• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.4
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• pp.452-459
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• 2019

In order to design and manufacture structures such as a guided missile, assembly process with fastener is an essential method of fabrication. In this study, the dynamic characteristics of a cylindrical structure with bolted joints were studied using experimental methods. The change of the natural frequency of the structure with the change of the fastening method and the tightening torque were measured by the test and the finite element analysis was performed using the stiffness model of the fastening part according to the fastening method and compared with the test results.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.199-202
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• 2003

The dynamic characteristics of composite tool bars depend on the clamping conditions such as clamping force, stiffness and surface characteristics of clamping parts as well as the basic structures. Therefore, in this work, the effects of clamping part conditions on the dynamic characteristics of cantilever type composite machine tool structures with clamped joint were investigated because the cantilever type machine tool structures are ideal cases for composite application to increase the natural frequency and damping of structures. New design of the clamping part was developed in order to improve shear properties of the clamping part and dynamic characteristics of composite tool bars. From FE analysis and Impulse response tests, dynamic characteristics were obtained with respect to the clamping part conditions of the new design.

• Steel and Composite Structures
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• v.21 no.3
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• pp.661-677
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• 2016

The quasi static test of the steel reinforced concrete (SRC) bridge piers and rigid frame arch bridge structure with SRC piers was conducted in the laboratory, and the seismic performance of SRC piers was compared with that of reinforced concrete (RC) bridge piers. In the test, the failure process, the failure mechanism, hysteretic curves, skeleton curves, ductility coefficient, stiffness degradation curves and the energy dissipation curves were analyzed. According to the $M-{\Phi}$ relationship of fiber section, the three-wire type theoretical skeleton curve of the lateral force and the pier top displacement was proposed, and the theoretical skeleton curves are well consistent with the experimental curves. Based on the theoretical model, the effects of the concrete strength, axial compression ratio, slenderness ratio, reinforcement ratio, and the stiffness ratio of arch to pier on the skeleton curve were analyzed.

• Advances in concrete construction
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• v.9 no.2
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• pp.115-123
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• 2020

The performance of steel fiber reinforced geopolymer concrete beam column joints under cyclic loading was investigated. The volume fraction of fibers considered were 0.25% (19.62 kg/㎥), 0.5% (39.24 kg/㎥), 0.75% (58.86 kg/㎥) and 1% (78.48 kg/㎥). A total of fifteen specimens were prepared and tested under reverse cyclic loading. Test results were analyzed with respect to first crack load, ultimate load, energy absorption capacity, energy dissipation capacity, stiffness degradation and load deflection behavior. Test results revealed that the addition of steel fibers enhanced the performance of geopolymer concrete beam column joints significantly. The joints were analyzed using finite element software ANSYS. The analytical results were found to compare satisfactorily with the experimental values.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.6
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• pp.88-97
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• 1998

Compliance elements such as bushings of a suspension system play a crucial role in determining the ride and handling characteristics of the vehicle. In this paper, a general procedure is proposed for the optimum design of compliance elements to meet various design targets. Based on the assumption that the displacements of elastokinematic behavior of a suspension system under external forces are very small, linearized elastokinematic equations in terms of infinitesimal displacements and joint reaction forces are derived. Directly differentiating the linear elastokinematic equations with respect to design variables associated with bushing stiffness, sensitivity equations are obtained. The design process for determining the bushing stiffness using sensitivity analysis and optimization technique is demonstrated.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.338-345
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• 2005

Recently, surface-wave methods have been widely used for site investigation due to economic advantage and improved reliability. Specially, the Spectral-Analysis-of-Surface-Wave (SASW) method has been used to evaluate soil properties in geotechnical engineering. In determination of subgrade stiffness by SASW measurements, only the vertical Rayleigh waves have been used. This study proposed a framework to determine shear-wave velocity profiles by using vertical and horizontal Rayleigh waves and Love wave all together. In addition, the Common-Array-Profiling(CAP) SASW method was employed, which subgrade stiffness of profile the local material under two fixed receivers. The procedure proposed in this study was verified by comparing the shear-wave velocity profiles with the shear-wave velocity profiles of downhole testing at two geotechnical sites.

• Earthquakes and Structures
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• v.22 no.2
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• pp.203-218
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• 2022

In this paper, quasi-static tests were carried out on three prefabricated reinforced concrete column-steel beam (RCS) sub-assemblages with floor slabs and one comparison specimen without floor slab. The effects of axial compression and floor slab on the seismic performance were studied, and finite element simulations were conducted using ABAQUS. The results showed that the failure of prefabricated RCS sub-assemblages with floor occurred as a joint beam and column failure mode, while failure of sub-assemblages without floor occurred due to beam plastic hinge formation. Compared to the prefabricated RCS sub-assemblages without floor slab, the overall stiffness of the sub-assemblages with floor slab was between 19.2% and 45.4% higher, and the maximum load bearing capacity increased by 26.8%. However, the equivalent viscosity coefficient was essentially unchanged. When the axial compression ratio increased from 0.24 to 0.36, the hysteretic loops of the sub-assemblages with floor became fuller, and the load bearing capacity, ductility, and energy dissipation capacity increased by 12.1%, 12.9% and 8.9%, respectively. Also, the initial stiffness increased by 10.2%, but the stiffness degradation accelerated. The proportion of column drift caused by beam end plastic bending and column end bending changed from 35% and 46% to 47% and 36%, respectively. Comparative finite element analyses indicated that the numerical simulation outcomes agreed well with the experimental results.

• PNF and Movement
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• v.16 no.1
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• pp.1-6
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• 2018

Purpose: Myofascial release (MFR) is an effective treatment for improving muscle stiffness and balance in neurological patients. This study examined long-term effects of MFR on the balance ability of stroke patients. Methods: MFR using a tennis ball was applied to the lower extremity and sacroiliac joint of the affected side of four stroke patients. The four subjects performed the Berg balance scale (BBS) and Timed up and go (TUG) test at the beginning of an 8-week intervention, directly after the intervention, and 2 years later. Results: The BBS scores indicated a trend toward maintenance of balance (p=0.05), but there was no difference in the TUG time (p=0.47). Conclusion: MFR may be a clinically meaningful intervention to maintain balance in stroke patients over a long period. However, the sample size in this study was too small to draw general conclusions. A larger study with more participants is needed.

• Structural Engineering and Mechanics
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• v.12 no.4
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• pp.397-408
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• 2001

Bolted connections are used commonly in the precast reinforced concrete structures. In such structures, to perform structural analysis, behaviour of connections must be determined. In this study, elastic rotation stiffness of semi-rigid bolted beam connections, applied in industrial precast structures, are determined by finite element methods. The results obtained from numerical solutions are compared with an experimental study carried out for the same connections. Furthermore, stress distributions of the connection zone are determined and a reinforcement scheme is proposed. Thus, a more appropriate reinforcement arrangement for the connection zone is enabled. The connection joint of the prefabricated frame is described as rigid, hinged or elastic, and a static analysis of the frame system is performed for each case. Values of bending moments and displacements obtained from the three solutions are compared and the effects of elastic connection are discussed.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1999.10a
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• pp.396-403
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• 1999

This experimental study investigates the hysterestic behavior of traditional timber frames subjected to lateral loads. Prototype frames for this study were selected from one of typical national treasures for timber structures in Korea. For simplicity roof structures and braket systems were excluded from specimens and the joint behavior of beam-to-column system were presumed to have crucial effect on their global behavior. The experimental observation showed stiffness degradation and slip after experiencing initial yield and the first cycle at a new larger displacement due to inherent gaps in traditional timber connection and gradual indentation of interfaces, The cyclic behaviors of all specimens were similar to those os modern timber frames with bolt and nail connections. Additional structural members such as an upper beam and clay-filled wall increased the initial stiffness strength and energy dissipation. It is expected that collapse of Korean traditional timber frames under lateral load is mainly caused from P-$\Delta$ effects rather than local member failure.