• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.2
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• pp.131-138
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• 2009

Analytical modal verification is considered as the process to provide an acceptable description of the subject structure's behaviour. In general, results of original analytical model are different with actual structure results to uncertainty like non-linearity of material, boundary and modified shape, etc. In this paper, the dynamic model of glider's wing is correlated with static deformation and vibration test results by goal-attainment method, multi-objects optimization technique. The structural responses are predicted by using finite element method and optimization is carried out by using the SQP(sequential quadratic programming) method which is widely used in the constrained nonlinear optimization problem. The MAC(Modal Assurance Criterion) is used to modify the mode shapes and quantify the similarity.

• Coupled systems mechanics
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• v.12 no.3
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• pp.277-295
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• 2023

Unsymmetrical high-rise buildings (HRBs) subjected to earthquake represent a difficult challenge to structural engineering, especially taking into consideration the effect of soil-structure interaction (SSI). L-shape in plan HRBs suffer from big straining actions when are subjected to an earthquake (in x- or y-direction, or both x- and y- directions). Additionally, the disastrous effect of seismic pounding may appear between two adjacent unsymmetrical HRBs. For two unsymmetrical L-shape in plan HRBs subjected to earthquake in three different direction cases (x, y, or both), including the SSI effect, different methods are investigated to mitigate the seismic pounding and thus protect these types of structures under the earthquake effect. The most effective technique to mitigate the seismic pounding and help in seismically protecting these adjacent HRBs is found herein to be the use of a combination of pounding tuned mass dampers (PTMDs) all over the height (at the connection points) together with tuned mass dampers (TMDs) on the top of both buildings.

• Journal of Korean Society of Steel Construction
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• v.24 no.4
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• pp.399-410
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• 2012

In this study, vibration tests are performed on cantilevered and clamped-clamped laminated composite rectangular plates using experimental modal analysis technique. The damages are simulated by applying progressive line cracks to the laminated composite plates for damage evaluations due to crack growth. The changes of frequency response functions(FRFs), MAC values, and modal parameters (frequency, mode shape and damping ratio) of the damaged composite plates, which are obtained by the modal testing of impact hammer, are investigated. Each experimental modal parameter of the progressively damaged composite plates is compared with natural frequencies and mode shapes obtained by finite element analysis. It is seen that the damage can be evaluated from the changes in the geometric properties and structural behaviors of the laminated composite plates resulting from the model updating process of the finite element model as a benchmark.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.3
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• pp.182-190
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• 1997

Recently to develope an automobile with better properties, much researches and investments are executed in many countries. In this paper, it is intended to minimize the weight of an engine block without changing the dynamic characteristics. The weight minimization is executed by the sensitivity of the natural frequency of the engine block. To decrease the engine weight, much less thickness than the original thickness of the engine is selected to initial value and the structure modification is performed to recover the dynamic characteristics of the engine. Here, the original thickness of the engine is 8mm and the initial thickness is selected to 5mm, 6mm and the number if the natural frequencies fitted are 2, 6, 7, respectively. As the results, it is found that; (1) the weight of each case could be reduced without changing the objective natural frequencies. Specially, in the case of fitting 2 natural frequencies with 5mm initial thickness the weight could be reduced to 4.21kg(23.3% for engine weight). (2) according to the driving frequency range of engine, the weight minimization could be performed choicely, (3) improving a vibration characteristics of a orignal structure, the weight minimization could be performed.

• Smart Structures and Systems
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• v.24 no.1
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• pp.27-35
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• 2019

This paper proposes a quantitative criterion for optimization of actuator placement for the Prestress-Accumulation Release (PAR) strategy of mitigation of vibrations. The PAR strategy is a recently developed semi-active control approach that relies on controlled redistribution of vibration energy into high-order modes, which are high-frequency and thus effectively dissipated by means of the natural mechanisms of material damping. The energy transfer is achieved by a controlled temporary removal of selected structural constraints. This paper considers a short-time decoupling of rotational degrees of freedom in a frame node so that the bending moments temporarily cease to be transferred between the involved beams. We propose and test a quantitative criterion for placement of such actuators. The criterion is based on local modal strain energy that can be released into high-order modes. The numerical time complexity is linear with respect to the number of actuators and potential placements, which facilitates quick analysis in case of large structures.

• Structural Engineering and Mechanics
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• v.81 no.1
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• pp.69-79
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• 2022

The dynamic responses of a pier-pile-soil system subjected to a barge/flotilla collision are analyzed. A coupled high-speed train and bridge system with a damaged pier after barge/flotilla collision is established by taking the additional unevenness of the track induced by the damaged pier as the self-excitation of the system. The whole process of a CRH2 high-speed train running on the 6×32 m simply-supported PC (prestressed concrete) box-girder bridge with a damaged pier is simulated as a case study. The results show that the lateral displacements and accelerations of the bridge with a damaged pier are much greater than the ones before the collision. The running safety indices of the train increase with the train speed as well as with the number of barges in the flotilla. In flotilla collision, the lateral wheel/rail forces of the train exceed the allowable values at a certain speed, which influences the running safety of the trains.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.6
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• pp.148-156
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• 2018

The integrity assessment of the bridge behavior is generalized by field data of a static load-deformation curve and dynamic properties such as impact factors and natural frequencies. Evaluating it with numerical analysis is a reasonable method. The results of the mockup test and the numerical analysis are corresponded with each other since the behavior of service load proceeds in elastic region. In case of the dynamic behavior of structure, especially for the analysis of vibration, the result of the mockup test differs from the result of numerical analysis a little due to the geometric shape and non-homogeneous materials. In order to converge on these tolerances, this study suggested several numerical models, analyzed the sensitivity and finally offered a practical modeling method for the estimation of bridge on the basis of the result of mockup test. Based on the model substituted concrete section for strands section, the natural frequency of the model composed with axial stiffness of strands or the model applied the modified modulus of elasticity was closest with the result of the mockup test.

• Journal of the Korea Convergence Society
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• v.6 no.5
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• pp.85-90
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• 2015

In this study, the life evaluation due to the structural configuration of bumper attached at the front side of ATV vehicle is studied on the basis of fatigue analysis. As the purpose of this study, the characteristic of bumper exposed on the repetitive loading condition like the vibration is understood. The position of crack happened at the fatigue situation is grasped in advance and complemented in advance. It is considered that the multipurpose vehicle is designed to not be driven on the paved general road but the rough road like the unpaved load. And the weak part of bumper is understood through the study of life evaluation on this driving environment. The durability can be improved by doing the safe design of automotive bumper on the basis of the analysis result. And it is possible to be grafted onto the convergence technique at design and show the esthetic sense.

• Transactions of the KSME C: Technology and Education
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• v.5 no.2
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• pp.127-134
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• 2017

The reactor internals shall be secured in safety and structural integrity under various vibrational loading conditions. Thus, U.S. NRC, Regulatory Guide 1.20 requires the evaluation for the reactor internals due to acoustic induced vibration including the response to the reactor coolant pump pressure pulsation. This paper suggests a methodology to develop an analytical model of the core support barrel accounting for the fluid around the structure and to analyze the responses to the pump pulsation loads using acoustic structure interaction analysis. The analysis results were compared with those of US Palo Verde 1 CVAP and showed a good agreement. Thus, it is expected that the suggested methodology could be an efficient way to evaluate the response of the core support barrel to the pump pulsation loads.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.4
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• pp.811-818
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• 1992

The sensor technology has becoming emerging area as the automation process in industry requires higher productivity, better quality, and the reliability. In this research, the dynamic measuring sensor such as piezoelectric accelerometers has been developed. Especially, the research concentrates on a design methodology, an analysis of the structural characteristics, and a method of the performance evaluation. The fabricated piezoelectric accelerometers show that the performance characteristics is better than commercial products available in the current market.