Chin-Ok Lee

Elastic Stability of Circular Arches with the Open Thin-walled Monosym- metric Section Considering the Prebuckling Deformation

The effect of prebuckling in-plane deformations on the elastic flexural-torsional buckling of arches is studied in this paper. Nonlinear strain-displacement relations considering initial curvature effects and higher order prebuckling de- formation terms with curvature in deriving process are substituted into the second variation of the total potential to obtain the buckling energy equation. The analytical solutions for the flexural-torsional buckling moment of arches in uniform bending, containing the effects of the prebuckling deformation, are proposed. Also, the influence of the higher order prebuckling deformation terms with the curvature effects is investigated according to the ratio of the minor axis flexural stiffness to the major axis flexural stiffness.

Design Consideration of Fish-bone Girder Pier using the Analysis of Torsional Behavior

Abstract A modular fish-bone girder pier consists of one main girder system named as “Spine Girder”. Therefore, this pier can be most affected by torsion as well as flexural bending. The design considerations of the fish-bone girder pier are proposed to assure the reasonable design in this study. In order to investigate the behavior characteristics, structural analysis F.E model is developed, and the verification of the developed model is performed by comparison with experimental data. From the investigation of the structural behavior, the vertical stiffener is required at the bottom of bone-beams to prevent the excessive local stress. Also, it is found that the normal stress of the flange and the shear stress of the web and flange are dominantly affected by the warping torsion and pure torsion, respectively. Key Words : Pier, Fish-bone girder, Spine girder, Bone beam, warping, torsion 본 연구는 국토해양부 지역기술혁신사업(09지역기술혁신 B-01)의 연구비지원에 의해 수행되었습니다. * Corresponding Author : Nam-Hyoung Lim(Chungnam National Univ.)Tel: +82-41-821-7005 email: nhrim@cnu.ac.krReceived November 28, 2013 Revised January 8, 2014 Accepted January 9, 2014

Mitigate Seismic Response of Three-Span Bridge Using MR Damping System

In this paper, a mitigation of earthquake response is aimed at by constituting an MR damping system in a three-span bridge. It is a system where bridge spans are connected by means of an MR damper to control their vibration. A model structure of three-span bridge (12 m long) was built with an MR damper applied to connect each span, one between span A and B, the other between span B and C, and the MR damping system for this study was designed to work as a single unit with five components, that is, three spans and two MR dampers. Shaking table tests were carried out by inflicting a 40% load of Kobe earthquake to see how effective the system would be in mitigating seismic responses. All the tests were done under various conditions (un controlled, passive off, control algorithm) in order to closely examine and analyze under which condition mitigation could be maximized and how mitigation could be effected. As a result of the tests, it was found that the MR damping system was effective in reducing three spans from pounding each other and its active performance decreased the relative displacement of the bridge structure. Therefore, it was proven to be effective in attenuating the seismic responses of three-span bridge.

Calculating a MR Damper`s Optimal Capacity for a Control of Structural Vibration

In the case where a MR-damper is employed for vibration control, it is important to decide on how much control capacity should be assigned to it against structural capacities (strength and load, etc). This paper aims to present a MR-dampers control capacity suitable for the capacities of the structure which needs to be controlled. First, a two span bridge was built equipped with a MR-damper, which constitutes a two-span MR-damper control system. Then, inflicting an earthquake load on the system, a basic experiment was performed for vibration control, and a simulation was also carried out reflecting specific control conditions such as MR-damper and rubber bearing. The comparison of the results against each other proved their validity. Then, in order to calculate an optimal control capacity of the MR-damper, structural capacity was divided into eleven cases in total and simulated. For each case, an additional load of 30 KN was inflicted everytime, thereby increasingly strengthening structural capacity. As a result of the study, it was found that the control capacity of MR-damper of 30 KN was safely secured only with lumped mass of more than 150 KN(case 6). Therefore, it is concluded the MR-damper showed the best performance of control when it exerted its capacity at around 20% of structural capacity.

Structural Dynamic Response Compressing Technique in Bridges using a Cochlea-inspired Artificial Filter Bank(CAFB)

In this study, a cochlea-inspired artificial filter bank (CAFB) was developed to efficiently obtain dynamic response of a structure, and a dynamic response measurement of a cable-stayed bridge model was also carried out to evaluate the performance of the developed CAFB. The developed CAFB used a band-pass filter optimizing algorithm (BOA) and peakpicking algorithm (PPA) to select and compress dynamic response signal containing the modal information which was significant enough. The CAFB was then optimized about the El-Centro earthquake wave which was often used in the construction research, and the software implementation of CAFB was finally embedded in the unified structural management system (USMS). For the evaluation of the developed CAFB, a real time dynamic response experiment was performed on a cable-stayed bridge model, and the response of the cable-stayed bridge model was measured using both the traditional wired system and the developed CAFB-based USMS. The experiment results showed that the compressed dynamic response acquired by the CAFB-based USMS matched significantly with that of the traditional wired system while still carrying sufficient modal information of the cable-stayed bridge.

Analysis Model of the Stress Ribbon Bridge considering the Construction Stage

요 약 스트레스 리본 교량(Stress Ribbon Bridge)이란 두께가 얇은 상부구조(바닥판)가 특정한 현수 형태(catenary type)로 유지되고 긴장된 바닥판 (Post-tensioned deck)이 하중에 의해 역 아치(Reverse arch) 거동을 보이는 PSC 구조물이다. 현재 스트레스 리본 교량의 경우 국외에서 자연파괴를 최소화 하고 아름다운 구조로 인식되어 차도교, 보도교 등에 활발하게 이용 되고 있으나 국내에서는 이와 관련된 연구가 매우 미흡한 실정이다. 본 연구에서 시공단계가 고려된 스트레스 리본교량의 비선형, 시간의존적 해석이 고려된 모델을 정립하는데 목표가 있다. 정립된 모델을 이용하여 시공단계에 따른 단면력을 이론 에 의한 수치와 비교하여 그 타당성을 입증하였으며, 시공단계에 따른 교량의 거동을 분석하였다.

Structural Analysis and Design of the H-typed Railway Tie

With speed up of railway, the demand for safety of the railroad transportation is on the increase in Korea`s conventional railways. In additions, freight trains with heavier axle load are required to run conventional railways. In order to solve these requirements, the increase of rail weight and the application of long rail system have been underway in conventional railways. However, the research on ties that is absolutely influencing the track stiffness in ballasted tracks has not been much progress. In this paper, the new H-typed tie is developed to increase the track stiffness and reduce the track irregularity. And from the structural analysis by FE program, the intial design drawing of the new H-typed tie is proposed.

Improvement Strategies for Coastal Zone Safety Facilities through Analysis of Domestic and Foreign Field Survey

Recently, the risk of safety accidents in the coastal zone has been increased due to revitalization of marine leisure and tourism. Because of a lack of regulations about technical and maintenance aspect for safety facilities, the effective measures to prevent safety accidents in the coastal zone have not taken with increasing rate of the accidents. The nature of land/sea and behavioral characteristics of a fisherman/port laborer/tourist/people at leisure should be taken into account properly when safety facilities to prevent safety accidents in the coastal zone are installed, since the characteristics of land/sea and many activities such as fishery, harbor works, tour, leisure are mixed in the geographic and environmental condition of the coastal zone. This study analyzes the current problems on the safety facility in the domestic coastal zone through the domestic and foreign(Hongkong, Macau) field survey. Also the direction of the improvement about the safety facility are proposed.

Development of the Light Emitting System embedded Concrete Curb

The safety accidents due to the insufficient visibility are frequently occurred at the coastal zone. Therefore, safety facilities that provide visibility are certainly required to prevent accidents. In order to solve this demand, the concept of the light emitting system embedded concrete (LESeCON) are established and then concrete curb is produced for application to the coastal zone. To investigate the mechanical and functional performance of concrete curb developed in this study, the bending strength test and the visibility test are conducted.

An Experimental Study on the Effects of Bolted Connection Type on the Block Shear Failure

Abstract Block shear failure is one of limit states, and demands great caution in designing the tension member or connection joint of steel structures. From many studies and design specification, it is shown that the effect of the bolted connection type on the block shear failure was not considered. In order to investigate the effect of the bolted connection type(bearing type connection and slip critical connection) on the mode/strength of the block shear failure, tensile experiment is conducted in this study. Differences about the failure mode according to the design specification, bearing type connection, and slip critical connection are proposed from the analysis of test results. The variation of the block shear failure strength due to the frictional force in the slip critical connection is also investigated. Key Words : Block shear, Bolted connection, Tension member 이 연구는 충남대학교 학술연구비에 의해 지원되었음. * Corresponding Author : Nam-Hyoung LimTel: +82-11-9402-1417 email: nhrim@cnu.ac.kr접수일 12년 10월 15일 수정일 12년 10월 29일 게재확정일 12년 11월 08일