• Wind and Structures
• /
• v.22 no.2
• /
• pp.185-209
• /
• 2016

Across-wind aerodynamic damping ratios are identified from the wind-induced acceleration responses of 15 aeroelastic models of rectangular super-high-rise buildings in various simulated wind conditions by using the random decrement technique. The influences of amplitude-dependent structural damping ratio and natural frequency on the estimation of the aerodynamic damping ratio are discussed and the identifying method for aerodynamic damping is improved at first. Based on these works, effects of turbulence intensity $I_u$, aspect ratio H/B, and side ratio B/D on the across-wind aerodynamic damping ratio are investigated. The results indicate that turbulence intensity and side ratio are the most important factors that affect across-wind aerodynamic damping ratio, whereas aspect ratio indirectly affects the aerodynamic damping ratio by changing the response amplitude. Furthermore, empirical aerodynamic damping functions are proposed to estimate aerodynamic damping ratios at low and high reduced speeds for rectangular super-high-rise buildings with an aspect ratio in the range of 5 to 10, a side ratio of 1/3 to 3, and turbulence intensity varying from 1.7% to 25%.

• Earthquakes and Structures
• /
• v.8 no.3
• /
• pp.779-799
• /
• 2015

The slosh height and the possibility of water spill from rectangular Spent Fuel Storage Bays (SFSB) and Tray Loading Bays (TLB) of Nuclear power plant (NPP) are studied during 0.2 g, Safe Shutdown Earthquake (SSE) level of earthquake. The slosh height obtained through Computational Fluid dynamics (CFD) is compared the values given by TID-7024 (Housner 1963) and American concrete institute (ACI) seismic codes. An equivalent amplitude method is used to compute the slosh height through CFD. Numerically computed slosh height for first mode of vibration is found to be in agreement the codal values. The combined effect in longitudinal and lateral directions are studied separately, and found that the slosh height is increased by 24.3% and 38.9% along length and width directions respectively. There is no liquid spillage under SSE level of earthquake data in SFSB and TLB at convective level and at free surface acceleration data. Since seismic design codes do not have guidelines for combined excitations and effect of higher modes for irregular geometries, this CFD procedure can be opted for any geometries to study effect of higher modes and combined three directional excitations.

• KCI Concrete Journal
• /
• v.11 no.3
• /
• pp.153-164
• /
• 1999

The objective of this research is to observe the actual response of a low-rise nonseismic moment-resisting masonry-infilled reinforced concrete frame subjected to varied levels of earthquake ground motions. The reduction scale for the model was determined as 1 : 5 considering the capacity of the shaking table to be used. This model was, then, subjected to the shaking table motions simulating Taft N2IE component earthquake ground motion, whose peak ground acceleration(PGA) was modified to 0.12g, 0.2g, 0.3g, and 0.4g. The g1oba1 behavior and failure mode were observed. The lateral accelerations and displacements at each story and local deformations at the critical portions of the structure were measured. Before and after each earthquake simulation test, free vibration tests and white noise tests were performed to find the changes in the natural period of the model. When the results of the masonry-infilled frame are compared with those of the bare frame, it can be recognized that masonry infills contribute to the large increase in the stiffness and strength of the g1oba1 structure whereas it also accompanies the increase of earthquake inertia forces. However, it is judged that masonry infills may be beneficial to the performance of the structure since the rate of increase in strength appears to be greater than that of the induced earthquake inertia forces.

• Structural Engineering and Mechanics
• /
• v.45 no.2
• /
• pp.233-257
• /
• 2013

Given the yield shear of a single-story inelastic structure with simple eccentricity, the problem of strength distribution among the resisting elements is investigated, with respect to minimize its torsional response during a ground motion. Making the hypothesis that the peak accelerations, of both modes of vibration, are determined from the inelastic acceleration spectrum, and assuming further that a peak response quantity is obtained by an appropriate combination rule (square root of sum of squares-SRSS or complete quadratic combination-CQC), the first aim of this study is to present an interaction relationship between the yield shear and the maximum torque that may be developed in such systems. It is shown that this torque may be developed, with equal probability, in both directions (clockwise and anticlockwise), but as it is not concurrent with the yield shear, a rational design should be based on a combination of the yield shear with a fraction of the peak torque. The second aim is to examine the response of such model structures under characteristic ground motions. These models provide a rather small peak rotation and code provisions that are based on such principles (NBCC-1995, UBC-1994, EAK-2000, NZS-1992) are superiors to EC8 (1993) and to systems with a stiffness proportional strength distribution.

• Journal of the Institute of Convergence Signal Processing
• /
• v.20 no.1
• /
• pp.57-62
• /
• 2019

In this paper, oneM2M based data monitoring and acquisition system is designed and implemented to measure and transmit the voltage, current, temperature, acceleration and vibration of the motor. The proposed system can detect electrical faults (overcurrent, reverse phase, phase loss, ground fault) and mechanical faults (MC counter, motor operation time, bearing and winding temperature, motor speed, insulation resistance). The system consists of sensor data collection, web server, php, database, wired/wireless communication system. The insulation resistance and the motor speed were measured, and the experimental results were similar for both the test resistance value and the reference input value.

• Nuclear Engineering and Technology
• /
• v.43 no.6
• /
• pp.573-582
• /
• 2011

The in-cabinet response spectrum is used to define the input motion in the seismic qualification of instruments and devices mounted inside an electrical cabinet. This paper presents a procedure for generating the in-cabinet response spectrum for electrical equipment based on in-situ testing by an impact hammer. The proposed procedure includes an algorithm to build the relationship between the impact forces and the measured acceleration responses of cabinet structures by estimating the state-space model. This model is used to predict seismic responses to the equivalent earthquake forces. Three types of structural model are analyzed for numerical verification of the proposed method. A comparison of predicted and simulated response spectra shows good convergence, demonstrating the potential of the proposed method to predict the response spectra for real cabinet structures using vibration tests. The presented procedure eliminates the uncertainty associated with constructing an analytical model of the electrical cabinet, which has complex mass distribution and stiffness.

• Journal of the Korean Society for Precision Engineering
• /
• v.18 no.1
• /
• pp.82-88
• /
• 2001

The demands of high data transfer rate and high recording density in optical disk memory device are being increased. In this paper, 4 design parameters for next generation optical disk are investigated. As for the high data transfer rate, two design parameters such as driving acceleration and transmissibility are introduced. As the high recording density is concerned, the minimum linearity and the tilt of the actuator are introduced. Two kinds of pickup actuator are used to evaluate the validity of the parameters through the simulation and the experiment. The 4-wire actuator has good linearity but bad stability and tilt characteristics, while the rotary and axis actuator has good stability for the external vibration but bad linearity. It is demonstrated that the newly proposed design parameters are available to design and evaluate quantitatively the performance of the actuator for the next generation optical disk.

• Smart Structures and Systems
• /
• v.18 no.3
• /
• pp.449-470
• /
• 2016

Energy harvesting is an emerging technique that extracts energy from surrounding environments to power low-power devices. For example, it can potentially provide sustainable energy for wireless sensing networks (WSNs) or structural control systems in civil engineering applications. This paper presents a comprehensive study on harvesting energy from earthquake-induced structural vibrations, which is typically of low frequency, to power WSNs. A macroscale pendulum-type electromagnetic harvester (MPEH) is proposed, analyzed and experimentally validated. The presented predictive model describes output power dependence with mass, efficiency and the power spectral density of base acceleration, providing a simple tool to estimate harvested energy. A series of shaking table tests in which a single-storey steel frame model equipped with a MPEH has been carried out under earthquake excitations. Three types of energy harvesting circuits, namely, a resistor circuit, a standard energy harvesting circuit (SEHC) and a voltage-mode controlled buck-boost converter were used for comparative study. In ideal cases, i.e., resistor circuit cases, the maximum electric energy of 8.72 J was harvested with the efficiency of 35.3%. In practical cases, the maximum electric energy of 4.67 J was extracted via the buck-boost converter under the same conditions. The predictive model on output power and harvested energy has been validated by the test data.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.20 no.9
• /
• pp.90-96
• /
• 2021

As real-time data of factories can be collected using various sensors, the adaptation of intelligent unmanned processing systems is spreading via the establishment of smart factories. In intelligent unmanned processing systems, data are collected in real time using sensors. The equipment is controlled by predicting future situations using the collected data. Particularly, a technology for the prediction of tool wear and for determining the exact timing of tool replacement is needed to prevent defected or unprocessed products due to tool breakage or tool wear. Directly measuring the tool wear in real time is difficult during the cutting process in milling. Therefore, tool wear should be predicted indirectly by analyzing the cutting load of the main spindle, current, vibration, noise, etc. In this study, data from the current and acceleration sensors; displacement data along the X, Y, and Z axes; tool wear value, and shape change data observed using Newroview were collected from the high-speed, two-edge, flat-end mill machining process of SKD11 steel. The support vector machine technique (machine learning technique) was applied to predict the amount of tool wear using the aforementioned data. Additionally, the prediction accuracies of all kernels were compared.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.26 no.2
• /
• pp.127-134
• /
• 2021

This study presents an overhang-type rail traction system using dual brushless AC (BLAC) motors with hall sensors. For an accurate position and moving length control of the designed rail traction system, instantaneous position controller using speed reference model and modified disturbance observer for BLAC motor with hall sensor are proposed. The presented speed reference model is designed to satisfy the required performance of 200 mm/s with proper acceleration and deceleration slopes to reduce mechanical vibration. Through the instantaneous speed reference model, instantaneous position and speed errors can be compensated together. Furthermore, the modified disturbance observer for BLAC motors with low-resolution hall sensors can improve the torque and speed control performance. The proposed disturbance observer is based on an actual motor speed. However, the feedback speed information of the hall sensor is not enough for use in the low-speed region. The practical adopted disturbance observer uses an activation speed band to the actual torque controller of the designed rail traction system. The proposed position control scheme is verified by the MATLAB-Simulink model and a practical manufactured traction system. In the computer simulation and experiments, the proposed position control scheme shows advanced control performance.