• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.562-567
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• 2001

The number of required modes to provide accurate force information in a truncated model of a flexible structure is investigated. In the case of modal truncation of a distributed parameter system, the difference in convergence rates between displacements and forces is discussed. The residual flexibility, a term from past literature, is used to recapture some of the lost force information in a truncated model. This paper presents numerical and experimental results of a study where the residual flexibility is used in conjunction with a Kalman filter so that accurate force information may be obtained from a small set of displacement measurements with a reduced-order model. The motivation for this paper is to be able to obtain accurate information about unmeasurable dynamic reaction forces in a rotating machine for diagnostic and control purposes.

• 한국정밀공학회지
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• 제19권1호
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• pp.150-157
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• 2002

The number of required modes to provide accurate force information in a truncated model of a flexible structure is investigated. In the case of modal truncation of a distributed parameter system, the difference in convergence rates between displacements and forces is discussed. The residual flexibility. a term from past literature, is used to recapture some of the lost force information in a truncated model. This paper presents numerical and experimental results of a study where the residual flexibility is used in conjunction with a Kalman filter so that accurate force information may be obtained from a small set of displacement measurements wish a reduced-order model. The motivation for this paper is to be able to obtain accurate information about unmeasurable dynamic reaction forces in a rotating machine for diagnostic and control purposes.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2008년도 춘계학술대회 논문집
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• pp.265-266
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• 2008

• 도시과학
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• 제7권1호
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• pp.5-9
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• 2018

The nickel-titanium shape memory alloy (SMA), referred to as Nitinol, exhibits a superelastic effect that can be restored to its original shape even if a significant amount of deformation is applied at room temperature, without any additional heat treatment after removal of the load. Owing to these unique material characteristics, it has widely used as displacement control devices for seismic retrofitting in civil engineering fields as well as medical, electrical, electronic and mechanical fields. Contrary to ordinarty carbon steel, superelastic SMAs are very resistant to fatigue, and have force-displacement properties depending on loading speed. The change for the mechanical properties of superelastic SMAs are experimentally inviestigated in this study when loading cycle numbers and loading speeds are different. In addition, the standardized force-displacement properties of such superelastic SMAs are proposed with an aim to efficiently design the seismic retrofitting devices made of these materials.

• Journal of Mechanical Science and Technology
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• 제15권12호
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• pp.1655-1663
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• 2001

The objective of this paper is to develop a logical procedure to determine the center roller displacement, in the three-roll bending process, which is required in the fabrication of curved rectangular plates with a desired curvature. To this end, the mechanics of the process was analyzed by both analytical and finite element approaches. Comparisons of the results reveal that a simple analytical procedure, based on the beam theory, yields a reasonably accurate relationship between the center roller displacement and residual curvature. With further development and refinement, the proposed in this work has great premise for practical application, particularly automation of the process.

• 대한족부족관절학회지
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• 제19권2호
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• pp.63-68
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• 2015

Purpose: The purpose of this study was to report impacts of the amount of displacement of percutaneous osteotomy on the clinical and radiologic results in the treatment of bunionette deformities. Materials and Methods: We retrospectively reviewed 36 cases of bunionette deformities treated with percutaneous modified Kramer osteotomies from 2009 to 2013. We measured amounts of displacement on anteroposterior and lateral plain radiographs as well as multiple parameters which represent degrees of the bunionette deformities. We also recorded radiological healing time, clinical healing time, residual symptoms, and the time of returning to daily activity. Results: No meaningful correlation was found between severity of preoperative deformity and amount of displacement of the osteotomy. The amount of displacement on a horizontal plane did not affect the healing time, duration of symptoms, or time of returning to daily activity. However, large sagittal displacement was related to duration of postoperative symptoms. Conclusion: Findings of this study suggest that the displacement in percutaneous osteotomy for bunionette deformity does not affect clinical results and healing time. We believe that we do not need to be excessively cautious about how large the displacement we make during the percutaneous modified Kramer osteotomy for the bunionette deformity.

• Structural Engineering and Mechanics
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• 제48권6호
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• pp.849-878
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• 2013

This paper consists of two parts, which broadly examines solution techniques abilities for the structures with geometrical nonlinear behavior. In part I of the article, formulations of several well-known approaches will be presented. These solution strategies include different groups, such as: residual load minimization, normal plane, updated normal plane, cylindrical arc length, work control, residual displacement minimization, generalized displacement control, modified normal flow, and three-parameter ellipsoidal, hyperbolic, and polynomial schemes. For better understanding and easier application of the solution techniques, a consistent mathematical notation is employed in all formulations for correction and predictor steps. Moreover, other features of these approaches and their algorithms will be investigated. Common methods of determining the amount and sign of load factor increment in the predictor step and choosing the correct root in predictor and corrector step will be reviewed. The way that these features are determined is very important for tracing of the structural equilibrium path. In the second part of article, robustness and efficiency of the solution schemes will be comprehensively evaluated by performing numerical analyses.

• Structural Engineering and Mechanics
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• 제63권4호
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• pp.497-507
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• 2017

During recent earthquakes, a significant number of concrete structures suffered extensive damage. Conventional reinforced concrete structures are designed for life-time safety that may see permanent inelastic deformation after severe earthquakes. Hence, there is a need to utilize adequate materials that have the ability to tolerate large deformation and get back to their original shape. Super-elastic shape memory alloy (SMA) is a smart material with unique properties, such as the ability to regain undeformed shape by unloading or heating. In this research, four different stories (three, five, seven and nine) of reinforced concrete (RC) buildings have been studied and subjected to near-field ground motions. For each building, two different types of reinforcement detailing are considered, including (1) conventional steel reinforcement (RC frame) and (2) steel-SMA reinforcement (SMA RC frame), with SMA bars being used at plastic zones of beams and steel bars in other regions. Nonlinear time history analyses have been performed by "SeismoStruct" finite element software. The results indicate that the application of SMA materials in plastic hinge regions of the beams lead to reduction of the residual displacement and consequently post-earthquake repairs. In general, it can be said that shape memory alloy materials reduce structural damage and retrofit costs.

• Steel and Composite Structures
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• 제23권3호
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• pp.285-302
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• 2017

Buckling-restrained braced frames (BRBFs) are commonly used as the lateral force-resisting systems in building structures in the seismic regions. The nearly-symmetric hysteretic response and the delayed brace core fracture of buckling-restrained braces (BRBs) under the axial cyclic loading provide the adequate lateral force and deformation capacity to BRBFs under the earthquake excitation. However, the smaller axial stiffness of BRBs result in the undesirable higher residual drift response of BRBFs in the post-earthquake scenario. Two alternative approaches are investigated in this study to improve the elastic axial stiffness of BRBs, namely, (i) by shortening the yielding cores of BRBs; and (ii) by reducing the BRB assemblies and adding the elastic brace segments in series. In order to obtain the limiting yielding core lengths of BRBs, a modified approach based on Coffin-Manson relationship and the higher mode compression buckling criteria has been proposed in this study. Both non-linear static and dynamic analyses are carried out to analytically evaluate the seismic response of BRBFs fitted with short-core BRBs of two medium-rise building frames. Analysis results showed that the proposed brace systems are effective in reducing the inter-story and residual drift response of braced frames without any significant change in the story shear and the displacement ductility demands.

• International Journal of Concrete Structures and Materials
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• 제11권2호
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• pp.403-413
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• 2017

Residual axial capacity from numerical analysis was widely used as a critical indicator for damage assessment of reinforced concrete (RC) columns subjected to blast loads. However, the convergence of the numerical result was generally based on the displacement response, which might not necessarily generate the correct post-blast results in case that the strain softening behavior of concrete was considered. In this paper, two widely used concrete models are adopted for post-blast analysis of a RC column under blast loading, while the calculated results show a pathological mesh size dependence even though the displacement response is converged. As a consequence, a nonlocal integral formulation is implemented in a concrete damage model to ensure mesh size independent objectivity of the local and global responses. Two numerical examples, one to a RC column with strain softening response and the other one to a RC column with post-blast response, are conducted by the nonlocal damage model, and the results indicate that both the two cases obtain objective response in the post-peak stage.