• Structural Engineering and Mechanics
• /
• v.51 no.4
• /
• pp.547-564
• /
• 2014

This study focuses on the application of an active tuned mass damper (ATMD) for controlling the seismic response of an 11-story building. The control action is achieved by combination of a fuzzy logic controller (FLC) and Particle Swarm Optimization (PSO) method. FLC is used to handle the uncertain and nonlinear phenomena while PSO is used for optimization of FLC parameters. The FLC system optimized by PSO is called PSFLC. The optimization process of the FLC system has been performed for an 11-story building under the earthquake excitations recommended by International Association of Structural Control (IASC) committee. Minimization of the top floor displacement has been used as the optimization criteria. The results obtained by the PSFLC method are compared with those obtained from ATMD with GFLC system which is proposed by Pourzeynali et al. and non-optimum FLC system. Based on the parameters obtained from PSFLC system, a global controller as PSFLCG is introduced. Performance of the designed PSFLCG has been checked for different disturbances of far-field and near-field ground motions. It is found that the ATMD system, driven by FLC with the help of PSO significantly reduces the peak displacement of the example building. The results show that the PSFLCG decreases the peak displacement of the top floor by about 10%-30% more than that of the FLC system. To show the efficiency and superiority of the adopted optimization method (PSO), a comparison is also made between PSO and GA algorithms in terms of success rate and computational processing time. GA is used by Pourzeynali et al for optimization of the similar system.

• Journal of the Korea Concrete Institute
• /
• v.20 no.5
• /
• pp.643-651
• /
• 2008

The purpose of this study is to evaluate seismic capacity of seismically isolated building according to the earthquake motion record selection method. To analyze the seismic behavior, 20-story building is designed, which has base isolation system. The using earthquake motion record were selected by two categories. The one is a proposed earthquake record according to soil type and response spectrum shape, and the other is a well known earthquake events such as El Centro (1940). The time history analysis results of base isolation buildings be induced difference results according to each ground motion records. Therefore detailed guidelines for the ground motion records selection method must be prepared. And the response of isolation story displacement and shear force show good seismic performance in consideration of the proposed earthquake records.

• Earthquakes and Structures
• /
• v.16 no.1
• /
• pp.109-118
• /
• 2019

This study, analyses the seismic response for a rigid massless square foundation resting on a viscoelastic soil layer limited by rigid bedrock. The foundation is subjected either to externally applied forces or to obliquely incident seismic body or surface harmonic seismic waves P, SV and SH. A 3-D frequency domain BEM formulation in conjunction with the thin layer method (TLM) is adapted here for the solution of elastodynamic problems and used for obtained the seismic response. The mathematical approach is based on the method of integral equations in the frequency domain using the formalism of Green's functions (Kausel and Peck 1982) for layered soil, the impedance functions are calculated by the compatibility condition. In this study, The key step is the characterization of the soil-foundation interaction with the input motion matrix. For each frequency the impedance matrix connects the applied forces to the resulting displacement, and the input motion matrix connects the displacement vector of the foundation to amplitudes of the free field motion. This approach has been applied to analyze the effect of soil-structure interaction on the seismic response of the foundation resting on a viscoelastic soil layer limited by rigid bedrock.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.10 no.6
• /
• pp.133-142
• /
• 2006

This study performed earthquake response analyses of underground structures using displacement responses of soil. In this study, spring coefficients of surrounding soil proposed by specifications and researchers were adopted and then their corresponding analysis results were compared. The free field analyses using ProShake were carried out in order to predict ground responses of the field without underground structures. Several earthquakes such as El Centro, Ofunato, and Hachinohe earthquakes were considered to calculate maximum displacements. Numerical examples were analyzed, and then the results were compared and commented depending on spring coefficients of soil for the analyses using displacement responses of soil. The soil coefficients ranged from 0.05 to 14.39 times of those calculated by Korean Bridge Design Specification (2005). In conclusion, the coefficients of soil proposed by standard specifications seemed to be overestimated compared with those by the finite element method(FEM).

• Journal of the Korean Society for Precision Engineering
• /
• v.22 no.1
• /
• pp.167-174
• /
• 2005

The design for cold extrusion dies is very important, because the die insert is subjected to very high radial and hoop stresses. The design of cold extrusion dies has many constrained conditions. In this paper, the used assumptions are such that the yield strength of each ring is selected according to the allowable tensile or compressive hoop stress in each ring and the maximum allowable inner pressure, when yielding occurs in one ring of the dies, is obtained by the proposed equation. In order to obtain design variables, such as diameter ratios and interferences, using the maximum inner pressure, the flexible tolerance method was used for shrink-fitted thick-walled cylinders. ANSYS APDL was used to perform the repeated analysis of deformation of the dies due to the variation of the design variables. The response surface methodology is utilized to analyze the relationship between the design variables and the maximum radial displacement of the die insert during extrusion. From the results, it is found that outer diameter of the die insert has the largest effect on the minimization of maximum radial displacement at the inner surface of the dies.

• International Journal of Precision Engineering and Manufacturing
• /
• v.9 no.4
• /
• pp.22-25
• /
• 2008

The dynamic response of the head arm assembly (HAA) of a hard disk drive to an impact load was obtained from a 3D non-linear finite element model using ANSYS/LS-DYNA and from experiments using a modified levitation mass method (LMM). In the finite element model, the impact load was created by modeling the mass as a rigid body and making it collide with the HAA. The velocity, displacement, acceleration, and inertial force of the mass were then obtained from the time history data of the finite element analysis. In the LMM, a mass that was levitated with an aerostatic linear bearing, and hence encountered negligible friction, was made to collide with the actuator arm, resulting in a dynamic bending test for the arm. During the collision, the Doppler frequency shift of the laser beam reflected from the mass was accurately measured with an optical interferometer. The velocity, displacement, acceleration, and inertial force of the mass were accurately calculated from the measured time-varying Doppler frequency shift. A good correlation between the experimental data and FEA results was observed. The FEA was also used to investigate the dynamic response of the HAA to impact by different masses.

• Journal of the Korean Geotechnical Society
• /
• v.26 no.6
• /
• pp.57-70
• /
• 2010

Recent earthquakes have demonstrated that the tunnels, which were once considered to be highly resistant to earthquakes, are susceptible to substantial damage under severe seismic loading. Among various modes of deformation under an earthquake loading, the response of the tunnel in the transverse direction is known to be the critical mode. This paper investigates the seismic response of the tunnel in the transverse direction using the method of seismic displacement, which is a type of pseudo-static analysis. Firstly, the methods of calculating the ground deformation are compared. It is shown that the single and double cosine may not provide an accurate estimation of the ground deformation, and that a one-dimensional site response analysis needs to be performed for a more reliable evaluation. Secondly, the tunnel responses are calculated using the simplified, analytical, and numerical solutions. It is demonstrated that the simplified method provides poor estimates of the tunnel response ground deformation. The analytical solution is shown to be effective in modeling circular tunnels in uniform ground, but has serious limitation in modeling tunnel response in non-uniform ground. Numerical analyses are shown to be applicable to all cases, and give the most accurate estimates of the tunnel response. It is also demonstrated that the linear solutions can be so conservative that the soil nonlinearity needs to be accounted for more accurate evaluation of the tunnel response.

• Journal of the Korean Society for Precision Engineering
• /
• v.16 no.1 s.94
• /
• pp.246-252
• /
• 1999

In this paper, the frequency response characteristics of the velocity controlled EHS system obtained by linear simulation method, nonlinear simulation method, and experimentation are compared one another, in order to verify propriety of the linearization method in case of analysis of hydraulic systems. The Bode diagrams are obtained by transforming time domain data of experimental results and nonlinear simulated ones with Fourier transform. The results of nonlinear simulation are more similar to the frequency response of the real systems than those of linear simulation. It is found that nonlinearity of hydraulic systems is mainly occurred from servo valve, and nonlinearity is increased as displacement of servo valve spool increases.

• International Journal of Aeronautical and Space Sciences
• /
• v.9 no.1
• /
• pp.85-99
• /
• 2008

The dynamic response analysis for large structures using finite element method requires a large amount of computational resources. This paper presents an efficient vibration analysis procedure by combining node-based substructuring reduction method with a response analysis scheme for structures with undamped, proportional or nonproportional damping. The iterative form of substructuring reduction scheme is derived to reduce the full eigenproblem and to calculate the dynamic responses. In calculating the time response, direct integration scheme is used because it can be applied directly to the reduced model. Especially for the non proportional damping matrix, the transformation matrices defined in the displacement space are used to reduce the system. The efficiency and the effectiveness of the present method are demonstrated through the numerical examples.

• Smart Structures and Systems
• /
• v.8 no.2
• /
• pp.157-172
• /
• 2011

A new method for both local damage(s) identification and input excitation force identification of beam structures is presented using the dynamic response sensitivity-based finite element model updating method. The state-space approach is used to calculate both the structural dynamic responses and the responses sensitivities with respect to structural physical parameters such as elemental flexural rigidity and with respect to the force parameters as well. The sensitivities of displacement and acceleration responses with respect to structural physical parameters are calculated in time domain and compared to those by using Newmark method in the forward analysis. In the inverse analysis, both the input excitation force and the local damage are identified from only several acceleration measurements. Local damages and the input excitation force are identified in a gradient-based model updating method based on dynamic response sensitivity. Both computation simulations and the laboratory work illustrate the effectiveness and robustness of the proposed method.