• Structural Engineering and Mechanics
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• v.29 no.6
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• pp.659-671
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• 2008

A procedure to analyse the space frame structure fixed at base as well as resting on sliding bearing using total or absolute displacement in dynamic equation is developed. In the present method, the effect of ground acceleration is not considered as equivalent force. Instead, the ground acceleration is considered as a known value in the acceleration vector at degree of freedom corresponding to base of the structure when the structure is in non-sliding phase. When the structure is in sliding phase, only a force equal to the maximum frictional resistance is applied at base. Also, in this method, the stiffness matrix, mass matrix and the damping matrix will not change when the structure enters from one phase to another. The results obtained from the present method using absolute displacement approach are compared with the results obtained from the analysis of structure using relative displacement approach. The applicability of the analysis is also demonstrated to obtain the response of the structure resting on sliding bearing with restoring force device.

• Journal of Korean Tunnelling and Underground Space Association
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• v.8 no.2
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• pp.101-113
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• 2006

Arching effect occurs around the unsupported excavation surface near to tunnel face when a tunnel is excavated in a stable rock mass. If a weak fracture zone exists in front of tunnel face, a displacement occurs between tunnel face and weak fracture zone due to stress concentration. If three-dimensional absolute coordinates (longitudinal, transverse, vertical direction) is measured at tunnel face by geodetic method, the ground change in front of the tunnel face can be predicted by analysing three-dimensional absolute displacement. The purpose of this study is to verify the analysis method of three-dimensional absolute displacement by comparing the trend of displacement ratio at crown and sidewall of tunnel and the influence line/trend line of crown settlement compared with TSP results in the same section.

• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.3
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• pp.229-240
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• 2007

The 3D absolute displacement monitoring system has been developed to analyze the tunnel convergence measured under construction of underground structures and to manage effectively the measured data. The system is comprised of the total station, the anchor-typed target pin and the 3D absolute displacement measurement and management program. In this paper, the types and specifications of the 3D total station were presented. The anchor-typed target pin, an improved model of traditional one, was developed and its sightable distance and measurement accuracy were checked by field tests. Also a 3D absolute displacement measurement and management program, TEMS 3D, was developed to provide some analysis tools including the trend and influence lines. L/C ratio, S/C ratio and the like. The developed system was applied the construction stage of a railway tunnel for testing purpose. It is verified that the developed system is capable of predicting weak zones ahead of tunnel face by comparing with results of TSP (Tunnel Seismic Prediction) survey.

• Journal of Mechanical Science and Technology
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• v.19 no.spc1
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• pp.283-291
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• 2005

Accurate seismic analyses of large deformable moving structures are still unsolved problems in the field of earthquake engineering. In order to analyze these problems, the nonlinear finite element method formulated by the absolute nodal coordinate approach is noticed. Because, this formulation has several advantages over the standard procedures on mass matrix, elastic forces and damping forces in the case of large displacement problems. But, it has not been fully studied to build frame structure models by using beam elements in the absolute nodal coordinate formulation. In this paper, we propose the connecting method of the beam elements formulated by the absolute nodal coordinate. The coordinate transformation matrix of this element is introduced into the frame structure. This beam element has the characteristic that the mass matrix and bending stiffiness matrix are constant even if in the case of large displacement problems, and this characteristic is being kept after the transformation. In order to verify the proposed method, we show the numerical simulation results of frame structures for a vibration problem and a large displacement problem.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.1
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• pp.72-78
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• 2009

We have developed a current range extension method to obtain the ratio error and phase displacement of a current transformer (CT) by using absolute evaluation method and two different CTs. The method was applied to CTs under test with the current ratios in the range of 5,000 A / 1 A - 20,000 A / 1 A. The ratio error and phase displacement of the CT under test obtained in this study are consistent with those measured at the national institute in Germany using the same CT under test within an expanded uncertainty (k = 2) in the overall current ratios.

• Geomechanics and Engineering
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• v.11 no.1
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• pp.41-58
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• 2016

This paper focuses on the deformation behavior of tunnels crossing a weak zone in conventional tunneling. A three-dimensional finite element model was adopted that allows realistic modeling of the tunnel excavation and the support installation. Using the 3D FE model, a parametric study was conducted on a number of tunneling cases with emphasis on the spatial characteristics of the weak zone such as the strike and dip angle, and on the initial stress state. The results of the analyses were thoroughly examined so that the three-dimensional tunnel displacements at the tunnel crown and the sidewalls can be related to the spatial characteristic of the weak zone as well as the initial stress state. The results indicate that the effectiveness of the absolute displacement monitoring data as early warning indicators depends strongly on the spatial characteristics of the weak zone. It is also shown that proper interpretation of the absolute monitoring data can provide not only early warning for a weak zone outside the excavation area but also information on the orientation and the extent of the weak zone. Practical implications of the findings are discussed.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.4
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• pp.431-436
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• 2008

We have extended an absolute evaluation method to obtain the ratio error and phase displacement of a current transformer (CT) up to primary current of 40,000 A by measuring four parameters of equivalent circuit in CT. The method was applied to CTs under test with the current ratios in the range of 5,000 A / 5 A - 40,000 A / 5 A. The ratio error and phase displacement of the CTs under test obtained in this study are consistent with those measured at the national institutes in Canada and Germany using the same CTs under test within an expanded uncertainty (k = 2) in the overall current ratios.

• The Journal of Engineering Geology
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• v.17 no.4
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• pp.567-576
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• 2007

In order to assess the on-site applicability of 3D absolute displacement monitoring of tunnel using digital photogrammetry, the displacement of the optical target placed at the measurement section was investigated, as planned in the OO tunnel construction site. The targets on 3 measurement lines only were considered for each point of measurement for the reconstruction of 3D cubic model for the digital vision monitoring. For each 3D model, 3 or more images have to be obtained at each point. On the last 2 measurement lines, 6 targets (crown, left and right walls) were continuously overlapped to construct 3D models so that 6 or more apices can be shared by 2 3D models. In order to compare the measurement methods of 3D absolute displacements in tunnel excavation, i. e, total station and digital image measurement, both the digital image measurement and optical measurement were conducted for 10 times in the same work section. The time and measurement results of both methods were compared.

• Journal of the Korean Society of Safety
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• v.30 no.4
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• pp.99-105
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• 2015

In this study, displacement estimation algorithm, which is not requiring an absolute reference point unlike the conventional displacement measurement method, is developed using the geophone. To estimate displacement of the bridge, measured velocity time signal is integrated in the frequency domain. And, the estimated displacement is compared with the measured result using a conventional method. Based on the dynamic field test results, it was found that the estimated displacement by the present algorithm is similar to that of a conventional method. The displacement estimation algorithm proposed in this paper can be effectively applied to measure the displacement of a structure, which is difficult to install a displacement transducer at the fixed point.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.2
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• pp.153-159
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• 2008

We have developed an absolute evaluation method to obtain the ratio error and phase displacement of a current transformer (CT) without any precise standard CT by measuring four parameters in a CT equivalent circuit. The excitation admittance in the CT equivalent circuit can be obtained by employing standard resistors with negligible reactive component. The secondary leakage impedance in the CT equivalent circuit can be measured using a universal impedance bridge. The method was applied to CTs under test with the wide current ratios in the range of 5 A / 5 A - 5,000 A / 5 A and 5 A / 1 A - 5,000 A / 1 A. The ratio error and phase displacement of the CT under test obtained in this study are consistent with those measured at the national institute in Canada using the same CT under test within an expanded uncertainty (k = 2) in the overall current ratios.