• Smart Structures and Systems
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• 제12권2호
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• pp.181-207
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• 2013

In this paper, a statistical reference-free real-time damage detection methodology is proposed for detecting joint and member damage of truss bridge structures. For the statistical damage sensitive index (DSI), wavelet packet decomposition (WPD) in conjunction with the log likelihood ratio was suggested. A sensitivity test for selecting a wavelet packet that is most sensitive to damage level was conducted and determination of the level of decomposition was also described. Advantages of the proposed method for applications to real-time health monitoring systems were demonstrated by using the log likelihood ratios instead of likelihood ratios. A laboratory truss bridge structure instrumented with accelerometers and a shaker was used for experimental verification tests of the proposed methodology. The statistical reference-free real-time damage detection algorithm was successfully implemented and verified by detecting three damage types frequently observed in truss bridge structures - such as loss of bolts, loosening of bolts at multiple locations, sectional loss of members - without reference signals from pristine structure. The DSI based on WPD and the log likelihood ratio showed consistent and reliable results under different damage scenarios.

• 한국해양공학회지
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• 제17권4호
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• pp.66-72
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• 2003

This paper proposes an optimum, problematic design for structural and control systems, taking a 3-D truss structure as an example. The structure is subjected to initial static loads and time-varying disturbances. The structure is controlled by a state feedback H$_{\infty}$ controller which suppress the effects of disturbances. The design variables are the cross sectional areas of truss members. The structural objective function is the structural weight. For the control objective, we consider two types of performance indices, The first function represents the effect of the initial loads. The second function is the norm of the feedback gain, These objective functions are in conflict with each other but are transformed into one control objective by the weighting method. The structural objectives is treated as the constraint, By introducing the second control objective which considers the magnitude of the feedback gain, we can create a design to model errors.

• Structural Engineering and Mechanics
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• 제10권1호
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• pp.1-15
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• 2000

It is inevitable that every space truss structure would be under some form of direct member loading. At least the structure self weight certainly affects the members directly, and in structures involving top concrete slabs or cladding, their weight is also likely to apply some lateral pressure on the members. In spite of that, direct member loading is usually ignored in space truss designs and assumed to lead only to a negligible effect on truss performance. This study is intended to explore this point and identify the actual effects that can arise from direct member loading, and eventually provide an answer to the question of whether the current design practice is satisfactory or certain modifications would be needed. After presenting two analytical techniques to allow the study of space trusses with laterally loaded members, the paper describes a wide parametric study involving practical-size space trusses with different configurations, aspect ratios, boundary conditions and number of chord panels.

• 한국기계가공학회지
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• 제19권5호
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• pp.27-37
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• 2020

Structural optimization problems with discrete design variables require more function calculations (or finite element analyses) than those in the continuous design space. In this study, a method to find an optimal solution in the discrete design of the truss structure is presented, reducing the number of function calculations. Because a continuous optimal solution is the Karush-Kuhn-Tucker point that satisfies the optimality condition, it is assumed that the discrete optimal solution is around the continuous optimum. Then, response values such as weight, displacement, and stress are predicted using approximate models-referred to as hybrid metamodels-within specified design ranges. The discrete design method using the hybrid metamodels is used as a post-process of the continuous optimization process. Standard truss design problems of 10-bar, 25-bar, 15-bar, and 52-bar are solved to show the usefulness of this method. The results are compared with those of existing methods.

• Wind and Structures
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• 제7권6호
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• pp.393-404
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• 2004

The design of truss type sign support structures is based on the guidelines provided by the American Association of State Highway and Transportation Officials Standard Specifications for Highway Signs, Luminaries and Traffic Signals and the American Institute of Steel Construction Design Specifications. Using these specifications, the column design strength is normally determined using the effective length approach. This approach does not always accurately address all issues associated with frame stability, including the actual end conditions of the individual members, variations of the loads in the members, and the resulting sidesway buckling for truss type sign support structures. This paper provides insight into the problems with the simplified design approach for determining the effective lengths and discusses different approaches for overcoming these simplifications. A system buckling approach, also known as a rational buckling analysis, is used in this study to determine improved predictions for design strength of truss type sign support structures.

• Advances in Computational Design
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• 제1권2호
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• pp.119-138
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• 2016

In this article, hybridization of enhanced colliding bodies optimization (ECBO) with upper bound strategy (UBS) that is called UECBO is proposed for optimum design of truss structures with frequency constraints. The distinct feature of the proposed algorithm is that it requires less computational time while preserving the good accuracy of the ECBO. Four truss structures with frequency limitations selected from the literature are studied to verify the viability of the algorithm. This type of problems is highly non-linear and non-convex. The numerical results show the successful performance of the UECBO algorithm in comparison to the CBO, ECBO and some other metaheuristic optimization methods.

• Structural Engineering and Mechanics
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• 제55권4호
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• pp.801-813
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• 2015

Flexural stiffness of bridge spans has become even more important parameter since Eurocode 1 introduced for railway bridges the serviceability limit state of resonance. For simply supported bridge spans it relies, in general, on accurate assessment of span moment of inertia that governs span flexural stiffness. The paper presents three methods of estimation of the equivalent moment of inertia for such spans: experimental, analytical and numerical. Test loading of the twin truss bridge spans and test results are presented. Recorded displacements and the method of least squares are used to find an "experimental" moment of inertia. Then it is computed according to the analytical method that accounts for joint action of truss girders and composite deck as well as limited span shear stiffness provided by diagonal bracing. Finally a 3D model of finite element method is created to assess the moment of inertia. Discussion of results is given. The comparative analysis proves efficiency of the analytical method.

• 한국강구조학회 논문집
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• 제24권6호
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• pp.637-645
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• 2012

슬래브와 트러스 보의 합성효과를 고려한 합성트러스의 경우 단순히 고정하중으로 취급되던 슬래브를 구조체로서 활용할 수 있으므로 구조재료를 매우 효과적으로 활용할 수 있게 되고 구조체의 강성이 증가하게 되므로 장스팬 설계의 중요 변수인 사용성 측면에서도 상당한 이점을 확보할 수 있게 된다. 이와 더불어 슬래브 하부에 다양한 설비 시설을 위한 공간이 확보되므로 보의 춤이 깊어지는데 대한 단점을 상당부분 상쇄할 수 있게 된다. 본 연구는 합성 트러스 시스템을 개발함에 있어 상하현재를 600MPa급 고강도강을 사용하여 실험과 수치해석을 통해 스터드 커넥터의 유 무에 따른 합성 트러스의 역학적 거동 특성을 평가하는 것을 목적으로 한다. 또한 상하현재로 일반강재를 사용한 연구결과와 비교하였다. 그 결과 고강도강으로 T형강을 사용한 경우는 일반강재를 T형강으로 사용한 경우보다 구조성능에서 더욱 효율적임을 알 수 있었다.

• 비파괴검사학회지
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• 제28권2호
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• pp.217-224
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• 2008

트러스는 교량이나 건축물 설계 등에 많이 사용되는 구조물로서 기본적인 설계요소이며, 설계자는 이러한 구조물의 원리를 완전히 이해하여 설계에 적용할 수 있어야 한다. 본 논문에서는 트러스 구조물의 힘을 기본역학에서 예측되는 오차범위 이내로 실험법으로 측정할 수 있는 기구설계 방법을 제시하였다. 상용으로 제작된 재래식 변형률 측정 장치는 고가이고 복잡하므로 구조를 이해하기가 어려우므로 본 측정기구에서는 휘트스톤브리지 회로를 적용, 스트레인 게이지 및 A/D 변환기 조립하여 하중과 변형률을 쉽게 측정할 수 있도록 하였다. 제작된 기구를 이용하여 구조물에 하중을 가하여 변형률을 측정하였으며, 측정결과를 이론적으로 예측한 값과 비교하여 실용성을 입증하였다. 이 측정 기구는 저렴한 값으로 제작할 수 있으며, 크기가 작아 탁상에서 교육용 실험 및 실습 장비로 적합할 것으로 사료된다.

• Steel and Composite Structures
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• 제34권6호
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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.