• Earthquakes and Structures
• /
• v.15 no.4
• /
• pp.361-367
• /
• 2018

In this paper, dynamic analysis of concrete pipe submerged in the fluid and conveying fluid is studied subjected to earthquake load. The structure is modeled by classical shell theory and the force induced by internal fluid is obtained by Navier-Stokes equation. Applying energy method and Hamilton's principle, the motion equations are derived. Based on Navier and Newmark methods, the dynamic deflection of the structure is calculated. The effects of different parameters such as mode number, thickness to radius ratios, length to radius ratios, internal and external fluid are discussed on the seismic response of the structure. The results show that considering internal and external fluid, the dynamic deflection increases.

• Proceedings of the KIEE Conference
• /
• 2006.07a
• /
• pp.212-213
• /
• 2006

Load models are important for improving the accuracy of stability analysis and power flow studies. Load characteristics change for different voltages and frequencies. In this research, ANN is used to construct the load model. Characteristics of some residential loads are tested under various voltage and frequency conditions. Acquired data are used to construct load models by ANN. Experiments and modeling results are presented in conclusions.

• 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.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.65 no.2
• /
• pp.253-256
• /
• 2016

In this paper, the power system with electric vehicles is analyzed considering the mobility and diffusion rate of electric vehicles in the smart grid environment. In the previous studies, load modeling and load composition rates have been researched and the results are applied to develop a new load model to explain the mobility of electric vehicles which could affect on the power system status such as power flow and stability. The results would be utilized to research and develop power system analysis methods considering movable charging characteristics of electric vehicles including movable discharging characteristics which could be affected by the diffusion progress of electric vehicles.

• Journal of Electrical Engineering and Technology
• /
• v.7 no.5
• /
• pp.653-658
• /
• 2012

Load modeling has a significant influence on power system analysis and control. In recent years, measurement-based load modeling has been widely practiced. In the load modeling algorithm, the model structure is determined and the parameters of the established model are estimated. For parameter estimation, least-squares optimization method is applied. The model parameters are estimated so that the error between the measured values and the predicted values is to be minimized. By introducing sliding window concept, on-line load modeling method can be performed which reflects the dynamic behaviors of loads in real-time. For the purpose of data acquisition, the measurement system including PMU is implemented in university level. In this paper, case studies are performed using real PMU data from Korea Univ. and Seoul National University of Science and Technology. The performances of modeling real and reactive power behaviors using exponential and ZIP load model are evaluated.

• Structural Engineering and Mechanics
• /
• v.59 no.4
• /
• pp.703-718
• /
• 2016

Masonry arch bridges present a large segment of Iranian railway bridge stock. The ever increasing trend in traffic requires constant health monitoring of such structures to determine their load carrying capacity and life expectancy. In this respect, the performance of one of the oldest masonry arch bridges of Iranian railway network is assessed through field tests. Having a total of 11 sensors mounted on the bridge, dynamic tests are carried out on the bridge to study the response of bridge to test train, which is consist of two 6-axle locomotives and two 4-axle freight wagons. Finite element model of the bridge is developed and calibrated by comparing experimental and analytical mid-span deflection, and verified by comparing experimental and analytical natural frequencies. Analytical model is then used to assess the possibility of increasing the allowable axle load of the bridge to 25 tons. Fatigue life expectancy of the bridge is also assessed in permissible limit state. Results of F.E. model suggest an adequacy factor of 3.57 for an axle load of 25 tons. Remaining fatigue life of Veresk is also calculated and shown that a 0.2% decrease will be experienced, if the axle load is increased from 20 tons to 25 tons.

• Journal of the Korean GEO-environmental Society
• /
• v.20 no.3
• /
• pp.31-38
• /
• 2019

To determine the optimum dynamic load test analysis for PCFT (Prestressed Concrete Filled steel Tube) hybrid composite piles that PCFT piles are connected to the top of PHC piles, the dynamic load tests and CAPWAP analyses were performed on two hybrid composite piles with steel pipe and PCFT piles as upper piles. The results of the dynamic load tests and CAPWAP analyses showed that the particle velocity measured in PCFT hybrid composite piles was equal to the wave speed of PHC piles when the strain gauges and accelerometers are attached to the surface of inner composite PHC pile after removing the steel pipe in the upper PCFT pile. In addition, when assuming that the material of that upper PCFT pile was the same as that of the lower PHC pile and the cross-sectional area of the steel pipe in upper PCFT pile was converted to that for concrete through the pile model (PM) in CAPWAP analysis, the accuracy of the CAPWAP analysis result for PCFT hybrid composite piles was very high.

• Steel and Composite Structures
• /
• v.25 no.1
• /
• pp.105-116
• /
• 2017

This paper presents the dynamic stability study of laminated composite plates with different force combinations and aspect ratios. Optimum non-diverging stacking is obtained for certain loading combination and aspect ratio. In addition, the stability force is maximized for a definite operating frequency. A dynamic version of the principle of virtual work for laminated composites is used to obtain force-frequency relation. Since dynamic stiffness governs the divergence or flutter, an efficient optimization method is necessary for the response functional and the relevant constraints. In this way, a model based on the ant colony optimization (ACO) algorithm is proposed to search for the proper stacking. The ACO algorithm is used since it treats with large number of dynamic stability parameters. Governing equations are formulated using classic laminate theory (CLT) and von-Karman plate technique. Load-frequency relations are explicitly obtained for fundamental and secondary flutter modes of simply supported composite plate with arbitrary aspect ratio, stacking and boundary load, which are used in optimization process. Obtained results are compared with the finite element method results for validity and accuracy convince. Results revealed that the optimum stacking with stable dynamic response and maximum critical load is in angle-ply mode with almost near-unidirectional fiber orientations for fundamental flutter mode. In addition, short plates behave better than long plates in combined axial-shear load case regarding stable oscillation. The interaction of uniaxial and shear forces intensifies the instability in long plates than short ones which needs low-angle layup orientations to provide required dynamic stiffness. However, a combination of angle-ply and cross-ply stacking with a near-square aspect ratio is appropriate for the composite plate regarding secondary flutter mode.

• Journal of the Korean Geotechnical Society
• /
• v.19 no.3
• /
• pp.93-104
• /
• 2003

The Disturbed State Concept (DSC) model, with simplified unloading/reloading formulation, is implemented in a nonlinear dynamic finite element program fur porous media named DSC_DYN2D. In this research, the DSC constitutive model is utilized using the HiSS model for relative intact (RI) part and the critical state model for the fully adjusted (FA) part in the material. The general formulation for implementation is developed. The cyclic loading tests from the field load test data on a pile segment were numerically simulated using the finite element program DSC_DYN2D and compared with field measurements and those from the previous analysis with the HiSS model. The DSC predictions show improved agreement with the field behavior of the pile compared to those from the HiSS model. Overall, the computer procedure with the DSC model allows improved and realistic simulation of the complex dynamic soil-structure interaction problems.

• Journal of Electrical Engineering and Technology
• /
• v.3 no.4
• /
• pp.451-459
• /
• 2008

Accurate load modeling is essential for power system static and dynamic analysis. By the nature of the problem of parameter estimation for power system load modeling using actual measurements, multiple local optimal solutions may exist and local methods can be trapped in a local optimal solution giving possibly poor performance. In this paper, Trust-Tech, a novel methodology for global optimization, is applied to tackle the multiple local optimal solutions issue in measurement-based power system load modeling. Multiple sets of parameter values of a composite load model are obtained using Trust-Tech in a deterministic manner. Numerical studies indicate that Trust-Tech along with conventional local methods can be successfully applied to power system load model parameter estimation in measurement-based approaches.