• Journal of Korean Association for Spatial Structures
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• v.10 no.3
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• pp.81-90
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• 2010

Large spatial structures have the different dynamic characteristics from general rahmen structures and many studies on dynamic behavior of it is conducted. But most studies was conducted about the particular shape of large spatial structures and, directly, the usable results of studies are very limited for seismic design of large spatial structures with the lower structure. So, this study is conducted about the truss arch structure that the basic dynamic characteristics of large spatial structure is inherent in, and the change of its seismic response is analyzed when columns have different length on both ends of it. According to the difference of column's length on both ends, the vertical acceleration response of truss arch structure is affected more than the horizontal acceleration response of it. Therefore, when the stiffness of lower structures that support the upper structure is different, the consideration of the vertical response is significantly required for the seismic design of large spatial structures.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.81-85
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• 2005

In this paper, the structural design optimization of a wafer grinding machine using a multi-step optimization with genetic algorithm is presented. The design problem, in this study, is to find out the optimum configuration and dimensions of structural members which minimize the static compliance, the dynamic compliance, and the weight of the machine structure simultaneously under several design constraints. The first design step is shape optimization, in which the best structural configuration is found by getting rid of structural members that have no contributions to the design objectives from the given initial design configuration. The second and third steps are sizing optimization. The second design step gives a set of good design solutions having higher fitness for lightweight and minimum static compliance. Finally the best solution, which has minimum dynamic compliance and weight, is extracted among those good solution set. The proposed design optimization method was successfully applied to the structural design optimization of a high precision wafer grinding machine. After optimization, both static and dynamic compliances are reduced more than $92\%\;and\;93\%$ compared with the initial design, which was designed empirically by experienced engineers. Moreover the weight of the optimized structure are also slightly reduced than before.

• Journal of Korean Association for Spatial Structures
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• v.13 no.4
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• pp.57-66
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• 2013

Spatial structures have the different dynamic characteristics from general rahmen structures. Therefore, it is necessary to accurately analyze dynamic characteristics and seismic response for seismic design of spatial structure. Keel arch structure is used as an example structure because it has primary characteristics of spatial structures. In case of spatial structures with different ground condition and time lag, multiple support excitation may be subjected to supports of a keel arch structure. In this study, the response of the keel arch structure under multiple support excitation and with time lag are analyzed by means of the pseudo excitation method. Pseudo excitation method shows that the structural response is divided into two parts, ground displacement and structural dynamic response due to ground motion excitation. It is known that the seismic responses of spatial structure under multiple support excitation are different from those of spatial structure under simple excitation. And the seismic response of spatial structure with time lag are different from those of spatial structure without time lag. Therefore, it has to be necessary to analyze the seismic response of spatial structure under multiple support excitation and time lag because the spatial structure supports may be different and very long span. It is shown that the seismic response of spatial structure under multiple support seismic excitation are different from those of spatial structure under unique excitation.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.10a
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• pp.501-508
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• 2000

It is demanded to find the dynamic model of a real structure to design a controller. However, as the structure has inherently infinite number of degree-of-freedom, it is impossible to obtain an exact dynamic model of the structure. Instead a reduction model with finite degree-of-freedom is used for the design of a controller. So there exists uncertainty between a real model and a reduction model which causes poor performance of control. All these uncertainties can degrade the control performance and even cause the control instability. Thus, robust control strategy considering the above uncertainties can be an alternative one to guarantee the performance and stability of the control. This study deals with the experimental verification of robust controller design for the active mass driver. $\mu$-synthesis technique is employed as a robust control strategy. Some weights are chosen based on the difference between the initial plant with which the controller is designed and the perturbed plant to be controlled having the actuator uncertainty. The robustness of $\mu$-synthesis technique is compared with the result of LQG strategy, which does not consider the uncertainty.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.7
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• pp.873-879
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• 2010

It is common to predict structural dynamic design parameters due to the change of design parameter, but to predict the amount of changed design parameter where the mass and stiffness are being modified are rarely found in previous literature. In this study, the changed design parameter in a proportional damping system is predicted by using sensitivity coefficients and an iterative method. The sensitivity coefficients are determined from the changes in eigenvectors; these changes are due to modification. This method is applied to a three-story shear structure. To validate the prediction of the changed design parameter, the results are compared to the reanalysis results; both results are in good agreement.

• Journal of the Earthquake Engineering Society of Korea
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• v.24 no.2
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• pp.87-93
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• 2020

Seismic responses due to the dynamic coupling between a primary structure and secondary system connected to a structure are analyzed in this study. The seismic responses are compared based on dynamic coupling criteria and according to the error level in the natural frequency, with the recent criteria being reliant on the error level in the spectral displacement response. The acceleration responses and relative displacement responses of a primary structure and a secondary system for a coupled model and two different decoupled models of two degrees-of-freedom system are calculated by means of the time integration method. Errors in seismic responses of the uncoupled models are reduced with the recent criteria. As the natural frequency of the secondary system increases, error in the natural frequency decreases, but seismic responses of uncoupled models can be underestimated compared to that of coupled model. Results in this paper can help determine dynamic coupling and predict uncoupled models' response conservatism.

• 한국태양에너지학회:학술대회논문집
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• 2008.04a
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• pp.348-358
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• 2008

Unlike structures in the air, the vibration analysis of a submerged or floating structure such as offshore structures is possibly only when the fluid-structures is understood, as the whole or part of the structure is in contact with water. Through the comparision between the experimental result and the finite element analysis result for a simple cylindrical model, it was verified that an added mass effects on the cylindrical structure. Using the commercial FEA program ANSYS(v.11.0), underwater added mass was superposed on the mass matrix of the structure. A frequency response analysis of forced vibration in the frequency considered the dynamic load was also performed. It was proposed to find the several important modes of resonance peak for these fixed cylindrical type structures. Furthermore, it is expected that the analysis method and the data in this study can be applied to a dynamic structural design and dynamic performance evaluation for the ground and marine purpose of power generator by wind.

• Structural Engineering and Mechanics
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• v.45 no.3
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• pp.311-321
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• 2013

In this study, to have a better judgment on the structural performance, the effects of dynamic Soil-Structure Interaction (SSI) on seismic behaviour and lateral structural response of mid-rise moment resisting building frames are studied using Finite Difference Method. Three types of mid-rise structures, including 5, 10, and 15 storey buildings are selected in conjunction with three soil types with the shear wave velocities less than 600m/s, representing soil classes $C_e$, $D_e$ and $E_e$, according to Australian Standard AS 1170.4. The above mentioned frames have been analysed under two different boundary conditions: (i) fixed-base (no soil-structure interaction), and (ii) flexible-base (considering soil-structure interaction). The results of the analyses in terms of structural lateral displacements and drifts for the above mentioned boundary conditions have been compared and discussed. It is concluded that the dynamic soil-structure interaction plays a considerable role in seismic behaviour of mid-rise building frames including substantial increase in the lateral deflections and inter-storey drifts and changing the performance level of the structures from life safe to near collapse or total collapse. Thus, considering soil-structure interaction effects in the seismic design of mid-rise moment resisting building frames, particularly when resting on soft soil deposit, is essential.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.33 no.4
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• pp.334-345
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• 1997

Reliability-based design approaches are needed for cylindrical shell structure whose design and operational experiences are few and which are subjected to external loads of random loads. In designing new type of structure, it is very difficult to evaluate the safety factors due to lack of previous design data and operational experience. To solve the above mentioned problem, much attention is being focussed on rational reliability based design approaches. This paper deals with weight-optional reliability-based design of cylindrical shell structure subjected to structural reliability constraints taking into account of the effect of local buckling and interactive behavior between local and global buckling. Present mentioned is compared with the exiting optional design method based only on safety factors. Numerical simulation reveals that the present method leads to lighter structure (4% reduction in weight compared to the existing optimal design) with the same reliability index. For larger structures with more number of structural members and possible failure modes, the present W0RBD procedure will be an efficient tool in designing cost-effective rationalized economic design.

• Steel and Composite Structures
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• v.2 no.2
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• pp.113-128
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• 2002

The performance of steel MRF with rigid connections, proportioned by adopting different capacity design criteria, is evaluated in order to highlight the effectiveness of static non-linear procedure in predicting the structural seismic behavior. In the framework of the performance-based design, some considerations are made on the basis of the results obtained by both dynamic time histories and push-over analyses, particularly with reference to the damage level and the structure ability to withstand a strong earthquake.