• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.2
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• pp.185-198
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• 2016

In this work, experimental errors from an impact hammer test were investigated to develop a statistic-based technique for updating a finite element model. Digital signal processing was analyzed by using theoretical models and experiments when errors occurred during the experimental procedure. First, the duration time and peak level of the excitation signal, the stiffness and position of elastic springs connecting the specimen as well as the support, position and mass of the accelerometer were considered as error factors during the experiment. Then the picket fence effect, leakage, and exponential window function were considered as candidate error factors during the digital signal processing. Finally, methods to reduce errors are suggested.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.3
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• pp.201-214
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• 2013

Lattice girders are widely used as a substitute for H-steel ribs at domestic tunnels. However, lattice girders have a weak point in terms of the support capacity compare to H-steel ribs because of the lower stiffness and the weakness of the welded parts. To improve the weakness of the lattice girder, reformed lattice girders are developed in Korea by adding one more spider and having flat welded surface. Laboratory tests and field measurements were performed for the original and the reformed lattice girders to evaluate the performance of the reformed lattice girders. According to the laboratory compression test, reformed lattice girders have 16% higher load bearing capacity than that of original lattice girders. Reformed lattice girders are more stable than original lattice girders because reformed lattice girders tend to bend less according to the field measurements.

• Journal of Korean Tunnelling and Underground Space Association
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• v.6 no.4
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• pp.279-290
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• 2004

The differential quadrature method (DQM) for a system of coupled differential equations governing the elastic stability of thin-walled curved members is presented, and is applied to computation of the eigenvalues of out-of-plane buckling of curved beams subjected to uniformly distributed radial loads including a warping contribution. Critical loads with warping, which were found to be significant, are calculated for a single-span wide-flange beam with various end conditions, opening angles, and stiffness parameters. The results are compared with the exact methods available. New results are given for the case of both ends clamped and clamped-simply supported ends without comparison since no data are available The differential quadrature method gives good accuracy and stability compared with previous theoretical results.

• International Journal of Highway Engineering
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• v.13 no.1
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• pp.229-237
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• 2011

This study was conducted to investigate the early-age performance of precast pavements constructed by replacing existing asphalt pavements for a bus stop section in urban bus only lanes. The behavior monitoring items included the differences in the levels between asphalt and precast pavements at the entrance and exit of the precast pavement, joint widths and level differences between precast slabs, slab settlement, and skid resistance at the slab surface. The applicability of diamond grinding techniques was also investigated. The results of this study showed that the slab level, joint width, settlement, and skid resistance were not much changed as time passed, which implied that the precast pavements stably sustained vehicle loads. It was also found that employing diamond grinding could much improve the leveling between precast slabs and the surface skid resistance.

• Journal of Korean Society of Steel Construction
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• v.12 no.1 s.44
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• pp.75-82
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• 2000

Recently, many studies on connections in steel structures have been performed. In practice, designers assume that the connection is a rigid- or pinned-one, however, actually the connection behaves as partially restrained one, neither fully restrained nor unrestrained. This paper concentrates on the behavior of double angle connections in the field of semi-rigid connections. The behavior of double angle connection. induced by abrupt axial tension load or by collapsed brace in medium or low rise building, is analyzed by 3D nonlinear finite element method using ABAQUS(ver 5.8). From the analytic results. a simplified model of double angle and a rotational stiffness at the corner of the angle are derived, which are fundamentally used for understanding the behavior of the double angle connection.

• Journal of the Earthquake Engineering Society of Korea
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• v.2 no.2
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• pp.13-22
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• 1998

This paper summarizes a study on the application of the friction pendulum system in bridge seismic isolation. Shaking table tests have been carried out on a model structure isolated with F.P.S and the obtained structural responses are compared to those of non-isolated. It can be concluded the F.P.S increases the earthquake resistance capacity of the isolated structure. It is also found that the stiffness of bearing, being controlled by the radius of curvature of the spherical sliding interface, is unaffected by the amplitude of the input excitation. Furthermore, the coefficient of sliding friction is velocity dependent so that in weak excitation the sliding velocity is low and, accordingly, the mobilized friction force is less than the one mobilized in strong excitation. Also, the frictional properties of the bearings remain markedly stable after extensive testing, and the permanent displacements are small and not cumulative in successive earthquakes.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.4
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• pp.245-253
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• 2020

In this study, natural frequencies are compared using several pile-soil interaction (PSI) models to evaluate the effects of each model on resonance safety checks for a monopile type of wind turbine structure. Base spring, distributed spring, and three-dimensional brick-shell models represented the PSIs in the finite element model. To analyze the effects of the PSI models on a natural frequency, after a stiffness matrix calculation and Winkler-based beam model for base spring and distributed spring models were presented, respectively; natural frequencies from these models were investigated for monopiles with different geometries and soil properties. These results were compared with those from the brick-shell model. The results show that differences in the first natural frequency of the monopiles from each model are small when the small diameter of monopile penetrates hard soil and rock, while the distributed spring model can over-estimate the natural frequency for large monopiles installed in weak soil. Thus, an appropriate PSI model for natural frequency analyses should be adopted by considering soil conditions and structure scale.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.217-220
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• 2008

A modified FRP-concrete composite deck applicable to cable stayed bridge with long girder-to-girder span is proposed, and its design and economical efficiency are presented. The existing FRP-concrete composite deck has low section stiffness due to adoption of GFRP panel with low elastic modulus, which arrives at difficulty in meet of serviceability limit such as deck deflection. So a new-type FRP-concrete composite deck, named precast FRP-concrete deck, is developed by extensioning concrete at the both ends of FRP-concrete composite deck, which brings the effect of reduction of net span length of deck. Compared to the existing FRP-concrete composite deck this modified deck has the advantage of increasing span length but slightly increases self weight. For this type of deck the section optimization is carried out for the cases of simply supported on girder and composite to girder. The optimized deck was applied to cable stayed bridge with a center span length of 540m, and as a result it is verified that PFC deck can be applied efficiently to cable stayed bridge due to reduction of quantity of upper structure.

• Magazine of the Korea Concrete Institute
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• v.8 no.3
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• pp.187-195
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• 1996

A finite element formulation based on the CFT(Compression Field Theory), considering the effect of compression softening in cracked concrete, and macro-scopic and rotating crack models etc., was presented for the nonlinear behaviour of structural concrete. Considering the computational efficency and the ability of modelling the post-ultimate behaviour as major concerns, the Incremental displacement solution algorithm involving initial material stiffnesses and the relaxation procedure for fast convergence was adopted and formulated in a type of 8-noded quadrilateral isoparametric elements. The analysis program NASCOM(Non1inear Analysis of Structural Concrete by FEM : Monotonic Loading) developed in this way enables the predictions of strength and deformation capacities in a full range, crack patterns and their corresponding widths, and yield extents of reinforcement. As the verification purpose of NASCOM, the predictions were made for Bhide's Panel(PB21) and Leonhardt's deep beam tests. The predicted results shows somewhat stiff behaviour for the panel test, and vice versa for deep beam tests. More refining process would be necessary hereafter in terms of more accurately simulating the effects of tension-stiffening and compression softening in concrete.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.6
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• pp.665-674
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• 2015

A TSL (Thin Spray-on Liner) which consists of polymers has a higher initial strength, faster construction time and higher waterproofing performance than the conventional cementitious shotcrete. Main supporting mechanism of TSL is the adhesion and tensile strength which is distinct from the conventional shotcrete. Even though highly in demand due to its outstanding characteristics, TSL is not yet well-known support material. In this study, to evaluate contact behavior of TSL, numerical analysis was performed with comparing result from laboratory tests. From the analysis, cohesive behavior at the contact surface between TSL and rock can be evaluated by using combination of cohesive and the damage model. In addition, results show that the cohesive stiffness controled slope between force and displacement, the fracture energy controled level of force at the contact.