• Title/Summary/Keyword: Truss

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Compressive and Bending Behavior of Sandwich Panels with Octet Truss Core Fabricated from Wires (와이어를 이용하여 제작된 옥데트 트러스 샌드위치 판재의 압축 및 굽힘 거동)

  • Lim Ji-Hyun;Nah Seong-Jun;Koo Man-Hoe;Kang Ki-Ju
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.3 s.234
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    • pp.470-476
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    • 2005
  • Ultra light metal structures have been studied for several years because of their superior specific stiffness, strength and potential of multi functions. Many studies have been focused on how to manufacture ultra light metal structures and optimize them. In this study, we introduced a new idea to make sandwich panels having octet truss cores. Wires bent in a shape of triangular wave were assembled to construct an Octet truss core and it was bonded with two face sheets to be a sandwich panel. The bending & compressive strength and stiffness were estimated through elementary mechanics for the sandwich specimens with two kinds of face sheets and the results were compared with the ones measured by experiments. Some aspects of assembling and mechanical behavior were discussed compared with Kagome core fabricated from wire, which had been introduced in the authors' previous work.

An integrated particle swarm optimizer for optimization of truss structures with discrete variables

  • Mortazavi, Ali;Togan, Vedat;Nuhoglu, Ayhan
    • Structural Engineering and Mechanics
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    • v.61 no.3
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    • pp.359-370
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    • 2017
  • This study presents a particle swarm optimization algorithm integrated with weighted particle concept and improved fly-back technique. The rationale behind this integration is to utilize the affirmative properties of these new terms to improve the search capability of the standard particle swarm optimizer. Improved fly-back technique introduced in this study can be a proper alternative for widely used penalty functions to handle existing constraints. This technique emphasizes the role of the weighted particle on escaping from trapping into local optimum(s) by utilizing a recursive procedure. On the other hand, it guaranties the feasibility of the final solution by rejecting infeasible solutions throughout the optimization process. Additionally, in contrast with penalty method, the improved fly-back technique does not contain any adjustable terms, thus it does not inflict any extra ad hoc parameters to the main optimizer algorithm. The improved fly-back approach, as independent unit, can easily be integrated with other optimizers to handle the constraints. Consequently, to evaluate the performance of the proposed method on solving the truss weight minimization problems with discrete variables, several benchmark examples taken from the technical literature are examined using the presented method. The results obtained are comparatively reported through proper graphs and tables. Based on the results acquired in this study, it can be stated that the proposed method (integrated particle swarm optimizer, iPSO) is competitive with other metaheuristic algorithms in solving this class of truss optimization problems.

A Study on Hot Spot stress in welded joints of steel Tubular truss (강관 트러스 연결부 Hot Spot 응력에 관한 연구)

  • Jang, Woo-Sun;Chung, Jee-Seung;Ahn, Young-Soo;Yoon, Sik-Jae;Yang, Seong-Don;Park, Gyeong-Jun
    • Proceedings of the KSR Conference
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    • 2010.06a
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    • pp.1430-1436
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    • 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.

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Optimum Design of Truss Structures with Pretension Considering Bucking Constraint (프리텐션을 받는 트러스 구조물의 좌굴을 고려한 최적설계)

  • Kim, Yeon-Tae;Kim, Dae-Hwan;Lee, Jae-Hong
    • Journal of Korean Society of Steel Construction
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    • v.22 no.2
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    • pp.197-208
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    • 2010
  • An under-tension system is frequently employed for large-span structures to reduce the deflection and member size. In this study, a microgenetic algorithm was used to find the optimum cross-section of truss structures with an undertension cable under transverse loading. Maximum deflection, allowable stress, and buckling were considered constraints. The proposed approach was verified using a 10-bar truss sample that shows good agreement with the previous results. In the numerical results, minimum-weight design of the under-tension structure was performed for various magnitudes of pretension.

Structural Layout Design for Concrete Structures Based on the Repeated Control Method by Using Micro Lattice Truss Model (마이크로 격자트러스모델을 이용한 반복강성제어법에 의한 콘크리트 구조형태의 최적화)

  • Choi, Ik-Chang;Ario, Ichiro
    • Journal of the Korea Concrete Institute
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    • v.20 no.6
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    • pp.705-712
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    • 2008
  • This study carried out simulation for structural layout design for concrete structures by using the models of the ground structure method. The micro lattice truss is modeled as assemblage of a number of unit cells. The progress of analysis repeat to undergo finite element analysis to feed-back results of stress to the stiffness of each member. Through the repeated this analysis, truss model is represented to form the topological materials and the structural shape with the use of the local stress condition without mathematical optimum tools. It is successful to analyse the shape-layout problem as numerical samples on the lattice truss model.

Compressive behavior of rectangular sandwich composite wall with different truss spacings

  • Qin, Ying;Chen, Xin;Xi, Wang;Zhu, Xing-Yu;Chen, Yuan-Ze
    • Steel and Composite Structures
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    • v.34 no.6
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    • pp.783-794
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    • 2020
  • Steel-concrete-steel sandwich composite wall is composed of two external steel plates and infilled concrete core. Internal mechanical connectors are used to enhance the composite action between the two materials. In this paper, the compressive behavior of a novel sandwich composite wall was studied. The steel trusses were applied to connect the steel plates to the concrete core. Three short specimens with different truss spacings were tested under compressive loading. The boundary columns were not included. It was found that the failure of walls started from the buckling of steel plates and followed by the crushing of concrete. Global instability was not observed. It was also observed that the truss spacing has great influence on ultimate strength, buckling stress, ductility, strength index, lateral deflection, and strain distribution. Three modern codes were introduced to calculate the capacity of walls. The comparisons between test results and code predictions show that AISC 360 provides significant underestimations while Eurocode 4 and CECS 159 offer overestimated predictions.

Optimum Design of Movable Hydraulic Crane Booms (이동식 크레인 붐의 최적설계)

  • Yoo, Kwang-Seon;Park, Jeong-Wan;Sinichi, Hidaka;Han, Seog-Young
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.19 no.6
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    • pp.776-781
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    • 2010
  • Optimum design of movable hydraulic crane's booms for weight reduction was performed in this study. Since the boom weight of the present used booms is very heavy, it is needed to make them lighter structure as possible as we can. Optimum design was performed for the booms by changing from the hexagonal cross section to triangular truss structure under the conditions, which are the allowable stress for the present cross section must be maintained, and the optimized weight must be minimized. CATIAV5 was used for stress analysis and design variables were established as the height and width of the triangular truss structure. As the results, it is found that the height of the truss structure is increased in proportion to the height of the booms and the maximum stress for optimal truss structure was obtained as 412MPa, which is lower than the allowable stress for the present hexagonal cross section. The optimized weight of the booms is reduced to about 19.88% comparing to the original weight.

Analytical Approach to Compression and Shear Characteristics of the Unit Cell of PCM Core with Pyramidal Configuration (피라미드 형상의 PCM 코어 단위 셀의 압축 및 전단특성에 관한 해석적 연구)

  • Kim, S.W.;Jung, H.C.;Lee, Y.S.;Kang, B.S.
    • Transactions of Materials Processing
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    • v.19 no.7
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    • pp.411-415
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    • 2010
  • A sandwich panel which is comprised of truss cores faced with solid face sheets is lightweight and multi-functional. So it is widely used to not only structural material but also heat transfer media in transportation field such as airplane, train and vessel. There are various core topologies such as pyramidal and tetrahedral truss, square honeycombs and kagome truss. The study focused on analytical approach to optimize compression and shear quality of the unit cell of PCM with pyramidal configuration. With various unit cell models which have the same core weight per unit area but different truss member angle, analytical solution for effective stress ($\bar{\sigma},\bar{\tau}$), peak stress ($\bar{\sigma}_{peak},\bar{\tau}_{peak}$) by yielding and buckling, relative density ($\bar{\rho}_c$) and effective stiffness ($\bar{E},\bar{G}$) have been computed and compared each other. With this approach, the most optimal core configuration was predicted. The result has become the efficient guidelines for the design of PCM core structure.

Time-history analysis based optimal design of space trusses: the CMA evolution strategy approach using GRNN and WA

  • Kaveh, A.;Fahimi-Farzam, M.;Kalateh-Ahani, M.
    • Structural Engineering and Mechanics
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    • v.44 no.3
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    • pp.379-403
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    • 2012
  • In recent years, the need for optimal design of structures under time-history loading aroused great attention in researchers. The main problem in this field is the extremely high computational demand of time-history analyses, which may convert the solution algorithm to an illogical one. In this paper, a new framework is developed to solve the size optimization problem of steel truss structures subjected to ground motions. In order to solve this problem, the covariance matrix adaptation evolution strategy algorithm is employed for the optimization procedure, while a generalized regression neural network is utilized as a meta-model for fitness approximation. Moreover, the computational cost of time-history analysis is decreased through a wavelet analysis. Capability and efficiency of the proposed framework is investigated via two design examples, comprising of a tower truss and a footbridge truss.

Shake Table Test on Seismic Performance Evaluation of the Bolted Connection Type Paneling System with Exterior Finish Material (외부마감재가 부착된 볼트접합 방식 패널링 시스템의 내진성능평가를 위한 진동대 실험)

  • Oh, Sang Hoon;Park, Jong Won;Park, Hae Yong
    • Journal of the Earthquake Engineering Society of Korea
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    • v.22 no.1
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    • pp.23-32
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    • 2018
  • In this study, we conducted a shake table test to verify the seismic performance of the paneling system with steel truss composed of bolt connections. The control group was set to the traditional paneling system with steel truss connected by spot welding method. Test results showed that the bolted connection type paneling system has excellent deformation capacity without cracking or brittle fracture of the steel truss connection parts compared to the welding type paneling system. Furthermore, in the bolted connection type, slight damage occurred at the time of occurrence of the same story drift angle as compared with the existing method, it is considered that it has excellent seismic performance. In compliance with the performance-based design recommended for the current code (ASCE 41-13) on non-structural components, it is judged that in the case of the bolted connection type paneling system, it can be applied to all risk category structures without restriction. However, in the case of traditional paneling system with spot welding method, it is considered that it can be applied limitedly.