• 한국산학기술학회논문지
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• 제11권7호
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• pp.2341-2348
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• 2010

본 논문에서는 충돌하중 하에서 스페이스 프레임을 사용하는 경주용 차량의 프레임 변형 및 응력을 분석한다. 충돌 시 변형을 최소한으로 줄이고, 취약부분을 파악하여 운전자의 안전을 확보한다. 탄소강의 물성치를 바탕으로 트러스 구조로 설계된 차량 프레임의 유한요소모델을 만들고, ANSYS 프로그램을 이용하여 정면충돌 시 속도 변화에 따른 충격량 증가가 프레임에 미치는 영향을 분석한다. 또한 정면, 측면, 후면 방향에 충돌하중을 적용하여 프레임의\ 변형을 해석한다. 정면 및 후면충돌에서는 운전석에 가해지는 영향이 적지만, 측면충돌 시 충격에 의한 변형이 운전석까지 진행된다. 이러한 변형에 대한 취약부분의 보강을 통하여 프레임의 안전성 설계를 증진시키고 시뮬레이션 해석의 결과를 실제 프레임 제작에 활용한다.

• Steel and Composite Structures
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• 제21권1호
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• pp.137-156
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• 2016

Due to excellent advantages such as better illuminative effects, considerable material savings and ease and rapidness of construction, the bolted ball-cylinder joint which is a new type joint system has been proposed in space truss structures. In order to reveal more information and understanding on the behaviour of bolted ball-cylinder joints, full-scale experiments on eight bolted ball-cylinder joint specimens were conducted. Five joint specimens were subjected to axial compressive force, while another three joint specimens were subjected to axial tensile force. The parameters investigated herein were the outside diameter of hollow cylinders, the height of hollow cylinders, the thickness of hollow cylinders, ribbed stiffener and axial force. These joint specimens were collapsed by excessive deformation of hollow cylinders, punching damage of hollow cylinders, evulsion of bolts, and weld cracking. The strain distributions on the hollow cylinder opening were mainly controlled by bending moments. To improve the ultimate bearing capacity and axial stiffness of bolted ball-cylinder joints, two effective measures were developed: (1) the thickness of the hollow cylinder needed to be thicker; (2) the ribbed stiffener should be adopted. In addition, the axial stiffness of bolted ball-cylinder joints exhibited significant non-linear characteristics.

• Steel and Composite Structures
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• 제18권1호
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• pp.165-185
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• 2015

The suspended zipper bracing system is suggested to reduce the flaws of ordinary zipper braced and concentric inverted V braced frames. In the design procedure of suspended zipper bracing systems, columns and top story truss elements are strengthened. This bracing system show different performances and characteristics compared with inverted V braced and ordinary zipper frames. As a result, a different response modification factor for suspend zipper frames is needed. In this research paper, the response modification factor of suspended zipper frames was obtained using the incremental dynamic analysis. Suspended zipper braced frames with different stories and bay lengths were selected to be representations of the design space. To analyze the frames, a number of models were constructed and calibrated using experimental data. These archetype models were subjected to 44 earthquake records of the FEMA-P695 project data set. The incremental dynamic analysis and elastic dynamic analysis were carried out to determine the yield base shear value and elastic base shear value of archetype models using the OpenSEES software. The seismic response modification factor for each frame was calculated separately and the values of 9.5 and 13.6 were recommended for ultimate limit state and allowable stress design methods, respectively.

• Structural Monitoring and Maintenance
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• 제5권3호
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• pp.417-428
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• 2018

In this paper, various model reduction methods were assessed using a shear frame, plane and space truss structures. Each of the structures is one-dimensional, two-dimensional and three-dimensional, respectively. Three scenarios of poor, better, and the best were considered for each of the structures in which 25%, 40%, and 60% of the total degrees of freedom (DOFs) were measured in each of them, respectively. Natural frequencies of the full and reduced order structures were compared in each of the numerical examples to assess the performance of model reduction methods. Generally, it was found that system equivalent reduction expansion process (SEREP) provides full accuracy in the model reduction in all of the numerical examples and scenarios. Iterated improved reduced system (IIRS) was the second-best, providing acceptable results and lower error in higher modes in comparison to the improved reduced system (IRS) method. Although the Guyan's method has very low levels of accuracy. Structures were classified with the excitation frequency. High-frequency structures compared to low-frequency structures have been poor performance in the model reduction methods (Guyan, IRS, and IIRS).

• 한국농촌건축학회논문집
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• 제14권3호
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• pp.109-119
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• 2012

This study aims to analyze architectural characteristics of railway station facilities which were built with development of railroads from Japanese Colonial Period to 1950's. To achieve this goals, 7 railway stations in Gyeongju area that are worth preserving were set up as research targets. For this study, I analyzed literature of the railway station and drawings which the KORAL Daegu Branch is keeping. Railway stations without a construction drawing investigated a direct visit. After analyzing the railway station facilities, the architectural properties such as plan, elevation and section have been identified. The results are as follows. First, Each modern railway station is usually consisted of waiting room and office, and ancillary spaces have been added. Over the years, however, the space was expanded horizontally. In that case, the structure and finish materials have been changed, like now. Second, Most of the roof shape is 'Matbae'(gable roof), especially Gyeongju station and Bulguksa Station are 'Woojingak roof. The roof structure is truss structure, especially as Pratt and Scissors type, but Gyeongju Station's structure is a reinforced concrete. Third, main doorway of waiting room is located in the center of the front gable. However, small stations like 'Ahwa' and 'Ipsil' station to ensure the passengers' waiting area are placed next to the office area.

• 한국해양공학회지
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• 제18권5호
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• pp.29-35
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• 2004

A new approach, referred to as a successive zooming genetic algorithm (SZGA), is proposed for identifying a global solution, using continuous zooming factors for optimization problems. In order to improve the local fine-tuning of the GA, we introduced a new method whereby the search space is zoomed around the design variable with the best fitness per 100 generation, resulting in an improvement of the convergence. Furthermore, the reliability of the optimized solution is determined based on the theory of probability, and the parameter used for the successive zooming method is optimized. With parameter optimization, we can eliminate the time allocated for deciding parameters used in SZGA. To demonstrate the superiority of the proposed theory, we tested for the minimization of a multiple function, as well as simple functions. After testing, we applied the parameter optimization to a truss problem and wicket gate servomotor optimization. Then, the proposed algorithm identifies a more exact optimum value than the standard genetic algorithm.

• 교육시설 논문지
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• 제25권6호
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• pp.11-20
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• 2018

In order to figure out the usability of various timber structures in the educational facility, the recent timber structure examples published in the Japanese architectural magazine, 'ShinKenchiku' over the past five years were surveyed. As the results, timber structures were presented in many cases of nursery schools and kindergartens overwhelmingly, and they also used in various school buildings, university facilities, and the roof structure of the school's gymnasium, with intention of having the differentiated design and space features. The examples show that span 6 to 10m is generally used with flexure structure system and flexure+compression structure system added the strut as compression members. In addition concerning stability, it was founded that the struts have an stability effect in the flexure+compression structure system, and flexure structure system examples using semi-rigid joints have open spaces liberally in two-way direction for about 9m span. For large spaces structures with span of 15~20m or more, the various structural system such as suspension structure, truss, flexure+compression, etc. was designed to overcome the material limitations of timbers and to make an design effect in structure system.

• Structural Engineering and Mechanics
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• 제77권5호
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• pp.613-626
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• 2021

In this paper, an enhanced Violation-based Sensitivity analysis and Border-Line Adaptive Sliding Technique (ViS-BLAST) will be utilized for optimization of some well-known structural and mechanical engineering problems. ViS-BLAST has already been introduced by the authors for solving truss optimization problems. For those problems, this method showed a satisfactory enactment both in speed and efficiency. The Enriched ViS-BLAST or EVB is introduced to be vastly applicable to any solvable constrained optimization problem without any specific initialization. It uses one-directional step-wise searching technique and mostly limits exploration to the vicinity of FNF border and does not explore the entire design space. It first enters the feasible region very quickly and keeps the feasibility of solutions. For doing this important, EVB groups variables for specifying the desired searching directions in order to moving toward best solutions out or inside feasible domains. EVB was employed for solving seven numerical engineering design problems. Results show that for problems with tiny or even complex feasible regions with a larger number of highly non-linear constraints, EVB has a better performance compared to some records in the literature. This dominance was evaluated in terms of the feasibility of solutions, the quality of optimum objective values found and the total number of function evaluations performed.

• Smart Structures and Systems
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• 제30권6호
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• pp.583-599
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• 2022

In this paper, a multi-objective wireless sensor network configuration optimization method is proposed. The proposed method aims to determine the optimal information and lifespan wireless sensor network for structural health monitoring of large-scale infrastructures. In particular, cluster-based wireless sensor networks with multi-type of sensors are considered. To optimize the lifetime of the wireless sensor network, a cluster-based network optimization algorithm that optimizes the arrangement of cluster heads and base station is developed. On the other hand, based on the Bayesian inference, the uncertainty of the estimated parameters can be quantified. The coefficient of variance of the estimated parameters can be obtained, which is utilized as a holistic measure to evaluate the estimation accuracy of sensor configurations with multi-type of sensors. The proposed method provides the optimal wireless sensor network configuration that satisfies the required estimation accuracy with the longest lifetime. The proposed method is illustrated by designing the optimal wireless sensor network configuration of a cable-stayed bridge and a space truss.

• Structural Monitoring and Maintenance
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• 제9권1호
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• pp.59-80
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• 2022

In the present study, the objective is to detect the structural damages using the responses obtained from the sensors at the optimal location under uncertainty conditions. Reducing the error rate in damage detection process due to responses' noise is an important goal in this study. In the proposed algorithm for optimal sensor placement, the noise of responses recorded from the sensors is initially reduced using the principal component analysis. Afterward, the optimal sensor placement is obtained by the damage detection equation based sensitivity analysis. The sensors are placed on degrees of freedom corresponding to the minimum error rate in structural damage detection through this procedure. The efficiency of the proposed method is studied on a truss bridge, a space dome, a double-layer grid as well as a three-story experimental frame structure and the results are compared. Moreover, the performance of the suggested method is compared with three other algorithms of Average Driving Point Residue (ADPR), Effective Independence (EI) method, and a mass weighting version of EI. In the examples, young's modulus, density, and cross-sectional areas of the elements are considered as uncertainty parameters. Ultimately, the results have demonstrated that the presented algorithm under uncertainty conditions represents a high accuracy to obtain the optimal sensor placement in the structures.