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Oh J.,Korea University | Ju Y.K.,Korea University | Hwang K.-J.,University of Seoul | Kim S.-D.,Korea University | Lho S.-H.,Korea Agency for Infrastructure Technology Advancement
Engineering Structures | Year: 2016

For free-form structures with a single layer envelope, the node is subjected to axial load, as well as moment. The purpose of this paper is to develop and evaluate a new hollow spherical connector, termed the FREE (Flexible, Resilient, Efficient, Economic) node, for single layer free-form spatial envelopes. Reducing material and efficient shape are important points in the space structure node. Therefore, hollow spherical node sections with different holes were proposed and finite element analysis was performed, to determine the prototype among these parameters. The parameters are the size and shape of the hollow sphere. Bending experiments were also performed, to evaluate the structural capacities of the proposed node; and the corresponding test results were compared with finite element analysis. As a result, it may be said the proposed FREE node satisfied the required capacities. © 2015 Elsevier Ltd. Source

Koh H.-M.,Seoul National University | Lim J.-H.,Seoul National University | Song J.,Seoul National University | Park W.,Korea Agency for Infrastructure Technology Advancement
Life-Cycle of Structural Systems: Design, Assessment, Maintenance and Management - Proceedings of the 4th International Symposium on Life-Cycle Civil Engineering, IALCCE 2014 | Year: 2015

As today’s urban environments and civil infrastructures are highly complex and interconnected, accidental events such as fire, explosion, dropped objects, and collision of vehicles or vessels are more frequent than in the past and are causing critical structural damage and socioeconomic costs. Therefore, in order to achieve structures that are robust against such hazards, accidental loads should be appropriately considered during the design process. To this end, this paper explores a reliability-based structural design framework for accidental loads based on recent research experience in bridge design against ship collision. The proposed design framework employs a scenario-based simulation in which the occurrence of an accidental event and the resulting structural loads are modeled in a probabilistic manner. The probability distribution of accidental loads is then determined based on the occurrence probabilities of identified scenarios and the conditional probability of structural loads given each scenario. In order to estimate the structural responses caused by accidental loads, an appropriate type of structural analysis is carried out for the prescribed limit states representing collapse or other types of structural failures. As an illustrative example, this paper presents reliability analysis of a cable-stayed bridge whose piers are subject to ship collision hazard. The probability distribution of ship collision load is determined by the scenario-based approach, and the limit state of structural resistance is defined by the P-M diagram after identifying critical sections in the structure. To consider the dynamic amplification of bridge response by ship-bridge collision, time history analysis is performed for the configuration of equivalent static ship collision loads. This paper also summarizes the research needs and challenges identified while exploring the proposed design framework. © 2015 Taylor & Francis Group, London. Source

Eom B.G.,Seoul National University of Science and Technology | Kim S.J.,Korea Agency for Infrastructure Technology Advancement | Lee S.I.,Korea National University of Transportation | Lee H.S.,Seoul National University of Science and Technology
Transactions of the Korean Society of Mechanical Engineers, A | Year: 2013

The speed-limit regulation on a turnout is the main factor inhibiting the speed-up of conventional lines. The specified speed for a train moving through a turnout system is lower than that for a train traveling over the general track. This is done to ensure the running safety of a railway vehicle moving through a turnout. In this study, the shape change example of the guard rail component of a turnout in the Daegu Metropolitan Transit Corporation (DTRO) system was studied. A theoretical examination of the geometrical interaction formula according to wheel/rail shape at the turnout was conducted. Running safety analysis by changing the length of the guard rail on the F10/F12 turnout using the developed analysis techniques (by VI-Rail) was achieved, and the effect on railway safety was examined accordingly. © 2013 The Korean Society of Mechanical Engineers. Source

Seong Y.-B.,Korea Agency for Infrastructure Technology Advancement | Yeo M.-S.,Seoul National University | Kim K.-W.,Seoul National University
Indoor and Built Environment | Year: 2014

Automated blinds need to be controlled to maximize benefits of daylight to enhance occupant comfort and to reduce energy consumption. However, previous control methods focused on minimizing the negative impacts of daylight, but failed to maximize the positive impacts of daylight and solar heat gain. The objective of this study is to develop an optimized control algorithm for automated venetian blind which would reduce the negative effects of incoming daylight on visual comfort of occupants, and to minimize psychological anxieties caused by frequent motions of the blind, by maximizing the positive effects of incoming daylight and solar irradiation, by opening/closing of the blind. Through implementation of the proposed methods and algorithms, the direct glare on work-planes could be prevented at all time, and also incoming daylight and solar irradiation could be increased. © The Author(s) 2013. Source

Lee C.-H.,DongYang Structural Engineers Co. | Lho S.-H.,Korea Agency for Infrastructure Technology Advancement | Kim D.-H.,Korea Advanced Institute of Science and Technology | Oh J.,Korea University | Ju Y.K.,Korea University
Engineering Structures | Year: 2016

An hourglass-shaped strip damper (HSD) was proposed to improve on the conventional slit damper. The damper has non-uniform strips which have a smaller cross-sectional area close to the middle height. To find the structural capacities of HSD subjected to monotonic and cyclic loadings, experimental tests were carried out in this study. Test parameters were loading rate, material strength, and the number of damper plates. The results showed substantial load-resistance capacity under monotonic loadings, and excellent ductility and energy dissipation were exhibited under cyclic loadings, with even distribution of damage over the entire height of strips. Based on the test results, a simple hysteretic model using a combined isotropic-kinematic hardening rule was also proposed. The comparison demonstrated that it represents the tested cyclic load-displacement hysteresis well. It is expected that the proposed model can be successfully used to predict the behavior of HSD in real-world applications. © 2016 Elsevier Ltd. Source

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