• Structural Engineering and Mechanics
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• v.14 no.1
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• pp.39-56
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• 2002

In order to trace a target in deep sky, a feed cabin 20 tons in weight used for a large radio telescope is drawn with six cables. To realize a smooth tracing all the time, optimal distribution of the cable tensions is explored. A set of cable-clog systems is utilized to control the wind-induced vibration of the cable-cabin structure. This is an attempt to apply the passive structural control strategy in the area of radio astronomy. Simulations of wind-induced vibration of the structure in both time and frequency domains offer a valuable reference for construction of the next generation large radio telescope.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.913-914
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• 2017

Structural analyses of a engine system is required in development stage for increasing structural reliability and reducing weight. Attitude of a launch vehicle during flight is controlled by combustion chamber rotation varying with TVC (thrust vector control) actuator displacements. In this study nonlinear static analysis is performed for a 75 tonf-class liquid rocket engine using before and after the TVC actuation.

• Structural Engineering and Mechanics
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• v.31 no.4
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• pp.393-405
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• 2009

The Purpose of this paper is to show the applicability of a methodology, developed by the authors, with which to perform the mechanical optimization of space truss structures strongly restricted. This methodology use a parameter call "Volumetric Displacement", as the Objective Function of the optimization process. This parameter considers altogether the structure weight and deformation whose effects are opposed. The Finite Element Method is employed to calculate the stress/strain state and the natural frequency of the structure through a structural linear static and natural frequency analysis. In order to show the potentially of this simple methodology, its application on a large diameter telescope structure (10 m) considering the strongly restriction that became of its use, is presented. This methodology, applied in previous works on continuous structures, such as shell roof and fluid storage vessels, is applied in this case to a space truss structure, with the purpose of generalize its applicability to different structural topology. This technique could be useful in the morphology design of deployable and retractable roof structures, whose use has extensively spread in the last years.

• Structural Engineering and Mechanics
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• v.45 no.2
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• pp.211-232
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• 2013

In this study a multi-objective optimization problem is solved. The objectives used here include simultaneous minimum construction cost in term of sections weight, minimum structural damage using a damage index, and minimum non-structural damage in term of inter-story drift under the applied ground motions. A high-speed and low-error neural network is trained and employed in the process of optimization to estimate the results of non-linear time history analysis. This approach can be utilized for all steel or concrete frame structures. In this study, the optimal design of a planar eccentric braced steel frame is performed with great detail, using the presented multi-objective algorithm with a discrete population and then a moment resisting frame is solved as a supplementary example.

• Steel and Composite Structures
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• v.17 no.5
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• pp.705-719
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• 2014

Composite steel-concrete box girders are frequently used in bridge construction for their economic and structural advantages. An integrated metaheuristic based optimization procedure is proposed for discrete size optimization of straight multi-span steel box girders with the objective of minimizing the self-weight of girder. The metaheuristic algorithm of choice is the Cuckoo Search (CS) algorithm. The optimum design of a box girder is characterized by geometry, serviceability and ultimate limit states specified by the American Association of State Highway and Transportation Officials (AASHTO). Size optimization of a practical design example investigates the efficiency of this optimization approach and leads to around 15% of saving in material.

• IEMEK Journal of Embedded Systems and Applications
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• v.6 no.5
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• pp.273-280
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• 2011

In this paper, we describe the structural reinforcement approach of the throwing-type firefighter assistance robot which can be thrown into a fire site to monitor inside the place and search trapped people while ensuring a firefighter's safety. The reinforcement design is focused on high strength with low weight for the robot. The in-depth structural analysis of the platform is carried out to track down the weakest part, especially with the 1.8m height of drop test. The analysis is verified by comparing with the 1.8m height of the drop test of the throwing-type firefighter assistance robot. The optimal approach for improving the strength of the weakest part aims at topological equivalent and equivalently stress distributed shape.

• Computers and Concrete
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• v.30 no.2
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• pp.113-126
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• 2022

Reinforced concrete bearing walls (RCBWs) are one of the most applicable structural systems. Therefore, vulnerability analysis and rehabilitation of the RCBW system are of great importance. In the present study, in order to the more precise investigation of the performance of this structural resistant system, pushover and nonlinear time history analyses based on several assumptions drawing upon experimental research were performed on several models with different stories. To validate the nonlinear analysis method, the analytical and experimental results are compared. Vulnerability evaluation was carried out on two seismic hazard levels and three performance levels. Eventually, the need for seismic rehabilitation with the basic safety objective (BSO) was investigated. The obtained results showed that the studied structures satisfied the BSO of the seismic rehabilitation guidelines. Consequently, according to the results of analyses and the desired performance, this structural system, despite its high structural weight and rigid connections and low flexibility, has integrated performance, and it can be a good option for earthquake-resistant constructions.

• Journal of Electrochemical Science and Technology
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• v.14 no.2
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• pp.120-130
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• 2023

PEMFC has high potential for future development due to its high energy density, eco-friendliness, and high energy efficiency. When it becomes small, light and flexible, it can be competitive as an energy source for portable devices or flexible electronic devices. However, the use of hard and heavy materials for structural rigidity and uniform contact pressure transmission has become an obstacle to reducing the weight and flexibility of PEMFCs. This review intends to provide an example of the application of a new structure and material for lightweight and flexibility. As a lightweight PEMFC, a tubular design is presented and structural advantages through numerical modeling are explained. Manufacturing methods to realize the structural advantages and possibilities of tubular PEMFCs are discussed. In addition, the materials and manufacturing processes used to fabricate lightweight and flexible PEMFCs are described and factors affecting performance are analyzed. Strategies and structural improvements of light and flexible movements are discussed according to the component parts.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.6
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• pp.103-108
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• 2020

Generally, the cargo tank of LPG carriers corresponds to an independent tank Type A defined by the International Maritime Organization (IMO). The outside of the tank is insulated by polyurethane foam, and the tank is made of expensive low temperature steel that can withstand temperatures as low as -50℃. The cargo tank is composed of outer shell plates, bulkheads, stiffeners, web frames, and stringers. Among them, the outer shell plates, bulkheads, and stiffeners can be designed without structural analysis by the Classification Rules and are constructed easily through optimal design. On the other hand, optimal design, including numerous structural analysis, is not performed because web frames and stringers should be designed and approved through structural analysis. Only adequate design, which determines the design dimensions through several dozen structural analysis, is performed. In this study, for finite element analysis, eight loading conditions were applied, and the deformation of the entire ship for each loading condition was considered. The minimum weight design was performed for the web frames of cargo tanks in the 82,000 ㎥ LNG carrier through the gradient-based optimization technique, and the weight was reduced by approximately 108 tons per ship.

• International Journal of Highway Engineering
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• v.12 no.2
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• pp.99-106
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• 2010

Until now, the thickness design of anti-freezing layer has been empirically conducted using the frost depth determined from the freezing index. This approach cannot consider the structural properties of anti-freezing layer, which can cause the over-design of pavement structure. This paper presents results of structural evaluation of anti-freezing layer using the Falling Weight Deflectormeter (FWD) deflections. The FWD testing was directly conducted on top of the subbase layer located at the embankment, cutting, and boundary area of each section. It is observed from this testing that the center deflections of pavement structure with anti-freezing layer are smaller than those without anti-freezing layer. The deflection reduction rates are 15~55% in the embankment, 11~64% in the cutting, and 2~38% in the boundary, respectively. It was also found that the use of antifree zing layer enables to reduce the Surface Curvature Index (SCI) values up to 24 percent. Fatigue lives show that pavement structure with antifreezing layer are about two times higher than the those without anti-freezing layer. This fact indicates that the anti-freezing layer should be considered as a structural layer in the asphalt pavement system.