• The Journal of the Acoustical Society of Korea
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• v.17 no.1E
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• pp.66-69
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• 1998

Idle shake vibration characteristics of a vehicle are mainly influenced not only by the stiffnesses of the beam type structures such as pillars and rockers, but also by the stiffnesses of the joint structures, at which several beam structures are jointed together. In the early design stage of the car body structure a simple FE model has been used, in which joints are modeled as linear springs to represent the stiffnesses of the joint structures. In this paper a new modeling technique for the joint structure is presented using an equivalent beam, instead of using a spring. The modeling technique proposed is utilized to design optimal joint structures that meet the required vibration performance of the total vehicle structure.

• Journal of Korean Vacuum Science & Technology
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• v.3 no.1
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• pp.30-32
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• 1999

Electron beam trajectory simulation results on the high voltage FED with cone-type field emitters predict that the cross-talk phenomena would be seen due to the divergence of the electron beam. In this study, computer simulations with design of experiment technique and the SNU-FEAT program were carried out for five input parameters of the aperture focusing structure. The results tell that the focusing voltage is a dominant factor. And, the beam divergence index could be reduced to 10.7$\mu\textrm{m}$ with the aperture focusing structure, however, the operating voltage of the field emitter is predicted to increase by 40% maximum.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.2
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• pp.183-195
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• 2003

In this study, the method of the finite element modeling for free vibration control of beam-type smart structures with bonded plate-type piezoelectric sensors and actuators is proposed. Constitutive equations for the direct piezoelectric effect and converse piezoelectric effect of piezoelectric materials are considered. By using the variational principle, the equations of motion for the smart beam finite element are derived. The proposed 2-node beam finite element is an isoparametric element based on Timoshenko beam theory. Therefore, by analyzing beam-type smart structures with smart beam finite elements, it is possible to simulate the control of the structural behavior by applying voltages to piezoelectric actuators and monitoring of the structural behavior by sensing voltages of piezoelectric sensors. By using the smart beam finite element and constant-gain feed back control scheme, the formulation of the free nitration control for the beam structures with bonded plate-tyPe Piezoelectric sensors and actuators is proposed.

• Earthquakes and Structures
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• v.11 no.2
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• pp.281-295
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• 2016

This paper presents a study on a non-seismically designed reinforced concrete (RC) frame structure. The structure was a existing three-story office building constructed according to the 1990s practice in Vietnam. The 1/3 scaled down versions of structure was tested on a shake table to investigate the seismic performance of this type of construction. It was found that the inter-story drift and the overall behavior of structure meet the requirements of the actual seismic design codes. Then, nonlinear time history analyses are carried out using the fiber beam- column elements. The comparison between the experimental and simulation results shows the performance of the time history analysis models.

• Steel and Composite Structures
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• v.19 no.3
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• pp.735-757
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• 2015

Composite bonding steel plate (CBSP) is a newly developed type of structure strengthened technique applicable to the existing RC beam. This composite structure is applicable to strengthening the existing beam bearing high load. The strengthened beam consists of two layers of epoxy bonding prestressed steel plates and the RC beam sandwiched in between. The bonding enclosed and prestressed U-shaped steel jackets are applied at the beam sides. This technique is adopted in case of structures with high longitudinal reinforcing bar ratio and impracticable unloading. The prestress can be generated on the strengthening steel plates and jackets by using the CBSP technique before loading. The test results of full-scale CBSP strengthened beams show that the strength and stiffness are enhanced without reduction of their ductility. It is demonstrated that the strain hysteresis effect can be effectively overcome after prestressing on the steel plates by using such technique. The applied plates and jackets can jointly behave together with the existing beam under the action of epoxy bonding and the mechanical anchorage of the steel jackets. The simplified formulas are proposed to calculate the prestress and the ultimate capacities of strengthened beams. The accuracy of formulas was verified with the experimental results.

• Smart Structures and Systems
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• v.12 no.3_4
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• pp.327-344
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• 2013

Beam string structure (BSS) is introduced as a new type of hybrid prestressed string structures. The composition and mechanics features of BSS are discussed. The main principles of wavelet packet transform (WPT), principal component analysis (PCA) and support vector machine (SVM) have been reviewed. WPT is applied to the structural response signals, and feature vectors are obtained by feature extraction and PCA. The feature vectors are used for training and classification as the inputs of the support vector machine. The method is used to a single one-way arched beam string structure for damage detection. The cable prestress loss and web members damage experiment for a beam string structure is carried through. Different prestressing forces are applied on the cable to simulate cable prestress loss, the prestressing forces are calculated by the frequencies which are solved by Fourier transform or wavelet transform under impulse excitation. Test results verify this method is accurate and convenient. The damage cases of web members on the beam are tested to validate the efficiency of the method presented in this study. Wavelet packet decomposition is applied to the structural response signals under ambient vibration, feature vectors are obtained by feature extraction method. The feature vectors are used for training and classification as the inputs of the support vector machine. The structural damage position and degree can be identified and classified, and the test result is highly accurate especially combined with principle component analysis.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.4_2
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• pp.587-594
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• 2022

In the 2000s, a lot of cable-type grand bridges are being built in consideration of economic aspects such as the reduction of logistics costs and the distribution of traffic volume due to rapid economic development. In addition, because the recently installed grand bridges are designed in an aesthetic form that matches the surrounding environment as well as the original function of the road bridge, and serves as a milestone in an area and is used as an excellent tourism resource, attracting many vehicles and people, there is an urgent need for a safety structure that can ensure the safety of not only vehicles but also people. In order to make cable-stayed bridge safe on wind for additional five safety structures, main girder models with and without safety structures for wind-tunnel experiments was made, and wind tunnel experiments was carried out to measure aerodynamic force coefficients. Also, wind-resistant analyses of 3D cable-stayed bridge were performed on the basis of wind-tunnel experiment results. From the wind tunnel experiments for the aerodynamic force coefficients of main girder with five safety structures and the wind resistant analyses of cable-stayed bridge without safety structure and with safety structure, it was concluded that the best form of wind-resistant safety was shown in the order of mesh, standard, bracing, hollow, and closed type. And wind-resistant safety of cable-stayed bridge with hollow and closed type on design wind speed 68.0m/sec was not secured. Finally, as five safety structures are installed, maximum rate of stress increments was shown in the order of steel main beam, steel floor beam, concrete floor beam and cables.

• Journal of the Architectural Institute of Korea Planning & Design
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• v.36 no.3
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• pp.69-78
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• 2020

This study is designed to find out the role and relation of the Nemok-dori support members in order to clearly specify the structure of the Dapogye architecture which adopts the Nemok-dori. The dori at the eaves in the Dapogye architecture was expanded to include Oemok-dori, Jusim-dori and Nemok-dori in cooperation with the bracket. The Oemok-dori is used to lengthen the eaves and the Jusim-dori makes the reasonable transfer of loads while the Namok-dori contributes to the stability of the building through the balancing of the bracket. Nemok-dori is located higher than Oemok-dori or Jusim-dori, depending on the slope of Jangyeon and the distance of Chulmok. But as it is not directly supported by bracket or beam, it needs an independent support. The vertical support of Nemok-dori is selectively involved with Cheomcha, lower Jangyeo, support Wall and upper Jangyeo. As the time went by, the vertical height increased, thus making the omitted members less. The horizontal support of Nemok-dori is made in various ways. There are also special cases such as the Nemok-dori □ type chain structure for small rectangular buildings, the 'Nemok-dori = Jung-dori' type for the buildings having small sides and the 'Nemok-dori = Meongechangbang' type appearing on the lower part of the Bankanmulrim type middle height buildings. The horizontal support of Nemok-dori usually uses either the support of the Toeryang type member, the support of beam directed Hwaban or the support through overlaying of internal Jegong. As the time went by and the number and distance of Chulmok increased, the multiple support structures acted together rather than as one support structure. Nemok-dori got stabilized as it has both the vertical and horizontal supports and this support structure also has he role of decoration.

• Special Issue of the Society of Naval Architects of Korea
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• 2005.06a
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• pp.84-89
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• 2005

The double hull VLCC(Very Large Crude Oil Tanker) have been designed to have each four(4) longitudinal bulkheads and transverse bulkheads in general. Actually, the inside longitudinal bulkheads among four(4) longitudinal bulkheads, which are extended up to the end of the aft cargo hold for continuity of the members, have been designed with knuckled type inboard due to the narrowed hull shape at bottom region, but sometimes the straight type of longitudinal bulkheads were adopted based on the degree of the hull lines shape. However, regardless the type of longitudinal bulkheads, inside and outside longitudinal bulkheads conflict each other in aft cargo hold region This makes the structure more complex thus giving difficulties to structural design and production. Recently, a vessel of straight type was reported to have cracks on bracket end and tripping bracket toe in aft cargo hold region. As a solution to this problem, in designing the first 60m Beam VLCC, DSME developed a new cargo hold structure which is good in production and structural point of view by structural strength and fatigue analysis of fore and aft cargo hold.

• Steel and Composite Structures
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• v.26 no.4
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• pp.463-471
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• 2018

The bolted end-plate beam-column connections have been widely used in steel structure and composite structure because of its excellent seismic performance. In this paper, the end-plate bolted connection is applied in the concrete structure, A new-type of fabricated beam-column connections with end-plates is presented, and steel plate hoop is used to replace stirrups in the node core area. To study the seismic behavior of the joint, seven specimens are tested by pseudo-static test. The experimental results show that the new type of assembly node has good ductility and energy dissipation capacity. Besides, under the restraint effect of the high-strength stirrup, the width of the web crack is effectively controlled. In addition, based on the analysis of the factors affecting the shear capacity of the node core area, the formula of shear capacity of the core area of the node is proposed, and the theoretical values of the formula are consistent with the experimental value.