• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.718-723
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• 2017

When structural analysis modelling methods of practical fields are investigated, a slab is generally modeled by a finite element mesh using plate elements and a shear wall is modeled using a shell element or wall element for 3-D structural analysis. The point worthy of notice in this practice is that a shear wall is modelled using only one wall or shell element divided by floors and column lines to produce structural models. The modeling method like this can cause analysis errors according to the type of computer programs in use, and these errors reduce the reliability of the analysis results. Therefore, to secure the reliability of structural analysis, studies of the causes of errors and finding reasonable modeling methods are necessary. In this study, the causes of analysis errors according to the modelling methods of a shear wall, which are used in practical fields, were investigated and some considering matters for modelling a shear wall are presented to reduce the analysis errors on these analysis results.

• Journal of Korean Society of Steel Construction
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• v.12 no.6
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• pp.661-670
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• 2000

To investigate the characteristics of the dynamic response of long-span cable-stayed bridges due to various dynamic loadings likes moving traffic loads, two different 3-D cable-stayed bridge models are considered in this study. Two models are exactly the same in structural configurations but different in finite element discretization. Modal analysis is conducted using the deformed dead-load tangent stiffness matrix. A new concept was presented by using divided a cable into several elements in order to study the effect of the cable vibration (both in-plane and swinging) on the overall bridge dynamics. Futhermore case of asymmetric traffic loading clustered in one direction are also considered to study the torsional response of the bridge. The result of this study demonstrates the importance of cable vibration on the overall bridge dynamics.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.3
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• pp.75-86
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• 1999

An analysis model is developed to evaluate the dynamic responses of a bridge system under seismic excitations, in which pounding actions between girders are considered in addition to other phenomena such as nonlinear pier motion, rotational and translational motions of foundations. The model also considers the abutment and restrainers connecting adjacent girders to prevent the unseating failures. Using the developed model, the longitudinal dynamic behaviors of a bridge system are examined for various peak ground accelerations, and the effects of the applied restrainers are investigated. It is found that the restrainers reduce the relative displacement with the shorter clearance length as well as the higher stiffness of the restrainers for moderate excitations. However, in the region with strong excitations the restrainers may yield due to the large relative displacement. Therefore, the extension of support length in addition to restrainers may need to prevent the unseating failure more effectively.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.1
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• pp.55-66
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• 1999

This paper presents an analytical prediction of the hysteresis behavior of reinforced concrete long column with rectangular section under the cyclic loading state. The mechanical characteristic of cracked concrete and reinforcing bar in concrete has been modeled, considering the bond effect between reinforcing bar and concrete, the effect of aggregate interlocking at crack surface and the stiffness degradation after the crack has taken place. The strength increase of concrete due to the lateral confining reinforcement has been also taken into account to model the confined concrete. The formulation of these models for concrete and reinforcing bar has been based on the smeared crack concept that the stress-strain relationship of reinforced concrete element would be defined using the average values. In addition to the material nonlinear properties, the algorithm for large displacement problem that may give an additional deformation has been formulated using total Lagrangian formulation. The analytically predicted behavior was compared with test result and they showed good agreement in overall behavior.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.867-870
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• 2008

Flat plate system has many advantages, story height reduction, a term of works shortening and changeableness of space, etc. However structures become a tendency of higher stories and when we use RC column, the size of column grow larger. For this reason the use of CFT column is increasing more and more. Accordingly, this study carried out the nonlinear finite element analysis. As a result of analysis moment strength of the connection increased but ductility decreased as the top reinforcement ratio in th effective width increased. And moment strength and ductility of the connection decreased as gravity load ratio decreased. In the case that shearhead length is not more than 0.27m, the effectiveness of shearhead length on the moment strength and ductility of the connection were small relatively to other variables. Initial stiffness and moment strength of connection increased as slab thickness increased

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.968-976
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• 2004

In the paper, deformation characteristics of fiber-mixed-soils, mixed polypropylene staple fibers of 0.3% fiber content with sands of various gradation, and their effectiveness of reinforcement were evaluated. A series of Resonant Column tests were performed with specimens prepared with varying Uniformity Coefficient and constant Curvature Coefficient. Maximum shear moduli 01 fiber-mixed-soils were increased by up to 30% and modulus reduction was also restrained in nonlinear range. Normalized shear modulus reduction curves of fiber-mixed-soils shift close to the upper limit of Seed curd Idriss's curves and are located within narrower band than those of unmixed soils, which proves the effectiveness on stiffness increment by reinforcing soils with fibers.

• Journal of the Earthquake Engineering Society of Korea
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• v.17 no.1
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• pp.1-10
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• 2013

In order to predict inelastic displacement response without nonlinear dynamic analysis, the equal displacement rule can be used for the structures with longer natural periods than the characteristic period, $T_g$, of earthquake record. In the period range longer than $T_g$, peak displacement responses of elastic systems are equal or larger than those of inelastic systems. In the period range shorter than $T_g$, opposite trend occurs. In the equal displacement rule, it is assumed that peak displacement of inelastic system with longer natural period than $T_g$ equals to that of elastic system with same natural period. The equal displacement rule is very useful for seismic design purpose of structures with longer natural period than $T_g$. In the period range shorter than $T_g$, the peak displacement of inelastic system can be simply evaluated from the peak displacement of elastic system by using the inelastic displacement ratio, which is defined as the ratio of the peak inelastic displacement to the peak elastic displacement. Smooth hysteretic behavior is more similar to actual response of real structural system than a piece-wise linear hysteretic behavior such as bilinear or stiffness degrading behaviors. In this paper, the inelastic displacement ratios of the smooth hysteretic behavior system are evaluated for far-fault and near-fault earthquakes. The simple formula of inelastic displacement ratio considering the effect of $T_g$ is proposed.

• Journal of Mechanical Science and Technology
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• v.17 no.7
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• pp.999-1010
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• 2003

Uninterrupted power supply has become indispensable during the maintenance task of active electric power lines as a result of today's highly information-oriented society and increasing demand of electric utilities. This maintenance task has the risk of electric shock and the danger of falling from high place. Therefore it is necessary to realize an autonomous robot system using electro-hydraulic manipulators because hydraulic manipulators have the advantage of electric insulation and power/mass density. Meanwhile an electro-hydraulic manipulator using hydraulic actuators has many nonlinear elements, and its parameter fluctuations are greater than those of an electrically driven manipulator. So it is relatively difficult to realize not only stable contact work but also accurate force control for the autonomous assembly tasks using hydraulic manipulators. In this paper, the robust force control of a 6-link electro-hydraulic manipulator system used in the real maintenance task of active electric lines is examined in detail. A nominal model for the system is obtained from experimental frequency responses of the system, and the deviation of the manipulator system from the nominal model is derived by a multiplicative uncertainty. Robust disturbance observers for force control are designed using this information in an H$\_$$\infty$/ framework, and implemented on the two different setups. Experimental results show that highly robust force tracking by a 6-link electro-hydraulic manipulator could be achieved even if the stiffness of environment and the shape of wall change.

• Earthquakes and Structures
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• v.18 no.5
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• pp.527-542
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• 2020

In traditional eccentrically braced steel frames, damages and plastic deformations are limited to the links and the main structure members are required tremendous sizes to ensure elasticity with no damage based on the force-based seismic design method, this limits the practical application of the structure. The high strength steel frames with eccentric braces refer to Q345 (the nominal yield strength is 345 MPa) steel used for links, and Q460 steel utilized for columns and beams in the eccentrically brace steel frames, the application of high strength steels not only brings out better economy and higher strength, but also wider application prospects in seismic fortification zone. Here, the structures with four type eccentric braces are chosen, including K-type, Y-type, D-type and V-type. These four types EBFs have various performances, such as stiffness, bearing capacity, ductility and failure mode. To evaluate the seismic behavior of the high strength steel frames with variable eccentric braces within the similar performance objectives, four types EBFs with 4-storey, 8-storey, 12-storey and 16-storey were designed by performance-based seismic design method. The nonlinear static behavior by pushover analysis and dynamic performance by time history analysis in the SAP2000 software was applied. A total of 11 ground motion records are adopted in the time history analysis. Ground motions representing three seismic hazards: first, elastic behavior in low earthquake hazard level for immediate occupancy, second, inelastic behavior of links in moderate earthquake hazard level for rapid repair, and third, inelastic behavior of the whole structure in very high earthquake hazard level for collapse prevention. The analyses results indicated that all structures have similar failure mode and seismic performance.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.6
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• pp.47-54
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• 2001

Unbond brace hysteretic dampers are generally used to prevent or decrease structural damage in building structures subjected to strong earthquake by its energy dissipating hysteretic behavior. In the study, a straightforward design procedure for unbond brace hysteretic dampers was developed. The required amount of equivalent damping to satisfy given performance acceptance criteria was obtained conveniently based on the capacity spectrum method without carrying out time-consuming nonlinear dynamic time history analysis. Then the size of the unbond braces is determined from the required equivalent damping. Parametric study has been performed for the design variables such as natural period, yield strength, the stiffness after the first yield stress of the unbond brace. The procedure was applied to 5-story and 10-story steel frames for verification of the proposed method. According to the earthquake time history analysis results, the maximum displacement of the model structure with unbond braces supplied in accordance with the proposed method corresponds well with the given target displacement.