• Steel and Composite Structures
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• v.39 no.5
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• pp.511-528
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• 2021

There are recently some advances in solving numerically topology optimization problems for large-scaled trusses based on ground structure approach. A disadvantage of this approach is that the final design usually includes many bars, which is difficult to be produced in practice. One of efficient tools is a so-called filter scheme for the ground structure to reduce this difficulty and determine several distinct bars. In detail, this technique is valuable for practical uses because unnecessary bars are filtered out from the ground structure to obtain a well-defined structure during the topology optimization process, while it still guarantees the global equilibrium condition. This process, however, leads to a singular system of equilibrium equations. In this case, the minimization of least squares with Tikhonov regularization is adopted. In this paper, a proposed algorithm in controlling optimal Tikhonov parameter is considered in combination with the filter scheme due to its crucial role in obtaining solution to remove numerical singularity and saving computational time by using sparse matrix, which means that the discrete optimal topology solutions depend on choosing the Tikhonov parameter efficiently. Several numerical examples are investigated to demonstrate the efficiency of the filter parameter control algorithm in terms of the large-scaled optimal topology designs.

• Smart Structures and Systems
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• v.31 no.4
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• pp.409-419
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• 2023

Structural integrity can be accessed from dynamic deformations of structures. Moreover, dynamic deformations can be acquired from non-contact sensors such as video cameras. Kanade-Lucas-Tomasi (KLT) algorithm is one of the commonly used methods for motion tracking. However, averaging throughout the extracted features would induce bias in the measurement. In addition, pixel-wise measurements can be converted to physical units through camera intrinsic. Still, the depth information is unreachable without prior knowledge of the space information. The assigned homogeneous coordinates would then mismatch manually selected feature points, resulting in measurement errors during coordinate transformation. In this study, a two-stage optimization method for video-based measurements is proposed. The manually selected feature points are first optimized by minimizing the errors compared with the homogeneous coordinate. Then, the optimized points are utilized for the KLT algorithm to extract displacements through inverse projection. Two additional criteria are employed to eliminate outliers from KLT, resulting in more reliable displacement responses. The second-stage optimization subsequently fine-tunes the geometry of the selected coordinates. The optimization process also considers the number of interpolation points at different depths of an image to reduce the effect of out-of-plane motions. As a result, the proposed method is numerically investigated by using a truss bridge as a physics-based graphic model (PBGM) to extract high-accuracy displacements from recorded videos under various capturing angles and structural conditions.

• Wind and Structures
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• v.23 no.5
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• pp.405-420
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• 2016

Section model wind tunnel test is currently the main technique to investigate the flutter performance of long-span bridges. Further study about applying the wind tunnel test results to the aerodynamic optimization is still needed. Systematical parameters and test principle of the bridge section model are determined by using three long-span steel truss suspension bridges. The flutter critical wind at different attack angles is obtained through section model flutter test. Under the most unfavorable working condition, tests to investigate the effects that upper central stabilized plate, lower central stabilized plate and horizontal stabilized plate have on the flutter performance of the main beam were conducted. According to the test results, the optimal aerodynamic measure was chosen to meet the requirements of the bridge wind resistance in consideration of safety, economy and aesthetics. At last the credibility of the results is confirmed by full bridge aerodynamic elastic model test. That the flutter reduced wind speed of long-span steel truss suspension bridges stays approximately between 4 to 5 is concluded as a reference for the investigation of the flutter performance of future similar steel truss girder suspension bridges.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.2 s.257
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• pp.245-252
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• 2007

Since the new millennium, truss PCMs(Periodic Cellular Metals) have drawn attention because of their superior specific stiffness, strength and multi-functionality. Prior studies have focused on the structural design and optimization. Kagome truss PCM has been proved to have the higher resistance to plastic buckling, more plastic deformation energy and lower anisotropy than other truss PCMs. In this study, we introduce a new idea to fabricate multi-layered Kagome truss PCM from continuous wires which can gain high strength as in piano wires and can be controlled to be defect free owing to drawing process. The relative density, the stiffness and the strength under bending and compressive load are estimated through elementary mechanics and compared with the results from experiments and FEA. The failure mechanisms are analyzed, and also mechanical performance and production are discussed.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.7
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• pp.147-156
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• 2019

The purpose of this study is to consider structural issues and analyze construction sequences when constructing hanging floors supported by Mega truss. Since suspended structures were supported by the Mega truss, vertical load on suspended structures was needed to transfer from low to high. Deflection management of structures was the primary point under construction. The results of this study were as follows; The steel structures, which has relatively lighter self-weight, were constructed upwards after the base floor steel truss erection. Concrete Placing, which has relatively heavier self-weight, were performed in two phases to minimize structure's deflection. Slab was placed downwards from the top floor to lower floor whereas column was places upwards. Deflection measurements were carried out at every construction sequences.

• Journal of Korean Society of Steel Construction
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• v.12 no.5 s.48
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• pp.515-525
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• 2000

The purpose of this paper was to develop size & shape optimization programming algorithm of plane trusses. The optimum techniques applied in this study were extended penalty method of Sequential Unconstrained Minimization Techniques(SUMT) and direct search method with multi-variables proposed by Hooke & Jeeves. Upper mentioned two methods were used iteratively at each level of size and shape optimization routines. The design variables of size optimization were circular steel tube(structural member) diameter and thickness, those of shape optimization were joint coordinates, and the objective function was represented as total weight of truss. During the optimum design, two level procedures of size and shape optimization were interacted iteratively until the final optimum values were attained. At the previous studies about shape optimization of truss, the member sectional areas and coordinates were applied as design variables. So that they could not apply the buckling effect of compression member. In this paper, actual sizes of member and nodal coordinates are used as design variables to consider the buckling effect of compression member properly.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.271-278
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• 2002

Structural optimization using improved higer-order convex approximation is proposed in this paper. The proposed method is a generalization of the convex approximation method. The order of the approximation function for each constraint is automatically adjusted in the optimization process. And also the order of each design variable is differently adjusted. This self-adjusted capability makes the approximate constraint values conservative enough to maintain the optimum design point of the approximate problem in feasible region. The efficiency of proposed algorithm, compared with conventional algorithm is successfully demonstrated in the Three-bar Truss example.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.6 no.2
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• pp.1-15
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• 1986

The algorithm Proposed utilizes the two-levels technique. In the first level which consists of two phases, the cross-sectional area of the truss member is optimized by transforming the nonlinear problem into SUMT, and solving SUMT utilizing the modified Newton-Rahson method. In the second level, the geometric shape is optimized utilizing the unindirectional search technique of the Powell method which make it possible to minimize only the objective function. The algorithm Proposed in this study is numerically tested for several truss structures with various shapes, loading conditions and design criteria, and compared with the results of the other algorithms to examine its applicability and stability. The numerical comparisons show that the two-Levels algorithm Proposed in this study is safely applicable to any design criteria, and the convergency rate is relathely fast and stable compared with other iteration methods for the geometric optimization of truss structures.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.2
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• pp.9-16
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• 2003

A strategy of the optimal shape design with FEA(Finite Element Analysis) for 2-D structure is proposed by comparing subproblem approximation method with first order approximation method. A cantilever beam with two different loading conditions, a concentrated load and an evenly distribute load, and truss structure with a concentrated loading condition are implemented to optimize the shape. It gives a good design strategy on the optimal truss structure as well as the optimal cantilever beam shape. It is found that the convergence is quickly finished with the iteration number below ten. Optimized shapes of cantilever beam and truss structure are shown with stress contour plot by the results of the subproblem approximation method and the first order approximation methd.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1993.10a
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• pp.81-90
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• 1993

The optimum design of a structure requires the determination of the economical member size and shape of the structure which satisfies the design condition and function. In this study, the process of design automatization of three-dimensional truss structure introduces the optimization technique tests its application in the design automatization, proposes its application method and applies the example structure of the parabolic antenna truss. Using the Formex Algebra of configuration function, the structure's mesh-generation is automatized. By using the program developed in this study, the input member array, member size and load condition designer can generate the input data file for the structure analysis and optimum design. This study is aimed at the development of a design automatization system that search for tile optimum value of a structure design by observing the structure's sensitivity from the modification of member array and member property.