• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2010.11a
• /
• pp.683-684
• /
• 2010

• Composites Research
• /
• v.12 no.3
• /
• pp.45-54
• /
• 1999

In this paper, an experimental study on the buckling and postbuckling control of a laminated composite beam with eccentrically embedded SMA wire actuators is performed. For the purpose of enhancing the critical buckling load, buckling control is investigated through the use of reactive moment associated with the shape recovery force of SMA wire actuators. To improve the control authority for the buckling and postbuckling control of the SMA-composite beam, closed-loop control is used. The buckling and postbuckling control behaviours are presented and discussed qualitatively and quantitatively on loaddeflection plots considering the stacking sequence of the laminate, slenderness ratio of the beam and activation conditions of the SMA wire actuators. By maintaining the desired deflection shape with the proper reactive moment, buckling control can be extended to the postbuckling of the SMA-composite beam subjected to an external load.

• Elastomers and Composites
• /
• v.39 no.3
• /
• pp.228-233
• /
• 2004

A bushing is a device used in automotive suspension systems to reduce the load transmitted from the wheel to the frame of the vehicle. A bushing is a hollow cylinder, which is bonded to a solid steel shaft at its inner surface and a steel sleeve at its outer surface. The relation between the force applied to the shaft and the relative deformation of a bushing is nonlinear and exhibits features of viscoelasticity. Since a force-displacement relation for bushings is important for multibody dynamics numerical simulations, the relation is expressed in terms of a force relaxation function and a method of determination by experiments on bushings has been developed. For the nonlinear viscoelastic axial response, Pipkin-Rogers model, the direct relation of force and displacement, has been derived from experiment. It is shown that the predictions by the proposed force-displacement relation are in very good agreement with the experimental results.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.33 no.3
• /
• pp.875-888
• /
• 2013

The researches have recently progressed toward the use of the superelastic shape memory alloys (SMAs) to develop new smart control systems that reduce permanent deformation occurring due to severe earthquake events and that automatically recover original configuration. The superelastic SMA materials are unique metallic alloys that can return to undeformed shape without additional heat treatments only after the removal of applied loads. Once the superelastic SMA materials are thus installed at the place where large deformations are likely to intensively occur, the structural system can make the best use of recentering capabilities. Therefore, this study is intended to propose new buckling-restrained braced frames (BRBFs) with superelastic SMA bracing systems. In order to verify the performance of such bracing systems, 6-story braced frame buildings were designed in accordance with the current design specifications and then nonlinear dynamic analyses were performed at 2D frame model by using seismic hazard ground motions. Based on the analysis results, BRBFs with innovative SMA bracing systems are compared to those with conventional steel bracing systems in terms of peak and residual inter-story drifts. Finally, the analysis results show that new SMA bracing systems are very effective to reduce the residual inter-story drifts.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.16 no.5
• /
• pp.41-53
• /
• 2012

The objective of this study is to evaluate the seismic capacity of RC piers with small aspect ratios. Test specimens were selected from the prototype piers among existing national roadway bridges which are expected to fail in shear and/or complex shear-flexural mode. Two groups of full scale RC pier models were constructed with aspect ratios of 2.25 and 2.67. Quasi-static tests have been implemented to investigate the failure behavior of the RC piers in terms of the lap-spliced longitudinal reinforcing steel and the aspect ratio. It is confirmed that regarding its shear-flexural behavior, the pier is very sensitive to the aspect ratio or details. In the case of a test pier with highly lap-spliced longitudinal bars, the bond failure of lap-splice steels was the dominant cause of failure before the occurrence of flexure or shear-flexural failure, despite a slight change in the aspect ratio. Finally, based on the test results and analysis, this paper proposes formulas for the yielding and ultimate displacements of circular reinforced concrete bridge piers without seismic details. These formulas will be useful for the investigation and upgrade of the seismic capacity of bridge piers without seismic details.

• Journal of the Korean Geotechnical Society
• /
• v.24 no.8
• /
• pp.137-148
• /
• 2008

In this study, 28 earthquake records with magnitudes from 5.3 to 7.9 are selected for dynamic analysis in order to assess applicability of the earthquakes for domestic seismic design. The assessment is performed using the seismic spectrum analysis of energy and acceleration. Based on results of the analysis, four acceleration time histories, which satisfy the Korean design standard response spectrum, are proposed. From the dynamic analysis using earthquake magnitudes from 6.4 to 7.9, it is found that horizontal displacements corresponding to earthquake magnitudes greater than 7 are two times larger than those with magnitude 6.5. Therefore, it can be stated that use of strong earthquakes, such as Miyagiken-ken-oki earthquake (Ofunato, $M_{JMA}=7.4$) and Tokachi-oki earthquake (Hachinohe, $M_{JMA}=7.9$), for the seismic design in Korea is not applicable, and may prove to be excessively conservative due to overestimated seismic force. From the dynamic analyses using the proposed acceleration time histories, effects of caisson quay wall dimension and the subsoil condition are investigated as well. The simplified design charts to evaluate horizontal displacements of caisson quay wall are also proposed based on earthquake magnitude 6.5 that is appropriate in Korea.

• Journal of Conservation Science
• /
• v.37 no.6
• /
• pp.626-637
• /
• 2021

The tomb complex of the royal family from the period of the Ungjin Baekje Kingdom (475 to 538 AD) in Gongju, Korea, contains the tomb of King Muryeong and other royal tombs. After the excavation of the tomb of King Muryeong in 1971, these tombs were opened up to the public, without the establishment of systems for their safety, conservation and management. The tombs have consequently experienced rapid environmental changes and suffered various damages. In this study, specific vulnerable parts inside the tombs were selected for deviation analysis using 3D scanning, and 3D image models were constructed on this basis. Progressive displacement was identified in tomb No. 5, and basic data for future investigations was acquired from tomb No. 6 and the tomb of King Muryeong. In the deviation analysis for the southern plastered wall of tomb No. 5, the damage was not found to exceed the ranges of ±18 mm and ±2 mm. However, the lintel stone was found to be sagging by 0.32 mm on average, and the distance between the walls to have increased by 0.36 mm on average. Direct water seepage occurring in tomb No. 5 is considered to be increasing the damage within the tomb, such as the dropping and sagging of the lintel. The 3D image models constructed in this study will play an important role as baseline data for future research, and can be used to discuss a secure conservation scheme for the tombs through cross-validation with precise measurement monitoring.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.13 no.3
• /
• pp.321-328
• /
• 2000

An improved formulation of thin-wailed curved beams with variable curvatures based on displacement field considering the second order terms of finite semitangential rotations is presented. From linearized virtual work principle by Vlasov's assumptions, the total potential energy is derived and all displacement parameters and the warping functions are defined at cendtroid axis. In developing the thin-walled curved beam element having eight degrees of freedom per a node, the cubic Hermitian polynomials are used as shape functions. In order to verify the accuracy and practical usefulness of this study, free vibrations and buckling analyses of parabolic and elliptic arche shapes with mono-symmetric sections are carried out and compared with the results analyzed by ABAQUS' shell element.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.11 no.4
• /
• pp.1192-1196
• /
• 2010

As the space for installation of automotive exhaust system is limited, the space should be optimized with relation to the endurance and shape of the system. Geometric nonlinear analysis was used and deflection of bellows was assumed 6mm. Obtained results are as follows; (1) The Von-Mises stress of bellows is increased with increase of thickness or radius of bellows linearly. (2) As the principal stress varies according to the radius of convolution, it is necessary to decide the optimal radius of convolution.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.13 no.4
• /
• pp.27-37
• /
• 1993

An efficient method to solve the minimum weight design problem for frame structures subjected to stress and displacement constraints is presented. The different cross-sectional shapes are conside red in order to apply engineering design in which usually required custom fabrication. To increase the efficiency of the optimization process, the structural response quantities(nodal forces, displacements) are linearized with respect to cross-sectional properties or their reciprocal, based on first order Taylor series expansion, while cross-sectional dimensions are considered as design variables. Numerical examples are performed and compared with other methods to demonstrate the efficiency and reliability of approximation method for frame structural optimization with different cross-sectional shapes. It is shown that the number of finite element analysis is greatly reduced and it leads to a highly efficient method of optimization of frame structures.