• Structural Engineering and Mechanics
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• v.23 no.6
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• pp.635-649
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• 2006

The static and dynamic responses of guyed telecommunication towers can be determined by using two models, the space truss element model, and the equivalent beam-column element model. The equivalent beam-column analysis is based on the determination of the equivalent shear, torsion, and bending rigidities as well as the equivalent area of the guyed mast. In the literature, two methods are currently available to determine the equivalent properties of lattice structures, namely: the unit load method, and the energy approach. In this study, an equivalent beam-column analysis is introduced based on an equivalent thin plate approach for lattice structures. A finite-element modeling, using suitably modified ABAQUS software, is used to investigate the accuracy of utilizing the different proposed methods in determining the static and dynamic responses of a guyed tower of 364.5-meter high subjected to static and seismic loading conditions. The results from these analyses are compared to those obtained from a finite-element modeling of the actual structure using 3-D truss and beam elements. Good agreement is shown between the different proposed beam-column models, and the model of the actual structure. However, the proposed equivalent thin plate approach is simpler to apply than the other two approaches.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.59-63
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• 2011

Friction damping is one of the attractive vibration control technique for space structures due to its simplicity and large damping capacity. However, passive approaches for friction damping have a limitation because energy is no longer dissipated at sticking. In order to overcome this problem, semi-active control methods to adjust normal force at frictional interface have been studied in previous researches. In this paper, two semi-active friction control method is compared by simulating SDOF model of truss structure. The first approach is on-off control to maximize rate of energy dissipation, whereas the second concept is variable friction force control to minimize amplitude ratio for each half period. The maximum friction force, control variable in on-off control method, is obtained to minimize 1% settling time, and is different from optimal friction force in passive control. Simulation results show that performance of on-off control is better than that of variable friction force control in terms of settling time and controlled friction force.

• Advances in Computational Design
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• v.1 no.2
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• pp.175-194
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• 2016

Nature has provided inspiration for most of the man-made technologies. Scientists believe that dolphins are the second to humans in smartness and intelligence. Echolocation is the biological sonar used by dolphins for navigation and hunting in various environments. This ability of dolphins is mimicked in this paper to develop a new optimization method. Dolphin Echolocation Optimization (DEO) is an optimization method based on dolphin's approach for hunting food and exploration of environment. DEO has already been developed for discrete optimization search space and here it is extended to continuous search space. DEO has simple rules and is adjustable for predetermined computational cost. DEO provides the optimum results and leads to alternative optimality curves suitable for the problem. This algorithm has a few parameters and it is applicable to a wide range of problems like other metaheuristic algorithms. In the present work, the efficiency of this approach is demonstrated using standard benchmark problems.

• Journal of Korean Society of Steel Construction
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• v.16 no.1 s.68
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• pp.123-134
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• 2004

In this research, a multilevel decomposition technique to enhance the efficiency of the configuration optimization of truss structures was proposed. On the first level, the nonlinear programming problem was formulated considering cross-sectional areas as design variables, weight, or volume as objective function and behavior under multiloading condition as design constraint. Said nonlinear programming problem was transformed into a sequential linear programming problem. which was effective in calculation through the approximation of member forces using behavior space approach. Such approach has proven to be efficient in sensitivity analysis and different form existing shape optimization studies. The modified method of feasible direction (MMFD) was used for the optimization process. On the second level, by treating only shape design variables, the optimum problem was transformed into and unconstrained optimal design problem. A unidirectional search technique was used. As numerical examples, some truss structures were applied to illustrate the applicability. and validity of the formulated algorithm.

• Journal of the Korea Furniture Society
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• v.19 no.2
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• pp.106-110
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• 2008

This paper investigated and validated the mechanisms and principles for constructing reticular structure of plant fiber through frothing solution approach. After process, plant fibers became low-density reticular-structured block with all properties meeting Chinese standards for cushion packing materials. The bonds between fibers acted as knots in a truss and were strong enough to keep space occupied by bubbles in the frothing solution from shrinking in the subsequent draining process. The formation of the reticular structure depends mainly on the pressure difference between inside and outside bubble, the effect of surface adsorbent force on bubble film, and hydrogen bond among fiber hydroxide.

• Magazine of the Korean Society of Agricultural Engineers
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• v.22 no.1
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• pp.87-95
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• 1980

General purpose programs are essential elements for the computerization of structural analysis. This paper is associated with actual formulation of such programs by matrix analysis. The basic theory of matrix analysis for skeletal structures, its implementation and techniques for developing efficient programs are discussed in this paper. Any shape of skeletal structure can be included in a single program for space frames. But in order to economize computing time and computer memory space, it is desirable to develop and operate seperate programs specialized into four categories; truss, planar frame, grid and space frame. As for general purpose programs, simplicity of input format and flexibility of output format should be duly considered. Compaction and solution of system equations are the most important aspects in computer programming of matrix analysis, and worth further study for more efficient computerization.

• Journal of Korean Association for Spatial Structures
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• v.18 no.1
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• pp.93-100
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• 2018

The retractable roof structures have actions of various types of loads and external forces depending on the retraction and operation conditions of the roof in terms of efficiency of control and maintenance as the aspect of structural plan. In particular, there is a need for studies on the establishment of retraction controlled wind velocity to maintain the stable control and usability of roof structure against strong winds or sudden gusts during the retraction of the roof. In this paper, it was intended to provide basic materials for the development of guidelines on the operation and maintenance of domestic retractable buildings with large space by analyzing the factors affecting the retraction controlled wind velocity for the overseas stadiums with the large spatial retractable roof structures where the sliding system was applied on the steel retractable systems. As a result, the controlled wind velocity tends to decrease as the retractable roof area increases. On the other hand, the controlled wind velocity tends to increase as the retraction time increases. In addition, in the space-grid roof structures, the spherical roof structures type showed the average controlled wind velocity of 10m/sec lower than that of 17.3m/sec for curved-roof structure type, and in the curved-roof structure type, the truss roof structure showed the average controlled wind velocity of 8.9m/sec which is lower than that of 17.3m/sec for the space for the space-grid roof structure.

• Journal of the Korean Institute of Educational Facilities
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• v.25 no.6
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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.

• Smart Structures and Systems
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• v.25 no.3
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• pp.345-368
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• 2020

The present work proposes a self-controlled multi-stage optimization method for damage identification of structures utilizing standard particle swarm optimization (PSO) algorithm. Damage identification problem is formulated as an inverse optimization problem where damage severity in each element of the structure is considered as optimization variables. An efficient objective function is formed using the first few frequencies and mode shapes of the structure. This objective function is minimized by a self-controlled multi-stage strategy to identify and quantify the damage extent of the structural members. In the first stage, standard PSO is utilized to get an initial solution to the problem. Subsequently, the algorithm identifies the most damage-prone elements of the structure using an adaptable threshold value of damage severity. These identified elements are included in the search space of the standard PSO at the next stage. Thus, the algorithm reduces the dimension of the search space and subsequently increases the accuracy of damage prediction with a considerable reduction in computational cost. The efficiency of the proposed method is investigated and compared with available results through three numerical examples considering both with and without noise. The obtained results demonstrate the accuracy of the present method can accurately estimate the location and severity of multi-damage cases in the structural systems with less computational cost.

• Journal of Korean Association for Spatial Structures
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• v.12 no.1
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• pp.59-68
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• 2012

The space frame structure is one of the large span structural system consisting of longitudinal and latitudinal members. The members are connected in three dimension. A space frame structure has high stiffness with a structure resisting external forces in steric conformation. According to many structural conditions, structural stability problems in the space frame are determined and considered very important. This study seeks to understand the space frame collapse mechanism using the 2-free nodes truss model in order to examine static structural instability characteristics of the latticed dome. According to geometrical shape, the star dome, parallel lamella dome and three way grid dome were selected as models. The models were examined for characteristics of instability under STEP Excitations behavior according to rise-span ratio(${\mu}$) and shape imperfection.