• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.403-410
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• 2003

A new semiactive control strategy for seismic response reduction using a neuro-controller and a magnetorheological (MR) fluid damper is proposed. The proposed control system adopts a clipped algorithm which induces the MR damper to generate approximately the desired force. The improved neuro - controller, which was developed by employing the training algorithm based on a cost function and the sensitivity evaluation algorithm replacing an emulator neural network, produces the desired active control force, and then by using the clipped algorithm the appropriate command voltage is selected in order to cause the MR damper to generate the desired control force. The simulation results show that the proposed semiactive neuro-control algorithm is quite effective to reduce seismic responses. In addition, the semi-active control system using MR fluid dampers has many attractive features, such as the bounded-input, bounded-output stability and small energy requirements. The results of this investigation, therefore, indicate that the proposed semi-active neuro-control strategy using MR fluid dampers could be effectively used for control of seismically excited structures.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.153-160
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• 2003

Nonlinear finite element analysis of reinforced concrete panels subjected to biaxial tensile loads are carried out by using a 9-node assumed strain shell element. The present study mainly focuses on the performance evaluation of material models such as cracking criteria, tension stiffening model and steel model in the membrane energy dominant situation. From numerical results, the exponential form of tension stiffening model together with the use of average yield stress model for the steel embedded in the concrete performs well in the panel analysis under biaxial tensile loading condition and it produces a good agreement with experiment results. Finally, the present results are provided as a benchmark test for reinforced concrete panel structures.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.477-484
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• 2003

Recently, sliding mode control(SMC) method has been investigated for control of building structures under earthquake loadings. SMC keeps responses of a structure in sliding surface while the structure is stable. This control method uses both linear controller and nonlinear controller such as bang-bang controller. This paper presents vibration control of a structure using saturated sliding mode controller, whose maximum conrtol force is limited. The effectiveness of SMC method with controler saturation is investigated based on two performance evaluation criteria: root mean square(RMS) and maximum values of floor drifts and accelerations. Simulation results indicate that SMC method is effective in reduction of displacement and acceleration utilizing the saturated controller's capacity efficiently.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.89-96
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• 2006

Nondestructive evaluation using surface waves needs an analytical solution for the reference value to compare with experimental data. Finite element analysis is very powerful tool to simulate the wave propagation, but has some defects. It is very expensive and high time-complexity for the required high resolution. For those reasons, it is hard to implement an optimization problem in the actual situation. The developed engine in this paper can substitute for the finite element analysis of surface waves propagation, and it accomplishes the fast analysis possible to be used in optimization. Including this artificial intelligence engine, most of soft computing algorithms can be applied on the special database. The database of surface waves propagation is easily constructed with the results of finite element analysis after reducing the dimensions of data. The principal wavelet-component analysis is an efficient method to simplify the transient wave signal into some representative peaks. At the end, artificial neural network based on the database make it possible to invent the artificial intelligence engine.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.631-638
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• 2006

This paper considers the nonlinear direct spectrum method to estimate seismic performance of mixed building structures without iterative computations, given dynamic property $T_1$ from stiffness skeleton curve and nonlinear pseudo acceleration $A_{1y}$ and/or ductility ratio $\mu$ from response spectrum. Nonlinear response history analysis has been performed and analysed with various earthquakes for evaluation of correctness and confidence of nonlinear direct spectrum method.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.741-748
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• 2006

Seismic performance evaluation was conducted for four wind-designed concentrically braced steel highrise buildings in order to check the feasibility of designing steel highrise buildings per elastic seismic design criterion (or strength and stiffness solution) in the regions of strong wind and moderate seismicity. The pushover analysis results revealed that the wind-designed highrise buildings possess significantly increased elastic seismic capacity due to the overstrength resulting from the wind serviceability criterion. The strength demand-to-capacity study showed that, due to the wind-induced overstrength, highrise buildings with a slenderness ratio of larger than four or five can withstand elastically even the maximum considered earthquake at the performance level of immediate occupancy. Based on the analytical results of this study, practical elastic seismic design procedure for steel highrise buildings in the regions of moderate seismicity is proposed.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.473-480
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• 2006

Liquefaction of soil foundation is one of the major seismic damage types of infrastructures. In this paper, deterministic and probabilistic approaches for the evaluation of liquefaction potential are briefly summarized and the risk assessment method is newly proposed using seismic fragility and seismic hazard curves. Currently the deterministic approach is widely used to evaluate the liquefaction potential in Korea. However, the there are a certain degree of uncertainties in the soil properties such as elastic modulus and resistant capacity, therefore the probabilistic approach is more promising. Two types of probabilistic approach are introduced including (1) failure probability for a given design earthquake and (2) the seismic risk of liquefaction of soil for a given service life. The results from different methods show a similar trend, and the liquefaction potential can be more quantitatively evaluated using risk analysis method.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.786-793
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• 2006

For the purpose of developing a vibration-based tension force evaluation procedure for hangers in suspension bridges, a 3D finite element model of hangers is constructed in this paper. With the developed finite element formulation, a frequency-based sensitivity-updating algorithm is applied to identify the target cable system the proposed method is also able to identify the flexural rigidity. the axial rigidity, and the torsion rigidity of a cable. For a field application, a vibration test on hangers of the Yong Jong Grand Suspension Bridge is carried out and the collected data is used to verify the proposed method.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1991.04a
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• pp.8-14
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• 1991

The finite element technique incorporating infinite elements is applied to analyzing the general three dimensional wave-structure interaction problems within the limits of linear wave theory. The hydrodynamic farces are assumed to be inertially dominated, and viscous effects are neglected. In order to analyze the corresponding boundary value problems efficiently, two types of elements are developed. One is the infinite element for modeling the radiation condition at infinity, and the other is the fictitious bottom boundary element for the case of deep water. To validate those elements, numerical analyses are performed for several floating structures. Comparisons with the results from culler available solution methods show that the present method incorporating tile infinite and the fictitious bottom boundary elements gives good results.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1523-1526
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• 2007

This study introduces the testing results of the carbody. The load test was performed to evaluate the structural characteristic and stability of the stainless carbody. The carbody is made of stainless steel. The body structure consisted of side frame, under frame, roof frame, and end frame. Of these components, the side frame and under frame were the most important components considering the vehicle and passenger loads. Loading test were performed under the condition based on "Performance Test Standard for Electrical Multiple Unit". The test results showed that the body structure is safe and stable under the condition of designed load.