In this paper, the suggested steel column-foundation connection was introduced. Moreover, exploring the seismic dynamic behavior under cyclic loading protocols and the famous earthquake records with different materials such as steel and interconnection equipment by superelastic shape memory alloys have been investigated. Then, the results were compared to demonstrate that such connections are ideal against the seismic behavior and energy dissipation.

• KIEAE Journal
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• 제7권6호
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• pp.99-106
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• 2007

Tower crane is a large construction equipment which is extremely tall for its section when it is erected, with its high slenderness ratio, and it has a heavy load by itself due to large lifting stuff to handle. In line with the construction projects in these days which increasingly tend to become higher, larger and complex, the stuff and height subject to lifting are also getting larger and higher, which has also increased the risk of disastrous accidents. A stable foundation design thus to deal with the increasing self load becomes more important. When a typhoon Maemi swept the nation in 2003, as many as 43 tower cranes fell down or collapsed, causing a severe damage to the people and the properties. Considering such fatal damages, a technical evaluation of the stability to prevent the safety accident with the tower crane must be very crucial. Tower cranes operation in domestic construction sites, in fact, have been simply dependent on personal experience and intuition of the engineers. Particularly when it comes to the foundation design, it mostly depends on manufacturer's recommendation. The study hence was intended to develop the fundamental measures for granting the objective stability, instead of following the individual's experience only. The simulation model recommended in the study is expected to make a good commitment to achieving an effective lifting work as well as preventing the safety accident.

• 한국안전학회지
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• 제23권4호
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• pp.72-78
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• 2008

In any form of construction work, it is essential that accidents be prevented at every stage from foundation preparation to build completion. For this, it is necessary to use models that can assess risk and provide instruction for safe work processes so that the risk of accidents is reduced. Currently, however, very few models can perform these tasks. In this paper, we presents a model that assesses risk quantitatively by analyzing risk factors involved in stage of construction such as foundation work, erection work, structural work, equipment work, finishing work and etc work. The model performs assessment based on examples of accidents and by investing actual conditions during construction. In addition, we presents in this paper a safety management system was developed to assess risk during construction and to effectively train laborers.

• 국제초고층학회논문집
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• 제5권3호
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• pp.205-211
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• 2016

This paper addresses the key technologies for supertall building construction based on the Lotte World Tower project in Korea. First, the mega-mat foundation construction technologies are shown, including ultra-low heat concrete, heat of hydration control programs, and the logistics plan. Then, high strength concrete technologies of 50~80 MPa are introduced and discussed within the context of the highest pumping record in Korea at 514.25 meters. Structural design concepts of gravity load and lateral force resistance systems are introduced, along with surveying systems using GNSS and temporary installation plans of special heavy equipment like tower cranes, hoists, and high pressure concrete pumps. If it is possible to coordinate these key technologies and others, optimizing for the building's design and construction, supertall building construction can be successfully completed.

• 한국안전학회지
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• 제24권6호
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• pp.124-131
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• 2009

In any form of construction work, it is essential that accidents be prevented at every stage, from foundation preparation to build completion. For this, it is necessary to use models that can assess risk and provide instructions for safe work processes so that the risk of accidents is reduced. Currently, however, very few models can perform these tasks. In this paper, we present a model that assesses risk quantitatively by analyzing the risk factors involved in each stage of construction, such as foundation work, temporary work, structural work, equipment work, and finishing work. The model performs assessment based on examples of accidents and by investigating actual conditions during construction. In addition, we present in this paper a safety management system developed to assess risk during construction and to effectively train laborers.

• 한국방재안전학회논문집
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• 제5권1호
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• pp.7-12
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• 2012

본 연구에서는 홍수발생시 재해응급복구에 관한 장비조합의 적정성을 판단하고, 장비운용의 전문성을 가지고 있는 건설실무 인력자원을 활용하여 경제적이고 신속한 재해응급복구가 이루어질 수 있는 방안을 제시하였다. 홍수피해복구 과정에 대한 절차와 방법을 조사하여, 현행 대처과정에 대한 이해를 정리하였고 이에 대한 법적근거를 조사 분석하였다. 지금까지는 장비자원과 전문건설실무자원에 대한 효과적인 응급복구장비 투입과정에 대한 연구가 부족하여 응급복구시 비용의 과다지출 및 응급복구 지체상황이 발생하였다. 이에 따라 장비자원과 기술자원을 효과적으로 응급복구과정에 투입하여 개선된 경험적 사례를 정리하고 이론적 근거를 조사, 분석하여 향후 효과적인 홍수피해 응급복구가 지방자치단체에 이루어질 수 있도록 하는 방안을 제시하였다. 이를 위해 복구장비의 응급복구투입에 따른 우선순위를 결정하고, 필요한 장비가 효율적으로 활용되도록 재해지역의 이동거리와 연관성을 분석하여 활용방안을 제시하였으며, 이러한 전문 인력이 자치단체 산하의 지역자율방재단에서 적절한 기능을 할 수 있는 새로운 방안을 제시하였다.

• Journal of Power Electronics
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• 제16권4호
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• pp.1513-1525
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• 2016

Rapid and accurate phase synchronization is critical for the reliable control of grid-tied inverters. However, the commonly used software phase-locked loop methods do not always satisfy the need for high-speed and accurate phase synchronization under severe grid imbalance conditions. To address this problem, this study develops a novel open-loop phase locking scheme based on a synchronous reference frame. The proposed scheme is characterized by remarkable response speed, high accuracy, and easy implementation. It comprises three functional cascaded blocks: fast orthogonal signal generation block, fast fundamental-frequency positive sequence component construction block, and fast phase calculation block. The developed virtual orthogonal signal generation method in the first block, which is characterized by noise immunity and high accuracy, can effectively avoid approximation errors and noise amplification in a wide range of sampling frequencies. In the second block, which is the foundation for achieving fast phase synchronization within 3 ms, the fundamental-frequency positive sequence components of unsymmetrical grid voltages can be achieved with the developed orthogonal signal construction strategy and the symmetrical component method. The real-time grid phase can be consequently obtained in the third block, which is free from self-tuning closed-loop control and thus improves the dynamic performance of the proposed scheme. The proposed scheme is adaptive to severe unsymmetrical grid voltages with sudden changes in magnitude, phase, and/or frequency. Moreover, this scheme is able to eliminate phase errors induced by harmonics and random noise. The validity and utility of the proposed scheme are verified by the experimental results.

• Nuclear Engineering and Technology
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• 제52권2호
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• pp.397-416
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• 2020

Investigations of the commercial aircraft impact effect on nuclear island infrastructures have been drawing extensive attention, and this paper aims to perform the safety assessment of Generation III nuclear power plant (NPP) buildings subjected to typical commercial aircrafts crash. At present Part II, based on the verified finite element (FE) models of aircrafts Airbus A320 and A380, as well as the NPP containment and auxiliary buildings in Part I of this paper, the whole collision process is reproduced numerically by adopting the coupled missile-target interaction approach with the finite element code LS-DYNA. The impact induced damage of NPP plant under four impact locations of containment (cylinder, air intake, conical roof and PCS water tank) and two impact locations of auxiliary buildings (exterior wall and roof of spent fuel pool room) are evaluated. Furthermore, by considering the inner structures in the containment and raft foundation of NPP, the structural vibration analyses are conducted under two impact locations (middle height of cylinder, main control room in the auxiliary buildings). It indicates that, within the discussed scenarios, NPP structures can withstand the impact of both two aircrafts, while the functionality of internal equipment on higher floors will be affected to some extent under impact induced vibrations, and A380 aircraft will cause more serious structural damage and vibrations than A320 aircraft. The present work can provide helpful references to assess the safety of the structures and inner equipment of NPP plant under commercial aircraft impact.

• 한국산학기술학회논문지
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• 제17권5호
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• pp.372-378
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• 2016

항만 구조물인 케이슨 및 블록 등을 수중에 거치하기 위해서는 기초사석을 투하하고 이 위에 구조물을 설치한다. 이때 기초 사석은 상구구조물을 지지하기 위한 기초 토대로서 사석의 규격, 비중, 중량 모양 및 치수 등이 균일하고 치밀하여야 하며 선정시험을 통과한 사석만을 사용하여 시공하야 한다. 또한 이러한 기초 사석을 고르게 만들어 주는 작업 구조물의 거치 이전에 반드시 이루어 져야 한다. 본 연구에서는 수중 고르기 작업 공정의 무인화를 위하여 수중 고르기 및 굴삭용 무인기계 뿐만 아니라 무인기계화 시공을 위한 원격제어용 운영시스템, 수중 물체 인식 및 수중위치 분석을 위한 수중 환경 모니터링 시스템이 개발되었다. 본 장비는 육상 및 수중 테스트를 통하여 검증을 완료 하여 우수한 성능을 확인하였다. 그러나 현장에 본 장비를 투입하기 위해서는 성능뿐만 아니라 건설 공정의 제안 및 분석 그리고 효율(경제성)이 분석되어야 한다. 본 연구에서는 수중고르기장비의 성능 및 기능, 건설공정절차, 기존의 공법과의 비교 분석하였다. 분석결과 기존의 잠수부를 투입하는 건설공법에 비하여 경제성, 효율성, 안전성이 향상되는 것으로 확인되었다.

• 한국건축시공학회지
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• 제9권5호
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• pp.95-101
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• 2009

최근 건축물의 고층화에 따라 양중 계획의 중요성이 증대되고 있다. 타워크레인은 중요한 양중 장비로서의 역할을 수행하고 있으나, 구조적 안전사고 발생 시 그 피해가 매우 크므로 철저한 안정성검토가 선행되어야 한다. 타워크레인은 구조적 안정성을 확보하기 위해 횡지지 보강과 독립기초 및 파일기초 설계 등 안정성확보에 대한 고려가 매우 중요하며, 그 중 현장의 특수한 상황으로 인해 지내력 확보가 곤란하거나 더 이상 기초 사이즈를 증가시킬 수 없을 때 파일기초를 사용한다. 파일기초를 사용할 경우 독립기초 사용 시 보다 더 많은 안정성 검토 항목을 고려 해야하므로 체계적이고 철저한 검토가 필요하다. 본 연구는 파일기초 설계 시 파일기초의 기본적인 안정성 확보 뿐 만 아니라 최소의 비용 발생을 위한 최적설계 알고리즘 개발이 목적이며, 파일기초를 사용하는 고정식 트롤리타입의 타워크레인으로 연구 범위를 제한하여 진행한다. 타워크레인 파일 기초의 안정성 검토 항목과 절차, 최적설계에 관한 연구 결과물을 토대로 관련 업무 담당자의 업무 효율성을 향상 시킬 수 있을 뿐 아니라 파일 기초 설계에 투입되는 시간 및 비용의 절감효과를 기대 할 수 있다.