• Wind and Structures
• /
• 제19권3호
• /
• pp.233-247
• /
• 2014

Vortex-induced oscillation is a type of aeroelastic phenomenon, to which extended structures such as long-span bridges are most susceptible. The vortex-induced vibration (VIV) behaviors of a concerned bridge were investigated conventionally in virtue of wind tunnel tests on string-mounted sectional models. This necessitates the building of a linkage between the response of the sectional model and that of the prototype structure. Although many released literatures have related to this issue and provided suggestions, there is a lack of consistency among them. In this study, some theoretical models describing the vortex-induced structural motion, including the linear empirical model, the nonlinear empirical model and the modified (or generalized) nonlinear empirical model, are firstly reviewed. Then, the concept of equivalent mass density is introduced based on the principle that an equal input of energy should result in identical structural amplitudes. Based on these, the theoretical linkages between the amplitude of a section model and that corresponding to the prototype bridge are discussed with different analytical models. Theoretical derivation indicates that such connections are dependent mainly on two factors, one is the presupposed shape of deformation, and the other is the theoretical VIV model employed. The theoretical analysis in this study shows that, in comparison to the nonlinear empirical models, the linear one can result in obvious larger estimations of the full bridges' responses, especially in cases of cable-stayed bridges.

• 제어로봇시스템학회논문지
• /
• 제11권1호
• /
• pp.77-83
• /
• 2005

This paper deals with determination of motions of a humanoid robot using genetic algorithm. A humanoid robot has some problems of the structural instability basically. So, we have to consider the stable walking gait in gait planning. Besides, it is important to make the smoothly optimal gait for saving the electric power. A mobile robot has a battery to move autonomously. But a humanoid robot needs more electric power in order to drive many joints. So, if movements of walking joints don't maintain optimally, it is difficult for a robot to have working time for a long time. Also, if a gait trajectory doesn't have optimal state, the expected life span of joints tends to be decreased. To solve these problems, the genetic algorithm is employed to guarantee the optimal gait trajectory. The fitness functions in a genetic algorithm are introduced to find out optimal trajectory, which enables the robot to have the less reduced jerk of joints and get smooth movement. With these all process accomplished by a PC-based program, the optimal solution could be obtained from the simulation. In addition, we discuss the design consideration for the joint motion and distributed computation of the humanoid, ISHURO, and suggest its result such as the structure of the network and a disturbance observer.

• Structural Engineering and Mechanics
• /
• 제54권2호
• /
• pp.337-362
• /
• 2015

This paper presents a feasibility study on structural damage alarming and localization of long-span cable-supported bridges using multi-novelty indices formulated by monitoring-derived modal parameters. The proposed method which requires neither structural model nor damage model is applicable to structures of arbitrary complexity. With the intention to enhance the tolerance to measurement noise/uncertainty and the sensitivity to structural damage, an improved novelty index is formulated in terms of auto-associative neural networks (ANNs) where the output vector is designated to differ from the input vector while the training of the ANNs needs only the measured modal properties of the intact structure under in-service conditions. After validating the enhanced capability of the improved novelty index for structural damage alarming over the commonly configured novelty index, the performance of the improved novelty index for damage occurrence detection of large-scale bridges is examined through numerical simulation studies of the suspension Tsing Ma Bridge (TMB) and the cable-stayed Ting Kau Bridge (TKB) incurred with different types of structural damage. Then the improved novelty index is extended to formulate multi-novelty indices in terms of the measured modal frequencies and incomplete modeshape components for damage region identification. The capability of the formulated multi-novelty indices for damage region identification is also examined through numerical simulations of the TMB and TKB.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2010년도 춘계학술대회 논문집
• /
• pp.1430-1436
• /
• 2010

Tubular member is hollow and is an excellent source of structural member with great buckling resistance and tortional resistance. With its development and simplicity in structure, steel tubular truss has the ability to be structured in long span bridges, without a stiffener. Recently, it has been used in many countries in Europe, Canada, Japan, and the US with the help of international committees such as CIDECT(International Committee for the Development and Study of Tubular Structures and International Institute of Welding). The most important problem when using the tubular member is the fact that it is difficult to test the fatigue stress determined by nominal stress, since geometrical stress concentration occurs due to the welded joint's nod of complexity. The purpose of this study is to compare and examine current theories and widely applied Hot Spot stress determinations through finite element analysis, which is about welded joints of steel tubular truss. We would like to suggest a way of design practice which involves a bridge plan with rarely domestically used steel tubular truss` basic research data as well as considering the future of tubular member.

• 한국강구조학회 논문집
• /
• 제23권5호
• /
• pp.523-533
• /
• 2011

최근에 구조물의 대형화와 단면성능의 구조적 장점 때문에 원형강관의 사용이 증가하고 있다. 그러나 원형강관의 사용이 증가함에도 불구하고 국내에서는 이에 대한 연구가 매우 미흡한 실정이다. 원형강관-거셋플레이트 접합부의 극한강도의 판단은 매우 복잡한 국부변형과, 실험 및 유한요소해석 결과의 하중변위곡선 상에서 최대강도가 일관성 있게 나타나지 않기 때문에 간단하지가 않다. 따라서 본 연구에서는 실험과 유한요소해석을 바탕으로 극한변형에 의한 극한내력을 도출하고 기존 접합부 내력식과 비교하여 거셋플레이트-원형강관 접합부에 적합한 내력식을 제안하고자 한다.

• Smart Structures and Systems
• /
• 제5권4호
• /
• pp.495-505
• /
• 2009

Bridges form crucial links in the transportation network especially in high seismic risk regions. This research aims to provide a quantitative methodology for post-earthquake performance evaluation of the bridges. The experimental portion of the research involved shake table tests of a 4-span bridge which was subjected to progressively increasing amplitudes of seismic motions recorded from the Northridge earthquake. As part of this project, a high resolution long gauge fiber optic displacement sensor was developed for post-seismic evaluation of damage in the columns of the bridge. The nonlinear finite element model was developed using Opensees program to simulate the response of the bridge and the abutments to the seismic loads. The model was modified to predict the bent displacements of the bridge commensurate with the measured bent displacements obtained from experimental analysis results. Following seismic events, the tangential stiffness matrix of the whole structure is reduced due to reduction in structural strength. The nonlinear static push over analysis using current damaged stiffness matrix provides the longitudinal and transverse ultimate capacities of the bridge. Capacity loss in the transverse and longitudinal directions following the seismic events was correlated to the maximum displacements of the deck recorded during the events.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2001년도 가을 학술발표회 논문집
• /
• pp.459-466
• /
• 2001

The floor vibration aspect for building structures which are in need of large open space are influenced by the interrelation between natural frequency and working loads. Structures with a long span and low natural frequency have a higher possibility of experiencing excessive vibration induced by dynamic excitation such as human activities. These excessive vibrations make the residents uncomfortable and the serviceability deterioration. Need formulation of loads data through actual measurement to apply walking loads that is form of dynamic load in structure analysis. The loads induced by human activities were classified into two types. First type is in place loads. the other type is moving loads. A series of laboratories experiments had been conducted to study the dynamic loads induced by human activities. The earlier works were mainly concerned to parameters study of dynamic loads. In this Paper, the walking loads have been directly measured by using the measuring plate in which two load cells were placed, the parameters, the load-time history of walking loads, and the dynamic load factors have been analyzed. Moreover, the shape of the harmonic loads which were gotten by decomposition the walking loads have been analyzed , and the walking loads modeling have been carried out by composition these harmonic loads derived by functional relation.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2005년도 춘계학술발표대회 개요집
• /
• pp.276-278
• /
• 2005

Bridge constructed recently is preferred to have a long span and a simple structure detail considering not only functions as bridge but scenic beauty, maintenance, construction term and life cycle cost, etc. Therefore, it demands a high quality steel like a thick plate steel and a high performance steel. A TMCP steel produced by theme-mechanical control process is now spotlighted due to the weldability for less carbon equivalent. It improved at strength and toughness in microstructure. Resently the SM570-TMC steel, a high strength TMCP steel whose tensile strength is 600MPa, is developed and applied to steel structures. But, for the application of this steel to steel structures, it is necessary to elucidate not only the material characteristics but also the mechanical characteristic of welded joint. In this paper, we investigated the characteristics of residual stresses generated by welding of SM570-TMC steels through an experimental study

• 한국방재학회 논문집
• /
• 제6권3호
• /
• pp.17-28
• /
• 2006

구조물의 건전성 모니터링은 구조물의 안전 및 사용성을 위하여 중요하다. 구조물의 변위는 직접적인 구조물 강성의 평가 지표가 되기 때문에 정확하고 주기적으로 모니터 되어야 한다. 그러나 이러한 변위 모니터를 위한 실용적인 방법이 아직까진 없고, 특히 고층 건물이나 장 스팬 교량과 같이 접근성이 어려운 구조물의 경우는 더욱 그러하다. 이러한 문제점을 해결하기 위하여 레이저 펄스를 이용하여 원격으로 물체 표면을 탐사하고 수많은 좌표를 생성할 수 있는 라이다 시스템을 제안하였다. 본 연구에서는 지상 라이다를 이용하여 구조물의 헬스 모니터링을 위한 새로운 변위계측모델을 개발하였고 검증을 위한 실험이 수행되었다.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2003년도 가을 학술발표회 논문집
• /
• pp.333-339
• /
• 2003

Recently, the bridges become greater according to development of a construction technology. This phenomenon requires long span bridge, so that increases the dead weight. The orthotropic steel deck bridges have much advantages such as the light dead weight and the reduction of construction period. And almost whole process of carried out is manufactured at factory, so it can cause the increase of quality authoritativeness. But orthotropic steel deck bridge is consist of structure by welding, it can not avoid a lot of welding jobs, defects and transformation by welding are becoming problem accordingly. Specially, topical stress concentration phenomenon in cross connection area of longitudinal and transverse rib causes fatigue failure. The Bulkhead Plate for prevention of this stress concentration phenomenon was applied by changing the orthotropic steel deck of Williamsburg bridge in USA. But, it is principle that a Bulkhead Plate is not established in the domestic design standard. Therefore, it is estimated that the study for installation of Bulkhead Plate is needed. This treatise with considering these circumstances proves efficiency of Bulkhead Plate and will be presented optimal design details through finite element analysis according to change the geometrical of Bulkhead Plate and tile cross-connection area of longitudinal and transverse rib.