• Journal of the Korea Concrete Institute
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• v.14 no.4
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• pp.467-473
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• 2002

The purpose of this study is to investigate the inelastic behavior and ductility capacity of reinforced concrete frame subjected to cyclic lateral load and to provide result for developing improved seismic design criteria. A computer program named RCAHEST(Reinforced Concrete Analysis in Higher Evaluation System Technology) for the analysis of reinforced concrete structures was used. Material nonlinearity is taken into account by comprising tensile, compressive and shear models of cracked concrete and a model of reinforcing steel. The smeared crack approach is incorporated. The strength increase of concrete due to the lateral confining reinforcement has been taken into account to model the confined concrete. In boundary plane at which each member with different thickness is connected local discontinuous deformation due to the abrupt change in their stiffness can be taken into account by introducing interface element. The effect of number of load reversals with the same displacement amplitude has been also taken into account to model the reinforcing steel. The proposed numerical method for the inelastic behavior and ductility capacity of reinforced concrete frame subjected to cyclic lateral load is verified by comparison with reliable experimental results.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.1 s.71
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• pp.73-83
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• 2006

The failure mechanism of a hollow bridge deck which is made of fiber reinforced polymer (FRP) to improve its durability and life time significantly is investigated using both experiments and analyses. While the Load-displacement behavior of the deck in the longitudinal direction is almost linear just before the failure, the behavior in the transverse direction shows a strong nonlinearity even in its initial response with relatively small magnitude of loads. We found that the nonlinearity is due to the imperfection of the connection between the flange and the web; a plastic deformation can t라e place in the connection. The argument is demonstrated using a simple structural model in which a rigid plastic hinge is introduced to the connection. We also checked the contribution of the delamination mechanism to the failure. But the delamination is not the main mechanism which initiates and causes the failure of the bridge deck. In order to improved the structural behavior of the deck in the transverse direction, we suggested that the empty space of the bridge deck is filled with a foam and confirmed the improved behavior by a numerical analysis.

• Steel and Composite Structures
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• v.21 no.5
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• pp.1121-1144
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• 2016

This paper presents a displacement-based finite element procedure for second-order distributed plasticity analysis of planar steel frames with semi-rigid beam-to-column connections under static loadings. A partially strain-hardening elastic-plastic beam-column element, which directly takes into account geometric nonlinearity, gradual yielding of material, and flexibility of semi-rigid connections, is proposed. The second-order effects and distributed plasticity are considered by dividing the member into several sub-elements and meshing the cross-section into several fibers. A new nonlinear solution procedure based on the combination of the Newton-Raphson equilibrium iterative algorithm and the constant work method for adjusting the incremental load factor is proposed for solving nonlinear equilibrium equations. The nonlinear inelastic behavior predicted by the proposed program compares well with previous studies. Coupling effects of three primary sources of nonlinearity, geometric imperfections, and residual stress are investigated and discussed in this paper.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.721-724
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• 2006

In the development of sheet-handling machinery, it is important to predict the static and dynamic behavior of the sheets with a high degree of reliability. Flexible media is very thin, very light and very flexible so it behaves geometric nonlinearity of large displacement and large rotation but small strain. In this paper, static and dynamic analyses of flexible media are performed by dynamic FEM considering geometric nonlinearity. Mass and tangent stiffness matrices based on the Co-rotational(CR) approach are derived and numerical simulations are performed by full Newton-Raphson(FNR) method and Newmark integration scheme.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.705-710
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• 2002

Magnetostrictive materials are used low frequency sonar transmitter instead of piezoelectric materials. But it is difficult to analyze due to the nonlinearity and hysteresis of magnetostrictive materials. This paper deals with the program development for the finite element modeling of magnetostrictive tonpilz transducers and for analyzing their acoustic characteristics. To take into account the nonlinearity of magnetostrictive materials, the magnetic field calculation is separated form the displacement calculation, and a curve fitting is adopted for the nonlinear behavior of the magnetic and mechanical strain fields. At first, the magnetic field is obtained by using a commercial FEM software and the displacement of the transducer is calculated by plugging the obtained magnetic field into forcing term. To verity the accuracy of the developed program, a comparison is made with a commercial code, ATILA.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.04a
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• pp.353-360
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• 2001

An analysis procedure of 2-dimensional bridge dynamics has been developed by using force-deformation model, which simulates the pier motion under biaxial bending due to the bi-directional input seismic excitations. A three-dimensional mechanical model is utilized, which can consider the other major phenomena such as pounding, rotation of the superstructure, abutment stiffness degradation, and motions of the foundation motions. The bi-directional dynamic behaviors of the bridge are then examined by investigating the relative displacements of each oscillator to the ground. It is found that the nonlinearity of the pier due to biaxial bending affects the pier motions, but the global bridge behaviors are greatly governed by the pounding phenomena and stiffness degradation of the abutment-backfill system. Especially, the relative displacement of the abutment system (A2) with movable supports to the ground is increased about 30% due to the abutment stiffness degradation.

• International Journal of Concrete Structures and Materials
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• v.19 no.1E
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• pp.3-9
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• 2007

This paper presents a numerical procedure for analyzing the joints between precast post-tensioned segments. A computer program for the analysis of reinforced concrete structures was run for this problem. Models of material nonlinearity considered in this study include tensile, compressive and shear models for cracked concrete and a model for reinforcing steel with smeared crack. An unbonded tendon element based on the finite element method, that can describe the interaction between the tendon and concrete of prestressed concrete member, was experimentally investigated. A joint element is newly developed to predict the inelastic behavior of the joints between segmental members. The proposed numerical method for the joints between precast post-tensioned segments was verified by comparison of its results with reliable experimental results.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.1
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• pp.42-47
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• 2018

This paper describes the dynamical behavior of the bicycle and its nonlinear effect when magnetic repulsive forces are applied to the bicycle cushion system. A finite-element method was used to obtain its reliabilities by comparing the experimental and numerical values and select the proper magnet sizes. The Equivalent spring stiffness values were evaluated in terms of both linear and nonlinear approximations, where the nonlinear effect was specifically investigated for the ride comfort. The corresponding equations of linear and nonlinear motion were derived for the numerical model with three degrees of freedom. Dynamic behaviors were observed when the bicycle ran over a curvilinear road in the form of a sinusoidal curve. The analysis in this paper for the observed nonlinearity of magnetic repulsive forces will be a useful guide to more accurately predict the cushion design for any vehicle system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.1
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• pp.42-47
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• 2003

Nonlinear models for a thin ring rotating at a constant speed are developed. The geometric nonlinearity of displacements is considered by adopting the Lagrange strain theory for the circumferential strain. By using Hamilton’s principle, the coupled nonlinear partial differential equations are derived, which describe the out-of-plane and in-plane bending, extensional and torsional motions. The natural frequencies are calculated from the linearized equations at various rotational speeds. Finally, the computation results from the nonlinear models are compared with those from a linear model. Based on the comparison, this study recommends which model is appropriate to describe the behavior of the rotating ring.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1995.05a
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• pp.141-153
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• 1995

An incremental Total Lagrangian Formulation is implemented for the finite element analysis of laminated composite pressure vessel with consideration of the material and geometric nonlinearities. For large displacements/large rotations due to geometric nonlinearities, the incremental equations are derived using a quadratic approximation for the increment of the reference vectors in terms of the nodal rotation increments. This approach leads to a complete tangent stiffness matrix. For material nonlinearity, the analysis is performed by using the piecewise linear method, taking account of the nonlinear shear stress-strain relation. The results of numerical tests include the large deflection behavior of the selected composite shell problem. When compared with the previous analysis, tile results are in good agreement with them. As a practical example, filament wound pressure vessel is analyzed with consideration of the geometrically and materially nonlinearity. The numerical results agree fairly well with the existing experimental results.