• Journal of the Korean Society for Advanced Composite Structures
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• v.3 no.3
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• pp.38-46
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• 2012

The method based on various mathematical characteristic equations for identifying tensile forces in the cable structure system are used as response data to reflect the properties of the dynamic sensitivity. The vibration tests have been conducted with respect to levels of applied weight for the sagged cable. In this study, a set of natural frequencies are extracted from the measured dynamic data. Next, existing characteristic equation methods based these extracted natural frequencies are applied to identify tensil forces of the sagged cable system. Through several verification procedures, the proposed methods could be applied to a sagged cable system when the initial material data are insufficiency.

• Magazine of the Korean Society of Agricultural Engineers
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• v.45 no.2
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• pp.68-77
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• 2003

Shell structure are widely used in a variety of engineering application and mathematical solution of shell structures are available only for a few special cases. The solution of shell structure is more complicated when it has such condition as winker foundation, variable thickness and other problem. In this paper, a simple finite element method is presented for the analysis of axisymmetric several types of shell structure subjected to axisymmetric loads and having uniform and varying wall thickness on elastic foundation. The method is based on the analogy with a beam on elastic foundation (BEF), foundation stiffness matrix where the foundation modulus and beam flexural rigidity are replaced by appropriate parameters pertaining to the shell under considerations. The technique is attractive for implementation on a numerical solution by means of a computer program coded in FORTRAN language with a few elements. To demonstrate this fact, it gives good results which compare well with SAP2000.

• Smart Structures and Systems
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• v.18 no.1
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• pp.117-138
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• 2016

In this paper a different formulation for the response of structural systems controlled by Tuned Liquid Column Damper (TLCD) devices is developed, based on the mathematical tool of fractional calculus. Although the increasing use of these devices for structural vibration control, it has been demonstrated that existing model may lead to inaccurate prediction of liquid motion, thus reflecting in a possible imprecise description of the structural response. For this reason the recently proposed fractional formulation introduced to model liquid displacements in TLCD devices, is here extended to deal with TLCD controlled structures under base excitations. As demonstrated through an extensive experimental analysis, the proposed model can accurately capture structural responses both in time and in frequency domain. Further, the proposed fractional formulation is linear, hence making identification of the involved parameters extremely easier.

• Wind and Structures
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• v.6 no.1
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• pp.41-52
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• 2003

Rain-wind induced vibrations of cables are a challenging problem in the design of cable-stayed bridges. The precise excitation mechanism of the complex interaction between structure, wind and rain is still unknown. A theoretical model that is able to accurately simulate the observed phenomena is not available. This paper presents a mathematical model describing rain-wind induced vibrations as movement-induced vibrations using the quasi-steady strip theory. Both, the vibrations of the cable and the movement of the water rivulet on the cable surface can be described by the model including all geometrical and physical nonlinearities. The analysis using the stability and bifurcation theory shows that the model is capable of simulating the basic phenomena of the vibrations, such as dependence of wind velocity and cable damping. The results agree well with field data and wind tunnel tests. An extensive experimental study is currently performed to calibrate the parameters of the model.

• Earthquakes and Structures
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• v.9 no.5
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• pp.1115-1132
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• 2015

The study considers earthquake shake table testing of bending-torsion coupled structures under multi-component stationary random earthquake excitations. An experimental procedure to arrive at the optimal excitation cross-power spectral density (psd) functions which maximize/minimize the steady state variance of a chosen response variable is proposed. These optimal functions are shown to be derivable in terms of a set of system frequency response functions which could be measured experimentally without necessitating an idealized mathematical model to be postulated for the structure under study. The relationship between these optimized cross-psd functions to the most favourable/least favourable angle of incidence of seismic waves on the structure is noted. The optimal functions are also shown to be system dependent, mathematically the sharpest, and correspond to neither fully correlated motions nor independent motions. The proposed experimental procedure is demonstrated through shake table studies on two laboratory scale building frame models.

• Applied Science and Convergence Technology
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• v.25 no.5
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• pp.92-97
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• 2016

Surface erosion using focused ion beam irradiation is the most promising technology for the realization of micro/nanofabrication. However, accurate fabrication of predefined structures is still challenging. This article introduces a single step surface driving method to fabricated predefined curved structures. The previously reported multi step surface driving method (MSDM) has been modified so that a single ion dose profile can be used instead of multiple ion dose profiles. Experimental realization of the method is presented with the fabrication of predefined curved surfaces as well as reference to surface propagation theory. For the purpose of verification, simulations are performed on the basis of a sound mathematical model.

• Structural Engineering and Mechanics
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• v.10 no.2
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• pp.181-195
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• 2000

A two-step procedure for the application of non linear constrained programming to the limit analysis of rigid brick-block systems with no-tension and frictional interface is implemented and applied to various masonry structures. In the first step, a linear problem of programming, obtained by applying the upper bound theorem of limit analysis to systems of blocks interacting through no-tension and dilatant interfaces, is solved. The solution of this linear program is then employed as initial guess for a non linear and non convex problem of programming, obtained applying both the 'mechanism' and the 'equilibrium' approaches to the same block system with no-tension and frictional interfaces. The optimiser used is based on the sequential quadratic programming. The gradients of the constraints required are provided directly in symbolic form. In this way the program easily converges to the optimal solution even for systems with many degrees of freedom. Various numerical analyses showed that the procedure allows a reliable investigation of the ultimate behaviour of jointed structures, such as stone masonry structures, under statical load conditions.

• Structural Engineering and Mechanics
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• v.18 no.2
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• pp.137-150
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• 2004

The optimization of active bars' placement and feedback gains of closed loop control system for random intelligent truss structures under non-stationary random excitation is presented. Firstly, the optimal mathematical model with the reliability constraints on the mean square value of structural dynamic displacement and stress response are built based on the maximization of dissipation energy due to control action. In which not only the randomness of the physics parameters of structural materials, geometric dimensions and structural damping are considered simultaneously, but also the applied force are considered as non-stationary random excitation. Then, the numerical characteristics of the stationary random responses of random intelligent structure are developed. Finally, the rationality and validity of the presented model are demonstrated by an engineering example and some useful conclusions are obtained.

• Journal of Korean Association for Spatial Structures
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• v.20 no.4
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• pp.35-44
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• 2020

In the study, a shape finding procedure for the tensegrity system model inspired by the movement pattern of animal backbone was presented. The proposed system is allowing a dynamic movement by introducing the concept of "saddle" for the variable tensegrity structure. Mathematical process and an algorithm for movable tensegrity to specified points were established. Several examples have applied with in established shape finding analysis procedure. The final tensegrity structures were determined well to a object shape.

• Earthquakes and Structures
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• v.24 no.6
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• pp.405-413
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• 2023

Various methods have been used to strengthen structures against earthquakes. Isolator systems are among the methods to control the structure's response. Instead of increasing the strength and capacity of the structure, these systems react to earthquakes. In this paper, an isolator system was investigated with the flexible piers of ∨ and ∧ elements, which were perpendicular to each other and connected by a rod hinged at both ends. The behavior of the isolator system was studied. Many structures have non-rigid connections; the effect of this issue was considered in the pendulum column's performance in this paper. Its mathematical equations were derived, solved with MATLAB software, and compared with ABAQUS results. Later on, the isolator system was investigated during different earthquakes. The results show that this mechanism is suitable as an isolator. The period was found to be longer in the flexible pier form. The flexible piers have an influential role in the system's response by reducing the system's stiffness considerably. Among the different damping ratios, those with more than 15% had better results. Finally, the tested model verified the theory.