• Composites Research
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• v.20 no.3
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• pp.63-66
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• 2007

Structural analysis of automotive engine cover under vibration excitation is performed by finite element analysis (FEA) in order to identify the critical area of the structure. Assembly load due to the tightening of the bolts as well as the vibration excitation were considered to describe the actual loading condition. Natural frequencies of the system were extracted considering the damping effect of the structure. Dynamic analysis was performed based on the extracted natural frequency of the system. Experimental modal analysis (EMA) and measurement of strains were performed to verify the results of the analysis. Analysis results correlated closely with the experimental results. Analysis and experiments showed that contribution of the assembly load should not be ignored to predict the structural failure of the engine cover.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.18 no.6
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• pp.642-651
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• 2009

The history of excavator design is not long enough which still causes most of the design considerations to be focused on static analysis or simple functional improvement based on static analysis. However, the real forces experiencing on each component of excavator are highly transient and impulsive. Therefore, the prediction and the evaluation of the movement of the excavator by dynamic load in the early design stage through the dynamic transient analysis of the excavator and ensuring of design technique plays an importance role to reduce development-cost, shorten product-deliver, decrease vehicle-weight and optimize the system design. In this paper, Commercial software DADS and ANSYS help to develop the track model of the crawler type excavator, and to evaluate the performance and the dynamic characteristics of excavator with various simulations. For that reason, the track of crawler type excavator is modelled with DADS Track Vehicle Superelement, and the reaction forces on the track rollers were predicted through the driving simulation. Also, the upper frame and cabin vibration characteristics, at the low RPM idle state, were evaluated with engine rigid body modelling. And flexibility body effects were considered to determine the more accurate joint reaction forces and accelerations under the upper frame swing motion.

• Earthquakes and Structures
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• v.15 no.3
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• pp.335-350
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• 2018

This paper presents numerical modelling, modal testing, finite element model updating, linear and nonlinear earthquake behavior of a reinforced concrete building model. A 1/2 geometrically scale, two-storey, reinforced concrete frame model with raft base were constructed, tested and analyzed. Modal testing on the model using ambient vibrations is performed to illustrate the dynamic characteristics experimentally. Finite element model of the structure is developed by ANSYS software and dynamic characteristics such as natural frequencies, mode shapes and damping ratios are calculated numerically. The enhanced frequency domain decomposition method and the stochastic subspace identification method are used for identifying dynamic characteristics experimentally and such values are used to update the finite element models. Different parameters of the model are calibrated using manual tuning process to minimize the differences between the numerically calculated and experimentally measured dynamic characteristics. The maximum difference between the measured and numerically calculated frequencies is reduced from 28.47% to 4.75% with the model updating. To determine the effects of the finite element model updating on the earthquake behavior, linear and nonlinear earthquake analyses are performed using 1992 Erzincan earthquake record, before and after model updating. After model updating, the maximum differences in the displacements and stresses were obtained as 29% and 25% for the linear earthquake analysis and 28% and 47% for the nonlinear earthquake analysis compared with that obtained from initial earthquake results before model updating. These differences state that finite element model updating provides a significant influence on linear and especially nonlinear earthquake behavior of buildings.

• Steel and Composite Structures
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• v.28 no.2
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• pp.223-231
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• 2018

Nowadays, there are a great number of various structures that have been retrofitted by using different FRP Composites. Due to this, more researches need to be conducted to know more the characteristics of these structures, not only that but also a comparison among them before and after the retrofitting is needed. In this research, a model steel structure is tested using a bench-scale earthquake simulator on the shake table, using recorded micro tremor data, in order to get the dynamic behaviors. Columns of the model steel structure are then retrofitted by using GFRP composite, and then tested on the Quanser shake table by using the recorded micro tremor data. At this stage, it is needed to evaluate the dynamic behaviors of the retrofitted model steel structure. Various types of methods of OMA, such as EFDD, SSI, etc. are used to take action in the ambient responses. Having a purpose to learn more about the effects of GFRP composite, experimental model analysis of both types (retrofitted and no-retrofitted models) is conducted to evaluate their dynamic behaviors. There is a provision of ambient excitation to the shake table by using recorded micro tremor ambient vibration data on ground level. Furthermore, the Enhanced Frequency Domain Decomposition is used through output-only modal identification. At the end of this study, moderate correlation is obtained between mode shapes, periods and damping ratios. The aim of this research is to show and determine the effects of GFRP Composite implementation on structural responses of the model steel structure, in terms of changing its dynamical behaviors. The frequencies for model steel structure and the retrofitted model steel structure are shown to be 33.916% in average difference. Finally, it is shown that, in order to evaluate the period and rigidity of retrofitted structures, OMA might be used.

• Smart Structures and Systems
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• v.19 no.1
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• pp.39-46
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• 2017

Finite element model updating is very effective procedure to determine the uncertainty parameters in structural model and minimize the differences between experimentally and numerically identified dynamic characteristics. This procedure can be practiced with manual and automatic model updating procedures. The manual model updating involves manual changes of geometry and analyses parameters by trial and error, guided by engineering judgement. Besides, the automated updating is performed by constructing a series of loops based on optimization procedures. This paper addresses the ambient vibration based finite element model updating of long span reinforced concrete highway bridges using manual model updating procedure. Birecik Highway Bridge located on the $81^{st}km$ of Şanliurfa-Gaziantep state highway over Firat River in Turkey is selected as a case study. The structural carrier system of the bridge consists of two main parts: Arch and Beam Compartments. In this part of the paper, the arch compartment is investigated. Three dimensional finite element model of the arch compartment of the bridge is constructed using SAP2000 software to determine the dynamic characteristics, numerically. Operational Modal Analysis method is used to extract dynamic characteristics using Enhanced Frequency Domain Decomposition method. Numerically and experimentally identified dynamic characteristics are compared with each other and finite element model of the arch compartment of the bridge is updated manually by changing some uncertain parameters such as section properties, damages, boundary conditions and material properties to reduce the difference between the results. It is demonstrated that the ambient vibration measurements are enough to identify the most significant modes of long span highway bridges. Maximum differences between the natural frequencies are reduced averagely from %49.1 to %0.6 by model updating. Also, a good harmony is found between mode shapes after finite element model updating.

• Tunnel and Underground Space
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• v.6 no.2
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• pp.157-165
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• 1996

In order to analyze the effects of ground vibration caused by underground blasting having an effect on structure, the particle velocity and acceleration are calculated by using DYNPAK program. The DYNPAK program analyzes nonlinear transient dynamic problem and adopts the very popular and easily implemented, explicit, central difference scheme. In this program, the material behavior is assumed to be elasto-viscoplastic. Using the particle acceleration history, modal analysis method is applied to the forced vibration response of multiple-degree-of-freedom(MDOF) systems using unclupled equations of motion expressed in terms of the system's natural circular frequencies and modal damping factors. AS a means of evaluating the vibration behavior of building structure subjected to underground blasting, the time response of the displacements relative to the ground of five-story building is determined. It is concluded that the amount of explosives consumed per round, the location of structure, the properties of rock medium, the stiffness fo structure, etc. act on the important factors influencing on the safety of building and that the response of a structure subjected to a forced excitation can usually be obtained with reasonable accuracy by the modal analysis of only a few mode of the lower frequencies of the system.

• Journal of KSNVE
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• v.5 no.3
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• pp.413-421
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• 1995

Synchrotron light source building of the accelerator has stringent vibration limits since the performance of the optical devices and electronic equipments in the laboratory is strongly influenced by the vibrations of the building. In this study, vibrations of the synchrotron light source building are estimated using experimental modal analysis and force response simulation technique. Dynamic properties of the building are identified from the modal parameters and vibration responses are predicted from the force response simulation. A double anti vibration system is designed and applied to the HVAC equipments and it has been shown that the measured vibrations of the building with the double anti vibration system satisfy the vibration criteria.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.4 s.121
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• pp.317-323
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• 2007

Non-contact underwater explosions against surface ships could cause extensive equipment damage and render the ship inoperative. As an analytical method, DDAM(dynamic design and analysis method) is used for ship shock design. In this paper, in order to verify the finite element model of large shipboard equipment, modal test of equipment was performed. Major objective of this paper is to describe shock analysis methodology for large shipboard equipment attacked to the top and bottom foundations.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.7 s.124
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• pp.587-595
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• 2007

Performance evaluation of advanced piezoelectric composite actuator is conducted with its application of structural vibration control. Characteristics of MFC(macro fiber composite) actuator are investigated by comparing traditional piezoceramic patch actuator. Finite element modeling is used to obtain equations of motion and boundary effects of smart hull structure with MFC actuator. Dynamic characteristics of the smart hull structure are studied through modal analysis and experimental investigation. LQG control algorithm is employed to investigate active damping of hull structure. It is observed that vibration of hull structure is suppressed effectively by the MFC actuators.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.1119-1124
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• 2007

Performance evaluation of advanced piezoelectric composite actuator is conducted with its application of structural vibration control. Characteristics of MFC (macro fiber composite) actuator are investigated by comparing traditional piezoceramic patch actuator. Finite element modeling is used to obtain equations of motion and boundary effects of smart hull structure with MFC actuator. Dynamic characteristics of the smart hull structure are studied through modal analysis and experimental investigation. LQG control algorithm is employed to investigate active damping of hull structure. It is observed that vibration of hull structure is suppressed effectively by the MFC actuators.